Reproduction in male broiler breeders
McGovern, Ruth Helen
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Male broiler breeders are feed restricted to achieve BW targets designed to maintain high and persistent semen quality and quantity resulting in high fertility. Experiments were conducted to examine the effects of (1) BW gain and loss at photostimulation on the carcass, external, and reproductive ability of caged males, (2) BW loss, from 35 wk of age, on the reproductive ability of caged males, and (3) rearing BW on mating behavior and fertility in a flock. (1) Male broiler breeders were assigned to one of four rearing feeding treatments at 1 d of age; standard (SF) (recommended BW profile), plus 15% (P15) (BW approximately 15% heavier that the SF), plus 30% (P30), and full fed (FF). External characteristics including, head width, comb height, chest width, keel length, and shank length increased with feeding level during rearing. Full fed males endured a short period of weight loss prior to production that resulted in a lower testis weight without negatively impacting the semen volume, concentration, or sperm motility. (2) Males were subjected to a BW loss from 35 wk of age, late loss (LL). Standard gain (SG) treatment males were reared to 62 wk following BW recommendations. In the LL treatment, the BW loss resulted in a 14.7% lower fertility from eggs 8-14d post-insemination compared to the SG treatment at 58 wk of age. Semen volume and concentration were not negatively affected by a BW loss. (3) Males were selected by intrinsic BW; low (2133 g), average (2624 g), and high (3100 g). Low and average BW males were subjected to a rapid (LR ans AR, respectively) increase in BW. Average standard (AS) and high standard (HS) males followed recommended BW. At 28 wk of age, high constant (HC) and high slow (HW) males had constant and minimal BW gain, respectively. At 26 wk of age, male BW was negatively correlated to the number of females in the scratch area (r=0.-65). At 54, 58, and 62 wk, the HC males had lower fertility compared to the HS treatment by 3.8, 9.6, and 7.5%, respectively. Males benefit from a consistent and gradual increase in BW.