Effects of Grape Extract Supplementation on Postpartum Reproductive Responses in Beef Cows: A Pilot Study

The postpartum period in beef cows is characterized by complex physiological and reproductive changes that may influence the postpartum reproductive changes and estrus expression. This exploratory pilot study evaluated postpartum reproductive responses in Angus cows receiving grape extract supplementation while investigating associations among thermographic, behavioral, hormonal, and reticulorumen temperature indicators associated with estrus expression. Nineteen Angus cows were assigned to a control group (C; n = 10) or a treatment group receiving slow-release grape extract boluses (T; n = 9). From calving until artificial insemination, ocular and vulvar thermographic images, blood samples, and physiological measurements were obtained weekly between 10:00 and 11:00 a.m. Reticulorumen temperature and activity data were continuously recorded using intraruminal sensors. Kaplan–Meier survival analysis demonstrated an earlier onset of postpartum estrus in supplemented cows compared with controls (p = 0.010). Mean time to first estrus was 23.88 ± 1.86 days in the T group and 39.82 ± 5.05 days in the C group. No significant differences were observed between groups for most individual physiological or hormonal variables. Exploratory correlation analysis revealed moderate associations among vulvar temperature, ocular temperature, activity, estrus index, and reticulorumen temperature indicators. However, because diagnostic accuracy was not evaluated, these findings should not be interpreted as validation of estrus detection performance. The results suggest that multimodal physiological monitoring may provide complementary information related to postpartum estrus expression in beef cows, while grape extract supplementation may be associated with earlier postpartum reproductive recovery. Due to the exploratory study design and limited sample size, further studies are required to validate these preliminary observations.