Influence of single or multiple sires and serving capacity on mating behavior of beef bulls

A study was conducted to determine the effect of serving capacity (SC) on sexual behavior of yearling bulls during single- and double-sire pasture matings. Approximately 60 crossbred virgin bulls were subjected to 3 SC tests, and 20 bulls were selected that were similar in age, BW, testes size and semen quality. Ten bulls were high SC (greater than or equal to 3 services/test) and 10 bulls were low SC (less than or equal to 2 services/test). Competitive order among the 20 bulls also was determined. Single-sire tests were conducted with 15 intact estrual heifers and 1 bull in a pasture for 6 h. Double-sire tests were conducted with 30 estrus-induced, ovariectomized heifers and 1 high SC and 1 low SC bull of approximately equal competitive order for 6 h. Bulls in double-sire tests had more (P less than .007) mounts than those in single-sire tests. High SC bulls in double-sire tests served more heifers (P less than .04) and had more services (P less than .04) than any other SC group and test type. There was no difference (P greater than .10) in the number of mounts or services between high and low SC bulls in single-sire tests. High SC bulls had a greater (P less than .002) percentage of mounts that culminated in a service that did low SC bulls. Conception rate was not different (P greater than .10) between SC groups in single-sire tests.(ABSTRACT TRUNCATED AT 250 WORDS)