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

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, 107o 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 nttmber 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 spennatids 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.