Controlled energy restriction and ad libitum feeding of broiler breeder males and their influence on weight gain, carcass traits, meat composition, testis weight and bone parameters at different age intervals during grower phase

The present study was intended to quantitatively restrict energy (ME) allowances in broiler breeder males and regulate their weight gain (WG) during rearing period (5–20 wk). Five feeding regimes were tested for the purpose, which included: 1. Controlled energy restriction (CER), constituted by calculating the ME required for maintenance, activity and growth targeting 100 g increase in BW/wk. Measured quantity of grower diet (160 g protein and 2600 kcal ME/kg) was offered to CER group, which increased with age from145 to 304 kcal/d. 2. In addition, two regimen were employed by either severely restricting energy (SER) by 20% (182 kcal/d) or moderately restricting (MER) by 10% (205 kcal/d) over CER (228 kcal/d) and in the fourth group 10% excess ME (EEF) (251 kcal/d) was offered. A fifth group was fed ad libitum (437 kcal/d) for comparison with ME restricted regimen. Results indicated that breeders raised on 20% ME restriction produced the targeted weight gain of 105 g/wk during the rearing period that was closer to the targeted BW. Further, the same regime supported higher tibia weight, bone mineralization and protein accretion with low fat in muscle, but with smaller testis at 20 wk of age compared to EEF and ad libitum fed breeders. It was possible that energy requirement under energy restriction was lesser than that anticipated. Age intervals (5–20 wk) exhibited significant impact on percent WG, which was higher between 5–8 wk across the ME restricted regimes compared to other age intervals. The differentiation in weights of abdominal fat pad and testis, tibia, bone mineralization and composition of muscle among the ME restricted groups occurred between 17and 20 wk, except for tibia weight at 12 wk. SER regime exhibited enhanced response of these parameters compared to other ME restricted regimen. In conclusion, the ME requirement of breeder males during rearing period was much lower (182 kcal/d) than that calculated (228 kcal/d) for achieving the targeted weight gain of l00g/wk, in broiler breeder males tested in our study. Age intervals during rearing period influenced the consistency of growth, bone mineralization and muscle composition in ME restricted groups, but not in those offered excess ME or ad libitum feeding warranting implementation of ME restriction