Resumen

ROA, Noris; LINARES, Tiburcio; DIAZ, Thais  y  CHACIN, Franklin. Ovarian follicular waves in Brahman and crossbred (Bos indicus x Bos taurus) cows, located in Venezuelan central plains. Zootecnia Trop. [online]. 2006, vol.24, n.3, pp.297-306. ISSN 0798-7269.

The aim of this study was to contribute to the knowledge of reproductive physiology in Brahman and Crossbred (Bos indicus x Bos taurus) cows located in the Central lowlands of Venezuela, using a ultrasound study of follicular dynamics in multiparous cows during the estrous cycle. Follicular growth and atresia were monitored in 30 multiparous cows during 30 consecutively days during the rainy season. The follicular wave was identified using the dominant follicle of each wave. Estrous cycles with one (6.7%), two (90.0%) and three (3.3%) follicular waves were observed. There was a difference (P<0.05) in estrous cycle length according the number of follicular waves, observing that estrous cycles with three waves were longer (27.0 days) than cycles with one or two waves (20.6 22.3 days, respectively). There was no difference (P>0.05) between Brahman and Crossbred cows, in estrous cycle length. Follicular dynamics in both breeds were characterized by a higher incidence of cycles with two waves. The reason for which cycles exist with 1, 2, 3 or more waves are not known. However, it is possible that in those cows with high progesterone levels present high number of follicular waves. In conclusion, the ovarian follicular dynamic of Brahman and Crossbred cows located in Central Plains of Venezuela was characterized to present a bigger frequency of estrous cycle with two follicular waves.

Palabras clave : follicular waves; estrous cycle; ultrasound; crossbred (Bos indicus x Bos Taurus); Brahman.