Combining feed restrictions and photoschedules in broiler breeders

Abstract

Adult broiler breeders tend to gain too much weight and put on excess fat. Therefore they must be submitted to feed restrictions to allow the expression of their reproductive potential at an economical feed-to-chick ratio. However, in adult cockerels previously fed ad libitum, such restrictions can decrease or even stop the sperm production within a few weeks. Restricted feeding during growth can delay the testicular development but does not prevent the cockerels from recovering a high sperm production some weeks after they are returned to an ad lib regime. But they tend to overeat and therefore rapidly recover too much weight and fat. Feed restrictions of cockerels must therefore be applied all over their life. This is feasible even in the case of natural mating, using a dual-feeding system for males and females. Increasing the daily photoperiod from 16 to 22 weeks of age can compensate the delay in sexual maturity. But maintaining the cockerels under long days induces a sharp decrease in the sperm production thereafter. Such a decrease does not occurs or occurs very slowly, when restricted cockerels are maintained under short days. The sperm production starts later then, but it also maintained at a high level if the cockerels are restricted from the 2nd week post hatching. This production starts earlier, but remains at a lower level in cockerels restricted later, from 6 weeks of age onwards. These results are particularly interesting in the case of artificial insemination because they allow to use no more than 1 cockerel per 100 hens. The reduction in the number of cockerels allows to use only those having the highest ability to transmit to their offspring a high growth rate and a good body conformation.