The main objective of this study was to investigate the effect of season and dietary L-carnitine (LC) supplementation on productive and reproductive performance of local duck breeds. A total number of 285 Domyati ducks (225 ducks and 60 drakes), 25-wk-old were taken for each experimental season (winter and summer). Ducks were weighed, divided into five experimental groups and fed diets supplemented with different LC levels (0, 150, 300, 450 and 600 mg/kg diet) during the experimental period (25-41 weeks of age) for each season.
Results indicated that some studied productive traits such as egg number (EN), egg mass (EM) and feed consumption (FC) were significantly decreased for ducks reared in summer than those reared in winter season. Moreover, dietary LC supplementation resulted in a significant improvement in EN, EM, FC and feed conversion ratio as compared to the control group during the period of 25-41 weeks of age. Reproductive traits such as egg fertility and hatchability (%) as well as semen quality parameters ( ejaculate volume, sperms concentration and mass motility) were significantly decreased for ducks reared in summer season than winter, while these parameters were significantly improved by dietary LC supplementation as compared to the control. Blood hemoglobin (HB) and lymphocytes (L) cells (%) were significantly decreased, while white blood cells (WBC) and heterophils (H) cells (%) were significantly increased for ducks reared in summer season than winter. However, supplementing LC with 300 up to 600 mg/kg diet significantly increased HB and L cells (%), while it decreased H cells (%) and H/L ratio than the control. Serum triglycerides, total cholesterol levels and liver enzyme activities (ALT&AST) were significantly higher for ducks reared in summer than winter season, whereas, these parameters were significantly decreased by dietary LC supplementation except for serum triglycerides. All nutrients digestibility coefficient, total digestibility of nutrients and metabolizable energy (ME kcal/kg) were significantly decreased for ducks reared in summer than winter season except for nitrogen free extract, whereas, all pervious parameters were improved with or without significant effect by dietary LC supplementation. Feeding economic efficiency and net return were significantly improved for ducks reared in summer season and dietary LC supplementation as compared to the control.