Reproductive Efficiency Of Thoroughbred Mares On Different Forage Regimens With Supplementation Of Retinyl Palmitate And Beta-carotene.

Greiwe-Crandell KM, SD Kronfeld, LS Gay, D Sklan, PA Harris. 1997. Vitamin A repletion in Thoroughbred mares with retinyl palmitate or ß-carotene. J. Anim. Sci. 75:2684-2690.

Reproductive efficiency in the mare is lowest among domestic livestock. Researchers set out to determine if this may be partly dependent on vitamin A status of mares.

To test this hypothesis, 45 Thoroughbred mares were depleted of vitamin A for 8 months and then repleted for 20 months. During the repletion phase, mares were given retinyl palmitate, b-carotene, or a placebo. Foals were weighed at birth and monthly thereafter. Reproductive rates were calculated for the years in which depletion and repletion were developing. Retained placenta and contracted tendons were observed clinically.

During the repletion phase, supplementation of retinyl palmitate resulted in higher pregnancy rate, foaling rate, and pregnancy loss than b-carotene.

Lack of vitamin A supplementation during pregnancy may increase the risks of retained placenta and congenital contracted tendons. Mares appear to benefit from supplementation with vitamin A but not water-dispersible b-carotene.

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