Effects of dietary valine-to-lysine ratio on placenta growth, the placental nutrient transporters, and reproductive performance in sows

Context Valine-to-lysine ratio (V:L) in the diet has been found to affect the placental development of sows, and thus the production performance, but the mechanism is still unclear. Aim To investigate the effects of the V:L on placental growth and reproductive performance of sow. Methods Twenty-seven sows (average parities = 5) from 85 days of gestation were randomly assigned into five experimental groups with five ratios of total V:L of 0.75:1, 0.87:1, 0.99:1, 1.11:1, 1.23:1. Litter size was recorded. The placenta and colostrum were collected immediately after farrowing for mRNA analysis. Key results The results showed that dietary valine increased the sows’ placental area and the fetal-to-placental weight ratio (P < 0.05). Dietary valine does not affect the litter size of sows, but significantly reduces the delivery time and accelerates the delivery process. Dietary valine improved the average daily feed intake of the sows in the lactation (P < 0.05) and decreased the number of stillborns (P < 0.05). Additionally, the placental gene expression of LAT1, 4F2hc, LAT2, LAT3, SNAT1, SNAT2, and SNAT4 increased in the groups whose diet contained higher V:L ratios (P < 0.01). The increase in the ratio of dietary V:L increased the expression of GLUT1, GLUT3 and GLUT4 genes in the placenta tissue (P < 0.01). Conclusions The results suggested that suitable V:L positively affects pregnant and lactating sow’s performance. Implications Therefore, V:L can be adjusted to promote sow reproductive performance and increase production efficiency.