Breeding soundness evaluation of extensively managed bulls in Costa Rica

This paper describes the results of single breeding soundness evaluations (BSE) in 898 Bos indicus, Bos taurus and B. indicus x B. taurus bulls, 1 to 12 yr old, extensively reared in different climatic regions of Costa Rica and representing approximately 2% of the total breeding bull population. Thirty-three percent (n= 296) of the bulls were classified as unsound for breeding owing to clinical problems (9.1%, n= 82), low scrotal circumference (SC) being the most common finding, followed by unsatisfactory sperm morphology (23.9%, n= 214). The prevalence of bulls unsound for breeding was lowest in Bos indicus (29%, P<0.01), intermediate in B. taurus (41%), and highest in B. indicus x B, taurus (48%). The percentages of abnormal sperm heads, acrosomes and midpieces tended to be higher in the ejaculates of bulls with softer testicular consistency (P<0.001), a long scrotum (P<0.01) or a low SC (P<0.05), and such bulls were more often classified as being unsound for breeding (P<0.05). Frequencies of sperm abnormalities were higher in bulls < 2 yr of age than in older males (P<0.01) and were highest in B. indicus x B. taurus bulls (P<0.001). The results confirm differences between species in their adaptability to a tropical environment and support earlier evidence of an association between SC, testicular consistency and scrotal length clinical parameters, and testicular function in bulls. (C) 1999 by Elsevier Science Inc.