Pubertal Relationships of Some Endocrine and Reproductive Criteria in Hereford Bulls

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Abstract
Levels of androgens, gonadotropins and spermatogenesis were studied in 51 Herefords 1 year of age. Results with 10 of these bulls in a preliminary trial revealed a correlation of −.67 between pituitary FSH and epididymidal sperm numbers. Gonadal sperm concentration in 41, year-old Herefords (60×106/g) was similar to that for year-old and mature Holsteins, but seminal vesicular fructose and citric acid in Herefords exceeded that of Holsteins. In jugular serum, LH concentrations increased in 29 Herefords from 10 to 12 months of age, but prolactin, testosterone and androstenedione decreased. Relative to concentrations determined in jugular serum at 12 months, prolactin, testosterone and androstenedione increased at slaughter (12.5 months) while LH decreased. Testosterone concentration exceeded androstenedione at 12.5 months in testes and in serum. None of the correlations between serum LH or prolactin and serum androgens at 10, 11 or 12 months of age was significant. Concentrations of serum LH at slaughter were correlated with serum testosterone (r=.38), testicular testosterone (r=.56) and testicular androstenedione (r=.55), but similar correlations for prolactin were not significant. LH in the serum and pituitary were unrelated to gonadal and extragonadal sperm numbers. However, serum prolactin was correlated with gonadal (r=.36) and epididymidal (r=.30) sperm numbers, and comparable correlations for pituitary FSH were −.45 and −.31, respectively. These results suggest that release of FSH limits spermatogenesis at 1 year of age. Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.

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