Sexual behaviour and fertility in broiler breeder domestic fowl

Abstract

An experiment was designed to investigate the reasons for the decrease in fertility which commonly occurs in broiler breeder domestic fowl in the later part of the laying year. Male broiler breeders were penned individually with 15 females and fed separately from them at various levels of energy, in order to attain different target body weights, and at two levels of protein. Sexual behaviour and fertility were recorded at 28, 38 and 58 weeks of age. The frequency of all sexual behaviour showed a large decrease with age which was suggestive of a decline in libido. There was also a significant effect of body weight, with heavier cocks showing more sexual displays and slightly more matings. Level of protein had little effect on sexual behaviour and fertility. Cocks which were more severely restricted showed a reduction in fertility and libido in Weeks 38 and 58. The decline in libido was not enought to account for reduced fertility in heavy cocks at 58 weeks and it was concluded that this was most probably a consequence of the large bulk or the conformation of the males at this age interfering in some way with the transfer of semen during copulations which otherwise looked normal.