Effects of weaning on somatotrophic gene expression and circulating levels of insulin-like growth factor-1 (IGF-1) and IGF-2 in pigs R.L. Matteri a, *, C.J. Dyer a , K.J. Touchette b , J.A. Carroll a , G.L. Allee b a Animal Physiology Unit, Agricultural Research Service, United States Department of Agriculture, Room S-107 Animal Sciences Research Center, University of Missouri, Columbia, MO 65211, USA b Department of Animal Sciences, University of Missouri, Columbia, MO 65211, USA Received 1 May 2000; accepted 10 July 2000 Abstract The present study evaluated somatotrophic gene expression in liver, muscle and adipose tissue 4 d after weaning, a time point corresponding to greatly reduced serum concentrations of insulin-like growth factor (IGF)-1 and IGF-2 in pigs. Two-week-old barrows were either cross-fostered to a sow (SOW, n = 8) or weaned and fed a phase 1 diet containing either 0 or 7% spray-dried plasma (NP, n = 8 and SDP, n = 8; respectively). Piglets were allocated such that two size groups were equivalently represented in each experimental group (small, 3.5– 4.3 kg and large, 4.6 –5.7 kg). Animals were weighed daily and sacrificed 4 d after weaning for blood and tissue collection. Daily gains of the SOW piglets were significantly greater than those of the weaned pigs for the first 3 d of the experiment (P  0.0001). Weight gains in the SOW and SDP pigs between d 3 and 4 were equivalently elevated relative to the NP pigs (P  0.0001). Serum IGF-1 and IGF-2 concentrations were decreased in both NP and SDP compared to SOW (P  0.0001). Serum IGF-2 levels were significantly lower in small piglets (P = 0.006). A Weaning Group X Size interaction was noted for liver IGF-2 mRNA (P  0.03), reflecting a higher level of expression in large SOW piglets relative to small SOW piglets. Weaning did not affect IGF-1, IGF-2, or growth hormone (GH) receptor mRNA levels in liver, muscle, or fat (P  0.05). Liver IGF-binding protein (IGFBP)-3 and acid-labile subunit (ALS) mRNA levels also were unaffected by weaning. Small pigs had lower levels of liver ALS (P = 0.0003), muscle IGF-2 (P = 0.02), and muscle GH receptor (P = 0.006) mRNAs. In contrast, adipose tissue IGF-1 and IGF-2 mRNA levels were greatest in the small piglets (P = 0.001 and 0.029, respectively). © 2000 Elsevier Science Inc. All rights reserved. * Corresponding author. Tel.: +1-573-882-1047; fax: +1-573-884-4798. E-mail address: matterir@missouri.edu (R.L. Matteri). Domestic Animal Endocrinology 19 (2000) 247–259 0739-7240/00/$ – see front matter © 2000 Elsevier Science Inc. All rights reserved. PII: S0739-7240(00)00081-3