Efeito da intensidade do estro ao final do protocolo de IATF, avaliado automaticamente, na taxa de concepção em vacas leiteiras mestiças

Abstract

Reproductive efficiency is related to the profitability of dairy herds. Failures in estrus detection compromise reproductive efficiency. Automatic activity monitoring systems (AAMS) can be efficient for estrus detection, since it is known that cows in estrus show behavioral changes, which can be evaluated by the variation in the number of daily steps. Studies have shown that estrus expression traits, such as intensity (relative increase in activity) and duration, are associated with higher conception and greater embryonic survival in Holstein dairy cows. The objective was to evaluate the effect of estrus intensity, assessed by AAMS, at the end of the fixed-time artificial insemination (FTAI) protocol on conception rate in crossbred dairy cows. A total of 254 estrus events were evaluated after the FTAI protocol in lactating cows from the dairy herd of the Fazenda Experimental do Glória at the Universidade Federal de Uberlândia (UFU), from January 2024 to August 2025. After calving, cows received collars with the device. Based on the magnitude of deviation of activity relative to the baseline, cows had estrus intensity categorized into four groups, according to the mean ± two standard deviations of the trait: absent (n=117), weak (n=15), moderate (n=65), and strong (n=57). The cows were inseminated on the 11º day after the beginning of the progesterone and estrogen-based FTAI protocol. Pregnancy diagnosis was performed by transrectal ultrasonography 32 days after FTAI. The statistical analyses were performed using logistic regression in MINITAB software. Statistical difference was considered when P ≤ 0.05. An effect of estrus intensity on FTAI conception rate in crossbred dairy cows was detected (P = 0.001). Cows with absent, weak, moderate, and strong estrus expression showed FTAI conception rates of 16.24%; 26.70%; 35.38%, and 40.35%, respectively. In conclusion, estrus intensity after the FTAI protocol affects conception rate in crossbred dairy cows. Cows showing greater estrus intensity achieving higher conception rates.