Jejunal Expression of Intestinal Growth-Promoting Genes in High and Low Efficiency Lambs

The objective of this study was to investigate the impact of diet type and feed efficiency status in growing lambs on jejunal expression of genes involved in small intestinal growth. Wethers (n = 77) of Rambouillet, Hampshire, and Suffolk breed types were randomly assigned to a concentrate-based (CONC; 50% corn and 31% wheat middlings; 12.1% CP, DM basis; n = 39) or a forage-based (FOR; 67.7% alfalfa and 27.5% wheat middlings; 16.2% CP, DM basis; n = 38) pelleted diet for 49 d. Residual feed intake (RFI) was estimated as the difference between actual and expected feed intake.  The 20% most (low RFI; n = 8) and 20% least (high RFI; n = 8) efficient lambs from each diet were slaughtered (n = 32). Mucosal samples from the jejunum were used to determine mRNA levels of glucagon-like peptide-2 (GLP-2), vasoactive intestinal polypeptide (VIP) and VIP receptors (VIPR1 and VIPR2) using real-time RT-PCR. Relative gene expression levels were analyzed for effects of diet type, RFI class and their interaction. There was no effect (P ≥ 0.10) of diet type, RFI class, or their interaction on jejunal expression of GLP-2, VIP, or VIPR2 genes. Lambs on the FOR diet had greater (P = 0.02) jejunal VIPR1 expression than CONC fed lambs, but no effect of feed efficiency status on VIPR1 expression was observed.  Results suggest that VIP is involved in changes associated with diet type in the ruminant small intestine through its receptor VIPR1.