Estrus expression and pregnancy rates in heifers primiparous and multiparous Nelore cows subjected to timed artificial insemination with strategic use of gonadotropin-releasing hormone

We evaluated the effects of nulliparous, primiparous, and multiparous conditions on estrus pregnancy rates in females that did not show but were treated with gonadotropin-releasing hormone (GnRH) at time timed artificial insemination (TAI). Nelore (n = 531) allocated according to following categories: nulliparous 144), primiparous 132), 255). The animals received a conventional TAI protocol, expression was identified by absence paint sacrococcygeal region day TAI. Females 10 μg GnRH together insemination. analyzed using logistic regression model (P < 0.05). lower 0.006) (61.36%) group than (76.39%) (75.69%) groups. Similar observed showed (nulliparous 84.54%, 86.42%, 80.31%; P 0.39) 41.18%, 56.86%, 58.06%; 0.24). total also similar 0.98) among categories 74.3%, 75.0%, 74.9%). had rate estrus, GnRH.