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A study of the albumen quality of shell eggs Eissinger, Ronald Carl 1969

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A STUDY OF THE ALBUMEN QUALITY OF SHELL EGGS by RONALD CARL EISSINGER B.S., Washington State University, 1949 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Poultry Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA August, 1969 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 the 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 t h e 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 and 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 the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It 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 w 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 Poultry Science The 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, Canada Date September 11. 1969 i i ABSTRACT Eggs from twelve strains,of layers i n the Ninth British Columbia Random Sample Egg Laying Test were examined over an eight month period to determine rate of decline of interior egg quality under three varying temperature conditions for one and two week periods. Differences among strains i n the i n i t i a l egg quality by period as well as the quality decline under different storage conditions were examined. Consideration was also given to the implications these results may have on sample size determinations i n a quality control program or interior egg quality assessment investigations. Highly significant differences were found among strains and treatments i n average Haugh unit score for each of the eight periods. Differences were also found i n rate of decline of interior egg quality among strains and treatments for most periods. Sample size estimates calculated from the data obtained along with the variations found among strains, treatments and periods suggest that our present sampling methods for quality control programs and interior egg quality assessment studies may need to be re-valuated. i i i TABLE OF CONTENTS Page INTRODUCTION 1 LITERATURE REVIEW 3 METHODS AND PROCEDURES 22 RESULTS AND DISCUSSION 24 SUMMARY 41 REFERENCES 43 APPENDIX 53 i v LIST OF TABLES Table Page I* F Values from the Analysis of Variance of Average Haugh Unit Scores by Periods 2 5 I I . Mean Haugh Unit Scores f o r Seven Treatments for Successive Periods Daring the Laying Year 2 6 III. Mean Haugh Unit Scores f o r Twelve Strains of Birds For Successive Periods During the Laying Year 2 7 IV. Results of the Analysis of Covariance of Rate of Quality Decline During Storage for Twelve Strains and Three Temperature Treatments by Period (Concomitant variable was i n i t i a l Haugh Unit Score) 2 9 V. Adjusted Mean Rate of Quality Decline from the Analysis of CovarianceJbr Each of Three Treatments by Period 30 VI. Adjusted Mean Rate of Quality Decline from the Analysis of Covariance f o r each of Twelve Strains by Period 31 VII. Mean Squares from the Analysis of Variance of Standard Deviation of Haugh Unit Soore for Treatment Combination a, b, c and d 33 V Table Page VIII. Mean Period Standard Deviations of Haugh Unit Scores for Each Treatment Combination y+ IX. Mean Strain Standard Deviations of Haugh Unit Scores for Each Treatment Combination 35 X. Results of Simple Linear Regression and Correlation Analyses of the Relationship of Estimated Sample Size (Y) Veraus Period (X) 39 A l . Strains of Birds and Entry Numbers Used i n This Study 53 A l l . Identification of Eggs Used i n This Study by Pen Number 5% AIII. Simple Linear Correlation Coefficients for the Relationship of Haugh Unit Score and Time of Storage 55 AIV. Average Estimated Sample Size (n) f o r Each Period Within Each Treatment Combination as Plotted i n Figure 1 61 AV. Average Estimated Sample Size (n) for Each Strain Within Each Treatment Combination as Plotted i n Figure 2 62 AVI. Standard Deviation of Haugh Unit Score and Estimated Sample Size (n) by Strain and Period—-Treatment Group (a) 63 v i Table AVT.I. Standard Deviation of Haugh Unit Score and Estimated Sample Size (n) by Strain and Period—Treatment Group (b) 64 AVTII. Standard Deviation of Haugh Unit Score and Estimated Sample Size (n) by Strain and Period—Treatment Group (c) 65 AIX. Standard Deviation of Haugh Unit Score and Estimated Sample Size (n) by Strain and Per Period—Treatment Group (d) 66 AX. Expected and Normal Frequency Distribution of Standard Deviation of Haugh Unit Score for Treatment Combination (a) 67 AXI. Mean I n i t i a l Haugh Unit Score for Strains and Successive Periods of Lay 68 v i i LIST OF FIGURES Figure Page 1. Average n Values for Each Period Within Treatment Combinations 37 2. Average n Values for Each Strain within Treatment Combinations 38 A l . Plot of the Percentage Cumulative Less Than Distribution of Standard Deviation of Haugh Unit Score (Treatment Combination a) 69 ACKNOWLEDGEMENT I wish to express my appreciation to Professor Jacob Biely, Department of Poultry Science, for his cooperation throughout my entire graduate studies program, and to Dr. James F. Richards, Assooiate Professor, Department of Food Science, for his counsel throughout this research project including the writing of this manuscript. I am also indebted to Mr. C.W. Wood, Test Manager, British Columbia Random Sample Test Station and other members of the staff for collecting the eggs used in this study, and to Miss Lynne Robinson, Laboratory Technician, Department of Food Science, for her assistance in recording and analyzing data. INTRODUCTION The internal quality of she l l eggs i s largely determined by measurements which ref lect the proportion of the albumen represented by the middle dense (thick) layer . Internal quality i s considered to increase as this proportion increases. The Haugh Unit score i s a widely used method of assessing internal qual i ty based upon the height of the middle dense layer of albumen i n a broken-out egg. In the United States of America she l l eggs may be assigned a grade on the basis of the Haugh Unit Score provided other qual i ty c r i t e r i a are sat i s f ied . The Haugh Unit Score i s known to vary with age of layer, age of egg, temperature and atmosphere during storage of eggs, she l l porosity, diet of layer, genotype of layer and other factors, Stadelman ( I965). In recent years programs have been developed to estimate the grade of a group of eggs on the basis of the average Haugh Unit Score of a randomly drawn sample; the sample s ize being determined empirically and applied under a variety of conditions. The intent of this thesis was to determine for monthly samples of shel l eggs from twelve commercial strains of layers : 1. the rate of decline of Haugh Unit Score of eggs stored under varying temperature conditions for two weeks. 2. the relationship of i n i t i a l Haugh Unit Score to rate of decline during storage. 3. the variation i n Haugh Unit Score among eggs following storage for varying periods at varying temperatures and the 2 implications of this variat ion to the establishment of sampling programs for internal quality assessment. LITERATURE REVIEW* A decline i n the i n i t i a l albumen quality of eggs as the b ird ages has been reported by a number of investigators. Hunter et a l . ( 1 9 3 ° ) found a seasonal trend i n the inter ior qual i ty of eggs with a decrease i n qual i ty from March through the summer months. The highest quality eggs produced between November and March. Wilhelm and Heiman (1938) reported a steady decline i n the albumen index of new l a i d eggs during the f i r s t nine four-week periods studied. There was no correlation between the time of day the egg was l a i d and i t s albumen index, and albumen qual i ty was not d i rec t ly affected by tempera-ture i n the pen. Greenwood and Bolton (195°) compared eggs from pul lets , one year old hens and aged hens for variations i n the amounts of thick and th in albumen. They found the proportion of thick albumen increased and thin albumen decreased with advancing age of the hen. Strain and Johnson (1957) reported a seasonal decline i n albumen quality for three strains of White Leghorn pul lets . The average decline was 7.1 Haugh units from October to February and 4.5 Haugh units from February to June. Funk et a l . (1958) investigated the seasonal variations i n egg quality over a three-year period and found l i t t l e or no change i n the percentage of thick albumen i n eggs l a i d throughout the year. They did f ind the quality of albumen, as measured by Haugh units, declined throughout the f i r s t test year and that this decline was not as evident during the next two years. k Froning and Funk (1958) found a seasonal variat ion i n Haugh Units for caged layers and their sisters on the f loor , but egg quality declined each month during a sixteenth-month study from November 1955 to March 1957 except for an increase i n July . The average Haugh unit score for caged layers was 73»8 and ?1.7 for f loor birds. There was no seasonal trend i n the percent of thick albumen. In a study of a l l eggs l a i d during one year by twelve birds , Jenkins and Taylor ( i 9 6 0 ) , found that albumen weight, yolk weight and shel l thickness a l l increased with time and that the increase i n albumen weight over the season was extremely variable among birds . The increases did not appear to be related to the or ig inal albumen weights. Mueller et a l . (I960) studied the effect of the age of layer on egg weight, shape index, albumen quality and she l l thickness and reported that albumen quality declined continuously from December of the pul let year u n t i l A p r i l of the second year of production. Their results also indicated that layers with high average Haugh unit scores during the pul let year had a greater decline i n albumen quality from the f i r s t to second year of production than layers with low Haugh unit scores i n the pul let year. Cunningham et a l . (i960) collected eggs bi-weekly for a period of one year from four groups of birds of four different ages, and found that Haugh unit score declined steadily u n t i l the layers were approxi-mately eighteen months of age, at which time i t level led off and i n some cases increased temporarily. They concluded the decline i n Haugh unit score was due entirely to aging of the b i rd and not to seasonal differences. They also concluded that the percentage of to ta l solids i n albumen declined steadily with age of b i r d . Snyder (1961) reported that the or ig ina l egg qual i ty of nine-5 month-old birds exceeded that of thirteen and sixteen-month-old birds by about 1 0 Haugh units. Although the rate of decline in albumen quality was more rapid during the first three days of storage with the younger birds' eggs, a parallel rate existed from three to seven days, and then a slower rate of decline was observed compared with the older birds. Huston and Carmon ( 1 9 6 1 ) reported a decline in both egg shell and albumen quality with increasing age of bird. They found no differences in albumen quality of eggs from birds raised under different environ-mental temperatures. Wilcox and Wilson ( 1 9 6 2 ) concluded that the decline of albumen quality with time is an effect of exhaustion rather than aging of the bird. They found that the length of pause in egg production between the first and second laying year was related to the change in albumen quality. When the pause was five weeks or less albumen quality near the start of the second laying year was decreased; when i t was six weeks or more, albumen quality was increased. These results are in agreement with the investigations on forced molting by Berg and Bearse ( 1 9 4 7 ) indicating that a rest period of ten weeks was not sufficient for maximum quality improvement. Noles and Tindell ( 1 9 6 7 ) reported an average decline in Haugh unit score of about 8 . 4 units between 2 0 0 to 3 5 0 days of age. Strains of birds with high Haugh unit scores at 2 0 0 days had the highest scores at 3 5 0 days. They also stated that initial albumen quality was primarily a function of age of bird and that absolute quality and the rate of quality decline were conditioned by the individual characteristics of the bird. There have been a number of studies conducted on the effects of egg size on albumen quality. 6 Knox and Godfrey ( 1 9 3 4 ) reported egg weight to be highly correlated with the weight of total albumen for both White Leghorns and Rhode Island Reds, although egg weight was not correlated with the percentage of thick white of total albumen. Lorenz and Almquist ( 1 9 3 6 ) conducted a two-year study on egg quality with results suggesting that the air temperature during the time the egg is being formed has no noticeable effect on the i n i t i a l percent-age of firm white, while the temperature to which the egg is exposed post-oviposition exerts a distinct effect. Wilhelm and Heiman ( 1 9 3 8 ) found no significant correlation between albumen index and egg weight or between albumen index and percent production. Harper and Marble ( 1 9 4 5 ) conducted a study on the relationship between egg shape and albumen quality and concluded that albumen is not a factor contributing to egg shape. Carmon and Huston ( 1 9 6 5 ) found that the amount of albumen, shell and yolk was proportional regardless of egg size or environment. They also found the percent water remained constant as the egg size increased or decreased. The o i l treatment of eggs as a means of reducing interior egg quality decline has been reported by a number of investigators. Korslund et a l . ( 1 9 5 7 ) found the effects of temperature and oiling of eggs were of greater magnitude than humidity in maintaining albumen quality. They also found that oiling of shell eggs resulted i n higher interior quality as compared to washed and non-treated eggs. These investigators also studied the effect of relative humidity and reported eggs stored at 3$ relative humidity were of lower quality than eggs held at 9 < # . 7 Proudfoot (1962) concluded that spray-oiling eggs prior to ship-ment or storage reduced interior quality decline. Hurray et al. (I963) found no significant difference in the albumen quality of eggs dipped in oil and those coated with amine alginate. Both treatments reduced the deterioration in albumen quality compared with untreated controls. Essary and Layman (1963) found that eggs oiled on the day of lay and held in the egg cooler for one week before washing showed comparable Haugh units to those broken out on the day of lay. Some rather unique egg storage and handling methods for the preser-vation of internal quality have been recorded in the literature. These include thermostabilization, the rotation of eggs, and the storage of eggs in atmospheres other than air. Bornstein and Nahari (1962) made a study of heat treatment (Thermostabilization) as a means of stabilizing the internal quality of eggs. They recommended two treatments, either immersion in water for fifteen minutes at 55° C. or eight to ten minutes at 58° C. Mukerji and Fry (I963) conducted studies using seven different egg treatments at three storage temperatures for one and two week storage intervals. Their results showed that al l treated eggs maintained good quality at 55° F. however, eggs in Cry-o-vac bags showed the least loss of weight and highest Haugh unit score at all temperatures studied. Thermostabilization (fifteen minutes at 135° F.) was second in maintain-ing interior quality, but ranked last in preventing weight loss. Rehkugler and Baker (I963) investigated the effect of rotation on egg quality and found that neither of the two rotation treatments employed had any effect on internal egg quality as measured by Haugh units or on market grade. 8 ELackshear et al. (196?) experimented with eggs to determine the effect that shaking and rolling would have on albumen quality and yolk mottling at different temperatures. These physical treatments had no effect on Haugh unit score. Haugh unit score declined as storage temper-ature and time increased. In an experiment in which eggs were broken out and placed in plastic bags in one of six different atmospheres for up to 96 hours, McKerley et al. (I967), found none of the treatments to have any signif-icantly beneficial effect on the retention of egg quality as measured by Haugh unit score. They concluded that pH increased with time at the same rate regardless of the individual hen producing the eggs within each treatment. Egg quality was best maintained when pH was close to 8.2. The effect of temperature and time of storage on the interior quality of eggs has been reported in the literature by a number of investigators. Wilhelm and Heiman (1938) examined eggs stored at four different temperatures for up to 192 days, and reported that egg quality mainte-nance under storage conditions was related directly to original quality. Wilhelm (1940) experimented with five different methods of storing eggs at four different temperatures and concluded that none of the methods investigated were superior to that of eggs stored in standard cartons for periods up to 45 days storage at 30° F. When eggs were held at temperatures of 70° F. and 90° F. for varying periods up to 46 days, the carbon dioxide treated eggs showed less quality loss than any other method. Jensen and Stadelman (1954) reported no difference in the rate of quality decline between eggs changed frequently from one temperature to another and those changed only once during one or two weeks storage. 9 These same investigators studied egg quality loss on the farm and found there was close to a 30$ loss i n albumen index during the f i r s t week holding period which they attributed mostly to the temperature of the egg holding room. Dawson and H a l l (1953) reported that albumen quality declined rapidly during the f i r s t three days of storage at a temperature of 75°* 45°, or 30° F . Spencer et a l . (1956) studied the effect of time lapse between break-out and albumen height measurement on the resultant Haugh unit score. They found a direct relationship between the rate of decline i n Haugh unit values and the mean egg qual i ty . The higher the quality the less the rate of decline i n Haugh units after break-out. Fry and Newell (1957) conducted investigations to determine the effect of management practices and the time-temperature relationship on inter ior egg qual i ty . They found that regardless of the temperature, the decrease i n Haugh unit score during the f i r s t 48 hours of storage was greater than the decrease for any succeeding 48 hour period. They also reported that eggs stored at 60° F . for one day were lower i n quality than those stored at 30° F . for seven days, and the eggs stored at 90° F . for one day were lower i n quality than those stored at 60° F . for seven days. A storage temperature of 45° F . was recommended by Parnell and Jaska (1958) based upon egg storage studies using ten different tempera-ture and humidity storage conditions for periods of one to eight days. They found relat ive humidity had l i t t l e effect on quality at temperatures of 45°; 55°; and 65° F . Baum et a l . (i960), i n an economic analysis of egg qual i ty , reported that quality declined as much i n one day at 72° F . as i t d id 10 in two days at 50° F. i f the original quality was similar. The pre-cooling of eggs was studied by Smith and Grover (19^ 3) by comparing eggs cartoned and cased immediately after gathering with eggs pre-cooled before being cartoned. They concluded that a producer may safely package eggs directly into cartons without the need for pre-cooling of either eggs or package material. A study by Tarver and Choate (1964) on rapid cooling of eggs prior to storage indicated that eggs, once cooled, should be maintained at a reduced temperature during the storage period. Differences in albumen quality between individual birds, strains and breeds have been reported in the literature by many investigators. Hoist and Almquist (1931) reported that the keeping quality of an egg is markedly a function of the individuality of the hen. Lorenz et al. (1934) presented data indicating that genetic factors exist which at least partially control the percent firm white of the eggs laid. Van Wagenen et al. (1937) reported significant differences among White Leghorn strains in albumen quality. In a study of heredity of interior egg quality, using 180 pedigreed Barred Plymouth Rock pullets, Munro (1938) found seven egg quality charac-teristics to be a function of the individuality of the hen, and concluded that much of the variability in the percentage of firm white was due to environmental factors. Knox and Godfrey (1940) reported that lines producing eggs with high and low percentage thick albumen were achieved through selection and that the ability of a hen to secrete thick albumen was an inherited characteristic. Lorenz and Taylor (1940) worked with two lines of birds which maintained an average difference of 11.37±. 0.46$ of firm albumen and 11 conducted that the percentage of firm albumen is heritable. Grimes (1953) reported a strain difference in albumen quality with eggs from standardbred strains being of superior quality to the crossbred and incross strains studied, although the standardbred strains laid eggs which were less uniform than the crossbred strains. Nordskog and Cotterill (1953) found repeatability estimates for albumen height and Haugh units which averaged 0.75 based on 497 eggs from several breeds. Their calculations showed that the genetic improvement possible by selecting hens from observations based on 1, 2 and 3 eggs is 87, 91 and 93$ respectively, of the maximum possible when the repeat-ability is this high. Cotterill and Winter (195*0 examined eggs of initially high and low albumen quality and found litt l e variation between the groups in total solids, protein or lysozyme activity. They did find, however, a signifi-cant difference between different birds and a highly significant differ-ence between strains of birds in their analysis of lysozyme activity. In further studies of this enzyme, Wilcox and Cole (1957) found no significant differences between strains or between sires, although their analysis did show differences due to dam in the lysozyme level. Farnsworth and Nordskog (1955) examined 2,520 eggs from several different lines and breeds over a four year period and found no differ-ences among lines for albumen height or Haugh unit score. They indicated from their estimates of heritability and repeatability obtained for the different traits that considerable improvement in albumen height, egg weight, shell color, shell thickness and shell texture is possible by mass selection. They also indicated that according to their repeat-ability estimates five to ten eggs per hen would be a sufficient number to sample for these egg quality factors. 12 Johnson and Merritt (1955) investigated the heritability of albumen height and specific gravity of eggs from White Leghorns and Barred Plymouth Rocks* They reported a negative phenotypic correlation between albumen height and egg production in both breeds, with a negative genetic correlation in the White Leghorns and a positive genetic correlation in Barred Rocks. The heritability estimates showed a difference between breeds for egg production, specific gravity and especially albumen height. They found a seasonal decline in the albumen quality of eggs from both breeds. The White Leghorns produced eggs with a higher initial albumen quality which declined more rapidly than the Barred Rock eggs. Mountney and Vanderzant (1957) found differences between breeds is interior quality of both fresh eggs and those aged two weeks. Strain and Johnson (1957) found strain differences in the seasonal decline of albumen quality. A greater decline in albumen quality took place from October to February than from February to June. May et al. (1957) found differences among strains in initial albumen quality as well as in the quality of seven day old eggs. They also found differences among strains in the rate of decline of albumen quality. The mean decline for a l l strains was 10.2 ±3.68 Haugh units over a seven day period. They reported a correlation coefficient of ±0.358 between the original albumen quality and loss of quality over a seven day storage period, indicating that eggs of low initial quality had a lower rate of quality decline than eggs of initial high quality. During the past forty years the interior quality of eggs has been evaluated by a number of methods including yolk index, albumen height, albumen index, albumen area index, percentage of thick and thin white, and Haugh unit score. 13 Sharp and Powell (1930) used height of the yolk divided by the width (yolk index) in studying interior egg quality. A modified yolk index method was reported by Funk (19^8) in which the yolk was measured in the broken-out egg without separating i t from the albumen. Hoist and Almquist (1931) used the percentage of thick white as an expression of egg quality. They found the percentage of solids to be the same in the thick and thin white from the same eggs. Helman and Carver (1936) developed the albumen index which they defined as the height of the thick white divided by its mean width. Wilgus and Van Wagenen (1936) developed the Van Wagenen chart consisting of a series of nine photographs used in the scoring of broken-out eggs on the basis of the observed condition of the thick white. A chart with twelve pictures of broken-out eggs was developed about this same time by the U.S. Department of Agriculture for visual grading of broken-out eggs (U.S.D.A. Agriculture Handbook Ho. 75* 1968). The Haugh unit was developed by Haugh (1937) and is widely used in research and industry as a measure of albumen quality. Haugh (1937) found egg quality to vary as the logarithm of the albumen height. He developed a correction factor for egg weight, multiplied the logarithm of the corrected albumen height by 100 and called this figure the Haugh unit. Haugh's formula is as follows:  100 Which may be simplified to: H.U. = 100 log (H - 1.7 W 0.37 + 7.6) H.U. = Haugh unit score H = Albumen height in mm G = 32.2 W = Weight of shell egg in grams 14 Hoover (1938) examined the logarithmic relationship between the area of thick white and the broken-out quality and found this to be a good objective measurement of interior quality. Parsons and Mink (1937) developed the albumen area index, which is the area of the dense albumen in square centimeters. Brant and Shrader (1951) recommended the use of either the Haugh unit or the "eye scoring1' method of determining the quality of a broken-out egg. They also stated that birds should be in production at least four months before quality determinations are made, and that the most critical tests for spring hatched birds can be made in July and August when egg quality is lowest. Brant et al. (1951) reviewed various methods of estimating egg quality and recommended the Haugh unit score. Wesley and Stadelman (1959) concluded that Haugh unit values were correlated to more quality measurements than any other after studying the relationships among thirteen different interior quality measurements of eggs. Questions have been raised recently by investigators on the validity of the Haugh unit scoring system even though i t is widely accepted by research workers and industry. Eisin et al. (1962) claimed the Haugh unit score did not adequately adjust albumen height of individ-ual eggs for egg weight. Eisin and Bohren (1963) concluded that the regressions of the volume of albumen layers on egg weight were linear as were the regressions on albumen height. Kidwell et al. (1964) concluded that the linear regression of albumen height on initial egg weight may differ according to lines of breeding. They also reported that the regression of albumen height on weight loss of eggs due to storage is about ten times as great as due to 15 initial or inherent differences in egg weight. Van Tijen (1968) reported data to support his conclusion that the correction recommended by Haugh (1937), which is applied to eliminate the influence of egg weight, is not valid in all circumstances. He suggested that when the correction for egg weight is necessary i t may be simpler i f , for each gram under or over the standard weight of 56.5 grams, 0.05 mm. were added to or subtracted from the measured height of the thick albumen. All characteristics of egg quality have a genetic basis according to Baker (i960). Hyre (i960) found that an improvement was made in the initial interior egg quality by selective breeding. King et al. (1961) reported a high heritability (.61) of albumen quality measured as Haugh unit score of both fresh and stored eggs. The heritability of albumen quality loss was .225 (additive). They found a small positive phenotypic correlation between Haugh units fresh and both Haugh unit loss and Haugh units stored of Haugh units fresh, indicating that eggs with higher Haugh units tend to have greater loss, but when expressed in terms of percent Haugh units stored of Haugh units fresh, they have less loss. Their genetic correlations indicated that early sexual maturity is associated with lower egg quality, which is in agreement with the findings of King (I96I). Data to support the concept that a high initial albumen score is related to a higher percentage of middle thick white was reported by Skala and Swanson (1962) in a study of initial interior quality using a group of White Leghorn hens laying high quality eggs as compared with a low quality group. Adams and Skinner (I963) studied the effects of management, strain and truck shipment on albumen quality and found differences in the initial quality due to management and strains before shipment, but no differences in the decline of quality during shipment was found associated with management or strain. They did find however, that case positions within the refrigerated truck had a significant effect on albumen quality. They also found that the ranking of the six strains used in their experi-ment agreed with the relative standing of these strains in Random Sample Test data. In data obtained from a five-year study to estimate some genetic parameters of egg quality, Quinn (I963), found a significant difference in Haugh units between December and July but not December and March with December the highest and July lowest. The evaluation of albumen quality in a breeding program was studied by Raff a (1963), using eleven test matings, in which he recom-mended that breeders must continue to conduct break-outs through the laying year in order to properly assess albumen quality in a breeding program. McClary and Bearse (1956) reported the genetic correlation between Haugh unit values of fresh and stored eggs was +..94 for one group and +.99 for a second group of hens differing in age by five weeks. They concluded that heredity had no measurable effect on the rate of loss in albumen quality of eggs from hens used in this study. Trail (1962) reported a significant difference in albumen quality between five breeds and crosses of commercial poultry produced in Uganda. He also found that the intensity of production did not affect interior egg quality. Kidwell et al. (1964) found li t t l e difference in the rate of decline of Haugh units among sixteen commercial strains of chickens in a two-year study of eggs stored at 58° F. for seven days and for twenty-one days. The results of this investigation failed to demonstrate Haugh unit loss is genetically determined. However, they did find significant differences among strains in Haugh units for freshly broken eggs. Morris (1964) reported that as pullets increased in age from 34 to 64 weeks, the mean loss in quality of eggs laid was 8.0 Haugh units when measured on stored eggs. The storage of eggs resulted in a loss of 18.6 Haugh units at 34 weeks of age and 21.4 Haugh units when the birds reached 64 weeks of age. This study also showed that eggs with the highest initial quality laid by pullets at either 3^  or 64 weeks of age, underwent a greater quality loss in storage than eggs with lower initial quality. In a study of the composition of eggs from three lines of White Leghorn hens, which were genetically different in egg size, Marion et al. (1964) concluded that most of the genetic variation in the component parts of an egg is probably only covariation with egg size, and that a selection program designed to alter parts of the egg would automatically alter the size of the egg. Their results showed that variation in proportionate parts of an egg is caused mostly by physiological changes associated with aging and environmental effects. They also found that for each one gram increase in egg weight albumen increased 0.2$ and the percent yolk decreased by a similar amount. Fry et al. (1965) sampled eggs quarterly from entries in the Florida Random Sample Egg Laying Test during 1960-61 and found that entries differed significantly in their rate of quality decline during storage in three of the four collection periods. They also found the decline in quality during the first seven days of storage was greater than either the seven to fourteen day or the fourteen to twenty-one day decline. Marlon et al. (1965) found no significant differences in Haugh unit values of eggs from five different stocks of laying hens, although significant differences in egg weight, percent shell, percent yolk, visual lightness of yolks, moisture content, lipid content, and content of some fatty acids were found between the lines examined. Kline et al. (19^5) reported data on the variability in the internal quality of eggs on day of lay as related to age of layer and showed a decline in Haugh units with increasing age of layer as well as an increase in the variability with increasing age as indicated by the standard deviation and the coefficient of variation. This variation is roughly 50$ greater for layers approximately eighteen months old than for layers eight to twelve months old, and over 100$ greater for the twenty month old layers. Holes and Tindell (196?) reported that strains of birds used in their study with high Haugh unit scores at 200 days had the highest scores at 350 days. Kinney and Lowe (1968) reported that data from nine generations of the Regional Red Control Population studied showed that albumen quality means increased significantly in time and exhibited a significant positive regression on time. The work reported by King et al. (1963) o n the Regional Cornell Control population stated no important genetic trends existed in egg quality traits among the six generations covered by his study. Strain differences were found in the density of egg contents by Carter (1968) in a study using eggs from seven different strains. The densities found were in range with those summarized by Romanoff and Romanoff (1949). Miller (1958) outlined an egg quality control program that was being studied by the Agricultural Marketing Service of the U.S.D.A. in which high quality eggs from controlled flocks would be produced, graded and marketed under a label of identification called "Fresh Fancy Quality". Hand candling was replaced, under this program, by the measurement of Haugh unit score and visual observation of yolk quality on a small sample of eggs from a flock or shipment. Kennett (i960) reported on the requirements which must be met to qualify for the "Fresh Fancy" or AA Grade program adopted by the U.S. Department of Agriculture on September 15, 1959. The present requirements for egg grade certification under U.S.D.A. quality control programs are listed in Agriculture Handbook No. 75 (Revised June I968). The minimum requirements for eggs packaged under "Fresh Fancy Quality" or AA grade mark are as follows for the procurement and dis-tribution programj 1. Eggs from each flock must be packed separately and identified. A flock consists of birds not varying in age by more than sixty days. 2 . Eggs should be gathered from the nest at least twice, and preferably, three times a day. 3. Eggs which require cleaning should be cleaned properly in accordance with the regulations. Eggs may be treated with oil which must also be done in compliance with requirements as provided in the regulations. 4. Eggs should be cooled to 60° or below and at a relative humidity of approximately 70 percent. 5. Eggs are to be transported and handled under such conditions as will prevent sweating and at a temperature of 60° or below. 20 6. Eggs are to be held and displayed at temperatures not exceeding 60° F . i n the r e t a i l store. 7. Periodic checks are to be made by government graders i n regards to the production and distr ibution programs. The minimum requirements at the packing plant include the sampling of eggs from each f lock. An i n i t i a l sampling of 25 eggs taken at random must average at least 76 Haugh units before a flock can qualify, or two samples of 25 eggs each may be drawn during two consecutive weeks and each sample average 74 Haugh units or higher. A flock w i l l not be e l ig ib le i f any sample contains more than one egg measuring less than 60 Haugh units, and the yolk of a l l eggs must have a well-rounded appearance with a reasonably uniform color. A moving average of at least 74 Haugh units must be maintained for a flock to remain on the program. Samples must be drawn at random from each flock every two weeks. A sample of 10 eggs must be tested when the moving average i s below 80 Haugh units and not more than one egg i n the sample measures less than 60 Haugh units . A f ive egg sample i s tested when the moving average i s 80 Haugh units or more. I f one egg measures less than 60 Haugh units , an additional f ive eggs are tested and the average of the 10 eggs are used. The moving average i s computed by averaging the results of the l a s t two biweekly Haugh unit entries of a flock or four weekly entries when required. Samples from a flock are tested every other week unless the breakout records indicate a variat ion i n individual eggs or averages beyond that normally expected, at which time the sampling i s done weekly. 21 Eggs falling to meet the AA quality requirements with respect to shell texture or shape are not to be selected as part of any sample. A flock that fails to meet the requirements and is dropped can be reinstated by the same procedure used to enter i t originally. Eggs from flocks meeting these requirements must be clean, unbroken with practically normal shells before they can be packaged and labeled as Fresh Fancy Quality or U.S. Consumer Grade AA. Eggs containing blood and meat spots as well as loss eggs are to be removed prior to packaging. An expiration date, not exceeding ten days from the date the eggs are packed, must be plainly marked on each package. The requirements set for eggs packaged under the U.S. Grade A mark are lowered to an average score of at least 64 Haugh units with a moving average of 62 Haugh units or higher, there is no restriction on the age variation of a flock under this program. METHODS AND PROCEDURES A total of 8,064 observations were made in this study of eggs from twelve entries in the Ninth British Columbia Random Sample Egg Laying Test. Eggs were collected one day every four weeks for eight consecutive four-week periods. The first collection of eggs was made on September 29, 1966 when the birds were 183 days of age and laying at approximately 60$6 production. All of the birds in the test were housed in multiple cages within one building. The cage house contained four double rows of cages with each of the twelve entries represented in each row. The four rows were considered as two groups for sampling. Group 1 included rows 1 and 2, while Group 2 included rows 3 and 4. Each entry number and strain is listed in Appendix Tables I and II including the group, row and pen numbers. The entire production of eggs on the day of collection was cased and labeled by group, entry, and pen number and placed under refrigera-tion overnight and transported to U.B.C. the following morning. Eggs from each entry or strain within each group were randomly assigned to treatments as follows: STORAGE TEMPERATURE CONDITIONS Room Temperature (70°F) Egg Cool Room (52°F) Fluctuating Temperature Length of Storage 1 week 6 eggs 6 eggs 6 eggs 2 weeks 6 eggs 6 eggs 6 eggs In addition, six eggs were randomly selected from each entry within groups and broken to determine i n i t i a l internal quality by Haugh unit score. The remaining samples of eggs were packaged i n egg cartons and assigned to the three treatments. The room temperature storage conditions averaged about 70°F. and varied from one to three degrees between the high and low reading each day. During the entire period of eight months, the room temperature was never lower than 64°F. nor higher than 76°F. as determined by a recording thermometer. The eggs placed i n the fluctuating temperature environment were f i r s t stored i n the egg cool room, and alternated from cool room to room temperature on Mondays, Wednesdays and Fridays during the one and two week storage periods. The temperature of the egg cool room remained between 50°F. and 55°F. Eggs were removed after one and two weeks storage and interior quality determined by Haugh Unit score. Data were obtained by weighing each egg to the nearest gram immediately prior to breaking. Each egg was then broken-out on a standard egg breaking table with glass plate. The height of the thick albumen was measured with a micrometer, and the Haugh unit soore then computed with the use of an Interior Quality Calculator for eggs. A l l quality determinations were made by the method described by Haugh (1937) and procedures l i s t e d i n the U.S.D.A. Agriculture Handbook No. 75 (1968). The data were subjected to analysis of variance, covariance and regression and correlation analysis, as appropriate, and Duncan*s new multiple range test as outlined by Steel and Torrie (i960). RESULTS AND DISCUSSION Analysis of variance of average Haugh unit scores for each period indicated highly significant differences (Ps^ O.01) among strains and treatments (Table I). No strain x treatment interaction was apparent* Treatment means reflected the well established effects of temper-ature and time of storage on albumen quality maintenance. Average Haugh unit score was highest for eggs stored under refrigeration, lowest for those stored at room temperature and intermediate for those stored at fluctuating temperatures. Mean Haugh unit score consistently declined as storage time increased (Tables II and III). The decline of interior egg quality with increases in time and temperature has been reported by a number of investigators, including Mukerji and Fry (1963), Fry et al. (I965), KLackshear et al. (I96?) and Skala (1968). The intermediate Haugh unit scores for eggs stored under fluctu-ating temperature conditions indicates that the temperature effect is additive rather than multiplicative. The rate of quality decline during storage was estimated for each strain-temperature combination by simple linear regression analysis of Haugh unit score (7) regressed on time of storage in weeks (X). The b-values (regression coefficients) were taken as estimates of rate of quality decline and were subjected to analysis of oovariance for each period separately with initial Haugh unit score as the concomitant variable. TABLE I F VALUES FROM THE ANALYSIS OF VARIANCE OF AVERAGE HAUGH UNIT SCORES BY PERIODS PERIOD F F SOURCES d.f. 1 2 3 4 5 6 7 8 value value F VALUE .05 .01 Strain 11 7.98** 20.17** 11.77** 8.92** 7.13** 12.35** 9.79** 8.98** 1.99 2.46 Treatment 6 222.25** 312.82** 248.40** 133.24** 91.97** 221.48** 135.98** 140.34** 2.22 3.04 SN X TR 66 0.77 1.13 1.06 0.84 O.69 0.91 0.66 O.98 1.48 1.75 Error 84 Total I67 * Significant at .05 probability level ** Significant at .01 probability level 2 6 TABLE II MEAN HAUGH UNIT SCORES FOR SEVEN TREATMENTS FOR SUCCESSIVE PERIODS DURING THE LAYING YEAR EGG PERIODS (4 weeks per period) STORAGE TREATMENTS 1 2 3 4 5 6 7 8 HAUGH UNIT SCORE 1 86.4 84.7 8G.5 78.4 7 5 . 9 75.1 7 3 . 3 73.0 Initial Breakout 2 60.9 56.8 56.6 5 ^ . 5 52.4 47.5 5 ^ . 9 52.8 Room Temperature for 1 week 51.0 53> 5^.2 45.8 41.4 34.2 43.0 35.7 Room Temperature for 2 weeks 69.2 64.7 59.0 62.8 61.7 50.6 49.6 54.0 Fluctuating Temperature for 1 week Fluctuating Temperature for 2 weeks 60.5 55.9 55.1 62.6 5^ .9 45.6 40.9 49.3 6 76.2 69.2 70.0 68.2 66.0 66.9 63.I 65.I Refrigeration for 1 week Refrigeration for 2 weeks 7 2 . 0 6 6 . 2 65.I 6 5 . 2 5 7 . 6 6 1 . 9 6 0 . 9 6 1 . 3 27 TABLE I I I MEAN HAUGH UNIT SCORES FOR TWELVE STRAINS OF BIRDS FOR SUCCESSIVE PERIODS DURING THE LAYING YEAR PERIODS (4 weeks per period) 1 2 3 4 5 6 7 8 STRAINS HAUGH UNIT SCORE 1 67.2 60.7 57.8 57.5 53.4 48.3 51.5 48.9 2 67.5 62.9 60.3 61.5 57.0 51.4 52.2 56.7 3 68.0 64.6 60.7 61.5 57.6 53.0 52.7 53.8 4 73.2 72.5 68.6 69.3 67.6 64.4 63.2 63.5 5 68.5 65.0 61.4 62.3 58.3 55.8 55.6 55.7 6 62.7 59.3 57.0 57.7 53.4 50.6 50.6 52.0 7 66.4 63.2 61.0 62.6 57.2 53.5 54.2 55.7 8 69.0 66.6 62.4 63.5 59.0 53.3 54.4 54.4 9 68.3 64.0 63.1 64.2 60.3 56.1 57.8 57.7 10 72.1 68.6 65.4 66.3 63.3 59.8 62.1 61.9 11 64.3 61.5 58.6 58.9 56.2 52.1 51.7 53.6 12 69.3 65.2 63.4 64.7 59.6 56.5 55.2 56.8 The results indicated a significant positive linear relationship between rate of quality decline and initial Haugh unit score for a l l but one period. This result supports and extends the findings of Morris (1964) who reported that for 34 or 64 week layers a higher rate of quality loss was encountered for eggs with high initial Haugh unit scores compared to those with low initial scores. May et al. (1957) also reported a signif-icant positive correlation (n = 0.358) between original albumen quality and quality loss during a seven day storage period. These results indicate that after any given period of storage up to two weeks the absolute difference in average Haugh unit score between two groups of eggs differing in initial Haugh unit score will have decreased, the amount depending upon the respective rates of quality decline, time of storage and temperature and other conditions of storage. Under the appropriate conditions the ranking of groups of eggs or strains of layers could be different on the basis of initial versus stored Haugh unit score. Furthermore, the results indicate that the provision of adequate storage facilities and the application of established quality preservation procedures is particularly critical for eggs of high initial quality. Analysis of the adjusted means indicated significant or highly significant differences among the strains and among the treat-ments in rate of quality decline for most periods (Tables IV, V and VI). No strain x treatment interaction was observed. Similar results were reported by Fry et al. (1965), but Kidwell et al. (1964) found litt l e difference in the rate of decline of Haugh unit score among eggs from 16 commercial strains. The standard deviation of Haugh unit score among eggs was calcu-lated for four treatment combinations within period and strain. The TABLE IV RESULTS CF THE ANALYSIS OF COVARIANCE OF RATE OF QUALITY DECLINE DURING STORAGE FOR TWELVE STRAINS AND THREE TEMPERATURE TREATMENTS BY PERIOD. (Concomitant variable was initial Haugh Unit Score) SOURCE PERIOD d.f. 1 2 3 4 MEAN SQUARES 5 6 7 8 Strain 11 8.1 14.8** 7.6* 8.6 23.1** 12.0 28.1** 21.4 * Temperature 2 694.2** 272.4** 593.3** 656.3** 499.5** 1102.4** 736.6** 992.5** S X T 22 3.0 1.7 3.6 5.9 10.6 4.5 3.4 5.4 Error 35 5.5 3.7 3.1 8.4 8.1 7.6 5.7 8.2 Total 70 Regression Coefficient 0.55** 0.59** 0.32* 0.24 0.45** 0.61** 0.46** 0.24* * Significant at .05 probability level. ** Significant at .01 probability level. 30 TABLE V ADJUSTED MEAN RATE OF QUALITY DECLINE FROM THE ANALYSIS OF COVARIANCE FOR EACH OF THREE TREATMENTS BY PERIOD TEMPERATURE TREATMENTS PERIODS 1 2 3 (if weeks period) Room Temperature Fluctuating Refrigeration Temperature - HAUGH UNIT DECLINE PER WEEK STORAGE -1 17.7A 12.9B 7.0° 2 15.6A I4.4b 9.2C 3 17.6A 12.7B 7.7° k I6.2A 7.8b 6.6B 5 17.5A 10.3B 9.1B 6 20.0A 14.5* 6.5° 7 15.1A 16. Oa 6.0B 8 18.7* 12.0B 5.8° The means within each row having the same superscript are not significantly different at the .05 level of probability. TABLE VI ADJUSTED MEAN RATE OF QUALITY DECLINE FROM THE ANALYSIS OF COVARIANCE FOR EACH OF TWELVE STRAINS BY PERIOD PERIOD STRAIN (4 weeks per period) 1 2 3 4 5 6 7 8 9 10 11 12 HAUGH UNIT DECLINE PER WEEK OF STORAGE 1 13.4abc 13.2 a b c 12 .5 a b c d 9.3 d 12.2 a b c d 15.la I4.4ab 12.0bcd 12.3 a b c d lo .5 c d 14.6 a b 10.8cd 2 I6.1a I4 .5 a b 12.7 b o d 8.8e 12.7 b c d l6.1 a 13.5 b c 10. T410 1 3 t 7ab 1 0 # 9cde I4 .5 a b 12.4bod 3 13.9ab I3.5* b 12.5b 9.3° 12.0b 15.5a 12.9b 12.5b 11.7b c 12.5b 12.9b 13.0b 4 8.5a 10.0* 10.3a 8.4a 11.4a 12.0a 11.3a 10.2a 8.8a 9.6a 11.3a 10.3a 5 12.9 a b 13.7* 12.8ab 6.4° 12.5 a b 15.4a 13.0*-h 12.5 a b 13.2ab 9.4 b e 13.7a 12.0ab 6 15.6a 15.5a 13.5 a b 9.0° 12.4abc 15.2a 14.6ab l 5 . o a b 13.8ab 11.4bc 15.0ab 12.8ab0 7 14.0abc 12 .5 a b c 15.1a 7.6 e 11 .3 b c d 15.1a I2.2 a b e d 13.2abc 10 . 9 ^ 9.2 d e I4.3 a b 13.1abC 8 I4.4a 8.8b 13.8a 8.6b 1 3 ^ 14.6a 11.2ab 12.4ab 13.6a 11.9 a b 11.9 a b 12. The means within each row having the same superscript are not significantly different at the .05 level of probability. 32 treatment combinations were as follows! (a) Initial, one and two week data; all temperature conditions; groups pooled. (b) One week data; all temperature conditions; groups pooled. (c) One and two week data; refrigeration temperatures only; groups pooled. (d) Initial data only; groups pooled. These treatment combinations were intended to simulate differing degrees of variability that might be encountered commercially. The standard deviations were calculated from a maximum n value of 84, 36, 24 and 12 eggs for treatment combinations a, b, c, and d respectively. The analysis of variance of the standard deviations indicated significant ( P £ 0 . 0 5 ) period effects for treatment combinations b, e and d, and the F value approached significance for treatment combination a. Significant ( P ^ 0 . 0 5 ) strain effects were evident for treatment combinations b and c (Table VII). Period and strain means and the results of Duncan*s Multiple Range Test are presented in Tables VIII and DC. For each treatment combination the standard deviations for each of the last four periods were higher than those in the first four periods. The difference in average standard deviation between the first and last four periods was 1.4, 1.1, 0 . 9 and 2.8 Haugh units for treat-ment combinations a, b, c and d respectively. This finding clearly indicates an increase in variability in Haugh unit score in both fresh and stored eggs but particularly in the former (treatment combination d) as layer age advances. Tills data supports and extends the findings of 33 TABLE VII MEAN SQUARES FROM THE ANALYSIS OF VARIANCE CF STANDARD DEVIATION OF HAUGH UNIT SCORE FOR TREATMENT COMBINATION a, b, c and d-*-Treatment Combination Source of variation d.f. a b c d —Mean Square — Period 7 11.01 8.70** 8.51** 31.15** Strain 11 3.46 7.91** 7.09** 13.29 Period X Strain 77 5.44 1.75 2.93 8.59 Total 95 •Significant at .05 probability level. ••Significant at .01 probability level. (a) Includes Initial, one and two week data; all temperature conditions; and both groups pooled. (b) Includes one week data; all temperature conditions; and both groups pooled. ^ (c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. ^ (d) Includes initial data only; and both groups pooled. TABLE VIII MEAN PERIOD STANDARD DEVIATIONS OF HAUGH UNIT SCORES FOR EACH TREATMENT COMBINATION TREATMENT COMBINATION PERIOD 1 2 3 4 5 6 7 8 — HAUGH UNIT SCORE -(a) 1 13.5ab 12.7*b 13.7ab 12.7b 13.9ab 15.4a l4.2 a b 14.7^ (b) 2 9.4° 9.5b0 10.2bc 9.8^ 10.2bc 12.1a 10.7b 10.4bc (c) 3 7.5b 7.2b 8.4ab 7.3b 9.8a 7.8b 8.5ab 8.0b (d) k 4.9d 5.9od 5.3°* 6 # 4abcd 8 # 0abc y i»abcd 9.0ab 9.1a (a) Includes Initial, one and two week data; all temperature conditions; and both groups pooled. 2 (b) Includes one week data; al l temperature conditions; and both groups pooled. 3 (c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. ^ (d) Includes initial data only; and both groups pooled. The means within each row having the same superscript are not significantly different at the . 0 5 level of probability. TABLE IX MEAN STRAIN STANDARD DEVIATIONS OF HAUGH UNIT SCORES FOR EACH TREATMENT COMBINATION TREATMENT STRAIN COMBINATION 1 2 3 ** 5 6 7 8 9 10 11 12 ~ HAUGH UNIT SCORE — (a) 1 13.7a 15.2a 13.9a 13.1a 13.1a l4.5 a 13.7* 14.7a 13.5a 13.6a 13.2& 13.6a (b) 2 10.2 b c d e fS 12.5a 10.3 b o d e f 9.3 c d e f g 9.8 0 d e f g 10.9 b c 11.2b 10.6*°* 9.3 c d e f g 8.7? 10.5 b c d e 9 . 9 c d " f g (c) 3 8.2 a b c d 9.6ab 8.3 a b o d 7.6cd 7.1cd 8.8abc 7.0^ 9.7* 8.3 a b c d 6.5d 8.2 a b o d 7.5od (d) k 7.7bcd 8.2bo 7#3^«ief 8.3b 6.kf& 6.0S11 5.5hi 9.4a 5.11 6.7 d e f g 7.5 b c d e (a) Includes Initial, one and two week data; all temperature conditions; and both groups pooled. (b) Includes one week data; all temperature conditions; and both groups pooled. 3 (c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. ^ (d) Includes initial data only; and both groups pooled. The means within each row having the same superscript are not significantly different at the .05 level of probability. 36 Kline et a l . (1965) who reported variat ion was 50$ greater for layers 18 months old than for layers 8 to 12 months o ld , and over 100$ greater for 20 month old layers . The calculated standard deviations were used to estimate the sample size required to predict Haugh unit scores according to the following formula from Cochran (1962): n - X t s f where: n = estimated sample size t = t-value corresponding to degree of .confidence; set at 95$ t = I.96 s = standard deviation d * margin of error acceptable; set at + 5 Haugh units . The resultant estimate sample sizes are presented i n Figures 1 and 2. The estimated sample sizes were regressed against time (period) i n a simple l inear regression analysis (Table X ) . The sample size required increased with time (period) for a l l treatment combinations and i n a s igni f icant ly l inear manner for treatment combinations a and d. The estimated sample size data c lear ly indicate the need to consider the age of layer and the s t ra in of layer when establishing the number of eggs to be sampled i n a quality assessment or control program. The increase i n magnitude of standard deviation with layer age corresponded to a general decline i n i n i t i a l Haugh unit score. However, the differences i n va r i ab i l i ty of Haugh unit score among strains did not correlate well to the respective Haugh unit scores, i . e . strains Ave. n 40 35 30 25 20 15 10 37 TREATMENT COMBINATION (a) 1 1 2 3 4 5 6 ^ 8 PERIOD FIGURE 1 AVERAGE n VALUES FOR EACH PERIOD WITHIN TREATMENT COMBINATIONS (a) Includes Initial, one and two week data; a l l temperature conditions; and both groups pooled. 2 (b) Includes one week data; a l l temperature conditions; and both groups pooled. 3 (c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. (d) Includes initial data only; and both groups pooled. Ave. v I. i 1 i i i i i i i i i i 1 2 3 4 5 6 7 8 9 10 11 12 STRAIN FIGURE 2 AVERAGE n VALUES FOR EACH STRAIN WITHIN TREATMENT C0MBIHATI0NS """ (a) Includes Initial, one and two week data; all temperature conditions; and both groups pooled. »> (b) Includes one week data; all temperature conditions; and both groups pooled. 3 (c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. ^ (d) Includes initial data only; and both groups pooled. TABLE X RESULTS OF SIMPLE LINEAR REGRESSION AND CORRELATION ANALYSES OF THE RELATIONSHIP OF ESTIMATED SAMPLE SIZE (Y) VERSUS PERIOD (X) Treatment Combination Regression equation F-Value r a 1 Y = 25.22 + 1.25 X 6.06* + 0.71 b 2 Y = 1.38 + .79 X 4.45 n.s. + O.65 c 3 Y = 9.51 + .36 X .75 n.s. + 0.38 Y = 1.76 + 1.64 X 35.29** + 0.93 * Significant at .05 probability level. ** Significant at .01 probability level. 1(a) Includes Initial, one and two week data; a l l temperature conditions; and both groups pooled. 2 (b) Includes one week data; all temperature conditions; and both groups pooled. -a (c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. 4 (d) Includes initial data only; and both groups pooled. 40 which Laid eggs with a relatively low average Haugh unit score were not consistently the most variable in Haugh unit score. Thus a program such as that outlined by the U.S. Department of Agriculture Handbook No. 75 (1968) which prescribes an increase in sample size only as Haugh unit score declines does not fully account for differences in variability due to strains. However, the increase in variation due to age of layer is accounted for to a much greater extent by such a program. SUMMARY Eggs were sampled over an eight month period from twelve strains of layers entered in the Ninth British Columbia Random Sample Egg Laying Test. Determinations were made on the rate of interior egg quality decline under three varying temperature conditions for one and two week periods. Differences among strains in initial egg quality as well as the rate of quality decline under different storage temperatures were investigated. Implications of these results were considered for the determination of size of sample in quality control programs or interior egg quality assessment studies. Highly significant differences in average Haugh unit scores were found among strains and treatments for each period in the study. The mean Haugh unit score consistently declined as storage time increased. The average Haugh unit score was highest for eggs stored under refrigera-tion, lowest for those stored at room temperature and intermediate for those stored at fluctuating temperatures. A significant positive linear relationship was found between rate of quality decline and initial Haugh unit score for all but one period. Differences in rate of quality decline were found among strains and among treatments for most periods. Data on treatment combinations simulating commercial marketing conditions indicated significant strain and period effects on variability of Haugh unit score. Variability of Haugh unit score in both fresh and stored eggs increased during the last four periods as compared with the first four periods of lay. 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Influence of breeding method on albumen quality. Poultry Sci. 32: 902. Harns, Vivian J., E.A. Sauter, Barbara A. McLaren and W.J. Stadelman, 1954. The effect of season, age and storage conditions on the flavor of eggs and products made using eggs. Poultry Sci. 33: 992-997. Harper, J.A. and D.R. Marble, 1945. Egg Shape I. Albumen influence. Poultry Sci. 24: 56-60. Haugh, R.R., 1937. The Haugh unit for measuring egg quality. U.S. Egg and Poultry Magazine 43: 552-555; 572-573. 46 Heiman, Victor and J .S . Carver, 1936. The albumen index as a physical measurement of observed egg qual i ty . Poultry S c i . 15: 141-148. Hoist , W.F. and H . J . Almquist, 1931. Distr ibution of so l id matter i n thick and thin egg white. Hilgardia 6: 49-60. Hoist, W.F. and H . J . Almquist, 1931. Measurement of deterioration i n the stored hens egg. Hilgardia 6: 49-60. Hoover, Sam R., 1938. Determination of egg quality by a sampling method. 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Go we, 1956. The performance of eight strains of White Leghorns at three locations with respect to egg quality-t r a i t s . Poultry S c i . 35: 1149. 47 Johnson, A.S. and E.S. Merritt, 1955. Heritability of albumen height and specific gravity of eggs from White Leghorns and Barred Bocks and the correlations of these traits with egg production. Poultry Sci. 34: 578-587. Kennett, H. Connor Jr., I960. U.S.D.A. Quality Control Egg Certifica-tion Program. Poultry Processing and Marketing 66: 23; 36-41. Kidwell, Margaret Gale, A.W. Nordskoy and R.H. Forsythe, 1964. Variation among commercial strains of chickens in loss of egg albumen quality. Poultry Sci. 43: 38-41. Kidwell, Margaret Gale, A.W. Nordskoy and R.H. Forsythe, 1964. On the problem of correcting albumen quality measures for egg weight. Poultry Sci. 43: 42-49. King, Steven C, 1961. Inheritance of economic traits in the regional Cornell control population. Poultry Sci. 40: 975-986. King, Steven C, J. David Mitchell, Wendell H. 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Poultry Sci. 13: 14-17. Lorenz, F.W. and Luis W. Taylor, 1940. The inheritance of an albumen quality characteristic of chicken eggs. Journal of Agricultural Research 54: 243-301. Marion, W.W., A.W. Nordskoy, H.S. Talman and R.H. Forsythe, 1964. Egg composition as influenced by breeding, eggs size, age and season. Poultry Sci. 43: 255-264. Marion, J.E., J.G. Woodroof and R.E. Cook, 1965. Some physical and chemical properties of eggs from hens of five different studies. Poultry Sci. 44: 529-534. May, K.N., F.J. Schmidt and W.J. Stadelman, 1957. Strain variation in albumen quality decline of hen's eggs. Poultry Sci. 36: 1378-9. Mc Clary, CF. and G.E. Bearse, 1956. The genetic correlation of albumen quality in fresh and stored eggs. Poultry Sci. 35: 1157. McKerley, Ray G., George W. Newell, Joe G. Berry, George V. Odell and Robert D. Morrison, 1967. The effects of some changes in pH and Haugh units in chicken eggs. Poultry Sci. 46: U8-132. M i l l er, Herman I. Agricultural Situation. U.S.D.A. Agricultural Marketing Service, Vol. 42:13. May 1958. 49 Morris, J.A., 1964. Estimates of genetic paremeters relevant in selection for certain aspects of egg quality. Australian Journal of Agricultural Research 15: 719-72?. Mountney, G.J. and C. Vanderzant, 1957. Relationship of selected egg quality measurements. Poultry Sci. 36: 908-913. Mueller, W.J., A.J.G. Maw and E.G. Buss, i960. The influence of season and the age of layers on egg weight, shape index, albumen quality and shell thickness. Poultry Sci. 39: 854*860. Munro, S.S., 1938. Effect of heredity on interior egg quality and shell composition. Poultry Sci. 17: 17-27. Mukerji, P.C. and Jack L. Fry, 1963. Studies on preserving quality in market eggs. Poultry Sci 42: 348-357. Murray, Marion W. and P.P. Rutherford, 1963. The relationship between the loss of water and carbon dioxide from eggs and the effect upon albumen quality. Poultry Sci. 42: 505-508. Nordskog, A.W. and Owen Cotterill, 1953. Breeding for egg quality; sampling hens for interior quality. Poultry Sci. 32: 1051-1054. Noles, R.K. and D. Tindell, I967. Observations on the inter-relation-ships of egg quality traits and their association with season, age and strain of bird. Poultry Sci. 46: 943-952. Paraell, E.D. and R.C. Jaska, 1958. Effect of temperature and relative humidity on market egg quality. Texas Agricultural Experiment Station MP-296. Aug. 1958. Parsons, CH. and L.D. Mink, 1937. The correlation of methods for measuring the interior quality of eggs. U.S. Egg and Poultry Magazine 43: 484-491. 50 Proudfoot, F.G., 19&2, The interior quality decline of spray-oiled versus unoiled eggs, stored at 70*%., among three strains of Leghorns. Canadian Journal of Animal Sci. 42: 88-94. Quinn, Joseph P., 1963* Estimates of some genetic paremeters of egg quality. Poultry Sci. 42: 792-793. Raff a, J., 1963. Evaluation of albumen quality in a poultry breeding program. Poultry Sci. 42: 344-348. Rehkugler, G.E. and R.C. Baker, I963. The effect of rotation on the internal quality of chicken eggs. Poultry Sci. 42: 1187-1190. Romanoff, A.L. and A.J. Romanoff, 1949. The Avian Egg. London: Chapman and Hall Ltd. Sauter, E.A., J.V. Hams, W.J. Stadelman and B.A. McLaren, 1953. Relationship of candled quality of eggs to other quality measure-ments. Poultry Sci. 32: 850-854. Sharp, Paul F. and C.K. Powell, 1930. Decrease in interior quality of hen's eggs during storage as indicated by the yolk. Industrial and Engineering Chemistry 22: 908-910. Skala, J.H. and Milo H. Swanson, 1962. Studies of variation in initial quality of chicken eggs. Poultry Sci. 41: 1533-1536. Skala, J.H., 1968. Studies of variation in initial quality of chicken eggs. 3* Interior quality decline under various storable conditions as related to initial quality. Poultry Sci. 47: 1849-1858. Smith, R.T. and Robert M. Grover, 1963. Effect of pre-cooling eggs and cartons upon quality after storage. Poultry Sci. 42: 793-795. 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A P P E N D I X APPENDIX TABLE I STRAINS OF BIRDS AND ENTRY NUMBERS USED IN THIS STUDY Entry Number Name of Entrant or Strain 1 DeZeeuw 752 2 Sex-Sal-Link "F" 3 Andrews B 31 4 Kimber Chick 137 A 5 Kimber Chick 141 6 Babcock B 300 7 Honnegger Layer 8 Dernier D-65 9 Stone H-56 10 Garber G-200 11 Kentville Control 12 Commercial Line (H & N) 54 APPENDIX TABLE II IDENTIFICATION OF EGGS USED IN THIS STUDY BY PEN NUMBER GROUP 1 Row 1 & 2 GROUP 2 Row 3 & 4 Entry Pen Entry Pen 1 13 & 34 1 53 & 61 2 15 & 23 2 56 & 75 3 4 & 22 3 41 & 74 4 3 & 32 4 42 & 63 5 1 & 26 5 43 & 71 6 6 & 33 6 44 & 62 7 11 & 36 7 55 & 65 8 5 & 31 8 45 & 64 9 16 & 21 9 51 & 76 10 2 & 24 10 46 & 72 11 14 & 35 11 54 & 66 12 12 & 25 12 52 & 73 55 APPENDIX TABLE III SIMPLE LINEAR CORRELATION COEFFICIENTS FOR THE RELATIONSHIP OF HAUGH UNIT SCORE AND TIME OF STORAGE GROUP I GROUP II TEMPERATURE TREATMENTS Room Fluctu- Refrig- Room Fluctu- Ref r i g -Temperature ating oration Temperature ating eration 1 2 3 1 2 3 STRAIN CORRELATION COEFFICIENTS Period 1 (n = 12-18) 1 -.92 -.82 -.73 -.88 -.82 -.56 2 -.91 -.91 -.70 -.76 -.90 -.47 3 -.83 -.82 -.46 -.79 -.92 -.76 4 -.88 -.73 -.53 -.84 -.90 -.86 5 -.83 -.80 -.87 -.90 -.82 -.71 6 -.85 -.85 -.71 -.95 -.72 -.76 7 -.90 -.86 -.62 -.84 -.95 -.82 8 -.87 -.82 -.79 -.79 -.87 -.42 9 -.91 -.93 -.50 -.78 -.92 -.67 10 -.84 -.80 -.75 -.92 -.79 -.63 11 -.75 -.83 -.74 -.89 -.86 -.72 12 -.89 -.92 Period 2 -.64 (n = 15-18) -.81 -.79 -.40 1 -.88 -.89 -.80 -.88 -.72 -.79 2 -.73 -.88 -.71 -.80 -.91 -.77 3 -.88 -.81 -.79 -.75 -.84 -.87 4 -.79 -.86 -.78 -.90 -.85 -.63 56 APPENDIX TABLE III (continued) GROUP I GROUP II TEMPERATURE TREATMENTS Room Temperature Fluctu-ating Refrig-eration Room Temperature Fluctu-ating Ref rig-era t i o i 1 2 3 1 2 3 STRAIN CORRELATION COEFFICIENTS 5 -.85 -.75 -.71 -.83 -.96 -.66 6 -.89 -.87 -.73 -.89 -.86 -.77 7 -.71 -.87 -.68 -.80 -.90 -.71 8 -.81 -.87 -.74 -.80 -.69 -.35 9 -.89 -.79 -.85 -.77 -.90 -.64 10 -.84 -.87 -.72 -.79 -.90 -.72 11 -.79 -.91 -.82 -.78 -.79 -.80 12 -.73 -.87 -.52 -.73 -.80 -.73 Period 3 (n = 17-18) 1 -.82 -.71 -.62 -.93 -.64 -.76 2 -.82 -.88 -.75 -.83 -.78 -.63 3 -.83 -.76 -.56 -.91 -.63 -.62 4 -.89 -.85 -.46 -.87 -.69 -.47 5 -.78 -.78 -.76 -.84 -.76 -.67 6 -.89 -.83 -.59 -.91 -.89 -.74 7 -.91 -.55 -.78 -.96 -.84 -.82 8 -.82 -.86 -.51 -.73 -.63 -.81 9 -.89 -.69 -.78 -.92 -.81 -.77 10 -.93 -.90 -.73 -.83 -.87 -.86 11 -.85 -.67 -.48 -.75 -.76 -.69 APPENDIX TABLE III (continued) GROUP I GROUP II TEMPERATURE TREATMENTS Room Temperature Fluctu-ating Refrig- Room eration Temperature Fluctu-ating Refrig-eratioi 1 2 3 1 2 3 FRAIN CORRELATION COEFFICIENTS 12 -.94 -.80 Period -.80 4 (n = 1>18) -.93 -.95 -.67 1 -.78 -.59 -.46 -.79 -.40 -.32 2 -.87 -.42 -.59 -.65 -.41 -.55 3 -.70 -.82 -.52 -.90 -.65 -.47 4 -.95 -.79 -.51 -.90 -.56 -.53 5 -.92 -.56 -.46 -.92 -.78 -.76 6 -.8? -.69 -.41 -.84 -.76 -.76 7 -.93 -.81 -.83 -.65 -.65 -.68 8 -.85 -.70 -.62 -.73 -.61 -.81 9 -.71 -.47 -.18 -.82 -.61 -.73 10 -.93 -.79 -.63 -.74 -.70 -.69 11 -.96 -.55 -.68 -.66 -.55 -.63 12 -.84 -.69 Period -.84 5 (n = 12-18) -.84 -.84 -.72 1 -.75 -.36 -.51 -.71 -.87 -.74 2 -.83 -.65 -.54 -.78 -.85 -.72 3 -.84 -.46 -.19 -.90 -.62 -.69 -.84 -.92 -.70 -.89 -.65 -.77 5 -.86 -.56 -.75 -.81 -.68 -.64 58 APPENDIX TABLE III (continued) GROUP I GROUP II TEMPERATURE TREATMENTS Room Temperature Fluctu-ating Refrig-eration Room Temperature Fluctu-ating Refrig-eratioi 1 2 3 1 2 3 rRAIN CORRELATION COEFFICIENTS 6 -.82 -.55 -.66 -.89 -.70 -.77 7 -.89 -.82 -.82 -.64 -.82 -.63 8 -.50 -.15 -.02 -.91 -.77 -.78 9 -.97 -.82 -.66 -.91 -.86 -.69 10 -.87 -.67 -.61 -.88 -.62 -.54 11 -.91 -.82 -.88 -.87 -.78 -.75 12 -.87 -.84 -.80 -.86 -.84 -.90 Period 6 (n = 1>18) 1 -.82 -.73 -.76 -.82 -.73 -.38 2 -.84 -.81 -.30 -.93 -.68 -.54 3 -.89 -.85 -.61 -.71 -.76 -.39 4 -.90 -.73 -.65 -.94 -.74 -.62 5 -.85 -.83 -.76 -.72 -.73 -.39 6 -.88 -.76 -.28 -.74 -.87 -.43 7 -.89 -.85 -.71 -.86 -.83 -.84 8 -.91 -.84 -.57 -.84 -.74 -.70 9 -.87 -.86 -.55 -.90 -.83 -.64 10 -.91 -.87 -.76 -.92 -.71 -.64 11 -.86 -.76 -.67 -.91 -.69 -.71 12 -.83 -.81 -.62 -.85 -.81 -.77 59 APPENDIX TABLE III (continued) GROUP I GROUP U TEMPERATURE TREATMENTS Room Fluctu- Refrig- Room Temperature ating eration Temperature Fluctu-ating Refrig-eration 1 2 3 1 2 3 STRAIN CORRELATION COEFFICIENTS Period 7 (n = 11-18) 1 -.90 -.89 -.74 -.8? -.82 -.38 2 -.*5 -.64 -.09 -.86 -.83 -.83 3 -.84 -.85 -.34 -.85 -.85 -.69 4 -.56 -.61 -.18 -.84 -.65 -.03 5 -.75 -.85 -.39 -.90 -.77 -.63 6 -.86 -.8? -.73 -.78 -.87 -.63 7 -.85 -.72 -.76 -.82 -.68 -.57 8 -.65 -.72 -.03 -.89 -.86 -.63 9 -.89 -.89 -.52 -.74 -.89 -.49 10 -.79 -.92 -.82 -.87 -.80 -.54 11 -.88 -.89 -.63 -.70 -.69 -.42 12 -.90 -.87 -.61 -.82 -.73 -.53 Period 8 (n = 11-18) 1 -.84 -.59 -.57 -.81 -.78 -.46 2 -.33 -.31 -.11 -.77 -.51 -.29 3 -.88 -.85 -.73 -.82 -.68 -.69 4 -.60 -.45 -.05 -.75 -.74 -.48 5 -.86 -.79 -.66 -.95 -.83 -.31 6 -.89 -.73 -.63 -.93 -.89 -.64 APPENDIX TABLE III (continued) GROUP I GROUP II TEMPERATURE TREATMENTS Room Fluctu- Ref rig- Room Fluctu- Refrig-Temperature ating eration Temperature ating eration 1 2 3 1 2 3 STRAIN CORRELATION COEFFICIENTS 7 -.86 -.82 -.34 -.90 -.74 -.58 8 -.84 -.72 -.48 -.81 -.76 -.36 9 -.92 -.79 -.74 -.90 -.85 -.77 10 -.92 -.92 -.79 -.87 -.78 -.59 11 -.89 -.71 -.52 -.91 -.80 -.50 12 -.67 -.43 -.19 -.93 -.89 -.69 61 APPENDIX TABLE IV AVERAGE ESTIMATED SAMPLE SIZE (n) FOR EACH PERIOD WITHIN EACH TREATMENT COMBINATION AS PLOTTED IN FIGURE 1 TREATMENT COMBINATION ( a ) 1 ( b ) 2 ( c ) 3 <d)* Period 1 29.0 14.4 9.2 4.0 2 25.8 14.5 8.6 6.0 3 29.9 17.1 12.4 4.7 4 25.4 15.5 8.8 7.3 5 31.0 16.9 16.6 12.8 6 38.1 23.6 10.4 9.6 7 32.6 18.8 12.2 13.1 8 35.0 17.9 10.7 15.7 1(a) Includes i n i t i a l , one and two week data; a l l temperature conditions; and both groups pooled. 2(b) Includes one week data; a l l temperature conditions; and both groups pooled. 3 ( c ) Includes one and two week data; refrigeration temperatures only; and both groups pooled. \ d ) Includes i n i t i a l data only; and both groups pooled. 62 APPENDIX TABLE V AVERAGE ESTIMATED SAMPLE SIZE (n) FOR EACH STRAIN WITHIN EACH TREATMENT COMBINATION AS PLOTTED IN FIGURE 2 TREATMENT COMBINATION ( a ) 1 ( b ) 2 («)3 <d)* Strain 1 3 0 . 3 1 7 . 2 1 0 . 9 1 0 . 8 2 37.4 25 .4 15 .7 1 2 . 6 3 31.4 1 7 . 2 11 .3 8 . 9 4 27 .6 13 .9 9 . 9 15 .7 5 27 .8 1 5 . 8 8 . 6 6 . 5 6 33.7 1 9 . 1 1 3 . 2 6 . 6 7 3 0 . 3 2 0 . 5 8 . 1 5 . 1 8 3 5 . 1 18.7 1 5 . 6 1 3 . 6 9 2 9 . 5 14.1 1 2 . 3 6 . 5 10 29.8 1 2 . 6 6 . 9 4 .5 11 28.1 17 .9 1 2 . 1 7.8 12 2 9 . 3 15.8 9 . 1 11 .1 ^(a) Includes i n i t i a l , one and two week data; a l l temperature conditions; and both groups pooled. 2 (b) Includes one week data; a l l temperature conditions; and both groups pooled. 3(c) Includes one and two week data; refrigeration temperatures only; and both groups pooled. ^(d) Includes i n i t i a l data only; and both groups pooled. APPENDIX TABLE VI PERIOD STANDARD DEVIATION OF HAUGH UNIT SCORE AND ESTIMATED SAMPLE SIZE (n) BY STRAIN AND PERIOD-TREATMENT GROUP (a) STRAIN JL 2 2 4 5 6 I 8 9 10 11 12 1 13.17 13.95 13.79 12.59 12.07 14.00 13.82 14.05 13.76 13.91 13.73 12.61 SD 27.75 31.14 30.43 25.36 23.31 31.36 30.56 31.58 30.29 30.96 30.16 25.44 n 2 13.77 13.35 12.46 13.67 11.23 12.13 12.40 13.58 12.84 12.54 12.06 12.22 SD 30.34 28.52 24.84 29.90 20.18 23.54 24.60 29.51 26.38 25.16 23.27 23.89 n 3 14.15 14.54 14.14 12.91 12.57 14.20 13.11 15.28 12.70 13.81 13.06 13.36 SD 32.04 33.83 31.99 26.67 25.28 32.26 27.50 37.36 25.81 30.51 27.29 28.56 n 4 11.57 13.67 11.77 12.88 13.32 13.97 12.92 11.89 11.79 12.22 13.29 11.53 SD 21.42 29.90 22.17 26.54 28.39 31.23 26.71 22.62 22.24 23.89 28.26 21.27 n 5 12.65 16.41 14.70 12.77 12.73 14.48 13.78 14.44 14.72 13.44 13.OI 13.53 SD 25.60 43.09 34.57 26.09 25.93 33.55 30.38 33.36 34.67 28.90 27.08 29.29 n 6 14.90 18.42 14.42 13.36 15.11 14.69 16.65 16.36 15.11 15.08 14.60 15.75 SD 35.52 54.29 33.27 28.56 36.53 34.53 44.36 42.82 36.53 36.39 34.11 39.69 n 7 14.02 16.09 16.32 12.85 13.12 15.72 14.37 15.65 11.48 13.54 13.73 13.42 SD 31.45 41.42 42.61 26.42 27.54 39.54 33.04 39.19 21.09 29.33 30.16 28.82 n 8 15.44 15.16 13.95 13.95 14.84 16.51 12.55 16.65 15.57 14.42 12.30 15.36 SD 38.14 36.77 31.14 31.14 35.24 43.61 25.20 44.36 38.79 33.27 24.21 37.75 n SD = Standard deviation of Haugh unit soore. n = Estimated sample size. APPENDIX TABLE VII STANDARD DEVIATION OF HAUGH UNIT SCORE AND ESTIMATED SAMPLE SIZE (n) BY STRAIN AND PERIOD— TREATMENT GROUP (b) STRAIN 6 8 10 11 12 PERIOD 1 3 4 5 6 9.04 13.08 8.79 12.36 8.77 12.31 9.06 13.13 11.72 21.98 12.90 26.63 9.48 14.38 12.07 23.31 10.94 19.15 11.75 22.09 10.78 18.59 11.32 20.50 12.46 24.84 13.77 30.34 10.01 16.03 8.86 12.56 10.62 18.05 9.19 13.51 11.36 20.65 12.23 23.93 9.63 14.84 9.77 15.27 8.25 10.89 9.40 14.14 9.68 14.99 7.34 8.62 9.21 13.57 8.35 11.16 10.32 17.04 8.28 10.97 II.67 21.79 12.03 23.16 10.90 18.61 7.64 9.34 10.46 17.51 12.04 23.19 10.16 16.52 11.66 21.35 8.91 12.70 9.33 13.93 11.84 22.43 11.34 20.58 11.48 21.09 14.00 31.36 11.12 19.78 8.44 11.40 11.22 20.14 8.22 10.81 8.87 12.59 13.52 29.25 9.49 14.41 10.47 17.54 9.01 12.99 8.56 11.72 8.88 12.62 11.19 20.03 6.47 6.70 9.79 15.34 9.87 15.59 8.39 11.26 8.05 10.37 10.68 18.25 8.61 11.86 9.95 15.84 12.94 26.79 11.85 22.47 8.56 11.72 12.36 24.44 14.86 9.62 9.41 11.03 11.88 13.16 11.21 8.12 9.98 9.82 35.33 14.81 14.17 19.47 aa.58 27.71 20.11 IO.55 15.94 15.43 14.24 10.66 10.70 32.44 18.18 18.32 7.68 12.16 9.38 12.58 9.01 9.44 23.66 14.08 25.32 12.99 6.66 9.68 7.10 14.99 8.81 SD 12.42 n 10.48 SD 17.57 n 8.84 SD 12.50 n 9.35 SD 13.99 n 9.34 SD 13.96 n 12.82 SD 26.30 n 9.75 SD 15.21 n 9.56 SD 14.62 n SD = Standard deviation of Haugh unit score, n = Estimated sample size. APPENDIX TABLE VIII STANDARD DEVIATION OF HAUGH UNIT SCORE AND ESTIMATED SAMPLE SIZE (n) BT STRAIN AND PERIOD-TREATMENT GROUP (c) STRAIN 1 2 3 4 5 6 7 8 9 10 11 12 HOD 1 8.69 12.08 8.98 12.90 6.96 7.75 5.13 4.19 6.55 6.86 8.06 10.39 7.87 9.91 9.50 14.44 8.6? 12.03 7.21 8.32 5.35 4.58 6.75 7.29 SD n 2 7.67 9.41 7.87 9.91 7.10 8.07 9.29 13.81 6.00 5.76 9.19 13.51 4.93 3.89 6.53 6.82 7.87 9.91 6.60 6.97 7.09 8.04 6.87 7.55 SD n 3 7.48 8.95 8.08 10.45 9.09 13.22 11.50 21.16 4.88 3.81 10.59 17.94 6.74 7.27 14.02 31.45 4.88 3.81 6.44 6.64 9.72 15.12 7.53 9.07 SD n 4 7.47 8.93 8.70 12.11 9.17 13.45 5.07 4.11 6.96 7.75 6.24 6.23 7.22 8.34 8.64 11.94 5.57 4.96 7.14 8.16 8.45 11.42 6.99 7.82 SD n 5 9.25 13.69 12.38 24.52 9.56 14.62 8.79 12.36 10.87 18.91 13.33 28.43 8.34 11.13 8.98 12.90 12.08 23.35 7.52 9.05 7.38 16.78 9.20 13.54 SD n 6 7.72 9.54 6.97 7.77 7.09 8.04 6.64 7.05 6.11 5.97 8.48 11.52 6.82 7.44 9.42 14.20 13.16 27.71 5.93 5.63 9.22 13.60 6.32 6.39 SD n 7 10.16 16.52 13.93 31.05 7.25 8.41 6.78 7.35 7.85 9.86 6.68 7.14 6.38 6.51 11.03 19.47 6.52 6.80 6.83 7.46 9.86 15.56 8.21 10.78 SD n 8 7.11 8.09 10.26 16.84 10.20 16.65 7.59 9.22 7.76 9.63 7.91 10.01 7.97 10.16 9.33 13.93 7.74 9.59 4.00 2.56 8.44 11.40 8.07 10.42 SD n SD = n = Standard deviation of Haugh unit soore Estimated sample size. APPENDIX TABLE IX STANDARD DEVIATION OF HAUGH UNIT SCORE AND ESTIMATED SAMPLE SIZE (n) BY STRAIN AND PER PERIOD— TREATMENT GROUP (d) STRAIN 1 2 3 4 5 6 7 8 9 10 11 12 SIOD 1 3.86 2.38 4.26 2.90 5.88 5.53 5.07 4.11 6.58 6.93 4.75 3.61 5.00 4.00 4.59 3.37 4.34 3.01 4.10 2.57 5.50 4.84 5.32 SD 4.52 n 2 8.02 10.29 5.56 4.92 5.01 4.02 5.70 5.20 6.27 6.29 3.05 1.49 6.64 7.05 6.90 7.62 4.33 3.00 6.37 6.49 4.82 3.72 8.40 SD 11.29 n 3 5.01 4.02 3.92 2.46 6.47 6.70 6.95 7.73 6.88 7.57 4.55 3.31 4.53 3.28 6.34 6.43 4.08 2.66 3.60 2.07 7.13 8.13 3.89 SD 2.42 n 4 6.89 7.60 9.62 14.81 6.76 7.31 4.29 2.94 5.90 5.57 5.86 5.49 4.39 3.08 4.93 3.89 11.45 20.98 5.13 4.21 5.49 5.65 5.99 SD 5.74 n 5 9.21 13.57 9.37 14.05 7.99 10.21 3.12 1.56 7.00 7.84 9.26 13.72 6.76 7.31 19.82 63.17 3.95 2.43 7.77 9.66 6.05 5.86 5.14 SD 4.23 n 6 11.37 20.68 7.72 9.54 9.17 13.45 6.61 6.99 6.54 6.84 10.29 16.69 3.71 2.20 8.46 11.45 6.53 6.82 4.96 3.94 7.76 9.63 6.49 SD 6.74 n 7 5.08 4.12 13.61 29.64 9.76 15.24 17.15 49.84 5.62 5.05 5.05 4.08 6.62 7.01 17.23 5.06 5.78 5.35 2.76 1.22 10.94 19.15 8.47 SD 11.48 n 8 12.26 24.05 11.84 22.43 7.51 9.02 17.18 47.22 6.08 5.91 5.08 4.13 6.43 6.62 7.01 7.86 7.00 7.84 6.20 6.15 5.89 5.51 16.23 SD 42.12 n SD = Standard deviation of Haugh unit score, n = Estimated sample size. 67 APPENDIX TABLE X EXPECTED AND NORMAL FREQUENCY DISTRIBUTION OF STANDARD DEVIATION OF HAUGH UNIT SCORE FOR TREATMENT COMBINATION (a) Cumulative Percentage Expected Normal Class Interval Frequency Frequency Frequency 1. 47.00 - 47.49 2. 47.50 - 47.99 3 3.12 2.5 3. 48.00 - 48.49 8 11.45 5.3 4. 48.50 - 48.99 8 19.79 8.9 5. 49.00 - 49.49 12 32.29 13.2 6. 49.50 - 49.99 17 50.00 15.7 7. 50.00 - 50.49 15 65.60 16.2 8. 50.50 - 50.99 11 77.08 13.2 9. 51.00 - 51.49 14 91.67 9.6 10. 51.50 - 51.99 4 95.83 5.6 11. 52.00 - 52.49 2 97.92 2.7 12. 52.50 - 52.99 2 100.00 1.1 13. 53.00 - 53.49 "96-Chi-square = 5.63; chi-square ^ Q5)(8) = ^ * 0 ^ l(Standard Deviation + 50.0)—Average Standard Deviation per strain within period per period 68 APPENDIX TABLE XI MEAN INITIAL HAUGH UNIT SCORE FOR STRAINS AND SUCCESSIVE PERIODS OF LAY PERIODS (4 weeks per period) 1 2 3 4 5 6 7 8 L RAINS HAUGH UNIT SCORE 1 83.2 83.6 78.0 69.2 72.6 68.2 75.1 70.8 2 85.8 84.2 83.5 78.4 77.8 70.9 71.4 65.4 3 86.2 87.7 81.1 78.1 73.7 74.5 73.3 71.7 4 90.7 89.9 87.6 83.7 84.8 82.5 74.8 75.2 5 86.3 83.6 79.0 78.5 73.2 75.9 73.4 74.6 6 82.8 81.3 74.7 72.9 71.6 67.3 71.6 74.0 7 84.3 82.3 77.6 82.4 74.9 76.8 74.6 73.2 8 86.8 87.7 84.2 80.4 72.8 76.1 71.6 71.2 9 88.4 84.3 82.8 77.9 77.0 76.8 72.0 76.3 10 90.1 88.4 86.6 81.8 78.2 81.1 81.1 81.4 11 84.6 82.2 74.9 78.2 76.1 72.5 68.8 71.2 12 87.8 82.8 81.7 81.3 79.7 77.9 72.6 72.5 THE PERCENTAGE CUMULATIVE LESS THAN DISTRIBUTION QF--STANDAHD DEVIATION CF HAUGH UNIT SCORE (TREATMENT COMBINATION a) "45" 49 49.5 ~5d 5075 51 51.5 (Standard Deviation + 50.0)—Average Standard Deviation per strain within period per period 52 3 2 . 

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