title: Effects of weaning and rearing environment on intestinal gene expression of IGF-I, IGFBP (1-6), and the IGF receptor and on specific binding of IGF-I to mucosal membranes in the pig.
abstract: The objective of this study was to investigate changes in gene expression of intestinal IGF-I, IGFBPs, and IGF-I receptor in pigs in response to weaning and different rearing environment. Pigs were weaned early at 12 days of age and either remained on-site in a separate facility (CON) or were moved to a segregated site with reduced infection pressure (segregated early weaning; SEW). Small intestinal samples were collected from a total of 15 pigs killed at 11 (pre-weaning), 15 (3 days post-weaning), and 34 days of age. Intestinal IGF-I mRNA levels were higher (P < 0.01) in SEW than in CON pigs at 3 days post-weaning, but not at 34 days of age. Weaning reduced (P < 0.05) both IGF-IR mRNA levels and specific binding of IGF-1 in the jejunum in both groups at day 34, but only in SEW pigs (P < 0.05) at day 3 post-weaning. Weaning resulted in a major reduction (P < 0.05) in intestinal IGFBP-2 mRNA, with no difference between SEW and CON. Intestinal IGFBP-3 mRNA levels were unaffected by weaning or post-weaning environment. Weaning did not affect intestinal IGFBP-4 mRNA levels, except for an increase (P < 0.05) in CON pigs compared to pre-weaning, and to SEW pigs at 3 days post-weaning. The abundance of IGFBP-5 mRNA in the gut was highly variable with no apparent treatment effect. Intestinal IGFBP-6 mRNA levels were reduced (P < 0.05) after weaning, with lower (P < 0.05) levels in SEW pigs than in CON pigs at 34 days of age. This study documents the changes in IGF-1, IGF-IR, and IGFBP mRNA abundance, and in IGF-1 binding during post-weaning adaptation of the intestine in early-weaned pigs. In addition, the relative differences observed in intestinal expression of IGF-1, IGF-IR, and in IGF-1 binding between the post-weaning environments are consistent with previous observations in a companion study indicating that segregated early weaning enhances post-weaning intestinal maturation in pigs.
authors.affiliation: Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Sask, Canada S7N 5A8.
authors.forename: Min
authors.initials: M
authors.lastname: Tang
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Van Kessel
authors.forename: Bernard
authors.initials: B
authors.lastname: Laarveld
mesh_terms: D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D004780:Environment, Controlled; D015870:Gene Expression; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007421:Intestine, Small / Q000254:growth & development*; D012333:RNA, Messenger / Q000032:analysis; D017526:Receptor, IGF Type 1 / Q000032:analysis*; D013552:Swine; D014886:Weaning
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1