AUTOMATED MONITORING OF DAIRY COW HEALTH AND IMPACT OF POSTPARTUM VOLUNTARY WAITING PERIOD DURATION ON DAIRY COW PHYSIOLOGY AND HERD PERFORMANCE

The objectives of the studies presented in Section I were to evaluate: the performance of an automated health-monitoring system (AHMS) that combines rumination time and physical activity into an alert system (i.e., health index score, HIS) for identification of cows with health disorders; the timing of alerts in relationship to clinical diagnosis (CD) of disorders; and the patterns of rumination time, physical activity, and HIS around CD of disease. The objectives of the experiments presented in Section II were: evaluating the reproductive performance, herd exit dynamics, lactation performance, and profitability of dairy cows managed with different duration of the voluntary waiting period and methods of submission for first service. The studies presented in Section I demonstrated that the sensitivity of the HIS to identify cows with health issues was high for metabolic and digestive disorders (93%) and moderate for cases of clinical mastitis (55%) and metritis (55%). Among mastitis cases, HIS was effective for identifying cows with mastitis caused by Escherichia coli (80.7%), but it was less effective in identifying cows with mastitis caused by other pathogens (45 to 48%). Cows diagnosed with metritis and flagged based on HIS had substantial alterations of their rumination, activity, and HIS patterns around CD, suggesting that the AHMS was effective for identifying cows with severe cases of metritis, but less effective for identifying cows with mild cases of metritis. The overall accuracy of the AHMS alerts combining rumination and activity indicated that it could be a useful tool for identifying cows with metabolic and digestive disorders, and more severe cases of mastitis and metritis. Experiments presented in Section II demonstrated that extending duration of VWP from 60 to 88 days increased pregnancies per artificial insemination to first service, but delayed time to pregnancy during lactation and increased the risk of leaving the herd, particularly for multiparous cows. This shift in pregnancy timing led to an extension of the lactation length, which resulted in greater total milk yield per lactation. Extending the duration of the VWP may increase profitability of primiparous cows and reduce profitability of multiparous cows, primarily due to differences in herd replacement dynamics and milk production efficiency. Therefore, farms may benefit from extending the duration of the VWP beyond 60 d for primiparous cows but not for multiparous cows. Finally, we also observed that reproductive management strategies that led to similar average days to the first service (~60 d) through a combination of inseminations at estrus with timed-artificial insemination (TAI) or all TAI resulted in reduced time to pregnancy after calving when compared with an all TAI program with a longer VWP