U.S. Department of Agriculture: Agricultural Research Service, Lincoln, Nebraska
Date of this Version
1979
Abstract
Concentrations of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were determined in serum of crossbred beef bulls during pubertal development. Serum LH ranged between .5 and 2.0 ng/ml with highest concentrations observed as 12 months of age. Serum FSH varied considerably among individuals but mean concentrations were within the normal range (50 to 100 ng/ml). Neither LH nor FSH increased at the time when testosterone increased or spermatogenesis entered meiosis.
Specific binding of 1 2 5 I-labeled human chorionic gonadotropin (hCG) and 1 2 5 I-labeled FSH to the bovine testis was demonstrated by autoradiographic localization techniques. Binding of 1 2 5 I-hCG and 1 2 5 I-FSH was preferentially located over interstitial tissue and seminiferous epithelial cells, respectively. An abundance of binding sites in newborn and 4-month-old calf testes shows that receptors for LH and FSH are present in the immature bovine testis.
Initiation of spermatogenesis was assessed by estimating the number of testicular sperm by histological and cytometric techniques following castration of bull calves at monthly intervals from birth to 12 months. Although spermatogenesis was qualitatively complete at 7 months, spermatogenesis and total daily sperm production were highest in 12-month-old animals. A high correlation (r = .98, P<.O1) was found between sperm per gram testis and total daily sperm production. A parallel increase in serum testosterone of young bulls and testes weight (r = .95, P<.01) and total daily sperm production (r = .87, P<.05) suggest that initiation of spermatogenesis could be dependent on increased testosterone.
Comments
Published in Journal of Animal Science (1979) 48:3, 591-597