ABSTRACT Variability in ovarian stimulation (OS) response limits the efficiency of ovum pick-up–in vitro production (OPU-IVP) programs, with a minority of donors often producing most embryos. Reliable indicators to predict OS response in individual cows remain limited. In this study, we evaluated and quantified the ability of 3 key performance indicators—follicular output rate (FORT), follicle-to-oocyte index (FOI), and ovarian sensitivity index (OSI) —to classify ovarian response in dairy cows. Records from 1, 090 FSH-stimulated OPU sessions in 481 Holstein cows were analyzed, accounting for repeated sessions within cow in inference. Using the joint distribution of aspirated follicles and recovered cumulus–oocyte complexes (COCs), sessions were classified as poor, normal, or high responders (overall mean ± 1 SD), representing 15. 6%, 62. 8%, and 21. 7% of sessions, respectively. FOIbov, FORTbov, and OSIbov increased progressively across response groups and were associated with OPU outcomes; OSIbov showed the strongest correlations with aspirated follicles, total COCs, and grade A+B COCs. In receiver-operating-characteristic analyses, OSIbov discriminated poor from normal + high responders (AUC = 0. 974, 95% CI 0. 962–0. 983) and high from poor + normal responders (AUC = 0. 951, 95% CI 0. 934–0. 966), exceeding the performance of FOIbov and FORTbov; the corresponding optimal OSIbov cut-offs were 11 and 25, respectively. OSIbov-based categories agreed well with the clinical classification (quadratic weighted κw = 0. 777). In single-predictor ordinal logistic regression, OSIbov yielded the lowest Akaike information criterion and the highest concordance index (C-index = 0. 956). Across cows with repeated sessions, AFC and yield traits were highly repeatable, whereas FOIbov and FORTbov showed greater within-cow variability. We conclude that OSIbov is a practical indicator of bovine OS response and may support donor ranking and individualized stimulation to improve embryo-production efficiency.
Yang et al. (Sun,) studied this question.