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United States Department of Agriculture

Agricultural Research Service

Title: Decreased Serum Concentrations of Lh in Undernourished Ewes Are Associated with Diminished Serum Igf-I and Igf-Binding Proteins (Bps) -2, -3 and -4

Authors
item Snyder, J - UNIV WYOMING, LARAMIE
item Clapper, J - UNIV WYOMING, LARAMIE
item Roberts, Andrew
item Moss, Gary - UNIV WYOMING, LARAMIE

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 1996
Publication Date: N/A

Technical Abstract: Effects of suboptimum body condition (BCS) on IGF-I and BPs were evaluated in ewes in which suppressed serum concentrations of LH were attributed to dietary energy restriction. Chronically ovariectomized ewes received 1 Silastic implant containing estradiol (d 1) and were fed 100 or 60% of NRC energy requirements. Blood samples were collected at 12-min intervals for 6 6h at d 7, 30, 60, and 75. Mean concentrations of LH (ng/ml) in ewes with BCS (1=emaciated, 9=obese) >3 (H; n=6) increased (p<.01) at the onset of the breeding season (d 60) to 4.5 +/- .5 and remained elevated at d 75 (3.3 +/- .5). In contrast, concentrations of LH in ewes with BCS </- 3 (L; n=8) remained suppressed (p<.05) to 1.2 +/- .4 and 1.4 +/- .4 at d 60 and 75, respectively. Concentrations of IGF-I (ng/ml) were similar (p<.05) in L and H ewes at 7 and 30 d but decreased (p<.01) in L vs. H ewes at 60 (85 +/- 13 vs. 144 +/- 14) and 75 d (100 +/- 13 vs. 163 +/- 14). Ligand blot analysis identified BP-2 (34 kDa), -3 (40 and 44 kDa), -4 (24 and 28 kDa), and a 29 kDa BP. Binding of 125I-IGF-I to 40 kDa BP-3 was similar among (p>.05) L and H ewes at d 7 and 30. At d 60, binding (arbitrary units) in L ewes (3.8 +/- .3) tended (p<.07) to be less than H ewes (4.0 +/- .3) and was depressed (p<.01) at d 75 (3.1 +/- .3 vs. 4.3 +/- .3). Binding of IGF-I by 44 kDa BP-3 and 24 kDa BP-4 was less (p<.01) in L than H ewes at d 7 through 75. Abundance of the 28 kDa BP-4, BP-2, and the 29 kDa BP did not differ (p>.05) among groups. In summary, concentrations of IGF-I and 40 kDa BP-3 decreased in association with diminished concentrations of LH in ewes in low body condition. Suboptimum nutrition may result in decreased serum concentrations of LH through mechanisms involving diminished serum concentrations of IGF-I and(or) BPs.

Last Modified: 10/20/2014
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