Characterization of the physical and ruminal activities related to estrus in dairy cows raised on Chinese commercial farms

This study aimed to describe the estrus-related changes in dairy cattle in parameters automatically recorded through an HR-Tag (SCR Engineers Ltd., Netanya, Israel) or a neck collar (Nedap Livestock Management, Groenlo, Netherlands). On two commercial dairy farms, the baseline period was defined as the mean of 3 d before and 3 d after estrus day. In the HR-Tag monitored herd, changes in physical activity and behavioral parameters (lying bouts, lying duration, total lying time, lying ratio) were studied in 78 estrous cycles. The cows were classified in groups according to parity (primiparous, n = 34; and multiparous, n = 44), milk production (MK1, n = 7, > 47 kg/d; MK2, n = 12, 42-47 kg/d; MK3, n = 43, 31-42 kg/d; and MK4, n = 16, < 31 kg/d) and lactation stage (DIM1, n = 34, ≤ 60 d; DIM2, n = 22, 61-120 d; and DIM3, n = 22, ≥ 121 d). In the neck-collar monitored herd, we investigated physical activity on estrus day and total daily feeding time, rumination time and inactivity time in 35 dairy cows during the peri-estrus period. On estrus day, the effects of parity and milk production on physical activity, and the differences in total daily feeding time, rumination time and inactivity time between estrus day and the baseline period were evaluated. The cows were classified in groups according to parity (primiparous, n = 9; and multiparous, n = 26), and milk production (MK1, n = 5, > 41 kg/d; MK2, n = 17, 32-41 kg/d; and MK3, n = 13, < 32 kg/d). ANOVA was performed to determine differences in the continuous data, and comparing means was performed to estimate differences within and between groups, using SPSS 23.0. Ordinal logistic regression was adopted to analyze the factors affecting physical activity on estrus day. Results from the HR-Tag monitored herd demonstrated that on estrus day, physical activity increased compared with the baseline period, and average number lying bouts on estrus day was markedly lower than at baseline, as well as total lying time and lying ratio, with values of-3.53 ± 0.55,-188.02 ± 21.46 and-14.05 ± 1.37, respectively. For the neck collar-monitored herd, when the TFT (total feeding time) of MK2 cows increased by one unit, physical activity was 3.19 times (P=0.03) more likely to increase by one unit compared to those without increased TFT. Overall, our data underscored the important physical, behavioral and ruminal changes related to estrus, which were accurately detected through the automated monitoring systems. Thus, it is suggested that HR-Tags and neck collars are suitable tools for estrus detection in commercial dairy herds.