Effects of dietary energy on semen production, fertility, plasma testosterone, and carcass composition of broiler-breeder males in cages.

One hundred-fifty broiler breeder males were raised to 17 wk of age in floor pens using standard procedures. The males were placed in individual cages at 18 wk of age in an environmentally controlled house and fed for recommended BW to 29 wk of age. At 30 wk of age, birds were randomly assigned to one of five dietary treatments. Diets consisted of 10% CP and 1,600, 2,000, 2,400, 2,800, or 3,200 kcal ME/kg feed (Groups 1600, 2000, 2400, 2800, and 3200, respectively). Birds were ejaculated twice weekly; semen characteristics, BW, and serum testosterone (T) were determined every 4 wk. Fertility determinations were made at 38 and 48 wk. At the end of the experiment (60 wk of age), body composition was measured. The percentage of body fat was reduced in Groups 1600, 2000, and 2400. Body weight, percentage of males producing semen, semen weight (SW), total spermatozoa per ejaculate (TS), and T were all reduced in Groups 1600 and 2000; semen concentration (SC) was reduced in Group 1600, compared to the other treatments. Group 2400 had the highest percentage of carcass protein; Groups 1600 and 3200, the lowest percentage. Body weight, percentage of protein, and percentage of fat were quadratically related to dietary energy. The T, SW, SC, and TS were linearly and positively related to the energy level.