Abstract Feeding low protein (LP) diets to weanling pigs without supplementation of limiting amino acids reduces growth performance and alters fecal microbiota composition. This study evaluated tissue expression of metabolic and inflammatory genes, gut histomorphometry and microbial composition of pigs fed LP diets after weaning. One hundred and sixty piglets with an initial body weight of 5.8 ± 0.92 kg were randomly divided into 5 treatment groups (n = 8/group) in a randomized complete block design for a 42-day nursery trial. The diets included a normal crude protein (CP) positive control (PC) diet, a low CP negative control (NC) diet, NC supplemented with branched chain amino acids (BCAA; NC+BCAA), NC supplemented with 9 g/kg of dietary nucleotides (NC09), NC supplemented with both BCAA and 9 g/kg of dietary nucleotides (NC+BAA+09). On d 42, intestinal tissues were collected from one pig per pen to evaluate morphology and mRNA expression, and colonic digesta were collected to assess microbiome composition. Pigs fed the NC diet had decreased (P 0.05) villus height (VH), villus height-to-crypt depth ratio (VH:CD), villus perimeter (VP), and area (VA) relative to PC. The NC+BCAA+09 group showed intermediate values for these parameters, which were not different from either PC or NC. The NC+BCAA group had intermediate VH, VP and VA, whereas NC09 had VH that did not differ from PC or NC. Low protein diets without BCAA supplementation (NC and NC09) increased (P 0.05) jejunal mRNA expression of phosphoglycerate dehydrogenase (PHGDH), and NC increased (P 0.05) phosphoserine aminotransferase 1 (PSAT1) expression. In the liver, LP diets without BCAA increased (P 0.0001) tumor necrosis factor-alpha (TNFA) expression, while NC09 increased (P 0.0001) IL-1β expression. Additionally, NC, NC+BCAA, and NC09 increased (P 0.0001) hepatic IL-10 expression relative to PC and NC+BCAA+09. β-diversity analysis of microbial community structures showed distinct differences (P 0.05) between PC and NC diets, and between NC09 and NC+BCAA. At the phylum level, the relative abundance of Spirochaetes and Verrucomicrobia was higher (P 0.05) in the NC+BCAA treatment group relative to others. Also, genus Bifidobacterium was more abundant in the NC+BCAA and NC09 groups compared to others (P 0.05). There was greater abundance of Escherichia across all diets relative to NC, whereas Akkermansia was enriched in NC+BCAA relative to NC (P 0.05). These results suggest that supplementing LP diets with nucleotides and BCAA partially ameliorated the negative effects of protein restriction on growth by improving jejunal morphology, modulating metabolic and inflammatory responses, and altering gut microbiota composition.
Lawal et al. (Wed,) studied this question.
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