Possible Role of Beta-Carotene in Improving Fertility in Dairy Cattle

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Abstract
Recent interest in .beta.-carotene was 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 was not determined; 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.