Performance of broiler breeder males given low protein feed.

One hundred and eight 24-wk-old broiler breeder males were arranged into 18 groups of six birds of equal average BW. Six groups were killed for carcass evaluation at 24 wk of age; the other 12 groups were divided between two dietary treatments. One treatment was a typical breeder-recommended male broiler breeder ration (standard, or ST; 12% CP, 3,160 kcal ME/kg), whereas the other was a low-protein, corn-based diet (all corn, or AC; 8% CP, 3,220 kcal ME/kg) formulated to approximate minimum amino acid requirements for positive nitrogen balance. All birds were fed at a rate of 325 kcal ME/day per bird to 68 wk of age. Body weight, semen volume, and sperm concentration were evaluated weekly. All birds remaining at 68 wk were killed for carcass evaluation. Feed and age effects on BW were highly significant (P less than .001). However, birds did not respond similarly to treatments with increasing age. Birds fed ST were heavier and surpassed breeder-recommended BW by 38 wk of age, whereas birds given AC were lighter and remained below breeder-recommended weights throughout the study. Semen production was measured by semen volume, sperm concentration, total sperm yield, and proportion of males producing semen; values were similar for treatments at all ages. Birds given the AC feed had more carcass fat than ST-fed birds at 68 wk of age, but ST-fed birds had the same proportion of fat at 68 wk as birds killed at 24 wk. Results suggest that the amino acid levels provided by the AC diet were less than adequate for optimal BW gain, but adequate for semen production.