Pigs that are divergent in feed efficiency, differ in intestinal enzyme and nutrient transporter gene expression, nutrient digestibility and microbial activity

Abstract

Feed efficiency is an important trait in the future sustainability of pig production, however, the mechanisms involved are not fully elucidated. The objective of this study was to examine nutrient digestibility, organ weights, select bacterial populations, volatile fatty acids (VFA's), enzyme and intestinal nutrient transporter gene expression in a pig population divergent in feed efficiency. Male pigs (n = 75; initial BW 22.4 kg SEM 2.03 kg) were fed a standard finishing diet for 43 days before slaughter to evaluate feed intake and growth for the purpose of calculating residual feed intake (RFI). Phenotypic RFI was calculated as the residuals from a regression model regressing average daily feed intake (ADFI) on average daily gain (ADG) and midtest BW 0.60 (MBW). On day 115, 16 pigs (85 kg SEM 2.8 kg), designated as high RFI (HRFI) and low RFI (LRFI) were slaughtered and digesta was collected to calculate the coefficient of apparent ileal digestibility (CAID), total tract nutrient digestibility (CATTD), microbial populations and VFA's. Intestinal tissue was collected to examine intestinal nutrient transporter and enzyme gene expression. The LRFI pigs had lower ADFI ( P < 0.001), improved feed conversion ratio ( P < 0.001) and an improved RFI value relative to HRFI pigs (0.19 v. −0.14 SEM 0.08; P < 0.001). The LRFI pigs had an increased CAID of gross energy (GE), and an improved CATTD of GE, nitrogen and dry matter compared to HRFI pigs ( P < 0.05). The LRFI pigs had higher relative gene expression levels of fatty acid binding transporter 2 ( FABP2) ( P < 0.01), the sodium/glucose co-transporter 1 ( SGLT1) ( P < 0.05), the glucose transporter GLUT2 ( P < 0.10), and the enzyme sucrase-isomaltase (SI) ( P < 0.05) in the jejunum. The LRFI pigs had increased populations of lactobacillus spp. in the caecum compared with HRFI pigs. In colonic digesta HRFI pigs had increased acetic acid concentrations ( P < 0.05). Differences in nutrient digestibility, intestinal microbial populations and gene expression levels of intestinal nutrient transporters could contribute to the biological processes responsible for feed efficiency in pigs.

Finishing pigs that are divergent in feed efficiency show small differences in intestinal functionality and structure

“…In the present study, however, we did not observe differences in the jejunal expression of nutrient transporters SGLT1 and MCT1 between RFI groups. In considering that Vigors et al [3] sampled the proximal jejunum (60 cm from the stomach), whereas in the present study we collected mucosal samples from the distal part of the jejunum, this may explain the contrasting observations between the previous and the present study.…”

“…In fact, we found a greater activity of maltase, sucrase and lactase at the duodenal brush border in low RFI pigs than in high RFI pigs but only in those from AT, although pigs from all locations were in the early postprandial state at slaughter. Vigors et al [3] also observed a greater expression of sugar transporters SGLT1 , GLUT2 and fatty acid transporter FABP2 in the jejunum together with an enhanced apparent total tract digestibility of dry matter, nitrogen and gross energy in low versus high RFI pigs. In the present study, however, we did not observe differences in the jejunal expression of nutrient transporters SGLT1 and MCT1 between RFI groups.…”

“…Due to this RFI-related variation in the duodenal morphology, we investigated if a diverging digestive capacity was also expressed in the activity pattern of digestive enzymes in the duodenum. Since Vigors et al [3] previously found an increased jejunal expression of sucrase-isomaltase in low versus high RFI pigs but not of proteases, we focused mainly on mucosal disaccharidases. In fact, we found a greater activity of maltase, sucrase and lactase at the duodenal brush border in low RFI pigs than in high RFI pigs but only in those from AT, although pigs from all locations were in the early postprandial state at slaughter.…”

“…Previous findings for RFI-related differences in GIT size, innate immune response and digestive efficiency in pigs were equivocal [2–5, 12,13]. Some studies reported an enhanced ileal digestibility of energy and expression of SGLT1 and GLUT2 in the jejunum of growing pigs [3,14], whereas other did not find RFI-related differences for digestive efficiency [2,12]. Likewise, gene expression data indicated that the ileal mucosal tight-junction-protein expression and innate immune signaling pathways may play a minor role for variation in RFI of pigs in an unchallenged condition [4,5].…”

Exploring a Possible Link between the Intestinal Microbiota and Feed Efficiency in Pigs

“…It demonstrated an increased abundance of Lactobacillus in the cecum of more feed-efficient pigs; however, only Firmicutes, Bacteroidetes, Bacteroides, Lactobacillus, and Enterobacteriaceae were measured (by quantitative PCR). Pigs with better FE also tended to have higher concentrations of total VFAs in the cecum and butyric acid in the colon, which may be explained by differences in microbial composition and function (14,23).…”