Selecting broilers for low or high abdominal fat : observations on the hens during the breeding period

Laying hens of a lean line (LL) and a fat line (FL) were compared for laying performance, feed consumption, carcass composition and some plasma parameters.Both lines exhibited the same egg output and the same age at sexual maturity.The LL hens laid larger eggs with a significantly lower percentage of yolk.The LL hens were always heavier than FL ones although the abdominal fat was always higher in the FL.The body weight gain during the laying period was not significantly different between the lines.Both lines presented the same energy maintenance and feed efficiency for egg synthesis.The feed requirement for body weight gain was more pronounced in the FL birds but the difference was not significant.As in the immature birds, a different glucose-insulin balance was observed between lines.It is concluded that this persisting metabolic deviation may explain the tendancy of the FL to preferentially use feed energy for lipid synthesis of yolk or adipose tissue.