Effect of Feeding Regimen and Age on Lipid Metabolism in Broiler Breeder Hens and Progeny

Age of hens and feed allocation can affect egg yolk lipid compositions which in turn directly relate to chick quality. A series of experiments were conducted to determine the effects of age and feeding programs on lipid metabolism in breeder hens and progeny. In the first trial, the rate of yolk absorption and fatty acid profiles in the yolk were compared among 28, 35, and 49wk old hens. The results revealed that the rate of yolk absorption was higher, but the absolute amount of fatty acids absorbed was lower in young hens than in the old hens. The second trial was hypothesized that young breeder hens synthesis egg yolk lipids from amino acids. The results indicated that both glucogenic and ketogenic amino acids as well as glucose were used as a substrates for de novo lipogenesis (DNL) in young hens. The third experiment was set to compare the rate of DNL between young (28wk) and old (40wk) breeder hens as well as their progeny. The results suggested that the rate of DNL was higher in young hens than the old ones. At 7d of age, progeny from old breeder hens illustrated the higher rate of DNL than those chicks from the young hens. The fourth trial was conducted to determine the partitioning of lipids into adipose tissue of 7-day-old chicks. At hatch, yolk-derived lipid was the main lipid in adipose tissue, while the feed-derived and DNL lipids play a bigger role after hatch. The fifth trial was conducted to determine the effect of palmitic acid supplementation. Palmitic acid showed positive effect on hatchability at early phase of production cycle with increasing of monounsaturated fatty acids in fresh yolk. The last trial was set to test the effect of various feeding programs on egg production and progeny growth as well as economic traits. The slower feed increase before peak production with feed adding at peak, and the normal feed increases to peak production with feed adding at 35wk of age showed the best egg production (169 and 171 eggs/HH, respectively) and economic trait expressing as cost for producing a dozen of eggs ($1.21 and $1.22/dozen eggs), whereas the practical feed withdraw program showed the worst effects (148 eggs/HH and $1.29/dozen eggs)