Breeder hen dietary L-carnitine affects progeny carcase traits

(1) Ross 308 broiler breeder hens were given diets containing 0 or 25 mg L-carnitine/kg from 21 weeks of age. (2) Hens were inseminated with semen from Ross broiler breeder males and subsequent growth performance and carcase traits, of progeny obtained from hatches at 30, 35 and 37 weeks of age, were evaluated. (3) Progeny were hatched in a common facility and separated by gender. Experimental treatments employed for the 30-, 35- and 37-week hatches, respectively, were: hen diet and progeny gender (16 replications with two subplots); hen diet, progeny diet (0 and 50 mg L-carnitine/kg of diet) and progeny gender (16 replications with 4 subplots); and hen diet and progeny diet (high and low density; 16 replications with two subplots). (4) Females had lower growth rate and less breast meat, but greater proportions of carcase fat and breast meat than males. Growth performance measurements of progeny were not affected by hen L-carnitine, but hen L-carnitine decreased abdominal fat in progeny. Increasing diet density in the chick diets increased growth and carcase weights. Hen and progeny dietary L-carnitine interacted to increase male mortality. However, dietary hen L-carnitine decreased carcase fat and increased breast meat in progeny fed on high nutrient density diets. (5) In conclusion, L-carnitine in the diet of hens affected carcase traits of their progeny.     

Mitochondrial respiratory metabolism and performance of cattle

Two groups of cows were sampled to study variation of mitochondrial metabolism. The first group included 10 lactating and five gestating Holstein cows, representing available phenotypic extremes for milk yield. The second group included 13 Angus, 13 Brangus and 13 Hereford cows, representing available extremes within breeds for growth breeding value ratios. Consistently poor mitochondrial samples were obtained from gestating cows; these were excluded from analyses. Linear correlations of Holstein mitochondrial respiratory activities with sire-predicted difference for milk and milk fat ranged from -.35 to .15. Correlations of dam and cow indices and cow yields for milk with acceptor-stimulated mitochondrial respiration, oxidative phosphorylation efficiency (adenosine diphosphate:oxygen ratio [ADP:O ratio]) and adenosine triphosphate (ATP) synthesis rate were .25 to .48, consistently higher than for milk fat, -.06 to .17. No differences among beef breeds in mitochondrial respiration rates, coupling of respiration to phosphorylation, ADP:O ratio or ATP synthesis rate were detected by repeated measures analyses of variance. No patterns were evident among correlations of the mitochondrial characteristics and growth and milk traits in beef cattle. These initial findings indicate that variability in the mitochondrial respiratory activities measured has less relation to weaning and yearling growth traits of beef cattle than to milk yield of Holstein cattle.