Effect of Bull Bio-stimulation on the reproductive parameters of post-partum anestrous cows

Background: Postpartum anestrus is a major reproductive challenge that hinders optimal productivity in dairy cattle, especially in tropical systems. Among non-hormonal strategies, bull bio-stimulation has emerged as a natural, low-cost approach to enhance ovarian resumption. Aim: This study investigated the influence of bull exposure on reproductive hormone profiles, hematological and biochemical parameters, and key fertility outcomes in postpartum Holstein Friesian crossbred cows under controlled farm conditions. Methods: Twenty-two non-cyclic postpartum cows, 60 days after calving, were divided into two groups: one exposed to a bull (BE; n=11) and the other not exposed (NBE; n=11). Over 21 days, estrus behavior, blood hormonal (E2, P4, LH, FSH), hematological, and biochemical parameters were assessed. Results: Bull exposure significantly accelerated the resumption of ovarian activity (81.82% vs. 27.27%) and improved progesterone levels (P<0.05). The exposed group showed fewer services per conception (1.33±0.16 vs. 1.85±0.34), and a higher conception rate (90.90% vs. 63.63%). Biochemical analysis revealed lower total protein and globulin levels, while hematological profiles showed elevated ESR, MCV, and MCH in the bull-exposed group. Conclusion: Bull bio-stimulation significantly improves postpartum reproductive efficiency in dairy cows through enhanced ovarian activity and favorable endocrine and hematological changes. This technique offers a practical, drug-free solution for improving fertility in resource-limited farming systems.