title: Testicular development in bulls treated with recombinant bovine somatotropin.
abstract: This study was conducted to test the hypothesis that administering recombinant bovine somatotropin (rbST) would affect testicular development in Holstein bulls. From 4 until 32 wk of age, bulls received a daily injection of either placebo (C) or rbST (.2 mg/kg BW.75, i.m.; n = 10/group). At 14-d intervals, blood was obtained and assayed for testosterone (T); BW, shoulder height (SH), and testis length (TL) were recorded. At 7, 12, and 24 wk of age, bulls were bled at 10-min intervals for 6 h to determine the secretory patterns of LH, growth hormone (GH), and IGF-I. All bulls were killed at 40 wk of age. One testis was used for determination of daily sperm production (DSP), and the number of spermatids per gram of parenchyma (SP/G); the remaining testis was perfused and fixed for histological analysis of numbers of Sertoli cell nuclei (SCN/ST) and spermatids per seminiferous tubule cross-section (SP/ST). Epididymal spermatozoa were collected to test effects of rbST on the integrity of spermatozoal chromatin structure. Administration of rbST increased (P < .0001) concentrations of GH (nanograms/milliliter) in plasma at all ages (C vs rbST; wk 7, 8.9 +/- 1.0 vs 51.9 +/- 6.8; wk 12, 12.8 +/- 1.4 vs 59.2 +/- 6.4; and wk 24, 5.2 +/- 1.5 vs 42.6 +/- 12.2). There was an age x treatment interaction (P < .0183) for concentrations of IGF-I (nanograms/milliliter) in plasma (C vs rbST; wk 7, 149.7 +/- 6.1 vs 148.6 +/- 8.6; wk 12, 184.1 +/- 12.8 vs 216.6 +/- 15.9; and wk 24, 392.8 +/- 24.8 vs 484.7 +/- 19.9).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Dairy and Animal Science, Pennsylvania State University, University Park 16802.
authors.forename: R D
authors.initials: RD
authors.lastname: MacDonald
authors.forename: D R
authors.initials: DR
authors.lastname: Deaver
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood / Q000254:growth & development* / Q000502:physiology; D013006:Growth Hormone / Q000097:blood / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D011897:Random Allocation; D011994:Recombinant Proteins / Q000494:pharmacology; D012708:Sertoli Cells / Q000187:drug effects; D012741:Sexual Maturation / Q000187:drug effects; D013087:Spermatids / Q000187:drug effects; D013091:Spermatogenesis / Q000187:drug effects; D013737:Testis / Q000187:drug effects* / Q000254:growth & development / Q000502:physiology; D013739:Testosterone / Q000097:blood
chemical_list: D011994:Recombinant Proteins; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D007986:Luteinizing Hormone; D013006:Growth Hormone