Precise evaluation of the nutritional value of yeast culture and its effect on pigs fed low-protein diets

Abstract

The purpose of the present study was to assess the nutritional value of yeast culture (YC) and to explore the effect of YC on growth performance and health of piglets fed low-protein diets. In Exp. 1, 12 growing barrows were allocated into control diet and YC diet treatments to determine the available energy of YC. Results showed that the digestible energy and metabolizable energy of YC are 12.12 and 11.66 MJ/kg dry matter (DM), respectively. In Exp. 2, 12 growing barrows were surgically equipped with a T-cannula near the distal ileum and were assigned to 2 dietary treatments (nitrogen-free diet and YC diet), and the amino acid digestibility of YC was determined. In Exp. 3, a total of 96 weaned piglets were randomly divided into 4 treatments, including low-protein basal diet (Basal), Basal + 0.5% YC (0.5%YC), Basal + 1.0% YC (1.0%YC), and Basal + 1.5% YC (1.5%YC). The results were as follows: YC supplementation linearly improved the weight gain and feed intake ratio (P < 0.001), linearly increased the activity of glutathione peroxidase on d 14 (P = 0.032) and linearly decreased the concentration of malondialdehyde on d 14 (P = 0.008) and d 32 (P = 0.004) in serum, and linearly decreased the concentration of total short-chain fatty acid on d 14 in feces (P = 0.045). Compared with other treatments, 1.5%YC group showed a greater abundance of various probiotics, such as Prevotellaceae, Prevotella and Turicibacter. In Exp. 4, twelve growing barrows with an ileal T-cannula were randomly assigned to Control and 1.5%YC treatments to clarify the impact of YC supplementation on nitrogen balance and nutrient digestibility. Results showed that YC had no significant effect on nitrogen efficiency and nutrient digestibility, except for trend of reducing the total tract digestibility of organic matter (P = 0.067). In conclusion, the present study assessed the digestible and metabolizable energy values (12.12 and 11.66 MJ/kg DM, respectively) and standardized ileal digestibility of amino acid (from 43.93% to 82.65%) of YC in pig feed and demonstrated that moderate supplementation of YC (1.5% of diet) can effectively improve feed conversion efficiency, enhance antioxidant capacity, and promote a balanced gut microbiota in piglets.

Keywords: Available energy; Digestible amino acids; Low-protein diet; Pig; Yeast culture.

Fig. 1

Fecal bacterial community at the phylum and genus levels of pigs fed a low-protein diet with different content of yeast culture (YC). Microbial community bar plot of phyla with an abundance of 0.015% or greater at 14 d (A), and at 32 d (C); microbial community bar plot of genus with a proportion of 0.015% or higher at 14 d (B) and at 32 d (D). Basal diet, 0.5%YC, 1.0%YC, 1.5%YC referred to supplementing with 0%, 0.5%, 1.0%, 1.5% YC in a low-protein diet.

Fig. 2

The α diversity of the fecal bacterial community of pigs fed a low-protein diet with different content of yeast culture (YC). Shannon index (A), Simpson index (B), ACE index (C), and Chao index (D) of the fecal bacterial community at 14 d; Shannon index (E), Simpson index (F), ACE index (G), and Chao index (H) of the fecal bacterial community at 32 d. Basal diet, 0.5%YC, 1.0%YC, 1.5%YC referred to supplementing with 0%, 0.5%, 1.0%, 1.5% YC in a low-protein diet. OTU = operational taxonomic units.

Fig. 3

Principal coordinate analysis (PCoA) of the microbiota from feces of pigs fed a low-protein diet with different content of yeast culture (YC). Principal coordinate analysis of treatment groups based on unweighted_unifrac analyses of bacterial communities at the operational taxonomic unit level. The distances between the symbols on the ordination plot reflect the relative dissimilarities in the community structures. Basal diet, 0.5%YC, 1.0%YC, 1.5%YC referred to supplementing with 0%, 0.5%, 1.0%, 1.5% YC in a low-protein diet. OTU = operational taxonomic units.

Fig. 4

LEfSe effect size results of the microbiota in fecal samples of pigs fed a low-protein diet with different content of yeast culture (YC). Histogram of the linear discriminant analysis scores computed for the differentially abundant features in the fecal bacteria between Basal, 0.5%YC, 1.0%YC and 1.5%YC treatments at d 14 (A) and at d 32 (C); the results of the comparison between each two treatments at d 14 (B) and at d 32 (D). The linear discriminant analysis bars indicate the microbial groups within treatments with linear discriminant analysis (LDA) scores higher than 2.0. The differentially abundant clades in each treatment are represented by colors in the cladograms, and the linear discriminant analysis scores of these clades indicate the degrees of statistical and biological differences. Basal diet, 0.5%YC, 1.0%YC, 1.5%YC referred to supplementing with 0%, 0.5%, 1.0%, 1.5% YC in a low-protein diet.