Effects of Dietary Net Energy Concentration on Reproductive Performance, Immune Function, Milk Composition, and Gut Microbiota in Primiparous Lactating Sows

Abstract

This study aimed to determine the optimal dietary net energy concentration for the reproductive performance, immune function, milk composition, and gut microbiota of primiparous sows during lactation. Forty primiparous lactating sows (Landrace × Yorkshire) with similar body backfat thicknesses were randomly allocated into five treatment groups and fed diets with different dietary net energy concentrations of 10.05 MJ/kg, 10.47 MJ/kg, 10.89 MJ/kg, 11.30 MJ/kg, and 11.72 MJ/kg. The results showed that there were no differences in the performance of piglets, while there was a decrease in the daily feed intake of sows (p = 0.079, linear) as dietary net energy concentration increased. With the increasing dietary net energy concentration, the plasma insulin levels of sows increased (p < 0.01, linear), the plasma glucose levels tended to increase (p = 0.074, linear), and the blood urea nitrogen levels tended to decrease (p = 0.063, linear). Moreover, the plasma total superoxide dismutase activity of sows increased (p < 0.05, quadratic) and the plasma malondialdehyde content of sows decreased (p < 0.05, quadratic) by increasing the dietary net energy concentration. Interestingly, with the increase in dietary net energy concentration, the plasma immunoglobulin M content of sows increased, the milk immunoglobulin M, immunoglobulin G, immunoglobulin A and the percentage of milk fat increased (p < 0.05, linear), and the milk secretory immunoglobulin A content also increased (p < 0.05, linear and quadratic). The milk immunoglobulins and milk fat content of sows fed with net energy concentration of 11.72 MJ/kg were highest. Moreover, there were significant differences in the α-diversity, β-diversity, and relative abundance of gut microbiota in sows fed with different dietary net energy concentrations. At the phylum level, Spirochaetota and Bacteroidota in the gut microbiota of sows were mainly affected by increasing the dietary net energy concentration. Furthermore, the correlation analysis showed that milk immunoglobulin content had a significant negative correlation with the relative abundance of Bacteroidota, and plasma malondialdehyde content also had a significant negative correlation with the relative abundance of Spirochaetota. In summary, these results suggest that increasing the dietary net energy concentration to 11.72 MJ/kg can increase immunological substances in milk, improve milk quality, and alter the composition of gut microbiota in primiparous lactating sows.

Keywords: gut microbiota; immune function; milk composition; net energy; primiparous lactating sows; reproductive performance.

Figure 1

Effects of different dietary net energy concentrations on α-diversity and β-diversity of sows. (A) Results of alpha diversity. (B) Principal co-ordinates analysis (PCoA) plot visualizing among sample beta diversity of microbiota. (C) Non-metric multidimensional scaling (NMDS) plot visualizing among sample beta diversity of microbiota. Values are presented as means ± SEM, n = 6. Differences were assessed using Tukey’s test for multiple comparisons and denoted as follows: * means a significant difference (p < 0.05) and ** means a highly significant difference (p < 0.01).

Figure 2

Gut microbial composition of sows in different treatment groups. (A) Relative abundances of main taxa at different levels. (B) Relative abundances of differential microflora at different levels. (C) Ratio of Firmicutes to Bacteroidota of sows in different treatment groups. (D) Differences in abundance, returned by LEfSe analysis. Values are presented as means ± SEM, n = 6. Differences were assessed using Tukey’s test for multiple comparisons and denoted as follows: * means a significant difference (p < 0.05). ^a,b means without a common letter indicate a significant difference (p < 0.05).

Figure 3

Spearman’s correlation analysis of significantly differential gut microbiota with milk composition, milk immunoglobulins, plasma antioxidant levels, plasma hormone levels, and biochemical indices in sows (P- = phylum; C- = class; O- = order; F- = family; G- = genus). * means a significant correlation (p < 0.05) and ** means a highly significant correlation (p < 0.01).