Seasonal effects on behavioral estrus signs and estrus detection efficiency in Holstein heifers

Abstract

In the study, 234 Holstein heifers were observed visually during a one-year period and 1622 estrus records were used to determine seasonal effects on behavioral estrus signs and estrus detection efficiency. Estrus records were classified as standing, mounting, vaginal mucus discharging, and the other estrus signs. The rates of these estrus signs were found to be 50.6%, 22.7%, 20.7% and 6.0%, respectively and the differences were significant (P<0.01). These results showed that standing behavior was the most observable estrus sign in Holstein heifers. In addition, the rates of standing behavior in each season (66.2%, 59.7%, 50.4% and 38.0% in summer, fall, spring and winter, respectively) showed that it was also more observable sign than the other signs. The rates of estrus records according to seasons were found to be 34.4%, 32.9%, 23.6% and 9.1% in winter, fall, spring and summer, respectively and the differences were also significant (P<0.01). In the study, the mean overall estrus cycle length was found to be 21.15±1.85 days. The mean overall estrus detection efficiency was calculated as 57.8%. The mean detection efficiencies according to seasons were found to be 79.5%, 75.9%, 54.6% and 21.1% in winter, fall, spring and summer respectively. These results could be interpreted that estrus detection efficiency was decreased significantly with increase of temperature.