Breeding soundness evaluation of extensively managed bulls in Costa Rica

摘要

Breeding soundness was evaluated in 898 Bos indicus, B. taurus and B. indicus X B. taurus bulls, 1-12 years of age, which had been extensively reared in 4 regions of Costa Rica. The bulls represented about 2% of the total breeding bull population. 39% of bulls were classed as unsuitable for breeding due to clinical problems (9.1%), mainly a low scrotum circumference or unsatisfactory sperm morphology. B. indicus bulls had the lowest percentage unsound for breeding (29%), followed by B. taurus (41%)and then B. indicus X B. taurus (48%). The percentage of spermatozoa with abnormal heads, acrosomes and mid-pieces was higher in ejaculates from bulls with a soft testicular consistency (P<0.001), a long scrotum (P<0.01) or a low scrotal circumference (P<0.05). Frequencies of sperm abnormalities were higher in bulls <2 years of age than in older bulls (P<0.01) and were highest in B. indicus X B. taurus bulls (P<0.001).