RESUMEN
ß-Carotene is an essential nutrient in cattle reproduction. The objective of this study was to evaluate the effect of ß-carotene supplementation on ovarian activities throughout the estrous cycle in nonpregnant Japanese Black cows. The estrous cycles of eight nonpregnant Japanese Black cows were synchronized using a double synch protocol, and the cows were divided into two groups. The cows in the ß-carotene (BC) group received supplementation with 1000 mg/day ß-carotene for 46 days including the synchronization period. The cows in the control (C) group did not receive ß-carotene supplementation. The results showed that ß-carotene supplementation at 1000 mg/day was sufficient to maintain a high plasma ß-carotene concentration and increase the plasma retinol concentration and that ß-carotene supplementation had no significant effects on the dominant follicle diameter, total number of estrus behaviors, or length of the estrous cycle. In contrast, the areas under the P4 concentration curves in the BC group were higher than those obtained for the C group. In conclusion, a high plasma ß-carotene concentration in Japanese Black cows promotes P4 production in the luteal phase of the estrous cycle and total P4 production throughout the estrous cycle without changing the length of the estrous cycle.