Abstract
Lindner (1959) and Lindner and Mann (1960) observed that the ratios of androstenedione to testosterone changed from 1:1 in testes of bulls at 4 months to 1:10 at 9 months of age. To our knowledge, levels of testosterone and androstenedione have not been quantified in peripheral plasma during sexual maturation in the bull, principally for lack of sufficiently sensitive techniques useful for routine analysis of large numbers of samples. The primary objective of the present study was to develop techniques to quantify testosterone and androstenedione in the testis and peripheral plasma of Holstein bulls between birth and 1 year of age. Another objective was to study the interrelationships between androgen levels and other reproductive and endocrine criteria previously studied in these bulls (Macmillan and Hafs, 1968a, b, 1969; Purchas, Macmillan and Hafs, 1970). Five Holstein bulls were slaughtered at birth and five at each monthly age-interval to 12 months of age. Copyright © 1972. American Society of Animal Science. Copyright 1972 by American Society of Animal Science.