LAUSR

The present study investigated the effect of optimizing the total dietary arginine-to-lysine ratios on metabolism of lactating sows and piglet performance by supplementation with L-arginine (Arg) during lactation. A total of 200 multiparous sows (3 to 6 parities, Yorkshire × Landrace) were selected and randomly and equally assigned to 5 groups in lactation, and finally 36, 34, 35, 36, and 33 dams completed the study in the dietary treatments, respectively, where the diets consisted of 5 step-up Arg-to-Lys ratios (0.9, 1.0, 1.1, 1.2, and 1.3) by the addition of 0, 0.10%, 0.20%, 0.30%, 0.40% Arg. The diets contained 3.37 to 3.38 Mcal of DE/kg energy, 17.73% to 17.75% crude protein (CP) and 0.98 to 1.01% Lys, and were fed ad libitum during lactation. The performance of sows and sucking piglets was measured, and plasma and milk samples were collected for analysis. The feed intake of sows as well as litter weight gain during lactation increased linearly (P ≤ 0.05) while maternal backfat and milk composition were not affected (P > 0.05) as the dietary Arg-to-Lys ratios increased. Analyzed plasma biochemical indices, including concentrations of free Arg, Orn and Glu, and prolactin, insulin, and follicle-stimulating hormone (FSH) responded linearly (P ≤ 0.05) to increases in dietary Arg-to-Lys ratios. The dietary Arg-to-Lys ratios of 1.01 and 1.02 were optimal for maternal feed intake and litter weight gain, based on broken-line models. Collectively, the results of this study indicate increasing total dietary Arg-to-Lys ratios in lactation was beneficial for the performance of lactating sows and sucking piglets, and dietary Arg-to-Lys ratios of 1.01 and 1.02 were optimal, from regression analyses, for the practical feeding of lactating sows.