The estrus behaviour and the plasma progesterone concentration were monitored during an induced and a natural subsequent estrus, in 35 Gir cows, during the winter and summer seasons of two consecutives years. The length of estrous cycle was influenced by the interaction between season and experimental year. The proestrus period was longer in the summer (51.82± 4.77h) compared to the one in the winter (33.43± 4.82h) season as far as in the natural (64.41± 4.95h) vs in the induced estrus (20.85± 4.64h). The total sexual activity was shorter in the induced than in the natural estrus (41.62± 4.81 vs 94.83± 4.56h in the winter, and 64.00± 4.14 vs 127.44± 4.04h in the summer). The length of estrus was similar between winter (12.33± 0.74h) and summer (11.82± 0.74h), and longer in the synchronized cows (13.24± 0.70 vs 10.91± 0.78h). The number of mounts accepted during the estrus was similar between winter (28.16± 2.61) and summer (22.98± 2.58), and greater in the synchronized animals (29.97± 2.48 vs 21.17± 2.17). It was observed effect of interaction between season of the year and luteolysis type on the total received mountings per hour in estrus. The winter was not a limiting factor to the estrus manifestation, once its length and intensity allowed heat detection, however, heat synchronization meddled the manifestation of sexual behaviour.
bovine; estrus; behaviour; season of the year
