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An investigation of egg shell quality Lee, James Hin Foon 1967

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AN INVESTIGATION OF EGG SHELL QUALITY by JAMES BIN FOON LEE, B. So. University of British Columbia, 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Poultry Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July . 1967 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r an a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r e e t h a t the; L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e a n d s t u d y , I f u r t h e r a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d v/i t h o u t my w r i t t e n p e r m i s s i o n D e p a r t m e n t o f P o u l t r y Science T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8 , C a n a d a D a t e J u l y 2 0 , 1967 - i i -ABSTRACT Egg shell quality was assessed in terms of breaking strength, elasticity, and energy absorbed by the shell up to failure. Two devices were used to determine these characteristics. Simple correlation and simple linear regression analyses showed that elasticity as determined by either device gave equally reliable estimates of breaking strength of the egg shell ( r = -.68). A study of the three calcium levels supplemented to a basal ration on shell quality of eggs from two reciprocal crosses of birds showed that each measurement (breaking strength, elasticity, and energy to failure) used to assess shell quality produced different conclusions. In the early part of the experiment, elasticity was significantly lower for the 2$ than for the 4$ or 6$ calcium diets i n both crosses of birds. However, there was no significant difference i n the effect of 4$ and 6% calcium diets on elasticity. On the basis of the energy absorbed to failure, there was no significant effect of dietary calcium in Cross I birds. In Cross 2 birds, 6% calcium produced significantly superior results on energy absorbed as compared to the 2$ and 4$ calcium diets. For Cross I birds, breaking strength of eggs from the 6$ and 4$ dietary calcium treatments were significantly higher than those from the 7$ calcium treatment. For Cross 2 birds, 4$ dietary calcium produced stronger shells than 2$\ shell strength from the 6£ calcium treatment was inter, mediate to and net significantly different than that of the 2$ or 4$ calcium diets. Ho significant difference i n the effect of the three calcium diets on shell quality as assessed by any one of the three - i i i -measurements was observed l n the latter part of the experiment. No consistent effect of the age of birds on egg shell strength was apparent. Significant variation l n shell strength was found among groups of birds within the same cross on the same ration. Eggs stored under selected environmental conditions for different durations showed that moisture affected egg shell elasticity and the effect Increased In magnitude with time of storage when the egg was not only Immersed i n water but also f i l l e d with water after removal of the albumen and yolk. Neither oiling nor storage temperature affected egg shell elasticity. There was no consistent effect of storage duration on egg shell elasticity except for the two treatments i n which eggs with or without the contents removed were stored under water. It was found that the difference between the two duplicate elasticity readings measured at the equator of the same egg did not change signi-ficantly with either storage condition or storage duration. -iv-TAHLE OF CONTENTS Chapter Page I INTRODUCTION 1 II REVIEW OF LITERATURE 3 H I MATERIALS AND METHODS 16 IV RESULTS AND DISCUSSION 28 Experiment 1: Comparison Between the Partial Load and the Bellows Bydrocheek Devices for Evaluating Egg Shell Strength. 23 Experiment 2: Effect of Different Calcium Levels i n the Laying Diet on Egg Shell Strength. 33 Experiment 3: Effect of Storage Conditions and Duration on Egg Shell Strength. 40 V SUMMARY 45 BTHLIOGRAPHT 43 APPENDICES - V -LIST OF TABLES TABLE PAGE I Analyses of Variance Performed on Data (Experiment 2 ) . Zk II Simple Correlation Coefficients, Means, and Coefficient of Variation (Experiment 1). 29 III Results of Simple Regression Analysis of Crushing Strength (OL) on Each of the Two Measures of Elasticity (E^ and Eg). Experiment 1. 30 IV Results of Duncan's Test on the Two Measures of Elasticity (E^ and Eg) and Crushing Strength (Ur,) as Influenced by Dietary Calcium Level (Experiment 1). 32 V Results of Duncan's Test on Elasticity (Eg), Energy Absorbed to Failure, and Crushig Strength (Ur,) as Influenced by Dietary Calcium Level for Each of Two Crosses of Leghorns (Experiment 2) . 34 VI Results of Duncan's Test on Elasticity (Eg), Crushing Strength (U^), and Energy Absorbed to Failure, as Influenced by the Age of the Birds for Each of the Two Crosses of Leghorns (Experiment 2) . 37 VII Results of Duncan's Test on Adjusted Mean Elasticity (E^) as Influenced by Storage Condition for Each of Eight Storage Durations. (Experiment 3) . Ifi - v i -LIST OF FIGURES FIGURE PAGE 1 Partial Load Device 17 2 Bellows Hydrocheck Device 18 3 Experimental Layout (Experiment 2 ) . 22 - v i i -AOOIOWLEDGEMENT The author wishes to express his deepest gratitude to his advisor* Dr. J.F. Richards, for his advice and constructive criticism throughout this study. He is also indebted to the following members of his committee, who critically read this manuscript. Professor J. Biely, Dept. of Poultry Science Dr. G.W. Eaton, Division of Plant Science Dr. W.D. Kitts, Dept. of Animal Science Professor B.E. March, Dept. of Poultry Science Professor L.M. Staley, Dept. of Agriculture Mechanics. He would also like to thank Professor Staley and the Dept. of Agriculture Mechanics for permitting the use of the Bellows Hydrocheck apparatus. Special thanks are extended to Mr. D.C. Crober, a fellow graduate student, for his advice and encouragement. - v i i i -LIST OF ABBREVIATIONS AND DEFINITIONS Cross 1: Female progeny of Mount Hope x UBC mating. Cross 2: Female progeny of UBC x Mount Hope mating. U^: Breaking strength (in grams) of the egg as determined on the Bellows Hydrocheck apparatus. Elasticity: The deformation (in microns) which took place in the egg shell as a result of one kilogram force exerted on i t . Energy: The energy absorbed by the egg shell up to the time of fracture calculated as 1/2 x Deformation x Breaking Strength. E^ : Elasticity as determined by the Partial Load apparatus, using the fl a t side of the platform. Elasticity as determined on the Bellows Hydrocheck apparatus. CHAPTER I INTRODUCTION The strength of the egg shell is important in relation to egg breakage sustained by the poultry industry. The average percentage of eggs cracked before reaching the consumer has always been substantial. Although a l l eggs cracked do not become a total loss, and may be marketed as "cracks" according to the Canadian Shell Egg Regulations (Canada Department of Agriculture, i 9 6 0 ) , the loss incurred because of shell f a i -lure amounted to approximately $590,000 in British Columbia and 4 . 2 million dollars i n Canada i n 1965 (Tung, 1 9 6 ? ) . Organisms of the Salmonella genus, a l l of wMch are potentially capable of resulting in salmonellosis in man, have been found frequently i n cracked eggs (Brooks, 1 9 5 8 ) . Conse-quently, the problem of egg breakage is of economic importance to the egg industry and important to the health and welfare of the general public. Before egg shell strength can be improved i t must be expressed in objective terms. Several direct methods have been used to measure egg shell strength. Shell strength has been measured on intact eggs by crushing or puncturing methods in which an increasing load is applied, and by an impact method i n which the egg is struck by an object of known weight and acceleration (Tyler, 1 9 6 1 ) . On the basis of these methods, several characteristics of the shell have been shown to be correlated with shell strength. These include quantity of shell material (i.e., shell thickness, percent egg as shell, and shell weight per unit surface area), shape of the egg, and the structural stress-strain properties such as hardness and elasticity of the shell. -2-The strength of the shell at the time an egg is laid is affected by hereditary factors, nutrition, age of the bird, season and temperature. A large amount of work has been done in the areas of physiology and nutri-tion, particularly with respect to the requirements for and metabolism of calcium, phosphorus, manganese and other trace minerals, and vitamin D, in relation to shell strength. The aforementioned are concerned only with factors affecting the i n i t i a l quality of the egg shell, but the maintenance of the i n i t i a l quality of egg shell is also important. It has generally been assumed that l i t t l e or no change takes place in the strength of the shell during the post-ovipositional period. This study was designed to investigate the effect of varying levels of calcium in the diet on i n i t i a l egg shell strength and the effect of storage under different environmental conditions on egg shell characteris-tics. -3-CHAPTER H LITERATURE REVIEW Direct Measurements on Egg Shell Strength. Shell strength has been measured on intact eggs by crushing, puncturing, or by impact methods. Crushing entails the application of an increasing load to the egg at the equator or the ends. The most common increasing load to the egg at the equator or the ends. The most common method of crushing is to place an egg between two flat plates and gradually apply an increasing load on the egg. This is done either by increasing the load at the fixed distance from the fulcrum or by using the same load at increasing distance from the fulcrum. In methods using puncturing devices, pressure can be applied to an egg by means of a pointed rod. If the rod is flat-ended and of a sufficiently large cross-section, then the effect approaches that produced by the crushing devices. Impact methods generally rely on a variation of falling ball techniques. In this method, the force with which the ball hits the egg is calculated from the impulse and momentum formula F = m/Zgh, assuming time is constant, and where F = force in dynes, m = weight of ball i n grams, h = height of f a l l (in cm.) when egg is cracked, and g = acceleration due to gravity in cm./sec^. A detailed and systematic review of most of these methods was done by Tyler (1961,2).. Several more recent methods for measuring shell strength were developed by Tyler and Geake (1963) t o assess shell strength at the broad and narrow poles as well as at the equator of the egg. It was found that a l l methods showed a highly significant relationship between shell strength and shell thickness. In general, methods using impact showed that, for a given thickness, the shell is strongest at the equator -4-and weakest at the narrow pole. With crushing methods, on the other hand, the opposite is the case. It was later concluded by these authors (Tyler and Geake, 1964, c,d) that Impact methods give much larger errors than do crushing methods. The same authors found that the results obtained with the various crushing methods are significantly correlated. Factors Which are Correlated with Shell Strength. 1. Amount of Shell An average egg of the domestic chicken weighs about 58 grams. Egg weight is influenced by age, breed, strain, environment, nutrition, and other factors. An egg of average size contains about 6.1 grams shell (without membranes) or about 11.0$ of the total weight of the egg. The shell contains about 0.1 gram of water, 0.2 gram of organic matter (largely protein) and 5*8 grams inorganic matter. Of the inorganic matter, calcium salts represent over 98$, with trace amounts of magnesium, phosphorus, iron, and sulfur. Each egg contains about 2.2 grams of calcium. The amount of shell present may be expressed in several methods. The four most commonly used methods are shell thickness, percentage of the egg as shell, shell weight per unit area, and the specific gravity of the whole egg. These methods have been described by Olsson (1934). The measurement of specific gravity has an obvious advantage over other methods of determining the amount of shell since i t does not require breaking of the egg, and for this reason i s perhaps the most commonly used method. Willard and Shaw (1909) stated that the weight necessary to perforate the shell i s closely related to thickness taken as the mean of the thickness at the two poles and two sides. They pointed out that, on the average, -5-thinner shells are perforated by less weight but admit that the data for individual eggs are extremely variable. Thickness was measured by Stewart (1936) by taking at least four readings around the equatorial region. For 1,003 eggs he found that the relationship of shell thickness with breaking strength gave a significant correlation coefficient of 40.509. Lund et a l . (1933) measured thickness after removing the membranes and found the correlation with breaking strength ( 40.633) highly significant. Shell thickness was not measured directly by either Edin et al . (1937) or Stewart and Hart (1933). The former used shell ash/cm^ and found a sig-nificant correlation of +0.608 with crushing strength. The latter deter, mined the absolute amount of calcium i n shell and membrane. Tyler (196l,b) plotted the data of Stewart and Hart (1933) and found the relation between thickness and breaking strength to be reasonably linear. Morgan (1932) used percentage shell as the criterion of thickness and found a signifi-cant correlation ( r = 0.493 ) between shell thickness and strength for eggs laid by both Single Comb White Leghorns and for Barred Plymouth Rocks ( r = 0.533 ). Godfrey (1949) found a correlation coefficient of +0.736 between crushing strength and specific gravity. Rauch (1959) measured thickness directly at the two poles and the equator and found that thick-ness versus strength gave a correlation coefficient of 40.55 for 3328 eggs. Richards and Swanson (1965) also measured thickness directly to the nearest ten-thousandth of an inch and found the correlation coefficient with crushing strength ranged from 40.74 to 40.76. It is clear that differences in shell strength have been only partially explained by differences in shell thickness. -6-2. Chemical Constituents The effect of chemical composition of the shell on its strength has also been investigated. The amount of protein in the membrane-free shell was studied by Almquist and Burmester (1934) and shown to be nega-tively correlated with strength ( r = -.389). However, when shell protein was corrected for thickness, the relationship became non-signifi-cant, since thin shells contained a higher proportion of protein than thick shells. Tyler (1961) found no relationship between shell nitrogen and shell thickness. Brooks and Hale (1955) suggested a direct corre-lation between shell magnesium content, shell hardness, and shell strength. 3. Shape of the Egg Egg shape was estimated by Stewart (1936) in a number of ways but he concluded that none of these was sufficiently well correlated with breaking strength (force applied at poles) to be of practical significance and that shell curvature did not affect strength. Edin et a l . (1937) found no significant correlation between strength and egg shape measurements. On the other hand, Lund et a l . (1938) found that the breaking strength of an egg was greater for the narrow pole. Richards and Swans on (1965) found that egg shape expressed as shape index was independent of shell thickness and accounted for 15 to 35$ of the variability i n crushing strength on the equator after shell thickness had been considered. -7 4. Structural Stress-strain Properties of the Shell Brooks (1958) shoved that there was a highly significant correla-tion between hardness and breaking strength of the shell. The gradient of hardness across the shell (from the Inner portion to the outer portion) was found to increase linearly, and this gradient was significantly steeper for the unusually strong shells. Recently, Tung (1967) found a significant correlation between hardness and crushing strength. Tung (1967) also showed that the gradient of hardness across the shell was parabolic. The hardness increased toward the inner and outer surfaces. A more recent criterion used for the estimation of shell strength is elasticity (deformation per unit load) which has also been expressed as stiffness (load per unit deformation). In 1958, Brooks described an apparatus designed to measure the weight required to crack the shell and the deformation which took place during loading. A highly significant correlation coefficient of -0.714 was found between crushing strength at the equator and the elasticity of the shell. These results were based on samples of 36 eggs drawn at random from lots obtained from several strains of birds at different times of the year. Hunt and Voisey (1966) found the correlations of elasticity and breaking strength ranged from 0.75 to 0.83 when force was applied at the equator while a correlation of 0 . 6 2 was found for force applied at the poles. Schoorl and Boersma (1959)* in collaboration with the Institute T.H.O. for Mechanical Constructions i n Delft, designed an apparatus for measuring the changes in shape or deformation of an egg shell which occur from the application of a load lower than that required to fracture the - 8 -shell. The apparatus, commonly referred to as the Partial Load Defor-mation Apparatus, was described by Schoorl and Boersma ( 1 9 6 2 ) . By using this device, Schoorl and Boersma found correlation coefficients between deformation and thickness ranging from - 0 . 7 4 to - 0 . 8 7 , and between deformation and breaking strength of - 0 . 8 8 . Rauch (1965) found a some-what lower correlation between deformation and breaking strength (r = - . 7 0 ) and correlations ranging from -0.80 to - 0 . 8 3 between deformation and thickness of the shell. Hereditary Factors Influencing Shell Quality From the results of studies in which impact method was used to assess shell strength of eggs from a flock of 312 White Wyandotte pullets, Hale (1956) reported that brown-shelled eggs had a higher breaking strength than white-shelled eggs. Romanoff (1929) produced the f i r s t evidence of individual bird differences i n breaking strength of shells from White Leghorn pullets. Taylor and Martin (1928) published data indicating that the ability to form a thick egg shell was controlled in part by hereditary factors. They pointed out that eggs from a flock of Barred Plymouth Rocks were significantly lower in percentage shell than eggs from a White Leg-horn flock. Within the White Leghorn flock, families of daughters from two males differed significantly in the percentage of shell in their eggs. Baskett et a l . (1937) found that the individuality of the hen was the most important factor i n determining the breaking strength of the egg shells produced. After having adjusted for individual variations, they found no significant difference between the White Leghorn, Wyandotte, and Rhode Island Red breeds. Morgan et al . (1930) found differences between -9-White Leghorns and Barred Plymouth Rocks, and much of this difference could be accounted for by difference in shell thickness. On the other hand, Godfrey and Jaap (19^9) found that the Ohio strain of New Hampshires gave a mean breaking strength of 2.63 kg., while the Oklahoma strain gave a value of 3.70kg., despite the fact that, on the basis of specific gravity determinations, there was l i t t l e difference in mean shell thickness between the strains. Munro (1938) published an analysis of a Barred Plymouth Rock flock which showed a significantly higher variance between the off. spring of different dams than within the progeny of individual dams in ash, both as a percentage of dry shell and of total egg. The differences between groups of daughters from individual dams were attributed to diffe-rences in genotype. In the study of the inheritance of egg shell thick-ness in White Leghorns, Taylor (1939) indicated that heritable factors were involved i n the determination of the amount, thickness, and percentage of egg shell characteristic of individual hens. The results of Tyler and Geake (1958) strongly indicated that, for a number of shell characteristics, there were marked variations between individual hens within a breed and significant variation between breeds. Therefore, any breeding program, to be successful, would require, f i r s t , an established optimum for a particular characteristic and, second, a knowledge of the effect of selection for this characteristic on other attributes such as productive performance. Genetic ability to lay eggs with strong shells is lacking in some hens. Commercial breeders continuously screen their breeding stock to make improvements through selection. In most cases, however, breeding stock is selected f i r s t for the number and size of eggs, and selection for shell strength i s , therefore, compromised (Tyler and Geake, 1958). -10-The Effects of Age of Bird, Season and Temperature on Shell Quality One of the major economic problems of egg production is that egg shell quality decreases after the f i r s t few months of laying and results i n a major problem of cracked and thin shelled eggs before birds have been i n production for ten months. The shell quality problem is at times severe enough to make i t necessary to dispose of a flock which may be laying at a satisfactory rate. Although increases i n calcium intake improve shell quality, high intake will not necessarily prevent this decline associated with age. Factors responsible for this decline are not understood. It is possible that calcium retention may be lower as birds become older. The retention studies of Hurwitz and Griminger (1962) were conducted with 13-15 month old hens. These investigators found that maximum calcium retention was 1.5 to 1.7 grams per bird per day. On the other hand, several reports with younger birds suggest calcium retention up to and above 2.0 grams per day. Tyler (1940) and others showed that the residue calcium varies with shell formation and i t is well established that skeletal calcium contributes a considerable portion of shell calcium. Decreasing shell quality may then, result from a reduction i n this source of calcium. Swanson and Snetsinger (1962) suggest that physiological aging of the shell secreting glands may be responsible for the normal decline of shell quality as the laying year progresses. It is generally accepted that egg shells become thinner during the summer season. Miller and Bearse (1934) determined the shell percen-tages of eggs of spring-hatched pullets from December to October and found a more or less consistent decrease beginning in March and extending -11-throughout the period. Variations of the percentage of the egg which is shell should be closely associated with shell thickness or strength. Baskett et al. (1937) found that there was a decrease i n breaking strength i n summer. Gutowska and Parkurst (1942 a,b) and Heuser and Norris (1946) likewise noted that breaking strength was lower during the months of high temperature. In an experiment designed to study the influence of high environmental temperatures on egg weight, Bennion and Warren (1933) observed that egg shells seemed to be more fragile when the birds were subjected to high air temperatures. However, these investigators did not objectively measure shell strength. Warren and Schnepel (1940) reported that hens and pullets held under controlled air temperatures showed a striking reduction i n thickness of their shells when subjected to 90° F. The results also suggested that high humidity accentuated the depressing effects of high temperature on shell thickness. The blood calcium content was reduced as was the shell thickness when the birds were subjected to high temperatures. The birds consumed about 26 percent less feed when the temperatures were raised from 60 to 95° F. Campos et a l . (I960) studied the influence of a rapid rise i n temperature upon shell quality. When the temperature was raised from 70 to 90°F. i n two days there was l i t t l e or no decrease i n shell quality. Subsequent increases during the next three days to 95 and 100°F. resulted i n a marked shell quality decrease. Mather et a l . (1961) studied the influence of 70 and 90° F. temperatures upon the histological differences i n the egg shell. They concluded that the changes occur i n the shell and not in the matrix and are due to basic differences i n mineral metabolism. An extensive experiment was conducted by Tyler and Geake (i960) covering -12-three laying seasons. These investigators shoved that shells were thinner i n summer, but not a l l birds vere equally influenced by the season. The winter months gave the lowest percentage values of cracked eggs after market handlings and cracking appeared to be associated with thinner shells. On the other hand, Tyler and Geake (1964a) showed that there was l i t t l e evidence to suggest that seasonal fluctuations i n thick, ness were always paralleled by fluctuations i n strength, nor to suggest that either thickness or strength necessarily declines i n summer. These investigators emphasized that measurements of strength or thickness or both, over a short period of time do not necessarily yield useful infor-mation about the performance of a given bird i n the future. nutrition and i t s Interaction with Other Environmental Factors Adequate nutrition of the hen i s important for the production of sound egg shells. Some nutrients, when deficient, can decrease egg shell strength. Calcium, phosphorus, and vitamin D-j deficiencies are most likely to produce inferior shells under practical conditions. Of these, calcium i s now of greatest interest. Stewart and Bart (1938) found both breaking strength and shell thickness were affected by dietary calcium content. The same investigators found that a deficiency of calcium i n the diet brings about a progressive thinning of the shell followed by a complete cessation of laying, probably as the result of an Inhibition of pituitary gonadotrophin secretion. Tyler et al. (1962) reported calcium requirements near 2.0 percent and found that 3*95 7* was detrimental to egg production and feed utilisation. Berg et a l . (1963) found 2.14 per-cent calcium adequate for the production of sound shells. Higher require-ments were reported by Evans et a l . (1944) who found that egg shell -13-thickness was best when the diet contained 3*0 percent. Common (1943) concluded that the calcium requirement for laying hens was about 4.0 grams per day. This is equivalent to approximately 3*5 percent dietary calcium for a high egg producing four-pound hen consuming one-fourth pound of feed per day. Based on the experimental evidence available, the National Research Council (1954) established the recommended nutrient allow-ance of laying hens for calcium at 2.25 percent of the complete ration. Petersen et al. (1960a) compared 2,25, 3.75. 4.5 and 5.25 percent calcium at both 55 and 75°F. environments. Egg production was excellent for a l l calcium levels (69.8, 70.7, 67.0, 70.0 percent respectively for the four calcium levels). The difference in production was significant at the 5$ level i n favour of the higher temperature. Egg shell quality as measured by specific gravity of the whole egg was not improved by calcium levels above 3*75 percent when the temperature was maintained at 55°F. At 75°F»» 375 percent calcium did not result i n shell quality equal to 55°F» or to 4.50 or 5«25 percent calcium. These data agreed with those of Mueller (1961) who reported that the calcium required increased when the laying house temperature was increased. In another study (Petersen et a l . 196l), 2.25 and 3.75 percent calcium intakes were compared for hens housed at either 75°F. uniform temperature or a fluctuating temperature of 75°F. during the day and 45° to 50° F. at night. The higher calcium level resulted in improved shell quality with both temperature treatments. However, there was only a slight and non-significant difference in shell quality between temperature treatments. This is in contrast to the report of Mueller (19^1) who found that in terms of breaking strength of the eggs produced, a 90o to 55° F. -14-fluctuating day-night temperature, was significantly better than a constant 90°F. but significantly inferior to a constant 55°F. temperature. The findings of Jenkins and Tyler (I960) indicated that the "high" calcium diet groups taken together gave a significantly thicker shell than the "normal" calcium diet groups taken together for a 12-month duration. But they found that "high" calcium diet significantly increased shell thick-ness only at the beginning of the experiment (i.e., near the onset of laying) and this increase diminished in the latter part of the experiment as the laying period progressed. (Calcium levels were not cited in their report). The Effects of Storage Duration and Storage Conditions on Shell Quality One of the f i r s t investigations on shell texture and its relation to shell quality was conducted by Hoist et al. (1932). They found that the pattern of translucent areas i n the shell is not a permanent charac-teristic of the shell and may vary considerably in the egg after i t is laid. It was also reported that translucent areas have a higher water content than the opaque areas surrounding them. Tyler and Geake (1964b) found that translucent areas are weaker than opaque areas of the same shell. In a series of three separate investigations, Tyler and Geake ( I 9 6 4 c,d,e) found that cracking, crushing, and piercing strength of shells were decreased by soaking the shell in water and increased by oven-drying and by treating with absolute alcohol. A water-alcohol mixture (1:1 v/v) gave values intermediate to those of each component separately. This was confirmed by Tyler and Thomas (1966) using shells from which the cuticle and membranes were removed. These results suggest that strength of the shell could be partly dependent on the degree of -15-hydration of the organic matter; the greater the hydration, the weaker the shell, Tyler and Geake (19&te) investigated the time factor i n storage with respect to shell quality. Shells of normal eggs kept in the labora-tory became stronger with time up to 28 days and were weakest immediately after laying. Swenson and James (1932) measured the effect of oiling on eggs and concluded that i t did not affect breaking strength while Bryant and Sharp (193*0 considered that neither washing nor sanding affected breaking strength. -16-CHAPTER H I MATERIALS AND METHODS Experiment 1. This experiment was designed to determine the correlations among partial load elasticity ( % )» Bellows Hydrocheck elasticity ( Efe ), and breaking strength ( )» and also to investigate the effect of different calcium levels i n the diet on these shell characteristics. Eggs were obtained from individually-caged Single Comb White Leghorn pullets (Cross 1) during the sixth and seventh months of production (June, 1966). Three rations differing only i n the level of calcium were fed throughout the laying period. The basal ration (Appendix 1) was supple-mented with calcium carbonate to yield the diets containing 2, 4, and 6 percent calcium, respectively. A total of 342 eggs collected at 2 p.m. on each day of the experi-ment were used. Each egg was identified by bird and ration. Elasticity by each of the two methods and crushing strength of each egg were measured within two hours of collection. Elasticity (E^) was f i r s t measured by the Partial Load Apparatus (Figure 1) and then crushing strength (D^) and elasticity (£2) were determined simultaneously on the Bellows Hydro, cheek Apparatus (Figure 2). -17-FIGURE 1 PARTIAL LOAD DEVICE -18-FIGURE 2 BELLOWS HYDROCEECK DEVICE -19-The Partial Load Device (Schoorl and Boersma, 1962) applies a constant load (500 grams) instantaneously on the egg and the amonnt of deformation (in microns) is read from a dial gauge. Partial Load elas-ti c i t y (microns per kilogram) was found by multiplying the deformation value by two. The Bellows Hydrocheck Device (Mohsenin, 1963; Richards and Staley, 1967) applies an iureasing load on the equatorial region of the egg by means of a compressed air driven piston (at 40 psi) which moves downward at a constant velocity of 44 t 2 microns per second. The egg rested on a slightly concave surface. A strain load cell below this sur-face served to translate the mechanical force (load) into electrical sig-nals which were recorded on the Y-axis of an X-Y recorder* A linear variable differential transformer (L.V.D.T,) attached to the side of the moving piston and i n contact tiih the load cell provided the means of deter-mining deformation of the egg as i t was loaded. The signal from the L.V.D.T. was recorded on the X-axis of the X-Y recorder. Both signals were thus recorded simultaneously to supply a force-deformation graph of the egg under test. The scale was 600 grams per inch on the Y-axis and 42.3 microns per inch on the X-axis. The calibration was checked after testing every 10 to 12 eggs throughout the experiment. Elasticity (Eg) was expressed as deformation of the egg i n microns per kilogram load. Crushing strength (U^) was expressed as total load (grams) required to fracture the shell. Deformation and load were measured to the nearest 1/40 of an inch on the recorder chart. Total load was -20-thereby measured to the nearest 15 grams and total deformation to the nearest 1.06 microns. A randomized complete block design with 3 treatments (calcium levels) and 10 bloeks (periods) was used. More than one observation (subsample) was taken from each experimental unit. The number of obser-vations per experimental cell was not equal but the analysis of variance was performed on randomly selected equal numbers of observations. The general model assumed to explain the sources of variation in this experiment was: X m tt + T + B + (TB) + (SE) ijk n 1 j i j ijk where X j ^ was an observation i n subsample in j * * 1 block i n the 1 t h treatment. (TB)^j was the experimental error or the interaction term for treatment and block. (SE)^^ was the subsampling error. Both treatment (T) and block (B) effects were considered to be fixed. The sampling error term was used to test for treatment and block effects i f there was significant interaction between treatment and block; the experimental error term was used to test for treatment and block effects i f there was no significant interaction between treatment and block. (Steel and Torrie, i960) Duncan's New Multiple Range Test (Duncan, 1955) was used to test for the significance of differences among treatment means i n this and sub-sequent experiment. The data were also subjected to simple correlation and regression analyses. -21-Experiment 2. This experiment was designed to investigate the effect of different calcium levels i n the diet on shell quality. The experiment began on August 10, 1966 and concluded on December 29* 1966. Individually-caged pullets of both Cross land Cross 2 received rations containing 2, 4, and 6% calcium as outlined in Experiment 1. In a l l , 3tU9 eggs were used in the experiment (1,474 from Cross 1, and 1,645 from Cross 2). Eggs were collected between 3 p.m. and 4 p.m. on each day of the experiment and were identified as to the individual bird and ration. Eg and measurements were made on each egg within 4 hours of collection. The methods used were the same as those discussed in Experiment 1. No partial load elasticity measurements (E^) were taken in this experiment. The design was a 3*3 latin square replicated 3 times (Figure 3). More than one observation (subsample) was taken from each experimental unit. -22-FIGURE 3 EXPERIMENTAL LAYOUT FOB EXPERIMENT 2 Square 1 Square 2 Square 3 Time Group 1 2 3 1 2 3 1 2 3 1 2* 2* 6* 25^  656 2 *4 2$ 636 256 6* - 2J6 6* 3 6* 2* 6* 456 2* 6£ 456 -23-Ninety birds were used i n this experiment. Each group consisted of 3d birds (15 birds from Cross 1 and 15 birds from Cross 2). Each period (time) consisted of 14 days and eggs were collected during the last 7 days i n each period. No eggs were collected during the f i r s t 7 days following a change i n diet. A total of 16 analyses of variance were performed on the data as indicated i n Table I. The general models assumed to explain the sources of variation were as follows (Steel and Torrie, I960; Federer,^lr955) : 1. Separate square analysis, without subsampling (based on experimental cell means): X = D. + P + R + T + B i j t i j t i j 2. Replicated square analysis, without subsampling: X =J1 + S + P + R + T + E qijt q i j t i j 3. Separate square analysis, with subsampling: X =;t + P + R + T + E + (SE) i j t s i j t i j i j s 4. Replicated square analysis, with subsampling: -24-TABLE I ANALYSES OF VARIANCE PERFORMED ON DATA (EXPERIMENT 2) Analysis Based on No, of Analysis Experimental cell means: Cross 1, Separate Square Analysis 3 Replicated Square Analysis 1 Cross 2, Separate Square Analysis 3 Replicated Square Analysis 1 Individual eggs (equal subsample size for each experimental cell): Cross 1, Separate Square Analysis 3 Replicated Square Analysis 1 Cross 2* Separate Square Analysis 3 Replicated Square Analysis 1 - 2 5 -Treatment (T) was assumed to have a fixed effect, whereas group (R), time (P), square (S), residual (£), and subsampling error (SE) were assumed to have random effects. Simple correlation and regression analyses were also performed on the data. Experiment 3. This experiment was designed to investigate the effect of storage conditions and storage-duration-on egg shell elasticity and breaking strength. Birds and rations used in this experiment were the same as those in Experiment 2. Eggs were collected on three consecutive days prior to randomly allotting them to each of the six storage conditions. The expe-riment began on July 21, 1966, and was concluded on September 18, 1966. Six treatments (storage conditions) and nine periods (storage duration) were used in the experiment. Forty five eggs were allotted to each of the following treatments: Treatment 2: Treatment 1: Eggs stored at room temperature (approximately 70° F). Eggs stored under water (approximately 70°F). Treatment 3: Eggs stored i n a carbon dioxide atmosphere created by flushing C02 into air-tight glass jars (approxi-mately 70°F). Treatment 4: Eggs with the albumen and yolk removed through two small holes at the poles and the remaining shell stored under water (approximately 70°F). -26-Treatment 5: Eggs stored under refrigeration (approximately 40°F). Treatment 6: Eggs sprayed with mineral o i l and stored under refrigeration (approximately 40°F). The nine periods were Q-day, 1-day, 3-day, 7-day, 14-day, 21-day, 28-day, 35-day, and 60-day storage. Two Partial Load elasticity (E^) values were taken on each egg for each of the f i r s t eight periods. A l l measurements were made on the equa-torial region of the shell. At the end of the 9th period of storage, elasticities by Partial Load (E^) and by Bellows Hydrocheck (E^), and crushing strength (UL) were measured. The partial load elasticity (Ej_) values for each of the last 8 periods were subjected to analysis of covariance (completely randomized design) using the Ej_ values obtained in the f i r s t period as the concomi-tant variable. The differences between the pair of Ej_ readings taken on each egg were subjected to analysis of variance in a randomized complete block design. The general model for the covariance analysis was: *ts = u + T t + B (*ts - + Ets where Y t s = the elasticity of the s^ h egg on the t ^ 1 treatment, u = population mean, Tt = effect of t ^ n treatment (asaamed to be fixed), (X^s - X..) = deviation of the t s * h covariate X from the mean of the covariate, B = common regression for a l l treatments, and E^s = random error component. -27-The general model for the analysis of variance on the differences of paired readings was the same as that used for Experiment 1. Correlation coefficients between elasticity and breaking strength, coefficients of variation, regression coefficients, and standard error of estimate were calculated on an individual-egg basis i n this experiment. -28-CHAPTER IV RESULTS AND DISCUSSION Experiment 1 Correlation and Regression Analyses on Partial Load Device and  Bellows Hydrocheck Device. It was found (Table II) that the linear correlation between elasticity derived from each of the two devices (r=.80) was highly significant (P <_ 0.01). Correlation coefficients of Eg versus U^ (r= - .68), and E^ versus U^ (r= -.67) were similar and significant ( P < 0.05). Thus, approximately 45$ of the variability i n the breaking strength of the egg shell was-attributable to elasticity as determined by either one of the two devices. The mean values of elasticity for E^ (53.42 microns/kg) was sig-nificantly ( P < 0.05 ) higher than that for \ ltfi*55 microns/kg). This finding suggested that the deformation resulting from the f i r s t 500 grams of force exerted on the egg may have been greater than that for sub-sequent 500 gram increases i n force. However, there was no indication of curvlinearity on the Eg output. It was found (Table III) that regression coefficients, standard error of estimate, and the F-ratios for crushing strength regressed on each of the two elasticity measurements were very similar. However, the Y-intercept (a-value) of the regression of U^ on E^ was almost 200 grams higher than that for the regression of on Eg. The difference in Y-intercept and the slightly but not significantly steeper slope of the latter regression resulted in differences no greater than 200 grams i n -29-TABLE II SIMPLE CORRELATION COEFFICIENTS, MEANS, AND COEFFICIENTS OF VARIATION (N=342) Coefficients Variable % E? Means of variation % - - 53.42 u/kg 18.0456 \ +0.8038** - 47.55 u/kg 20.0356 \ -0.6759** -0.6824** 3376.00 g 15.69* ** P^O.Ol -30-TABLE U I RESULTS OF SIMPLE REGRESSION ANALYSES OF CRUSHING STRENGTH (tL.) ON EACH OF THE TWO MEASURES OF ELASTICITY and Eg) 1 Independent Y-intercept Regression Standard variables coefficient error of F estiate \ 5360 -37.13 391 285** E2 5180 -37.94 388 295** ** P * 0.01 n=342 -31-crushing strength as predicted from elasticity measured by each of the two devices. Preliminary Experiment on the Effect of Calcium Level in the  Diet on Egg Shell Quality. The data for this experiment were subjected to analysis of variance (Appendix 2). Calcium level was found to have a significant (p«0.05) effect on elasticity (either E^ or Eg) but not on crushing strength. Neither period nor the period x calcium level interaction were found to have a significant effect on elasticity or crushing strength. This was to be expected as each period consisted of only one day and the experiment was conducted during a two week period. It i s evident from the results i n Table IV that the 4# calcium diet was the optimal level as determined by E^. There was no significant difference between 2$ and k-$ as determined by E^ and no significant difference between 2% and 6$ i n either E^ or Eg. No significant difference i n crushing strength was found among dietary calcium levels. Reference to Appendix 2 will show that the subsample percent sums-of squares was greater i n the analysis of crushing strength (U^) than of E^ and Eg. Therefore, error variation was higher for crushing strength than for Ej_ and Eg. These results indicate that Ej_ and E? were more likely to indicate significance of mean differences. However they are only estimates of shell strength and the significance was not supported by the analyses of crushing strength. -32-TABLE IV RESULTS OF DUNCAN'S TEST ON THE TWO MEASURES OF ELASTICITY (E, AND E L , ) AND CRUSHING STRENGTH (tL) AS INFLUENCED Bx DIETARY CALCIUM LEVEL EXPERIMENT 1 \ h *L Calcium Levels 6# 2% 4# 6% 2% 4# 4# 2% 6% Means 5%6? 52.20 49.26 48.26 45.47 3430 3411- 3300 The means underlined by the same line were not significantly different ( P^O.05) -33-Experiment 2 Effects of Different Calcium Levels In Diet on Egg Shell Quality. From the results of the Duncan* s Test on the analysis of the individual egg data (Table V), i t was found that for both crosses of birds, Bellows Hydro check elasticity (Eg) was significantly lower for the 2$ than for the 4$ and 6$ calcium treatments. However, there was no signi-ficant difference i n the effect of 4$ and 6$ calcium i n the diet. According to the energy absorbed by the shell there was no significant difference among the three levels of calcium i n the diet of Cross 1 birds. In Cross 2 birds, 6% calcium resulted i n significantly superior results as compared to 2% and 4$ calcium. The breaking strength (U^) of eggs from Cross 1 birds recei-ving 6$ and 4$ calcium diets were significantly higher than those from the 2$ calcium treatment. But for Cross 2 birds, 4$ calcium was superior to 2$; 6f> calcium was intermediate to and not significantly different than 2% or 4£. The results based on the analysis of the mean values of the same data (Table V) produced essentially the same results. The only exception was that i n the mean analysis of the data for Cross 2 birds there was no significant effect of calcium level on energy absorbed. From the results of the analysis of variance (Appendices 5 to 16) calcium level i n the diet was found to significantly affect Bellows Hydrocheek elasticity (E,) and breaking strength (U^) i n most cases. However, only i n a few cases did the diet have a significant -34-TABLE V RESULTS OF DUNCAN'S TEST ON ELASTICITT ( E j , ENERGY ABSORBED TO FAILURE, AND CRUSHING STRENGTH ( U r J AS INFLUENCED BY DIETARY CALCIUM LEVEL FOR EACH OF TWO CROSSES OF LEGHORNS EXPERIMENT Zr~ Eg ENERGY \ -Based on individual eggs-Cross 2$ 4# 6$ 4# 6# 2$ 6$ 2% 1 52.76 48.00 47.12 265.901 264.305 260.936 3376 3370 3196 Cross 2$ 4* 6# 14 2$ 6$ U$ 656 2% 2 52.44 49.11 48.87 269.627 266.385 258,299 3326 3271 3210 -Based on experimental cell means-Cross 2# 4* 6* 4* 6# 2% 6# 4# 2$ 1 52.07 48.13 47.39 264.338 263.455 259.527 3370 3348 3180 Cross 2$ 6$ 4* 4* 2% 6% 4* 6* 2% 2 52.21 49.42 49.32 269.618 262.275 260.456 3321 3290 3195 1 The means underlined by the same line were not signifcantly different ( PSQ.05) -35-effeet on energy absorbed to failure by the eggs. A possible explanation for the result is that when breaking strength increased as a response to a particular calcium level, deformation generally decreased. Since energy was calculated as half of the product of deformation and breaking strength (Energy = 1/2 x deformation x U^), i.e., the area under the curve, i t i s reasonable that energy would not respond to the effect of different calcium levels. It was evident that the measurements used to assess shell strength (i.e., U^, Eg, Ej_, and energy absorbed) gave different results (Table V) . The results with respect to the effect of dietary calcium level on shell strength are therefore inconclusive and dependent upon the measurement used to indicate strength. Bmaking strength (OL) is the only direct measurement of shell strength included in the study and therefore could be considered the most logical single measurement on which to rely for interpretation of the results. It was apparent from the individual latin square analysis, from the replicated latin square analysis, and from Duncan's test (Table V) that the two crosses of birds responded differently to dietary calcium levels. Thus, genetic effect with respect to calcium levels in the diet should also be considered in studies of egg shell strength. The results here seemed to be i n agreement with those of Tyler and Geake (1958), who found that for a number of shell characteristics there were marked varia-tions between individual hens within a breed and significant variation between breeds. Since the birds used i n the present investigation were two reciprocal crosses (UBCdf x Mount Hope £ and UBC $ x Mount Hope a*), a maternal effect may also be involved. -36-Age of bird had no consistent effect on shell characteristics (Appendices 15 and 16, Table VI). It was apparent (Table VI) that each measurement (U^, Eg, Energy absorbed) used to assess shell characteristic gave different conclusions with respect to the age effect. The results from this experiment did not agree with Hurwitz and Griminger (1962), who suggested that calcium retention may decrease as birds become older, nor with Swans on and Snetsinger (1962), who suggested that physiological aging of the shell secreting glands may affect egg shell strength as the laying year progresses. However, the duration of this experiment (126 days) may not have been of sufficient duration to reveal an age effect on egg shell strength. The analyses of the data for each square separately (Appendices 5 and 6, 9-14) indicated that the effect of dietary calcium level on the shell measurements diminished with age. The result agreed with the findings of Jenkins and Tyler (i960), who reported a similar change and suggested that the diminished effect in the latter part of their experiment was caused by adaptive or regulative physiological mechanisms of the birds. Differences among groups of birds within squares (Appendices 7 and 8, 15 and 16) was found to be significant i n every case except in Bellows Hydrocheck elasticity (Eg) for Cross 1 birds. A breakdown of this source of variation indicated the significance was due to differences among groups and not due to the group x square interaction. The groups were randomly selected at the beginning of the experiment and the only known difference among the groups within each of the three squares was the sequence i n which the diets were administered (Figure 3)* It is possible that this difference could account for the significant group within square -37-TABLE VI RESULTS OF DUNCAN'S TEST ON ELASTICITY (EU), CRUSHING STRENGTH (UL) , AND ENERGY ABSORBED TO FAILURE* AS INFLUENCED BY THE AGE 1 OF THE BIRDS FOR EACH OF THE TWO CROSSES OF LEGHORNS EXPERIMENT 2 2 ENERGY Period 1 3 2 3 2 1 3 1 2 Cross 1 51.42 49.53 45.93 3348 3342 3253 272.697 266.393 252,052 Eeriod 1 3 2 2 1 3 1 3 2 Cross 2 51.58 51.30 47.53 3301 3283 3223 276,411 262,771 255*130 Each mean i s based on the eggs collected during a period of 42 days. 1 = First period. 2 = Second period. 3 = Third period. The means underlined by the same line were not significantly different ( PS0.05) -38-effect although no supporting evidence could be found i n the literature. The interaction of diet and age of bird (square) was found to be significant only for the energy absorbed by the eggs of Cross 2 birds. Ho significant effect of diet on productive performance was found i n any of the analyses. The birds used i n this experiment had not been selected for high egg production. Therefore, varying dietary calcium levels might be expected to have only a minimal effect on egg production. It i s also possible that the Zf> and 6$ calcium levels were not extreme enough to affect egg production. Two percent calcium may not have resulted i n a depletion of reserves severe enough to affect production and 6$ calcium may not have been high enough to affect production through the interference with metabolism of minerals other than calcium. Simple Correlation and Regression Analyses on fe. ^ and Energy  Absorbed. It was found (Appendix 17) that correlation coefficients between Energy and Eg were statistically significant (P 0 . 0 5 ) but were low in a l l cases. The r values ranged from -O .II56 to .0.2829* Therefore, only 2.3$ to 3 . 0 $ of the variability i n elasticity of the egg was attributable to energy absorbed to fracture. The highest correlation was between energy absorbed and (r=0.7999 to 0 . 8 4 0 7 ) . Thus, approximately 65$ of the variability i n crushing strength of the egg was accounted for by energy absorbed. Correlation between Eg % 1 0 2 1 8 slnH* 1* to that found i n experiment 1 (Table II). Approximately 4-5$ of the variability in the 39-breaking strength of the egg shell was attributable to elasticity. There were no significant differences between the crosses i n the magnitude of the correlation coefficient for any pair of shell characteris-tics. Coefficients of variation for energy absorbed to failure and Eg were found to be higher than that for U^. This result seemed reasonable because both and energy were derived from and deformation (i.e., Eg Reformation / ^  (kg), and Energy = 1/2 x Deformation x OL). Coefficients of variation were i n every case lower i n Cross 2 birds than those i n Cross 1 birds (Appendix 1 7 ) , but the differences were small i n most instances. The simple linear regression coefficients for regressed on each of energy absorbed and Eg were found to be highly significant (Appendix 1 8 ) and differed only slightly with age or cross. There were differences i n the y-intereepts (a-values) among ages and crosses but the differences i n the crushing strength predicted from the derived regression equations using elasticity or energy as the independent variable differed among ages or crosses by no more than 200 grams. -40-Ecperiment 3. Effect of Different Storage Conditions and Storage Durations on  Egg Shell Elasticity, The storage treatments were feund to have a highly significant effect on the Partial Load elasticity values (E^). From the results i n Table VII and Appendix 21, i t is evident that eggs stored under water either with or without contents had the highest elasticity values among the six selected storage conditions. Of these two storage conditions, the eggs of treatment 4 (egg contents removed) had significantly higher elasticity values than those of treatment 2 (egg contents intact) after 14 or more days of storage. There was no significant difference i n elasticity of untreated eggs stored under refrigeration (treatment 5) and oiled eggs stored under refrigeration (treatment 6), These results seem to be in agreement with those of Swenson and James (1932), who concluded that oiling of eggs did not affect breaking strength. Eggs stored i n a normal atmosphere at room temperature (treatment 1) and eggs stored i n a carbon dioxide atmosphere (treatment 3) had slightly lower elasticity values than eggs of treatments 5 and 6, However, this difference was not statistically significant and the results changed slightly with storage duration. There was no significant difference i n mean elasticity values of eggs stored at room temperature either under a normal atmosphere or under a COg atmosphere. There was no significant difference between elasticity values (El) of eggs stored under refrigeration and eggs stored at room temperature. It was evident that storage temperature had no effect on egg shell strength. -CI-TABLE VU RESULTS OF DUNCAN'S TEST OH ADJUSTED MEAN ELASTICITY (E,) AS INFLUENCED BY STORAGE CONDITION FOR EACH OF 8 STORAGE DURATIONS * EXPERIMENT 3 Storage Adjusted Treatment Means of Partial Load Duration Elasticity (E^) 1-day 2 6 4 5 3 i 61.26 60.30 60.34 59.90 57.98 57.14 3-day 4 2 6 5 1 3 61.96 61.22 59.80 58.90 58.08 57.78 7-day 4 2 6 5 3 1 62.92 g L^Qg 60.06 58.22 57.86 57.68 14-day 4 2 6 5 . 3 1 64.28 61.38 59.42 58.80 57.80 57.68 21-day 4 2 6 3 5 1 66.26 60.54 60.00 58.58 57.72 56.76 28-day 4 2 6 5 1 3 70.34 61.14 59.60 58.10 58.08 58.06 35-day 4 2 6 5 3 l 72.78 62.64 61.14 59.42 59.38 58.38 60-day 4 2 6 1 3 5 76.52 64.74 59.40 57.46 57.44 57.24 1 Duncan1 s test performed at the 5$ level of probability. 2 Treatment 1: Intact eggs stored at room temperature. 2: Intact eggs stored under water. Jt Intact eggs stored i n 002 atmosphere at room temperature. 4: Eggs with contents removed and stored under water. 5: Intact eggs stored under refrigeration. 6: Eggs sprayed with mineral o i l and stored under refrigeration. -42-The experimental results (Table VU) indicated no consistent effect of storage duration on egg shell elasticity except for the two treatments i n which eggs with or without the contents removed were stored under water. Elasticity values of eggs from the other four storage con-ditions fluctuated without consistent pattern up to 60 days of storage. The results are not in complete agreement with those of Tyler and Geake (1964, c), who found that eggs stored at room temperature began to show an increase i n strength from the time they were laid and that this increase was rapid at f i r s t and gradually declined up to 28 days. Further-more, they reported that shell strength of eggs with contents intact stored under water decreased significantly during the f i r s t three days of storage and then increased up to 28 days. This finding was not supported by the results of the experiment reported herein. Elasticity fluctuated up to 28 days and then increased slightly at 35 and 60 days of storage. Nevertheless, i t was evident Horn the results of this experiment and from the work of Tyler and Geake (1964 a,b,c) that moisture affects egg shell elasticity and that the effect increases in magnitude when the egg i s not only immersed i n water but also f i l l e d with water after removal of the albumen and yolk. Effect of Storage Condition and Storage Duration on the Difference  Between Two Partial Load Elasticity (E)) Values Taken From the Equatorial Region of the Same Egg. The variation of elasticity around the equatorial region (i.e., difference between the two(Ej_) readings from the same egg) did not change significantly with either storage condition or duration (Appendix 22.) Mean Ej_ differences for the 45 observations in each of -43-the experimental cells are presented i n Appendix 23, The grand mean difference between the two readings was 1.126 microns. The results of the analyses indicate that storage condition and storage duration affect elasticity to the same extent i n different positions in the equatorial region of an egg. Simple Correlation and Regression Analyses of Crushing Strength (Pt.) on Each of the Two Measures of Elasticity (Eh . B P) for Eggs Which  Had been Stored for 60 Days. Simple correlation coefficients, means, and coefficients of variation for individual storage conditions and for a l l storage conditions pooled are presented i n Appendices 24. 26 and 27, respectively. Correlation between % and Eg ranged from 0.6247 to 0.8616, (pooled r = .8253) with untreated eggs stored in refrigeration having the lowest r value and untreated eggs stored i n carbon dioxide having the highest r value. The correlation between E^ and Eg for freshly laid eggs i n experiment 1 was 0.8038 (Table II). Correlation between E^ and % ranged from -0.5212 to -0.7870 (pooled r = -.7734) with untreated eggs stored at room temperature having the lowest r value and oiled eggs stored i n refrigeration having the highest r value. The correlation between E«L and for freshly laid eggs in Experiment 1 was -0,6759 (Table II). Correlation between Eg and ranged from -0.5929 to -0.7721 (pooled r = -.7614) with eggs stored at room temperature having the lowest r value and eggs with contents removed and stored under water having the highest r value. This correlation as found by freshly laid eggs i n Experiment 1 was -0.6824 (Table II). Bo explanation was apparent -44-for the difference between stored and those of freshly laid eggs in the magnitude of the correlation coefficients between each pair of shell characteristics. Results of simple regression analysis of regressed on each of % and Eg for individual storage conditions are presented i n Appendix 25. A l l regression coefficients were found to be highly significant (P^O.01) but differed considerably among storage treatments. Standard error of estimate was highest for untreated eggs stored in refrigeration i n both the E^ and Eg analyses but the reason for this finding was not apparent. On the basis of the pooled analysis the mean values of Eg was lower than that of Ej_, a finding which is similar to that reported in Experiment 1 based on freshly-laid eggs (Table II). -45-CHAPTER V SUMMARY Experiment 1 This experiment was designed (i) to determine the correlation between elasticity as determined on two devices (Bellows fiydrocheck and Partial Load), ( i i ) to determine the correlation between elasticity as determined by either device and the crushing strength of the egg shell, ( i i i ) to study the effect of dietary calcium level on egg shell elasticity. The results showed highly significant correlations between the two elasticity measurements (r = 40.8038) and between each of these measurements and crushing strength (Bellows Hydrocheck, r = .0.6824; Partial Load, r = -0.6759). Thus, 45$ of the variability in the crushing strength of the egg shell was attributable to elasticity as determined by either one of the two Devices. Regression analysis showed that elasticity as deter-mined by either of the two devices gave an equally reliable estimate of crushing strength of the egg shell. Dietary calcium level was found to have a significant (P< 0.05) effect on elasticity (either or Eg) but not on breaking strength. Experiment 2 This experiment was designed to investigate the effect of varying calcium levels supplemented to a basal ration on shell quality of eggs from reciprocal crosses of Single Comb White Leghorns. Shell quality was measured by elasticity, breaking strength, and energy absorbed to failure of the shell. In the early part of the experiment dietary calcium level was found to have a significant effect on shell quality but each of the -46-three measurements used to assess shell quality produced different con-clusions with respect to the effect of dietary calcium level. In the latter part of the experiment there was no significant difference i n the effect of the three calcium levels on shell quality as assessed by any one of the three measurements. The results with respect to the effect of dietary calcium level on shell strength were, therefore, inconclusive and dependent upon the measurement used to indicate strength and on the duration of the experi-ment. Age of the bird had no consistent effect on egg shell strength during the experiment (126 days). Significant variation in shell strength was found among groups of birds within the same cross and receiving the same ration. Varying calcium levels supplemented to a basal ration did not have a significant effect on the rate of egg production of the birds. However, the birds used i n the present experiment were not a commercial strain selected for high egg production. The average percentage production in these birds was approximately 60$. Therefore, the same conclusion may not apply to commercial strains selected for high egg production. -47-Experlment 3 This experiment was designed to investigate the effect of storage on egg shell quality. It was found that moisture affected egg shell elasticity and the effect increased in magnitude with time of storage when the egg was not only immersed in water but also f i l l e d with water after removal of the albumen and yolk. Neither oiling nor storage temperature affected egg shell elasticity. No consistent effect of storage duration on shell elasticity was found except for the two treatments i n which eggs with or without the contents removed were stored under water. i It was found that the difference between two elasticity, readings measured at the equator of the same egg did not change significantly with either storage condition or storage duration. -48-BIBLIOGRAPHY Almquist, H.J., and B.R. Burmester. 1934. Characteristics of an abnormal type of egg shell. Poultry Sci. 13: 116-122 Baskett, R.G., W.H. Dryden, and R.W. Hale. 193?. Investigations on the strength of hen eggs. J. Mia. Agric, H. Ire. 5: 132-142. Bennion, N.L., and D.C. Warren. 1933* Temperature and its effects on egg size in the domestic fowl. Poultry Sci. 12:69-82. Berg, L.R., G.E. Bearse, and V.L. Miller, I960. A comparison of two methods of supplying calcium to laying pullets. Wash. Agric. Exp. Sta. Bui. No. 458 Brooks, J. 1958* Strength in the egg. Society of Chemcal Industry Monograph Ho. 7. Texture in Foods, London. S.C.I. 149-178. Brooks, J., and H.P. Hale. 1955* Strength of the shell of the hen's egg. Nature, May 14. pp. 848-850 Bryant, R.L., and P.F. Sharpe. 1934, Effect of washing on the keeping quality of hens* egg. J. Agric, Res, 48: 67-89. Campos, A.C., F.A. Wilcox, and C.S. Shaffner. I960. The influence of fast and slow rises in temperature on production traits and mortality of laying pullets,- Poultry Sci. 39: 1119-1129. CanadauDepartment of Agriculture. I960. Canada Agricultural Products Standard Act and Shell Egg Regulations.. P.C. 1959-1331. Duncan, D.B, 1955. Multiple range and multiple-F tests. Biometrics, 11: 1-42 Edin, H,, T. Helleday, and A. Anderson. 1937. Beziehung zwisehen Oberflfische und Gestalt der Htthnereier. Z. Untersuch. Lebensmltt. 73: 313-326 Evans, R.J., J.S. Carver, and A.W. Brant. 1944. The influence of dietary factors on egg shell quality II. Calcium. Poult. Sci. 23:36-42 Federer, W.T, Experimental Design. 1955* Hew York: MacMillan Co., pp. 162 Godfrey, G.F., and R.G. Jaap. 1949. The relationship of specific gravity, 14-day incubation might loss and egg shell colour to hatchabillty and egg shell quality. Poult. Sci. 28:874-889 -49-Gutowska, M.S., and R . T . Parkhurst. 1942 a. Studies in mineral nutrition of laying hens. I. The manganese requirement. Poult. Sci. 21 :277-287. . 1942 b. Studies i n mineral nutrition of laying hens, U Excess of calcium in the diet. Poult. Sci. 2 1 , 321-328. Hale, R.W. 1956. Observations on the shell strength of hen eggs. Ministry of Agriculture, Northern Ireland. Vol. LV pp. 34-40 Herrasti, G. 1916. The strength of egg shells. (Letter to Editor). Sci. Amer. 115:321, i l l u s . Hoist, W.F., H.J. Almquist, and F.W. Lorenz. 1932. Poult Sci. Vol XT. 3: Hunt, J.R., and P.W. Voisey. 1966. Physical properties of egg shells. Poult. Sci. 45: 1398-1404. Huritz, S., and P. Griminger. 1962. Estimation of calcium and phos-phorus requirement in laying hens by balance techniques. J. Sc. Food & Agric. 13: 185-191 Jenkins, N.K. and C. Tyler, i 9 6 0 . Changes in egg thickness and white and yolk weight and composition over a period of a year. J. Agric. Sci. 55.323 Kennard, D.C. 1925. Essential minerals for chicks and laying hens. Poult. Sci. 4 : 109-117 Lund, W.A., Heiman, V., and L.A. Wilhelm. 1938. The relationship between egg shell thickness and strength. Poult. Sci. 17:372:376 Mather, F.B..P.A. Thornton, and G.P. Epling. I 9 6 I . The effects of heat on the microscopic structure of the egg shell matrix. Poult. Sci. 40:1428-1429. Miller, M.W., and G.E. Bearse. 1934. Phosphorus requirements of laying hens. Wash. Agric. Exp. Sta. Bull. 3Q6. Mohsenin, N.N. 1 9 6 3 . A testing machine for determination of mechanical and rheological properties of agricultural products. Perm. State Agr. Exp. Sta. Bui. No. 701 -50-Morgan, C.L. 1932. Relationship between breaking strength and the percent of egg shell. Poultry Sci. II; 172-175. Morgan. C.L., J.H. Mitchell, and D.B. Roderick. 1940. The value of cod liver o i l i n rations for laying hens. S. Carolina Sep. Sta. 43rd Ann. Rep., pp. 91-92 Mueller, W.J., 196l. The effect of constant and fluctuating environ-mental temperatures on the biological performance of laying pullets. Poult. Sci. 40:1562-1571. . 1964. Improving shell quality - an evaluation of some of the factors that affect egg shell quality, with particular emphasis on the role calcium plays. The Poultry Farmer, Oct. 31, 1964. Munro, S.S. 1938. Effect of heredity on interior egg quality and shell composition. Poultry Sci. 17:17-27 Nutrient requirements for poultry. National Research Council Publica-tion 301, 1954. Olsson, N. 1934. Studies on specific gravity of hen's egg. A new method of determining the percentage of shell i n hen's eggs. Leipzig, Otto Harrasiowi. Petersen, C.F., D.H. Conrad, D.H. Lumijarvi, E.A. Sayter, and C.E. Lampman. I960 a. Studies on the calcium requirement of high producing white Leghorn hens. Idaho Agr. Sep. Sta. Res. Bui. 44. Petersen, C.F., E.A. Sauter, C.E. Lampman, and A.C. Wiese. 1961. Influence of uniform versus fluctuating daily temperature on egg shell quality. Poultry Sci. 40:1444. Poult. Proc. and Market., July, 1964, pp. 32-33 Rauch, W. 1959. Mathematische-statistische Beziehungen zeishchen eignelltltsmerkmalen (Korrelationen und Regressionen). Arch. Geflugelk. 23:108-121. . 1965. The elastic malformation of eggs as a standard for the assessment of the firmness of the shells. Archiv. Geflugelk. Heft 5. Oktober 1965. XXIX Jahrgang. Richards, J.F., and L.M. Staley. 1967* The relationship between crushing strength, deformation and other physical measurements of the hen's egg. Poultry Sci. 46j 430-437. Richards, J.F., and M.H. Swanson. 1965. The relationship of egg shape to shell strength. Poultry Sci. 44; 1555-1558. -51-Bom&noff, A.L. 1929. Study of the physical properties of the hen's egg shell in relation to the function of shell-secretary glands. Biol. Bull. 56:351-356. Romanoff, A.L., and A.J. Romanoff. 1949. The Avian Egg. John Wiley and Sons, Inc., New York. pp. 115 and 353* Schoorl, P., and H.Y. Boersma. 1962. Research on the quality of the egg shell ( a new method of determination ). XUth World's Poult. Cong. Proc. Sydney, Australia. Steele, R.C.D., and I.H. Torrie. Principles and Procedures of Statis-tics. i960. New York: McGraw-Hill Book Co. pp. 74, 144, 153. Stewart, G.P. 1936. Shell characteristics and their relationship to breaking strength. Poult. Sci. 15:119-124. Stuart, H.O., and C.P. Hart. 1938. The effect of different calcium intake levels on egg production, shell strength and hatchability. Poult. Sci. 17:3-7. Swaason, M.H., and B.C. Snetsinger. Improving egg shell quality Minn. Farm and Home Science. Vol. XX, No.l, pplO - 11, Fall 1962. Swenson, J.L., and L.H. James, 1932. Oiling does not make shell eggs more brittle. U.S. Egg and Poult. Mag. 38:14-16, 58. Taylor, L.W. 1930. Inheritance of eggshell thickness i n white Leghorn Pullets. J. Agric. Res., Vol. 58, No. 5. Taylor, L.W., and I.M. Lerner. 1939. Inheritance of egg shell thickness in white Leghorn pullets. J. Agric. Res. 58:386 Taylor, L.W., and J.H. Martin. 1928. Factors influencing thickness of egg shells. Poult. Sci. 8:39-44. Taylor, T.G., T.R. Morris, and F. Hertelandy. 1962. The effect of pituitary hormones on ovulation in calcium deficient pullets. Vet. Rec. 74:123 Tully, W.C., and Franke, K.W. 1934. Comparative metabolism of several calcareous materials used in poultry feeding. S. Dak. State Coll. Agric. Exp. Sta. Bull. 287. Tung, M. 1967. Unpublished M.S.A. thesis. University of British Columbia, Vancouver, Canada. -52-Tyler, C., 1940. Studies of calcium and phosphorus metabolism in relation to the chemical structure of bone. I. Biochem. J. 34: 202-212. . 1961, a. Shell strength: Its measurements and its relation-ship to other factors. Brit. Poult. Sci., Vol. 2, 1:3-19. . 1961,b. Studies on egg shells. XVII - Variations in mem-brane thickness and in true shell nitrogen over different parts of the same shell. J. Sci. Food and Agric. 6: 470 - 475. Tyler, C. and F.H. Geake. 1958. Studies on egg shells. IX. The influence of individuality, breed and season on certain characteristics of egg shells from pullets. J. Sci. Food and Agric. 4:584-590. . i960. Studies on egg shells. XIII. Influence of individuality, breed, season, and age on certain characteristics of egg shells. J. Sci. Food and Agric. 9: 535-547. . 1963. A study of various impact and crushing methods used for measuring shell strength. Brit. Poult. Sci., Vol. 4, 1: 49-61. . 1964,a. Egg shell strength and its relationship to thickness with particular reference to individuality in the domestic hen. Brit. Poult. Sci. Vol. 5. 1:3-18. . 1964,b. The effect of water on egg shell strength including a study of the translucent areas of the shell. Brit. Poult. Sci., Vol.5 3:277-284. . 1964,c. The testing of methods for cracking egg shells, based on paired readings from individual eggs and the measurement of some effects of various treatments. Brit. Poult. Sci. 5: 19«28. . 1964,d. The testing of methods for crushing egg shells, based on paired readings from individual eggs and the measurement of some effects of various treatments. Brit. Poult. Sci. 5*29-35. . 1964,e. The effect of water on egg shell strength including a study of the translucent areas of the shell. Brit. Poult. Sci., S: 277-284. Tyler, C, and H.P. Thomas, 1966. A study of the snapping strength of egg shells and the effect on various factors on i t . Brit. Poult. Sci. Vol.7, 3:277-38. Warren, D.C, and R.L. Schnepel. 1940. The effect of air temperatures on egg shell thickness i n the fowl. Poult. Sci. 19:67-72. Willard, J.T., and R.H. Shaw, 1909. Analysis of eggs. Kansas State Agric. College. Expt. Sta. Bull. 159, pp.143-177. APPENDIX 1 COMPOSITION OF THE BASAL RATION Ingredients Amount in lbs. Ground wheat I4l6 Soya bean meal (44* protein) 300 Dried cereal grass 30 Dried fermentation solubles 40 Iodized salt 7 Feeding o i l 10 Bj^ premix 9mg/lb 1.20 Tallow 100 Manganese sulfate 0.3L Premix 95.20 1999.71 APPENDIX 2 MEAN SQUARES AND PERCENT SUMS OF SQUARES FROM THE ANALYSIS OF VARIANCE ON ELASTICITY (E^ AND Eg) AND ON CRUSHING STRENGTH (UL). EXPERIMENT 1. Sources Degree PERCENT SUMS of of Variation Freedom MEAN SQUARES OF SQUARES h °L *2 °L Calcium levels 2 286.16* 347.40* 442,690 2.41 3.13 o.Tl Period 9 50.10 147.03 181,660 1.90 5.96 1.31 Ca x Per. (Exp.Error) 18 40.45 44.35 192,710 3.06 3.59 4.11 Subsample Error 240 91.55 80.81 293,990 92.58 87.31 93.86 • P i 0.05 APPENDIX 3 EXPERIMENTAL CELL MEANS FOR CROSS 1 BIRDS EXPERIMENT 2 SQUARE 1 SQUARE 2 SQUARE 3 TIME 1 2 3 1 2 3 1 2 3 U L 3004.84 3311.03 3430.00 3173.45 3312.93 3486.61 3306.84 3279.29 3271.43 Group E2 57.20 48.26 47.96 48.00 41.17 44.66 48.61 45.20 51.13 1 Energy 253513 262025 278807 240323 222007 266425 257126 241325 270241 Prod, per. {%) 63.3 59.2 55.1 56.1 69.0 70.2 54.3 53.3 66.7 3202.08 3107.96 3316.09 3296.04 3069.30 3332.18 3139.81 3049.07 3412.71 Group 52.66 55.65 50.83 47.03 46.50 48.79 52.00 54.20 51.41 2 Energy 264727 265521 275101 251491 221761 266792 254293 248548 292651 per?*(#) 54.1 55.1 50.5 52.7 70.1 71.4 58.2 59.3 6U.83 % 3320.00 3459.52 3312.81 3575.86 3426.00 3224.42 3471.35 3423.62 3368.60 Group E2 47.98 46.74 51.94 43.78 43.85 53.03 49.13 48.80 53.49 3 Energy 258395 273656 280675 272631 2U7256 269698 280166 272146 298579 pei%*(#) 54.1 63.3 62.6 63.7 51.0 53.1 57.1 51.6 58.2 APPENDIX L EXPERIMENTAL CELL MEANS FOR CROSS 2 BIRDS. EXPERIMENT 2 SQUARE 1 SQUARE 2 SQUARE 3 TIME 1 2 3 1 2 3 1 2 3 U L 30it7,97 3303.73 3341.23 3189.92 3204.81 3212.74 3074.21 3100.34 3261.89 Group E2 56.01 57.75 53.90 51.13 45.38 51.46 54.49 50.11 53.35 1 Energy 2561*60 281241 300085 259556 230790 264528 253736 240047 282229 Prod. Per . (%) 60.2 60.2 61.9 60.0 59.3 68.1 58.2 60.2 54.1 % 3254.85 3023.U8 3417.97 3411.21 3273.48 3277.94 3290.95 3199.53 3253.67 Group E2 49.00 54.25 48.83 46.00 46.11 48.74 49.34 50.37 51.60 2 Energy 257990 246808 282893 267022 242021 255941 263500 256017 267342 Prod. Per . (%) 64.8 62.8 64.8 72.5 70.4 64.3 60.0 61.0 57.1 U L 3353.60 3500.94 3334.94 3499.24 3417.39 3285.79 3195.25 3200.00 3322.93 Group E2 48.39 47.30 52.33 44.93 44.04 50.60 49.06 49.54 54.64 3 Energy 268218 287U31 286739 271318 253444 266303 246313 250331 292837 Prod, p e r . (%) 51.0 65.3 60.2 67.3 65.7 54.3 56.2 52.4 63.7 APPENDIX 5 ANALYSIS OF VARIANCE BASED ON MEAN VALUES, CROSS 1 BIRDS EXPERIMENT 2 Source Degrees of of Variation Freedom SQUARE 1 MEAN SQUARES SQUARE 2 E ENERGY UT PROD. PER. E2 ENERGY UT PROD. PER. E„ SQUARE 3 ENERGY Xh PROD. PER. Time Group Diet Error 2 2 2 2 5.68 28xl0 7 41.02 12.00 35xl07 4858 80.80 5.74 87xl0 7 7566 60.19 13.01 28xl0 6 *L954l 7.58 6.01* * l l x l 0 8 20982 45.76 13.38 59xl0 7 37145 19.77 *34.33 44xl06 *k0912 24.66 11.16 l l x l O 7 57716 86.46 9.38 26xl06 17371 1.96 0.85 27x10* 503 16.66 2.72 26xl0 6 9282 84.25 2.75 73xl0 6 I3876 18.57 * P - 0.05 *»P ^ 0.01 APPENDIX 6 ANALYSIS OF VARIANCE BASED ON MEAN VALUES, CROSS 2 BIRDS EXPERIMENT 2 Source Degrees of of Variation Freedom SQUARE 1 MEAN SQUARES SQUARE 2 Eg ENERGY U L PROD. PER. Eg PROD. SQUARE 3 ENERGY U L PER. E 2 ENERGY U L PROD. PER. Time Group Diet Error 2 2 2 2 0.33 *31xl0 7 16213 15.12 *19.57 *50xl0 7 8947 14.82 8.04 16,35 *64xl07 27210 21.58 * 6.83 12xl0 7 *29868 43.78 3,89 18,92 *28xl0 7 51386 21.40 * 6.86 62xl0 6 7949 41.23 7.29 1.79 UpclO6 5436 18,30 0.33 l 6x l0 6 959 36.27 0.68 87xl0 7 10862 O.Uj. 6^ 17x10^ 23x10*' 9713 3.61 3790 22.57 52x10° 3026 24.12 * P * 0.05 « p s 0.01 APPENDIX 7 ANALYSIS OF VARIANCE BASED ON MEAN VALUES, CROSS 1 BIRDS, REPLICATED SQUARE. EXPERIMENT 2 Source D< agrees MEAN SQUARE of of Variation Freedom ENERGY PROD. PER. Square 2 68.54** 894 x 10 6 ** 5910 57.50 Groups/Square 6 10.81* 321 x 10 6 ** 25888 47.19 Group 2 27.72** 761 x l©6** 75160* 30.36 G x S 4 4.36 101 x 10 6 1253 55.61 Time/Square 6 7.72 743 x 1 0 5 12244 37.86 Time 2 12.33* 173 x 10 7 ** 17000 42.3L T x S 4 5.59 247 x 10 6 * 9911 35.62 Diet 2 47.12** 591 x 105 94600** 11.37 Diet x Square 4 3.87 610 x 1 0 5 10700 50.85 Error 6 2.10 341 x 1 0 5 7885 39.83 * P i 0.05 ** P £ 0.01 APPENDIX 8 ANALYSIS OF VARIANCE BASED ON MEAN VALUES, CROSS 2 BIRDS, REPLICATED SQUARE. EXPERIMENT 2 Source of Variation Degrees of Freedom MEAN SQUARES ENERGY *L PROD. PER. Square 2 42.18** 735 x 10 6 ** 23394** 96.75 Group/Square 6 54.13** 147 x 10 6 * 22262** 22.99 Group 2 23.56** 199 x 10 6 * 52420** 59.08 G x S 4 1.75 120 x 10 6 7184 6.45 Time/Square 6 55.86** 671 x l©6** 12006 10.02 Time 2 20.19** 132 x 10 7 ** 7374 T x S 4 3.86 345 x 10 6 ** 14323 13.82 Diet 2 30.97** 212 x 10 6 * 39060** 16.66 Diet x Square 4 1.05 183 x 10 6 * 12032 34.28 Error 6 0.93 274 x 10 5 * 3140 13.82 * p . 0.05 **PS 0.01 APPENDIX 9 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS SQUARE 1, CROSS 1 BIRDS1 EXPERIMENT 2 Source Degrees MEAN SQUARES of of Variation Freedom h ENERGY *L Time 2 263.33 110 x 10 8 1033700* Group 2 733.06** 113 x 10 7 968450* Diet 2 1722.10** 386 x 10 7 1862600** Error 2 23.31 129 x 10 7 76544 Sampling error 405 97.99 368 x 10 7 269570 * P s0 . 0 5 ** P s 0.01 From Appendices 9 to 16, where ratio of MS error / MS sampling error was not significant, the pooled error mean square with the pooled degrees of freedom was used to test for significant effects. Otherwise, MS error with i t s degrees of freedom was used. APPENDIX 10 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS SQUARE 2, CROSS 1 BIRDS1 EXPERIMENT 2 Source of Variation of Freedom MEAN SQUARES ENERGY Time Group Diet Error Sampling error 2 2 2 2 405 472.77** 615 * 108** 618180 91.88 210 x 108** 1248900* 757.19** 440 x 107 2558200** 243.73 187 * l©7 736800 82.70 346 x 107 „ 295700 * P < 0.05 ** p 7 o . o i APPENDIX 11 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS SQUARE 3, CROSS 1 BIRDS EXPERIMENT 2 Source Degrees MEAN SQUARES of of Variation Freedom Eg ENERGY U^ Time 2 431.68** 422 x 10 8 ** 458400 Group 2 635.86** 194 x 10 8 ** 1385700** Diet 2 3L9.20* 876 x 1 0 6 483900 Error 2 125.66 175 x 10 7 545570 Sampling error 405 87.03 378 x 10 7 294430 * P < 0.05 ** p Z 0.01 APPENDIX 12 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS SQUARE 1, CROSS 2 BIRDS1 EXPERIMENT 2 Source of Variation Degrees of Freedom MEAN SQUARES ENERGY \ Time 2 204.30* 225 x 108** 205700 Group 2 394.80** 305 x 108** 1947800** Diet 2 522.61** 887 x 10? 1360200** Error 2 163.62 145 x 10? 519200 Sampling error 432 68.76 338 x 10 7 2IIO3O * P < 0.05 ** P " 0.01 1 Op dt APPENDIX 13 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS SQUARE 2, CROSS 2 BIRDS 1 EXPERIMENT 2 1 Source of Variation Degrees of Freedom MEAN SQUARES ENERGY Time 2 1094.90** 223 x 108** 63382O Group 2 427.01* 168 x 108** 2704400** Diet 2 512.75* 351 x 10 7 767580* Error 2 7.35 349 x 10 7 85120 Sampling error 432 77.35 322 X 10 7 249950 * p < 0.05 ** P < 0.01 1 Op cit APPENDIX 14 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS SQUARE 3, CROSS 2 BIRDS EXPERIMENT 2 Source of Variation Degrees of Freedom. ~, MEAN SQUARES % ENERGY UL Tine 2 482.54** 491 x 10 8 ** 626660 Group 2 131.81 242 x 10? 517410 Diet 2 391.30* 905 x 10 7 159170 Error 2 23.71 185 x 10 7 102180 Sampling error 432 88.99 343 x 10 7 25459O * p < 0.05 ** p 7 0.01 1 Op cit APPENDIX 15 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL EGGS REPLICATED SQUARES, CROSS 1 BIRDS EXPERIMENT 2 Source of Variation Degrees of Freedom - MEAN SQUARES ENERGY *L Square 2 3226.5©** 464 x 10 8 ** II743OO** Time/Square 6 411.02 348 x 10 8 ** 3889500** Time 2 3^7.4? 848 x 10 8 ** 1166300** T x S 4 442.81 124 x 10 8 ** 400260 Group/Square 6 446.03 142 x 10 8 ** 1136042** Group 2 797.67 346 x 10 8 ** 3176700** G x S 4 270.22 393 x 10? 115710 Diet 2 2525.10* 275 x 10? 4306300** Diet x Square 4 284.73 303 x 107 646720* Error 6 262.92** 481 x 10 7 402130 Sampling error 1188 86.17 360 x 10 7 286760 * p < 0.05 ** P ~ 0.01 1 Op cit APPENDIX 16 ANALYSIS OF VARIANCE BASED ON INDIVIDUAL ESGS REPLICATED SQUARES. CROSS 2 BIRDS1 EXPERIMENT 2 Source of Variation Degrees of Freedom MEAN SQUARES \ ENERGY \ Square 2 2129.70** 482 x 108** 688450 Time/Square 6 577.81** 235 x 108** 393088 Time 2 1256.30** 476 x 108** 94464 T x S 4 238.54 114 x 108* 54240 Group/Square 6 35L.03** 183 x 108** 815380** Group 2 776.03** 306 x 108** 1714900** G x S 4 138.53 121 x 108* 365630 Diet 2 1650.00** 142 x 108* 1405700** Diet x Square 4 53.56 146 x 10? 227970 Error 6 119.93 715 x 10? 346430 Sampling error 1296 118.88 464 x 10 7 237390 * p < 0.05 ** P < 0.01 1 Op c i t APPENDIX 17 SIMPLE CORRELATION COEFFICIENTS, MEANS, AND COEFFICIENTS OF VARIATION1 EXPERIMENT 2 Variable CORRELATION COEFFICIENTS MEANS COEFFICIENTS OF VARIATION CO ENERGY E 2 SQ.l SQ.2 SQ.3 SQ.l SQ.2 SQ.3 SQ.l SQ.2 SQ.3 SQ.l SQ.2 SQ.3 -gm-u-Cross 1 267800 251200 269500 22,3k 24.83 23.39 ENERGY Cross 2 274100 257000 261100 21.79 22.6U 23.08 -u/kg-Cross .K-}}. # 1 -0.1991 -0.1267 -0.2829 51.04 46.24 50.17 19.77 21.5U 20.63 E 2 Cross ft ^ ftft 2 -0.1156 -0.1436 -0.2002 51.34 47.52 51.34 16.79 18.88 18.79 -kg-Cross ftft ftft ftft ftft ftft ftft 1 0.8034 0.7999 0.81(07 -0.7221 -0.6677 -0.7217 3372 3329 3309 16.19 17.08 16.78 UL Cross ->Bf- -IKS- -JB:- -JBS- -JHS-2 0.8238 0.8133 0.8404 -0.6427 -0.6682 -0.6772 3284 3312 3211 14.51 15.36 15.71 1 Cross 1 birds, Square 1 (n»499), Square 2 (n=486), Square 3 (n=U88) Cross 2 birds, Square 1 (n«549), Square 2 (n=569), Square 3 (n=527) n=number of observations « P s 0.01 * P £ 0.05 APPENDIX 18 RESULTS OF SIMPLE REGRESSION ANALYSIS OF CRUSHING STRENGTH ON ENERGY AND E 2 EXPERIMENT 2 Independent variable Y-intercept Standard Error FwRatio Regression Coefficient of Estimate  SQ.l SQ.2 SQ.3 SQ.l SQ.2 SQ.3 SQ.l SQ.2 SQ.3 SQ.l SQ.2 SQ.3 ENERGY Cross 1 Cross 2 Cross 1 Cross 2 1368 1499 1344 .0071 .0073 .0073 315 341 301 9 0 5 * * 861** 1171** U+83 l U 8 i i 1374 .0066 .0071 .0070 270 296 274 1154** 1107** 1262** $188 5091 5252 -37.52 - 3 8 . 1 0 -38.72 366 423 385 5 4 2 * * 3 9 0 * * 5 2 8 * * 5108 5112 5033 -35 .53 -37 .87 - 3 5 . 5 0 365 379 372 3 8 5 * * 457** 445** * P * 0 . 0 5 » p s 0 . 0 1 * Analysis based on individual eggs APPENDIX 19 SIMPLE CORRELATION COEFFICIENTS, MEANS, AND COEFFICIENTS OF VARIATION, REPLICATED SQUARES1 EXPERIMENT 2 Variable ENERGY *2 MEANS Coefficients of Variation^) ENERGY. Cross 1 Cross 2 262900 gm-u 264000 gm-u 23.80 22.65 % Cross 1 -.1730** 49.17 u/kg 21.08 Cross 2 -.1331** 50.02 u/kg 18.49 Cross 1 .8030** -.6958** 3304 ga 16.65 Cross 2 .8158** -.6599** 3270 ga 15.24 ** P £ 0.01 1 Analysis based on individual eggs. Cross 1 (n=l473), Cross 2 (n=l645) APPENDIX 20 RESULTS OF SIMPLE REGRESSION ANALYSIS OF CRUSHING STRENGTH ON ENERGY AND Eg 1 EXPERIMENT 2 Independent Variable Standard Y-intercept Regression Error of F-Ratio coefficients Estimate ENERGY Cross 1 1444 .0071 328 2672** Cross 2 1475 .0068 288 3269 ** Cross 1 5L21 -36.97 396 1382** &2 Cross 2 5049 -35.55 374 1268** ** P < 0.01 1 Analysis based on individual eggs. APPENDIX 21 ADJUSTED TREATMENT MEAN SQUARES FROM THE ANALYSIS OF COVARIANCE OF PARTIAL LOAD ELASTICITY (%) VALUES CORRECTED FOR INITIAL TREATMENT DIFFERENCES FOR EACH OF EIGHT STORAGE DURATIONS1 EXPERIMENT 3 Source of Variation Degrees of Freedom ADJUSTED MEAN SQUARES STORAGE DURATION 1-day 3-day 7-day LU-day 21-day 28-day 35-day 60-day Treatment (Storage condition) 5 29.6** 31.9** 50.1** 71.6** 128.^** 257.9** 323.3** 61+9.5** Error 263 6.8 7.7 7.4 7.7 8.3 9.3 9.4 10.8 1 The analysis of covariance was performed on elasticity per 500 gram load (E^ / g) and the resultant means doubled for presentation in Table VII. ## P - 0.01 APPENDIX 22 ANALYSIS OF VARIANCE OF MEAN DIFFERENCES IN ELASTICITY (E,) BETWEEN TWO READINGS TAKEN FROM THE EQUATORIAL REGION OF THE SAME EGG EXPERIMENT 3 Source of Degrees of Mean Squares Variation Freedom Storage condition 5 1.74 H S 1 Storage duration 8 1.55m Exp. Error (C x D) 40 1.20 B Subsampl. error 2376 1.01 1 Not statistically significant (P * 0.05) APPENDIX 23 MEAN DIFFERENCES IN ELASTICITY (E-. ) BETWEEN TWO READINGS TAKEN FROM THE EQUATORIAL REGION OF.THE.SAME EGG (n=45). EXPERIMENT 3 STORAGE DURATION STORAGE Fresh CONDITION eggs 1-day 3-day 7-day LU-day 21-day 28-day 35-day 60-day Room 1.46 1.60 1.47 0.96 1.21 1.11 1.12 1.14 1.02 Water 1.26 1.14 1.01 0.94 1.06 1.23 1.09 1.00 1.30 Carbon dioxide 1.24 1.02 1.01 1.18 1.03 1.02 1.27 1.17 0.72 Blown, water 1.32 1.30 1.31 1.08 1.27 1.01 1.00 1.07 1.12 Refrigeration 1.16 0.88 0.90 1.38 1.16 1.16 1.13 0.97 0.75 Oil and refrigeration 1.09 0.98 1.16 1.07 1.30 1.13 1.15 1.32 0.87 APPENDIX. 24 SIMPLE CORRELATION COEFFICIENTS, MEANS, AND COEFFICIENTS OF VARIATION, FOR INDIVIDUAL STORAGE CONDITIONS EXPERIMENT Variable Storage Condition \ % COEFFICIENT OF MEANS VARIATION^) Room 57.44 16.5 Water 65.52 21.1 Co2 59.67 17.6 Blown, water 76.76 16.6 Refrigeration 53.96 14.1 Oil and refrigeration 58.64 19.2 Room 0.75712 59.12 22.3 Water 0.7772 59.70 22.4 C02 0.8616 54.82 17.1 Blown, water 0.8461 74.19 22.8 Refrigeration 0.6247 49.89 16.8 Oil and refrigeration 0.7462 53.43 21.4 Room -0.5212 -0.5929 2875 14.8 Water -0.6772 -0.7281 2470 20.6 002 -0.7288 -0.6814 3039 14.8 Blown, water -0.7580 -0.7721 2110 20.4 Refrigeration -0.6357 -0.6826 3373 16.2 Oil and refrigeration -0.7870 -0.7686 3040 20.3 1 Egg stored for 60 days (n=45) 2 All correlation coefficients shown here were highly significant (P < 0.01) APPENDIX 25 RESULTS OF SIMPLE REGRESSION ANALYSIS OF CRUSHING STRENGTH ON % ABD % FOR INDIVIDUAL STORAGE CONDITIONS EXPERIMENT 3 1 Independent Variable Storage Condition Y-intercept Regression Coefficient Standard Error of F-Ratio Estimate . Room 4227 -23.53 368 16.04** Water 4102 -24.92 379 36.42** C02 4902 -31.22 311 48.71** Blown, water 4090 -25.79 285 58.07** Refrigeration 5839 -45.70 428 29.16** Oil and refrigeration 5553 -42.86 385 69.99** Room 4007 -19.15 349 23.30** Water 4119 -27.63 353 48.5L** °°2 4826 -32.60 332 37.27** Blown, water Refrigeration 3559 -19.53 277 63.47** 5617 -44.98 405 37.51** Oil and refrigeration 5261 -41.55 399 62.06** ** P < 0.01 1 Eggs had been stored for 60 days (n=45) APPENDIX 26 SIMPLE CORRELATION COEFFICIENTS, MEANS, AND COEFFICIENTS OF VARIATION FOR THE POOLED DATA FOR ALL STORAGE CONDITIONS EXPERIMENT 3 Variable h MEANS COEFFICIENTS OF VARIATION (£) 62.00 u/kg 21.4 0.8253** 58.52 u/kg 24.9 PL -0.7734** -0.7614** 2818 g 23.0 ** P < 0.01 1 Eggs had been stored for 60 days (n=270) APPENDIX 27 RESULTS OF SIMPLE REGRESSION ANALYSIS OF CRUSHING STRENGTH ON En AND Eo FOR THE POOLED DATA FOR ALL STORAGE CONDITIONS. EXPERIMENT 3 1 Independent variable Y-intercept Regression Coefficient Standard Error of Estimate F-Ratio \ 5157 -37.73 411 399** E 4795 -33.79 421 370** 2 ** P < 0.01 Eggs had been stored for 60 days (n=270) 

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