Behavior of lactating Holstein-Friesian cows during spontaneous cycles of estrus

The objectives of the present study were to describe, in detail, behavior associated with standing estrus (STE) in lactating dairy cows and behavioral changes during complete estrous cycles. Estrus signs were monitored by continuous video recording of 20 Holstein-Friesian (HF) cows housed on an outdoor wood-chip pad during 1 estrous cycle (22 d). Other social behavior was recorded during STE and, for comparison, during 1 selected day when none of the cows were in estrus. Standing stationary when mounted was defined as the primary estrus sign. Anogenital sniff, chin rest, attempt to mount, and mount were defined as secondary estrus signs. Ovarian cyclicity was onfirmed by progesterone measurements. This study reports short mean duration of STE (7.1 ± 1.44 h) and estrus (mount period; 12.9 ± 1.84 h) of the 13 cows expressing these signs. All mounting activities involved at least one cow in, or within 4 h of, STE. The most frequent sign during STE was anogenital sniff initiated, followed by chin rest received, chin rest initiated, chase up initiated, anogenital sniff received, mount initiated, head butt, mount received, attempt to mount initiated, push away received, play rub, attempt to mount received, follow initiated, threat received, flehmen, avoid, bellow, and social lick received. Standing and mounting activity in HF cows was inconsistent during estrus, indicating that other signs could be of greater use. The frequency of secondary estrus signs initiated and received increased gradually during the last 12 h before STE, revealing significant differences between periods from 4 to 6 and 1 to 3 h before STE. A considerable increase in receptive behavior (secondary estrus signs received) was identified between 1 to 3 h prior to STE and STE. Both frequent initiated and received behaviors were associated with STE. A significant decrease in the frequency of secondary estrus signs initiated and received occurred 3 h after STE. Cows in STE simultaneously predominantly chose the other standing cow as mate and expressed secondary estrus signs more frequently. Based on the results of this study, we suggest that chase up could be regarded as a reliable indicator of estrus and that the changes in proceptive (initiated) and receptive (received) behavior could be used as predictors of different stages in estrus. Knowledge of these behavioral signs may improve heat detection rates and the ability to predict the optimum breeding time for dairy cows.