Reproductive Capacity of Beef Bulls. VI. Daily Spermatozoal Production, Spermatozoal Reserves and Dimensions and Weight of Reproductive Organs

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Abstract
Daily testicular spermatozoal production (DSP) and extragonadal spermatozoal reserves (EGR) were determined hemacytometrically using tissue homogenates from beef bulls. The first experiment involved 7-year-old Angus (N = 7) and Hereford (N = 7) bulls and the second involved one group of 3-year-old Charolais (N = 8) and another group of 5- to 6-year-old Charolais (N = 11). Each bull was sexually rested ≥ 29 days prior to slaughter. Breeds differed widely in testicular weight, DSP and EGR. Testicular weight of Angus exceeded (P<.05) that of Herefords (363 vs 323 g), as did DSP (6.9 vs 5.9 × 109) and EGR (55.3 vs 39.4 × 109). Characteristics of the two groups of Charolais did not differ significantly; testicular weight, DSP and EGR for the 19 bulls averaged 386 g, 8.9 × 109 and 63.5 × 109. Thus, Charolais bulls attained sexual maturity by 3 years of age. Correlations between testicular weight and DSP per testis for Angus and Charolais bulls of .70 and .81 were significant (P<.01), but that of .41 for Herefords was not. Efficiency of spermatozoal production was higher (P<.01) for 3-year-old than 5- to 6-year-old Charolais bulls (14 vs 12 × 106 spermatozoa daily/g testicular parenchyma), but did not differ significantly between Angus and Hereford bulls (10 × 106 spermatozoa daily/g testicular parenchyma for each breed). For mature beef bulls, paired testicular weight and body weight were not significantly correlated. Reproductive organ dimensions and weights were summarized by breeds and ages. Copyright © 1979. American Society of Animal Science . Copyright 1979 by American Society of Animal Science.