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

The purpose of this research was to determine whether serum concentrations of steroids, IGF-I, and relative amounts of serum IGF-binding proteins (IGF BP) differ in growing boars (n = II), barrows (n = II), 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 begin ning at 70 d of age. Serum concentrations of IGF-I and steroids were determ ined by RIA and relative amounts of IGFBP were determined by ligand blot an alysis. By 84 d of age and continuing through 140 d of age, mean serum conc entrations of IGF-I were greater (P < .05) in boars than in barrows or gilt s. Relative amounts of 46-kDa IGFBP-3 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. Rel ative 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 amou nts 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 IGFBP-2 were greater (P < .05) in barrows than in gilts or boars at 98 d of age, but by 140 d o f age relative amounts were greater (P < .05) in boars and barrows than in gilts. Mean serum concentrations of estradiol-17 beta were similar (P > .05 ) between gilts and boars at 70 d of age, but by 98 d of age, and continuin g through 140 d of age, mean serum concentrations of estradiol-17 beta were greater (P < .05) in boars than in gilts. Mean serum concentrations of tes tosterone in boars increased (P < .05) with increasing age and were greates t at 128 and 140 d of age. Serum concentrations of testosterone were negati vely correlated (P < .01) with relative amounts of serum IGFBP-2 but positi vely correlated (P < .01) with serum concentrations of IGF-I and estrsLdiol -17 beta. Serum concentrations of estradiol-17 beta were positively correla ted (P < .01) with serum concentrations of IGF-I in boars. Changes in serum concentrations of IGF-I and relative amounts of IGFBP resulting from chang es in serum concentrations of estradiol-17 beta and testosterone may contri bute to growth differences observed among sexes.