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Reproductive Capacity of Dairy Bulls. IX. Changes in Reproductive Organ Weights and Semen Characteristics of Holstein Bulls During the First Thirty Weeks After Puberty¹

Dairy Breeding Research Center, The Pennsylvania State University, University Park 16802

ABSTRACT

Data were from 25 Holstein bulls killed either at 34 weeks of age, at puberty or at 10, 20 or 30 weeks after puberty. Puberty (50 x 10⁶ sperm/ejaculate, 10% motile sperm) was attained at 41 ± 4 weeks of age; postpuberal increases in ejaculate volume, total sperm per ejaculate, testis and epididymis weights, and the number of spermatids per gram of testicular parenchyma were rapid for the next 20 weeks. Except for ejaculate volume, sperm content of the ejaculate and sum of spermatids per testis, the rates of change for all characteristics diminished between 20 and 30 weeks after puberty. Nevertheless, the development toward adult reproductive capacity was adequately described by linear regression equations. Correlations between organ weights and postpuberal age were not significantly greater than those with postnatal age.

¹ Authorized for publication June 5, 1972 as Paper 4231 in the journal series of the Agricultural Experiment Station.

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