Serum concentrations of IGF-I, estradiol-17beta, testosterone, and relative amounts of IGF binding proteins (IGFBP) in growing boars, barrows, and gilts.

Abstract

The purpose of this research was to determine whether serum concentrations of steroids, IGF-I, and relative amounts of serum IGF-binding proteins (IGFBP) differ in growing boars (n = 11), barrows (n = 11), and gilts (n = 12) from 70 to 140 d of age. Pigs of similar age and weight were housed in pens of three or four and given ad libitum access to a 17% CP corn-soy diet and water. Pigs were weighed and blood samples were collected every 14 d beginning at 70 d of age. Serum concentrations of IGF-I and steroids were determined by RIA and relative amounts of IGFBP were determined by ligand blot analysis. By 84 d of age and continuing through 140 d of age, mean serum concentrations of IGF-I were greater (P < .05) in boars than in barrows or gilts. Relative amounts of 46-kDa IGFBP3 and 28-kDa IGFBP-4 were similar (P > .05) among pigs at 70 d of age; however, boars and barrows had greater (P < .05) relative amounts of 24-kDa IGFBP-4 and 41-kDa IGFBP-3 than gilts. Relative amounts of IGFBP-2 were greater (P < .01) in barrows than in gilts or boars at 70 d of age. From 84 d of age through 140 d of age, relative amounts of both forms of IGFBP-3 and the 28-kDa IGFBP-4 were greater (P < .05) in boars than in gilts or barrows. Relative amounts of IGFBP2 were greater (P < .05) in barrows than in gilts or boars at 98 d of age, but by 140 d of age relative amounts were greater (P < .05) in boars and barrows than in gilts. Mean serum concentrations of estradiol-17beta were similar (P > .05) between gilts and boars at 70 d of age, but by 98 d of age, and continuing through 140 d of age, mean serum concentrations of estradiol-17beta were greater (P < .05) in boars than in gilts. Mean serum concentrations of testosterone in boars increased (P < .05) with increasing age and were greatest at 128 and 140 d of age. Serum concentrations of testosterone were negatively correlated (P < .01) with relative amounts of serum IGFBP-2 but positively correlated (P < .01) with serum concentrations of IGF-I and estradiol-17beta. Serum concentrations of estradiol-17beta were positively correlated (P < .01) with serum concentrations of IGF-I in boars. Changes in serum concentrations of IGF-I and relative amounts of IGFBP resulting from changes in serum concentrations of estradiol-17beta and testosterone may contribute to growth differences observed among sexes.