Low fertility in aging roosters is related to a high plasma concentration of insulin and low testicular contents of ACTH and lactate

Fertility in roosters peaks between 30 and 40 weeks of age and declines rap idly from about SO weeks of age. Low-fertility, aging roosters have a highe r density of elongated spermatids attached to Sertoli cells than do high-fe rtility roosters, but display normal spermatogenesis and ejaculated spermat ozoa. Plasma levels of insulin and lactate and testicular contents of ACTH and lactate were compared in Cornish roosters aged 27 weeks (early state of sexual maturity), 37 weeks (high fertility), 67 weeks (reduced fertility), and 72 weeks (low fertility). Insulin may act as an endocrine regulator of Sertoli cell function, and ACTH as an autocrine regulator of Leydig cells for androgen production and as a paracrine regulator of Sertoli cells by am plifying FSH response. Lactate is the primary energy substrate of spermatoc ytes and spermatids in the adluminal compartment. Roosters aged 67 and 72 w eeks had higher (P < 0.05) plasma insulin levels but lower (P < 0.05) testi cular lactate content than roosters aged 27 and 37 weeks. The lower lactate content in testes of low-fertility roosters may reflect an increased consu mption of lactate due to the higher density of elongated spermatids. Furthe rmore, the content of testicular ACTH was lower in low-fertility roosters t han in 27-week-old roosters. These results suggest that ACTH may be involve d indirectly in the mechanism responsible for the high density of spermatid s in the tubuli and the lower spermatozoa concentration in the ejaculate of low-fertility roosters, as was reported in previous studies, since this ho rmone may serve as a paracrine regulator of Sertoli cell function. (C) 1999 Academic Press.