Effect of optimizing dietary valine-to-lysine ratio in late gestation or lactation on biochemical indices and performance of lactating primiparous sows

A study was conducted to investigate the effect of optimizing valine-to-lysine ratio by dietary supplement with valine (Val) in late gestation (starting on day 85) or lactation on biochemical indices and lactation performance. Sixty pregnant gilts (Yorkshire x Landrace) were randomly allocated to one of four treatments in a 2 x 2 factorial experimental design, where the factors were supplementation with L-Val (optimizing total valine: lysine to 0.87:1) or with L-alanine (Ala, isonitrogenous control) in late gestation and/or lactation. The diets contained 14.02 MJ of ME/kg energy and 203.1 g/kg to 203.3 g/kg crude protein (CP), were fed at 2 kg daily during late gestation and ad libitum during lactation. Feeding the Val-supplemented diet compared with control during late gestation improved the weaning body weight (BW) and of sucking piglets (P < 0.05), and a marked increase in maternal feed intake (P < 0.05); there were no differences in backfat loss, weaning-to-estrus interval (WEI) or biochemical variables. With Val-supplementation of the lactation diet, weaning SW of sucking piglets and BW gain of litters were greater than the controls (P < 0.05). Improvement of milk fat (day 7 to day 14 of lactation), milk protein (day 7 of lactation) and non-fat solids (day 7 to day 14 of lactation) were noted from the sows fed Val-supplemented diet during lactation (P < 0.05). On day 14 of lactation, plasma concentrations of free Val and prolactin in sows and concentrations of some free amino acids (AA) in milk were greater (P < 0.05), and plasma glucose was lower (P < 0.05), in response to Val supplementation during lactation. There was no gestation x lactation Val interaction on the performance of sows and their suckling piglets. Collectively, results indicate the beneficial effects of optimizing the total dietary Val: Lys to 0.87:1 in late gestation and lactation on improving the performance of lactating sows.