Relationships of sexual activities in estrous cows to different frequencies of observation and pedometer measurements.

Sexual activities were observed continuously for 120 h in Holstein dairy cows during moderate climate. Pedometer measurements of motor activity were correlated with total activities initiated, total activities received, mounts received, and time in estrus. Twelve of 14 individual sexual activities also were correlated on a within-cow basis with pedometer-measured increases in motor activity; disoriented mounts and licking front were not correlated to pedometer increases. Although observations of four 1-h and four or six 30-min observations accounted for greater variation, pedometer increases in activity accounted for as much variation in total sexual activities as periodic observations of 30 min or 1 h for 1 to 3 X /d. Combining periodic observations with pedometer measurements resulted in greater coefficients of determination for analyses of sexual activities than with each individual factor. Sexual activities and pedometer increases also were correlated positively with body condition score and day postpartum, and they were correlated negatively with milk production and body weight change since calving. Although mounting and total sexual activities were shifted significantly from expected on a quartile basis, shifts were probably not of practical significance and provided little evidence for more frequent occurrence of estrous activity during nocturnal periods. Rather, the most marked decrease in mounting and total sexual activities occurred at milking and feeding times, indicating that dairy farmers should be more concerned with disruptions of activities by management practices rather than nocturnal occurrence of estrus.