The observation of estrus behavior at night in dairy cattle on a free stall barn

The objective of this study was to investigate the estrus behavior at night in dairy cows that were housed in a free-stall barn, which would improve estrus detection. This experiment was performed in a dairy farm attached to Rakuno Gakuen University and 31 Holstein cows were studied in which 98 estrus cycle were detected. The cows were observed dairy for 7 months, from May 2003 to November 2003 for a period, of 7 h, i.e., between 2100-0400, and the results obtained were compared with those obtained during a 24- h observation period. Video Camera were used to monitor the estrus activities of the cows. The results are summarized as follows: Mounting activity and standing behavior was observed in 75% of naturally estrus cows and in 82% of the Prostaglandin F2alpha(PG)-administered cows. Among the naturally estrus cows, 43% and 21% showed estrus behavior only during the night (2100-0400)and only during the day(0400-2100), respectively. Among the PG-administered cows, 44% and 37% showed estrus behavior only during the night and only during the day, respectively. These results indicate that a greater number of cows show estrus activities at night than during the day. The average distance covered during the walking activities by the naturally estrus cows and PG-administered cows were 762 m and 577 m, respectively: Staying time on passage of naturally estrus cows and PG-administered cows were 257 min and 210 min, respectively. A significant difference with regard to the walking time was observed between the estrus and anestrus days (P0.01) with a considerable increase in the walking time was observed during the estrus days. During the 24-h observation period, the average distance covered during the walking distance by the naturally estrus and PG-administered cows were 1403 m and 2647 m, respectively. On the other hand, the anestrus cows walked a distance of 660 m. It is evident from our experiment that the walking distances in the PG-administered cows were twice that in the naturally estrus cows. In naturally estrus cows, 41% of mounting activity and standing behavior was observed between 2100-0000; this was the highest rate observed in this study. No peak was observed at any particular time point. The increase in the frequency of the mounts and walking distances was greater in the plural number of estrus cows than the single estrus cow. In this study, it is confirmed that many cows showed active estrus behavior during the night. Therefore, in order to increase the pregnancy rate, it is necessary to develop assistance measures for the walking activity during the night.