Influence of dietary L-carnitine and lysine–methionine levels on reproductive performance and blood metabolic constituents of breeder ducks

The present study aimed to evaluate the influence of dietary supplementation of different levels of L-carnitine and/or lysine–methionine (Lys-Met) on reproductive performance of breeder ducks. Three L-carnitine (0, 75 and 150 mg/kg) and three lysine–methionine (100%, 110% and 120% above the NRC (Nutrient requirements of poultry, 1994, National Academy Press) recommendations) levels were fed to 180 breeder ducks (144 females and 36 males) in a completely randomized design for 49 days. Laying performance and reproductive traits were evaluated; additionally, uric acid, total protein total, triglycerides, total cholesterol, low-density lipoprotein, high-density lipoprotein, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were assessed. The Lys-Met above 100% NRC (Nutrient requirements of poultry, 1994, National Academy Press) recommendations with or without L-carnitine improved feed utilization (p <.05). Furthermore, Lys-Met above 100% recommendations without L-carnitine improved egg fertility and hatchability. Fertility and hatchability improved in breeders fed on L-carnitine with 120% Lys-Met (p <.05). Serum glucose increased and total cholesterol reduced on 100% Ly-Met without L-carnitine or 110% Ly-Met with 150 mg L-carnitine (p <.05). Glucose was reduced, while total cholesterol increased on 75 mg L-carnitine and 100% Lys-Met (p <.05). Increasing Lys-Met without L-carnitine reduced serum protein (p <.05). Albumin and ALT increased on 75 mg L-carnitine–100% Lys-Met and reduced on 150 mg L-carnitine–120% Lys-Met (p <.05). There were no interaction effects on globulin, uric acid and AST (p >.05). Thus, based on findings, breeder ducks responded to dietary Lys-Met more efficiently than L-carnitine; however, more research is needed to evaluate also economic aspects related to L-carnitine dietary supplementation.