Reproductive performance, metabolism and oxidative stress profile in Chinese yellow-feathered broiler breeder hens fed multiple levels of isoleucine.

1. This experiment was conducted to evaluate the effects of dietary isoleucine (Ile) on reproductive performance and certain indices of metabolism and oxidative stress in Chinese yellow-feathered broiler breeder hens.2. A total of 600, 40-week-old Chinese yellow-feathered broiler breeder hens were fed a basal diet formulated with maize, corn gluten meal and spray-dried blood cell meal containing 3.3 g/kg Ile, or supplemented to contain 4.5, 5.7, 6.9, or 8.1 g/kg Ile for five weeks. Each dietary treatment had six replicates with 20 birds per replicate. After three weeks of receiving the trial diets, 24 eggs were collected at random from each replicate to measure egg quality. Starting after four weeks of treatment, 50 settable eggs per replicate were collected for 7 d in succession for hatching. After five weeks of being fed the treatment diets, birds were slaughtered for tissue and organ collection.3. For the overall period, laying rate, egg weight, egg mass and hatchling weight linearly (P < 0.05) and quadratically (P < 0.05) increased with dietary Ile levels. Final body weight, feed intake and relative liver weight of birds fed 3.3 g/kg Ile was lower compared to birds fed the other diets (P < 0.05). There was no effect of Ile level on egg quality (P > 0.05). Hatchling weight was linearly (P < 0.05) and quadratically increased (P < 0.05) in line with dietary supplemental Ile.4. After three weeks on the trial diets, birds fed the diet containing 3.3 g/kg Ile had decreased blood TG concentrations compared to breeders fed 6.9 or 8.1 g/kg Ile (P < 0.05). Activities of CK were significantly higher in breeders fed the 3.3 g/kg Ile diet compared to all other levels of dietary Ile after five weeks of treatment. A quadratic effect (P < 0.05) was evident for glucose at 8.1 g/kg Ile level. After five weeks of treatment, plasma TG concentrations in birds fed 3.3 g/kg Ile were significantly lower than in birds fed all other levels of Ile. Glucose concentrations in breeder hens receiving the 3.3 g/kg Ile diet were lowest and the highest concentrations were in birds fed 5.7 g/kg Ile (P < 0.05). Plasma activities of LDH were highest in breeders on the 3.3 g/kg Ile diet but were only significantly different (P < 0.05) for birds fed 5.7 g/kg Ile.5. The current study indicated that Ile deficiency decreased reproductive performance and appeared to serve as a stressor. The optimal dietary Ile for Chinese yellow-feathered broiler breeder hens in the laying period was 5.79 g/kg feed (0.75 g/d).