Residual feed intake in pigs is associated with organ weight, nutrient digestibility and intestinal nutrient transporter gene expression

Abstract Text:

Increases in nutrient digestibility mediated by changes in intestinal nutrient transporter gene expression could possibly explain the differences in efficiency between animals differing in residual feed intake (RFI). The objective of this study was to examine the effect of divergent selection for RFI on organ weights, nutrient digestibility and intestinal nutrient transporter gene expression in pigs. Male pigs  (n=75; initial BW 22.4 kg were fed a standard finishing diet (8.3 g/kg lysine and 16.4 MJ/kg gross energy) for 43 days to evaluate feed intake and growth for the purpose of calculating RFI. Phenotypic RFI was calculated as the residuals from a regression model regressing DMI on ADG and midtest BW^0.75(MWT). Data was analysed using the GLM procedure of SAS. On day 43, 16 animals (average weight 85kg sem 2.84kg), designated as 8 high RFI (HRFI) and 8 low RFI (LRFI) were slaughtered and digesta from the ileum and rectum were collected for the purpose of calculating the coefficient of apparent ileal (CAID) and total tract nutrient digestibility (CATTD). Tissue was collected from the jejunum, duodenum and ileum for the purpose of examining intestinal nutrient transporter gene expression. As expected LRFI pigs had lower ADFI (2.44kg vs. 1.87kg, sem 0.07) and improved feed conversion ratio (1.96 vs. 2.48) than HRFI pigs (P<0.001) with no difference in ADG or MWT. When comparing weights of organs between RFI groups, HRFI pigs had increased weight of heart and visceral organs (P<0.05) compared to the LRFI. There was a linear positive correlation between RFI and weight of large intestine (r=0.57; P<0.05). For the digestibility parameters measured RFI was negatively correlated with CATTD of nitrogen (N) (r=- 0.46; P<0.05) and GE (r= -0.51; P<0.05). RFI was negatively correlated with the intestinal glucose transporters SGLT1 (r=-0.56; P<0.05) and GLUT2 (r=-0.44; P=0.09). LRFI pigs had increased CAID of gross energy (GE) than HRFI pigs (P<0.05). Similarly LRFI pigs had improved CATTD of GE, while also having improved digestibility of nitrogen (N) and dry matter (DM). LRFI pigs had higher gene expression of the fatty acid transporter FABP2 (P<0.01) and glucose transporters SGLT1 (P<0.05) and GLUT2.  In conclusion differences in nutrient digestibility, intestinal nutrient transporter gene expression and differential organ weight are possibly some of the biological processes responsible for differences in feed efficiency in pigs.    

Keywords:

Residual Feed Intake: Nutrient Transporter Gene Expression: Pigs