Abstract
The present study was carried out to study the effects of varying dietary DL-methionine (0, 0.5, 1.5, 2.5, and 3.5 g/kg) levels on the productive and reproductive performance, egg quality and blood biochemical parameters of quail breeders. In total, 150 mature Japanese quails at eight weeks of age were randomly allotted to five groups of 30 for each group. Each group included five replicates, each of six quails (four females and two males). The results showed that egg number, egg weight and egg mass were higher (p < 0.05) with the addition of all DL-methionine levels than that of the control group. Quails from the control group had a lower feed intake (p < 0.001) and a worse feed conversion ratio (FCR) than those from the DL-methionine-treated groups. Supplementation of DL-methionine up to 2.5 g/kg in quail diets increased fertility and hatchability percentages. Birds fed DL-methionine at 1.5 g/kg had the best egg production indices, better FCR and the highest values of fertility and hatchability. Egg weight, yolk %, Haugh unit, egg shape index and unit surface shell weight (USSW) were increased and eggshell % was decreased in quail supplemented with DL-methionine levels compared with the control quail (p < 0.05). Dietary DL-methionine levels did not affect (p > 0.05) the hemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs) and packed cell volume (PCV) of quails. DL-methionine levels (0.5 and 2.5 g/kg) augmented lymphocytes and basophile (p < 0.05). Low DL-methionine levels (0.5 or 1.5 g/kg) improved liver enzymes and kidney functions. Dietary DL-methionine levels (except 3.5 g/kg) declined serum lactate dehydrogenase (LDH) and decreased lipid profile parameters (except high-density lipoprotein-HDL). Supplementation of DL-methionine at 0.5 and 1.5 g/kg increased immunoglobulin (IgG, IgM and IgA) and superoxide dismutase (SOD), total antioxidant capacity (TAC), catalase (CAT) and reduced glutathione (GSH) (p < 0.001) compared with the control. In conclusion, dietary supplementation of DL-methionine (1.5 g/kg) can enhance the reproductive performance and egg quality of quail breeders. DL-methionine use at levels of 0.5 or 1.5 g/kg improved the liver and kidney functions, lipid profile, immunity and antioxidant parameters of Japanese quail.