Estrus detection efficiency and the effects of using prostaglandin-F2α in a commercial dairy herd

The purpose of this study was to define the biological efficiency of a standard estrus detection regimen, both with and without use of prostaglandin-F2α, under commercial dairy conditions. At regular pre-breeding examinations, cows were allocated randomly to two cohorts: (1) prostaglandin (PT) - cows with palpable corpora lutea were injected with 25 mg dinoprost tromethamine and bred 72 and 96 h later; and (2) heat detection (HD) - cows identified as being "in heat" through twice daily observation with tail chalking were bred ∼ 12 h later. Age, body weight, milk production and reproductive data were collected for all cows, as were milk samples for progesterone analysis. Prostaglandin use significantly affected the sensitivity of the estrus detection test, lowering it by half (0.26 vs. 0.53), plus it increased the proportion of false negatives by 61% (0.34 vs. 0.21) over controls. Consequently, the predictive value of a positive test in the PT cohort was lowered by 14% (0.79 vs. 0.90) compared with control animals. Over both cohorts, the standard estrus detection test displayed a low sensitivity and a high specificity, characteristic of a diagnostic test, but not of a screening test. The findings from this dairy suggest that current recommended estrus detection procedures may be inappropriate for their declared purpose of being screening tests for estrus and that routine prostaglandin use may exacerbate the problem.