Sexual behavior of Brahman heifers in the tropics under pharmacological control of estrus

Thirty - three Brahman heifers were used, with similar ages and weights, and three groups were formed to evaluate sexual behavior through pharmacological control of estrus. Each group was randomly assigned one of the following treatments: Control group, consisting of nine heifers (G1); Day zero: subcutaneous implant on the external face of the ear with 3 mg of norgestomet, plus 3 mg norgestomet muscle injection and 5 mg estradiol valerate. Day seven: muscle injection of 0.15 mg of (D +) cloprostenol. Day nine: removal of the implant. Group two (G2), same as G1, but on day nine 3 heifers were introduced in heat. Group three (G3), same as G1, but on day nine were introduced 3 heifers in anestrous. Heifers were observed for 96 continuous hours. The data were collected by the method of “Record of sequences”. The information was analyzed using descriptive statistics and the groups were compared to establish differences. 100% of the heifers expressed signs of estrus and their onset was not altered with the inclusion of heifers in estrus or anestrous. After removal of the implant, the onset of estrus for G1 was at 29.5 ± 4.8 h; For G2 at 26.1 ± 4.7 h and for G3 at 26.36 ± 4.6 h. The duration of estrus for groups in the same order was 13. 6 ± 9.1 h; 12.7 ± 6.5 h and 18.7 ± 4.7 hours. The highest percentage of estrus and number of sexual behaviors was reached between 30-34 hours post-removal of the implants (G1: 100%, G2: 88.8%, G3: 100%). The inclusion of heifers on day nine of the protocol did not alter the onset or the delay of estrus exposure of the heifers of the experimental groups.