In dual purpose crossbreed cattle (DPC), deficient estrus detection affects the artificial insemination diffusion and reproductive efficiency. To study the formation and characteristics of sexually active groups (SAGs), 300 crossbred postpartum Red Brahman (
Bos indicus
) x Red Holstein (
Bos taurus
) cows were studied and milked manually twice a day with support from the calf, grazing German (
Echinocloa polistachia
, 12% crude protein) and Paez (
Panicum maximun
) grass in pasture lands, accompanied by teaser bulls at a 25:1 ratio. They were observed four times, from 5am to 6:00 am at cement pen area, and from 6:00 am to 10:00 am in the pasture area. Finally from 2:00 pm to 6:00 pm, and from 6:00 pm to 7:00 pm at the cement pen and pasture area respectively. This was performed in a commercial farm located in a Humid Tropical Forest area in the Maracaibo Lake basin, in the Bolivarian Republican of Venezuela. Only the groups constituted of no less than three animals in standing mount interaction were considered SAGs. 51 SAGs were detected, 76% heterosexual, and 24% homosexual, 69% were observed in cement pens and 31% at pasture area, 41% in the morning and 59% in the afternoon. SAGs accounted for 67% of the standing estrus observed; the duration time of those SAGs was of 20±2, 8 minutes. In most of the heterosexual SAGs the teaser bull was beginning the mounting chain. The detection, registration and evaluation of SAGs in DPC can contribute to improve the efficiency of estrus detection.
