2026 Volume 97 Issue 3 Pages 121-131
We developed and evaluated a paper-based indicator tool for estimating elapsed time since estrus onset─based on the wicking distance of red fluid released at the first standing event (ST)─to predict the optimal timing for artificial insemination in cows (6-24 h after the onset of estrus). The elapsed time prediction model was constructed using the Lucas-Washburn and Andrade equations, with the indicator wicking distance and daily mean temperature as explanatory variables. Additionally, model coefficients were estimated by least-squares analysis using observational data from six Japanese Black cows. Subsequently, 33 Japanese Black cows were used for the model validation. The following parameters were examined : timing of the first observed ST, estrus detection rate, changes in the indicator wicking distance over time from device activation, timing of artificial insemination, and pregnancy results. At 16 h after the first ST, the mean absolute error of the predicted indicator wicking distance was 20.7 mm, estrus detection rate was 87.9%, and pregnancy rate was 79.2%. These findings indicated that the developed tool and prediction model may provide high pregnancy rates.
