Reproductive potential of Nelore bulls (Bos taurus indicus) mated with a large number of cows

Fourteen sexually mature Nelore bulls were evaluated by physical and morphological characteristics of semen and testicular biometry (Test 1) and sexual behavior (Test 2) and classified as ''excellent'', ''very good'', ''good'' and ''questionable''. The bulls were divided into two experimental groups and placed with 300 (five bulls - group 1) and 360 cows (nine bulls - group 2), giving respectively bull: cow proportion of 1:60 and 1:40. All females were multiparous dry Nelore cows. Mean pregnancy rates at 30, 60, 90 and 120 days of the breeding season were 59.6, 91.3, 95.0 and 97.0% and 48.3, 78.3, 87.7 and 91.9% for groups 1 and 2, respectively (P<0.01). The results indicate that bulls to be utilized in the breeding season should be evaluated by a reproductive capacity scoring system in order to use the superior animals more intensively.