Possible role of beta-carotene in improving fertility in dairy cattle.

Recent interest in beta-carotene has been stimulated by reports that reproductive performance in cattle was improved with dietary supplementation of beta-carotene even when the diet was supplemented with vitamin A. Vitamin A requirements for cattle are based on studies with beta-carotene as the vitamin A source and with studies with vitamin A in the ester or alcohol form. Most of the studies with cattle that demonstrate the need for vitamin A for optimum reproduction were when beta-carotene was the source of vitamin A. Recent German reports show an improvement in conception rate, intensity of estrus, and changes in luteinizing hormone patterns when cattle received beta-carotene supplementation of low carotene diets. These diets were supplemented with vitamin A. A similar study from Israel did not detect benefits of beta-carotene. The active form of vitamin A for reproduction in rats and other species has not been determined; however, vitamin A does meet the reproductive requirements. The ruminant animal does have differences in carotene metabolism from the rat. Before the role of beta-carotene for reproduction in cattle can be clarified, the specific function of carotene or the specific form of vitamin A for reproduction needs to be determined.