Relationships of plasma insulin-like peptide 3, testosterone, inhibin, and insulin-like growth factor-I concentrations with scrotal circumference and testicular weight in Japanese Black beef bull calves

• Published in: Journal of Reproduction and Development Vol. 64; no. 5; pp. 401 - 407
• Main Authors: SAKASE, Mitsuhiro, KITAGAWA, Keita, KIBUSHI, Masahiko, KAWATE, Noritoshi, W. W. P. N. WEERAKOON, HANNAN, M. A., KOHAMA, Namiko, TAMADA, Hiromichi
• Format: Journal Article
• Language: English
• Published: Japan THE SOCIETY FOR REPRODUCTION AND DEVELOPMENT 2018; The Society for Reproduction and Development
• Subjects: Animals; Body Weight; Bull calf; Cattle; Immunoassay; Inhibin; Inhibins - blood; Insulin - blood; Insulin-Like Growth Factor I - metabolism; Insulin-like growth factor-I (IGF-I); Insulin-like peptide 3 (INSL3); Male; Organ Size; Original; Peptides - chemistry; Proteins; Scrotum - anatomy & histology; Scrotum - growth & development; Testicular size; Testis - anatomy & histology; Testis - growth & development; Testosterone - blood; Insulin-like growth factor-I (IGF-I); Insulin-like peptide 3 (INSL3); Testicular size; Bull calf; Inhibin
• ISSN: 0916-8818; 1348-4400
• DOI: 10.1262/jrd.2018-034

This study was conducted to clarify the relationships of plasma concentrations of insulin-like peptide 3 (INSL3), testosterone, inhibin, and insulin-like growth factor-I (IGF-I) with scrotal circumference and testicular weight in Japanese Black beef bull calves (n = 20), from birth to pre-puberty. Monthly blood sampling (0 to 7 months) and scrotal circumference measurements (0 to 7 months) were performed. Testicular weight was recorded immediately after castration at 7 months. Plasma INSL3, testosterone, inhibin, and IGF-I concentrations were measured either by enzyme immunoassay or time-resolved fluorescence immunoassay. The correlation coefficients of these hormonal concentrations with scrotal circumference were significant (P < 0.0001) and it was higher for INSL3 (r = 0.647) than for testosterone (r = 0.597), IGF-I (r = 0.400), and inhibin (r = –0.453). Calves with heavier testes (> 60 g) at castration (7 months) had higher (P < 0.05) plasma INSL3 (from 3 to 7 months) and inhibin (from 1 to 4 months) concentrations than those with lighter testes (< 60 g). The calves with heavier testes at castration had larger (P < 0.05) scrotal circumference than those with lighter testes from 3 to 7 months. In conclusion, blood INSL3 concentrations may be the best functional indicator among the hormones analyzed for determining total testicular volume during pre-puberty in bull calves. In addition, inhibin and INSL3 concentrations in early calfhood may be functional predictors for testicular weight at pre-puberty.