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UBC Theses and Dissertations

Dietary factors that influence amino acid, protein and nucleic acid metabolism in the chicken Akinwande, Amos Ifeolu

Abstract

THE METABOLISM OF DNA, RNA, PROTEIN AND AMINO ACIDS W/A"S:E STUDIED IN CHICKS FED DIETARY PROTEINS OF DIFFERENT NUTRITIVE VALUE. DNA AND RNA CONTENT OF THE GASTROCNEMIUS MUSCLE AND LIVER WERE MEASURED BY MEANS OF AN ULTRAVIOLET ABSORPTION TECHNIQUE AND PROTEINS GRAVIMETRI CALLY AND BY SPECTROPHOTOMETRY. AN ISOTOPE TECHNIQUE WAS USED TO STUDY THE EFFECTS OF DIETARY LYSINE ON THE DEGRADATION AND SYNTHESIS OF TISSUE PROTEINS, RNA SYNTHESIS AND THE METABOLIC FATE OF LYSINE AND THREONINE. RESULTS SHOWED THAT MUSCLE DNA (MG./G. FRESH TISSUE) CONTENT WAS UNAFFECTED BY THE LEVEL OF DIETARY LYSINE AT 14 AND 28 DAYS OF AGE. LIVER DNA CONTENT INCREASED AT 14 DAYS AND WAS UNAFFECTED AT 28 DAYS WITH INCREASED LEVEL OF DIETARY LYSINE. MUSCLE PROTEIN/DNA AND RNA/DNA RATIOS INCREASED AT 14 AND 28 DAYS OF AGE BY INCREASING DIETARY PROTEIN FROM 15 TO 20%, BY SUPPLEMENTING WHEAT WITH SOYBEAN MEAL OR WITH LYSINE. THE RATIOS DECREASED AT DIETARY LYSINE LEVELS HIGHER THAN 0.86%. LIVER PROTEIN/DNA AND RNA/DNA DECREASED PROGRESSIVELY WITH INCREASED DIETARY PROTEIN AND LYSINE AT 14 DAYS OF AGE AND INCREASED AT 28 DAYS. LIVER PROTEIN/RNA RATIO AT BOTH 14 AND 28 DAYS WAS CONSTANT AND INDEPENDENT OF LYSINE INTAKE INDICATING THAT RNA IS CORRELATED WITH PROTEIN BIOSYNTHESIS. PROTEIN ACCUMULATION WAS DEPRESSED MORE SEVERELY IN BOTHTISSUES THAN DNA BY PROTEIN AND LYSINE DEFICIENCY. EXCESS DIETARY LYSINE DEPRESSED FEED INTAKE, CHICK GROWTH AND PROTEIN/DNA AND RNA/DNA IN BOTH TISSUES. THESE DEPRESSIONS WERE ALLEVIATED BY SUPPLEMENTARY ARGININE. HALF-LIFE OF 7.2, 4.9 AND 5.2 DAYS CORRESPONDING TO 10.4, 7.1 AND 7.5 DAYS TURNOVER TIME, AND 9.6, 14.0 AND 13.3% DAILY NET DEGRADATION WERE OBSERVED FOR LIVER PROTEINS AT 0.36, 0.86 AND 1.24% DIETARY LYSINE RESPECTIVELY. LIVER RATE OF PROTEIN SYNTHESIS WAS 20.0, 49.2 AND 52.9 MG./DAY RESPECTIVELY. THE TURNOVER RATES OF BOTH THE MUSCLE AND LIVER PROTEINS INCREASED IN A MANNER SIMILAR TO THE GAIN IN BODY WEIGHT WITH THE LEVELS OF DIETARY LYSINE. LYSINE DEFICIENCY DEPRESSED RNA SYNTHESIS IN THE LIVER MARKEDLY AND IN THE MUSCLE SLIGHTLY. LYSINE-U-¹⁴ C OXIDATION INCREASED WHILE RETENTION IN LIVER AND MUSCLE PROTEINS DECLINED WITH INCREASING DIETARY LYSINE. THREONINE-U-¹⁴C OXIDATION WAS INCREASED AND RETENTION DECREASED IN LYSINE DEFICIENCY AND TOXICITY. THE FOLLOWING CONCLUSIONS ARE EVIDENT FROM RESULTS OF THIS STUDY: (1) MUSCLE GROWTH IN THE CHICK IS BY AN INCREASE IN CELL SIZE AND NOT IN THE NUMBER OF CELLS FROM HATCH TO 28 DAYS OF AGE WHEREAS THE LIVER UNDERGOES RAPID CELL MULTIPLICATION DURING THE FIRST 14 DAYS AND LIVER GROWTH AT 28 DAYS IS MOSTLY BY CELL HYPERTOPHY. (2) PROTEIN DEFICIENCY INHIBITS CHICK GROWTH SEVERELY AND CAUSES A REDUCTION IN CELL SIZE WITH NO DEGENERATION OF CELLS. THE RESULT EXPLAINS WHY CHICKS UNDER SEVERE PROTEIN DEFICIENCY ACHIEVEA NORMAL SIZE WHEN REHABILITATED ON ADEQUATE PROTEIN DIETS. (3) ARGININE BECOMES LIMITING FOR TISSUE GROWTH WHEN EXCESS LYSINE IS PRESENT IN THE CHICK DIET. (4) TURNOVER RATE OF LIVER PROTEIN AND SYNTHESIS OF RNA IN LYSINE DEFICIENCY ARE CONSIDERABLY LOWER THAN NORMAL. (5) A LARGE PROPORTION OF LYSINE IS USED FOR PROTEIN SYNTHESIS WHEN PRESENT IN SUBOPTIMAL AMOUNTS. INCREASED OXIDATION OF THE CARBON SKELETON TO CO₂, OCCURS AS THE DIETARY SUPPLY EXCEEDS THE ANIMAL NEEDS FOR PROTEIN SYNTHESIS. LIMITED PROTEIN SYNTHESIS CAUSED BY A LIMITATION IN DIETARY LYSINE RESULTS IN A LOSS OF THREONINE WHEREAS WITH ADEQUATE LYSINE, PROTEIN SYNTHESIS UTILIZES A LARGE PROPORTION OF DIETARY LYSINE AND THREONINE, THEREBY REDUCING THE AMOUNTS OF THREONINE AVAILABLE FOR OXIDATION. (6) CELLULAR DNA, RNA AND PROTEIN CONTENT ARE USEFUL PARAMETERS FOR EVALUATING DIETARY PROTEINS AND THE NUTRITIONAL STATUS OF THE AN IMAL.

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