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Field Study of Reproductive Performance with an Automated Activity Monitoring System Vs. a Synchronized Breeding Program in Dairy Herds
Leblanc J.S., Neves Camargos R...
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Objectives: the objective was to compare reproductive performance with an automated activity monitoring system relative to a synchronized breeding program under field conditions.
Materials and Methods: A pen-level randomized trial was performed over 1 year using 3 commercial herds in ontario, canada. Pens were assigned to an automated heat detection ( A Hd ) system based on monitoring activity (Heatime, SCR ) or a timed artificial insemination program ( TA I; ovsynch); cross-over occurred after 6 months to avoid confounding treatment with parity. A I based on additional detection of estrus by observation was practiced in all pens. Herds a, B, and C milked 495, 305 and 260 cows on average, providing 1303, 726, and 986 A I analyzed throughout the study period, respectively. Herd-level analyses were conducted using pen as the experimental unit. at the individual cow level, time to pregnancy throughout the study period (n = 1985 cow 6-month-periods) was analyzed with a cox proportional hazards model accounting for herd effect; parity, period and calving season were not significant covariates.
Results: the proportion of TA I in the TA I pen was 49%, 72% and 55% and the proportion of A I in after a heat signaled by the A Hd system was 69%, 63% and 61% for herds a, B, and C ; other A I in both groups were by observation of estrus. the mean annual 21-d pregnancy rates (Pr ) across the 3 herds (6165 cow-21-d-periods) were compared controlling for herd. there was no difference (P = 0.25) in the overall Pr between TA I (15.9%) and A Hd system (14.6%) or in the probability of pregnancy per A I ( CR = 30 to 33%). overall, time to pregnancy was not different (Hazard ratio (H R ) = 1.13, P = 0.2) between cows assigned to management by A Hd or TA I. However, an interaction between herd and breeding program indicated that time to pregnancy was not different in herd A (median = 151 and 136 days; H R = 0.93, P = 0.52) and herd C (median = 99 and 124, Hr = 1.24, P = 0.08) whereas herd B had a median time to pregnancy of 119 d and 146 d (Hr = 1.3, P = 0.02) in the A Hd and TA I groups, respectively.
Conclusions: under conditions in which a substantial minority of A I in both groups was based on visually detected estrus, herd pregnancy rate and cow-level interval to pregnancy were not different between taI and A Hd-based programs. However, factors that influence the variability in relative performance of these management systems between herds require further investigation.
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Affiliation of the authors at the time of publication
University of Guelph, Canada
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