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United States Department of Agriculture

Agricultural Research Service

Title: Effects of Weaning on Somatotrophic Gene Expression and Circulating Levels of Growth Hormone (Gh), Insulin-Like Growth Factor-1 (Igf-1), and Igf-2

item Matteri, Robert
item Dyer, Cheryl
item Carroll, Jeffery

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 21, 1999
Publication Date: N/A

Technical Abstract: Weaning the piglet results in reduced growth, increased GH secretion, and reduced circulating IGF-1 and IGF-2 levels. Our objective was to evaluate postweaning changes in the secretion of these hormones and the expression of genes involved with their production. At 14 d of age, piglets were either crossfostered to a sow (S, n=8) or weaned onto phase 1 diets containing 0 (NP, n=8) or 7% (SDP, n=8) spray-dried plasma. Animals were sacrificed after 4 d for blood and tissue collection. Weight gain over this 4-d period was significantly greater in S, compared to NP and SDP groups (1.3+/.09, .11+/.06, and .07+/.04 kg, respectively; P<.001). Respective gains over the last day of the study were .23+/.05, .05+/.03, and .29+/.04 kg (P<.001). Serum GH concentrations at sacrifice were higher in NP and SDP, compared to S piglets (P<.001). Conversely IGF-1 and IGF-2 concentrations were equivalently lower in NP and SDP, compared to S piglets s(P<.001). The level of pituitary GH mRNA did not differ among groups (P=.3). Levels of IGF-1 and IGF-2 mRNA were equivalent among groups in liver, muscle (l. dorsi), and fat tissue; however, a tendency was noted for lower liver IGF-1 mRNA in S piglets (P=.09). Liver IGFBP-3 mRNA also was unaffected by treatments (P=.4). A strong tendency for lower liver GH receptor mRNA was noted in S piglets (P=.06), but muscle GH receptor mRNA was equivalent among groups (P=.7). The results indicate that the abundances of specific mRNAs in the present tissues are not the immediate determining factors of circulating GH and IGF levels. The high rate of gain between d 3 and 4 in the SDP piglets is not accompanied by a normalization of GH or IGF secretion, suggesting a significant lag time between recoveries of postweaning gain and somatotrophic axis function.

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