This study aimed to evaluate the effects of rectal temperature (RT) on conception rate (CR), as well as the effects of seasonality (spring-summer vs. autumn-winter) and timing of artificial insemination (AI) (morning vs. afternoon) on RT and CR in crossbred dairy cows (Holstein x Gyr). The experiment was conducted on a dairy farm in Centralina, MG, where 1,219 conventional and fixed-time inseminations were analyzed. The RT was measured immediately before AI using a digital thermometer. Pregnancy diagnosis was performed using ultrasonography between 28 and 60 days after AI. T The effects of seasonality and timing of AI on RT were analyzed with a Mann-Whitney U test and the effects of RT (above or below the average), seasonality and timing of AI on CR were analyzed with a Chi-squared test, both using the SAS program. The RT average was 39.4°C. Cows with RT ? 39.4°C had lower CR than cows with RT < 39.4°C (25.78% vs. 32.54%; P = 0.0096). During spring-summer, cows had higher RT (39.44°C ± 0.025 vs. 39.27°C ± 0.022; P < 0.0001) and lower CR (25.49% vs. 31.75%; P = 0.0146) compared with autumn-winter. Cows inseminated in the morning had lower RT (38.96°C ± 0.022 vs. 39.60°C ± 0.018; P < 0.0001) and higher CR (32.86% vs. 26.06%; P = 0.0102) than cows inseminated in the afternoon. In conclusion, crossbred dairy cows with rectal temperature equal to or greater than 39.4°C had lower conception rate. Moreover, rectal temperature and conception rate were affected by seasonality and insemination time.
Effect of SpermVital® technology on conception rate in repeat breeder multiparous dairy cows: preliminary results