The effect of intake of carotene on reproduction in sheep.

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Abstract
Ewes aged initially 3-7 years were kept in pens for periods of 3-4 years on diets which supplied only about 10 µg carotene per kg body weight per day but were adequate in other respects; supplements of carotene ranging from 25 to 200 µg per kg body weight per day were added during the five gestation periods of the experiments. Signs of vitamin A deficiency such as night-blindness and low concentrations of vitamin A in the blood did not appear until the sheep had been receiving the deficient diets for at least 16 months. The levels of vitamin A in the blood rose during periods of supplementation by amounts proportional to the intakes, but the increases brought about by a carotene concentrate were smaller than those with equivalent amounts of carotene as lucerne meal. Reproduction was satisfactory when the intake of carotene was 50 µg or more per kg body weight per day, and when at least 80 per cent. of this carotene was supplied as lucerne meal.