End-of-Season Carcass and Reproductive Traits in Original and Replacement Male Broiler Breeders

Reproductive efficiency of male broiler breeders declines toward the end of a production cycle. It is common to add young, replacement males (spiking) to a breeder flock to maintain or increase fertility. To date, no study has reported if there are differences in the carcass and reproductive morphology between original and spiked males at the end of the breeding period. In this study, the weight, fleshing traits, footpad condition, and testes size of 327 Hubbard males (237 original and 90 replacement) from a commercial operation were examined. The original birds (63 wk of age) had significantly higher BW, breast weight, girth measurement, keel length, and spur length than the spiked males (48 wk of age). While external indicators of size and fleshing differed betweenreplacement and original roosters, testis weight was not affected by the age of the bird. It was found that average testis weight correlated well with BW in birds in which testicular regression had not taken place but only weakly with spur length. Because original males had a higher BW and were more heavily fleshed than replacement males, their ability to successfully complete matings may have been impeded. Further research is needed to link growth profiles with semen quality, sexual behavioral, and longevity of a male breeder in a commercial flock.