Effects of adding methionine in low-protein diet and subsequently fed low-energy diet on productive performance, blood chemical profile, and lipid metabolism-related gene expression of broiler chickens.

This study was conducted to evaluate the effects of supplementing methionine (Met) in a low-protein (Low-CP) diet during d 11 to 24 and subsequently feeding with a low-metabolizable energy diet (Low-ME; -75 kcal/kg) or a normal ME diet during d 25 to 42 on the productive performance, blood chemical profile, and lipid metabolism-related gene expression of broiler chickens. The 1,600 broiler chicks were divided into 5 groups as follows: 1) Normal CP, then Normal ME; 2) Low-CP, then Normal ME; 3) Low-CP, then Low-ME; 4) Low-CP+Met, then Normal ME; and 5) Low-CP+Met, then Low-ME. During d 11 to 24, the growth performance of the control group was better than those of the other groups (P < 0.01). In Low-CP diets, the addition of Met resulted in an improvement in the growth performance, breast meat yield, protein conversion ratio, plasma total protein, and albumin (P < 0.01). Moreover, the supplementation significantly increased the plasma triglyceride content (P < 0.01). Feeding Low-CP or Low-CP+Met diets increased the abdominal fat content compared to the control group (P < 0.01). Feeding the Low-CP+Met, then Normal ME (d 25 to 42) resulted in compensation in the feed conversion ratio (FCR), protein conversion ratio, and energy conversion ratio equal to or better than the control group (P < 0.01). The body weights of birds fed Low-CP diets were still inferior to the control group (P < 0.01), except in the Low-CP+Met group followed by the normal ME diet. Feeding with the Low-ME diet tended to decrease the expression of the carnitine palmitoyl transferase I gene in the liver (P = 0.08). In conclusion, supplementing Met in the Low-CP diet during the grower period and subsequently feeding with a control diet improved the feed and protein conversion ratios, reduced fat accumulation, and reduced the production cost of broiler chickens with regard to fat deposition compared to the control diet.