Effect of the timing of posthatch feed restrictions on the deposition of fat during broiler breast muscle development.

The effect of the timing of posthatch feed restriction on adipose deposition and adipogenic gene expression in the broiler pectoralis major muscle was studied by applying a 20% feed restriction either the first or second week after hatch. Broiler chicks at hatch were divided into a full-fed (control) group and a 20% feed restriction group. The expression of adipogenic genes, peroxisome proliferator-activated receptor gamma (PPARγ), and CCAAT/enhancer-binding protein alpha (C/EBPα) were measured. The expression of both PPARγ and C/EBPα was affected by the wk 1 feed restriction with expression significantly increased during the first week posthatch. The deposition of fat within the pectoralis major muscle was affected by the timing of the feed restriction. Extensive fat depots were present by 27 d of age in the pectoralis major muscle of the wk 1 restricted group compared with the control. Fat deposition was eliminated when the 20% feed restriction occurred in wk 2. Taken together, these results demonstrate that the timing of early posthatch feed restrictions in chicks is critical in the deposition of fat in the pectoralis major muscle and expression of adipogenic genes.