Effects of metabolizable energy and crude protein levels on laying performance, egg quality and serum biochemical indices of Fengda-1 layers

This study was conducted to investigate the effects of dietary ME and CP levels on laying performance, egg quality and serum biochemical indices of Fengda-1 layers. In a 2 × 3 factorial arrangement, 2,400 Fengda-1 layers (32 wk of age) were randomly assigned to 6 experimental diets with 2,650 and 2,750 kcal of ME/kg of diet, each containing 14.50%, 15.00% and 15.50% CP, respectively. Each dietary treatment was replicated 5 times, and feed and water were provided ad libitum. The trial lasted for 10 wk, including a 2-week acclimation period and an 8-week experimental period. Our results showed that ADFI decreased as the ME level of diet increased from 2,650 to 2,750 kcal/kg (P < 0.05). Layers fed diets with 2,750 kcal/kg ME exhibited higher mortality than those fed with 2,650 kcal/kg ME (P < 0.05). Birds fed with 14.50% and 15.00% CP had higher egg production (EP) and egg mass (EM) than those fed with 15.50% CP (P < 0.05). Yolk color increased as the ME level of the diet increased from 2,650 to 2,750 kcal/kg, however, the eggshell thickness decreased (P < 0.05). Serum concentrations of uric acid and triglyceride in layers fed diets with 2,750 kcal/kg ME were higher than those fed diets with 2,650 kcal/kg ME (P < 0.05). There was no significant interaction between ME and CP on laying performance, egg quality, or serum biochemical indices (P > 0.05). Based on the data under the experimental conditions, the optimal dietary ME and CP levels of Fengda-1 layers are 2,650 kcal/kg and 15.00% (33 to 41 wk of age).