[The level of beta-karotene and vitamin A in the blood of nursing calves and their mothers].

The level of beta-carotene and vitamin A was studied in the blood plasma of the calves of the Bohemian Spotted breed (heifers, n = 24) and in the blood plasma of their mothers (n = 24). The experimental animals were divided according to the date of birth or parturition into two groups: from the 0th to the 7th day and from the 8th to the 14th day after birth or parturition. All the animals showed no manifest signs of disease, the over-all health condition of the herd was good. Examinations were performed in the period from September to October. The composition of calf feed ration guaranteed the supply of beta-carotene to the organism. The average vitamin A level in the cows 0 to 7 days after parturition was 66.0 mug per 100 ml and the average level of beta-carotene in the same animals was 950.9 mug per 100 ml of plasma. In calves 0 to 7 days after birth the average level of vitamin A reached 16.7 mug per 100 ml and that of beta-carotene 87.5 mug per 100 ml of plasma. The mentioned average values are higher than levels considered as deficient. The levels of both substances increased in calves with the time of sucking: hence an average vitamin A level of 29.8 mug per 100 ml of plasma and beta-carotene level of 280.1 mug per 100 ml of plasma were found in the calf category from the 8th to the 14th day after birth. In this age category the level of vitamin A in blood plasma was still highly significantly lower than in the blood plasma of their mothers; however, in beta-carotene the difference was not statistically significant. While the levels of vitamin A and beta-carotene in calf plasma increased with the time of sucking, the level of both substances in the plasma of their mothers decreased. However, the drop of the level of vitamin A in cow plasma 8--14 days after parturition is not statistically significant; on the other hand, the drop of beta-carotene was found significant. This suggests that the reserve of these substances, especially of beta-carotene, in the cows decreases in the post-partal period which would justify, in breeding practice, an increased supply of vitamin A and beta-carotene, both with respect to calf nutrition and with respect to the biological value of milk used for human consumption.