Abstract

ALONSO ALANUZA, Liliana et al. Fertility assessment of bos indicus cows according to the estrus intensity, in a fixed time artificial insemination program under tropical conditions. Rev. Cient. (Maracaibo) [online]. 2009, vol.19, n.6, pp.639-644. ISSN 0798-2259.

The aim of this study was to evaluate the fertility obtained in a herd, according to two times of fixed time AI: 48 and 72 hours, following an estrus synchronization program, taking into consideration the manifestations and the intensity of estrus. One hundred and fourteen Bos indicus females were used; synchronized with 2mg of estradiol benzoate and a progesterone-releasing intravaginal device (PRID), which remained in situ for 9 days. After the removal of the PRID, the animals were divided into two groups: 61 and 53 females that were inseminated, respectively, 48 and 72 hours posttreatment. All were continuously observed for 90 hours, with the objective of detecting sexual behavior and classifying them according to heat intensity into two categories: high and low. Chi-square test was used for the comparison of proportions. The percentage of females with estrus manifestation was 68.4%, without difference between high and low intensity categories (37.7 and 30.7%, respectively). Of the animals with signs of estrus, 85.4% ovulated; different from the females without estrus manifestation, with 63.8% (P<0.05). Global pregnancy rate was 25.4%; 86.2% of these gestations correspond to the group of females that manifested estral behavior. According to the moment of AI and the intensity of the estrus, the percentages of pregnancy for AI at 48 hours were 1) high: 91.6%, 2) low: 84.6% (P<0.05) and 3) without estrus: 25%, on the other hand, in females inseminated at 72 hours, the percentages were: 1) high: 8.4%, 2) low: 15.4% and 3) without estrus: 75% (P<0.05). It is concluded that females with estral manifestation are more likely to get pregnant after AI at 48 hours following hormonal treatment, while for animals without estral manifestation, the higher pregnancy percentages are at 72 hours.

Keywords : Artificial insemination; fixed time; pregnancy; Bos indicus; synchronization.