Effect of Season, Breed and Species of Ruminants on the Vitamin A Potency of Butterfat

Abstract

Summary The seasonal variations in vitamin A potency of butterfat and other consituents in herd milk of Hariana cows have been investigated. The vitamin A potency varied with the level of carotene intake. The potency was maximal in the monsoon periods (July, August and September) when the cows were getting sufficient carotene from grazing and again during the winter months (February and March) when large quantities of cultivated fodders were available. The average maximum total potency approximated 24,972 I.U. per lb., of which 2,700 I.U. were due to carotene. The average minimum potency of 16,093 I.U., of which 1,322 I.U. were due to carotene, was obtained in November, December and January, when very little green feed was available. The maximum variations in carotene, vitamin A, and total vitamin A potency were 212.0, 56.6, and 55.0 per cent, respectively. The vitamin A potency was not influenced by the stage of lactation. Except for fat content, which was about 25 per cent higher in November, December and January, and for calcium and phosphorus, the solids-not-fat, protein and ash content of the milk remained unchanged throughout the experimental period. The Polenske values of the butterfat were higher in summer than in winter but the Reichert-Meissl and saponification values did not show any seasonal change. The saponification value was the same as that reported in the literature for American butterfat, but the Reichert-Meissl number was approximately 20 per cent lower and the iodine number was about 10 per cent higher. The inclusion, of green feed in the ration tended to increase the iodine value. There was practically no difference in the carotene and vitamin A contents of butterfat from the cows of the Hariana and Sahiwal breeds. Although butterfat from goats contained only traces of carotene, the vitamin A content was as high as the total potency in the butterfat from cows. Buffalo butterfat examined in this investigation resembled that of goats in respect to carotene, but the vitamin A content was comparatively low.