Estrous expression in dairy cows and heifers (Bos taurus) following repeated PGF2α injection and choice of selecting a mounting partner

Abstract Research findings on the behavioral patterns of animals in estrus have indicated a strong relationship between social structure of the herd and estrous expression. It was therefore of interest to know if the liaisons established during a previous heat are maintained through subsequent estrous periods, particularly with respect to the choice of mounting partners. Fourteen Holstein cows and ten heifers were synchronized on six occasions. Every 11 days, each animal received an i.m. injection of 25 mg PGF 2α , except for the fifth and sixth trials, when only half of the animals were treated. Sexual behavior of both groups was observed continuously from 40 to 100 h following injection. The ‘consistency value’ representing the repeatability of mounting behavior during estrus was higher in cows than in heifers (0.18 ± 0.1 vs. 0.13 ± 0.01; P P P P