III. Nutritive value as estimated in laboratory andVitamin B, (pyridosrin) after parturition contained 14, 25, 36 and 29/xg./g. fat (0-9,1-1, 1-3 and 1-3 mg./l.) of carotene and 48, 91, 67 and 165 jig./g. fat (2-8, 3-7, 3-0 and 6-9 mg./l.) of vitamin A, and the effects of the supplements were still evident in later samples of colostrum. It is of interest that the addition of carotene did not increase the vitamin A, and that the administration of vitamm A did not depress the .carotene, in colostrum.Unpublished work at Shinfield(77) gave very similar results, but the high vitamin A ration depressed the carotene content of the colostrum. Corroborative evidence comes from Russia (78), and from the U.S. Bureau of Dairy Industry (79). The colostrum of two cows which had been on pasture had a higher vitamin A potency than that of two cows on a ration low in vitamin A (79).Several authors have studied the vitamin A and carotene content of colostrum of different breeds under normal and experimental conditions. Valuable information comes from the Ohio State University herd for which two sets of values are available, one for groups of five to nine Ayrshire, Guernsey, Friesian (Holstein) and Jersey cows which calved while on winter feed (80) and another for similar cows of the same breeds, with the addition of Brown Swiss, which calved a year or two later on pasture (81). The values are not strictly comparable as they are given for separate days in the first study and for separate milkings in the second. On both occasions the carotene concentration in the first sample was lowest for Friesian cows (1-97 and 2-89 mg./l.) and highest for Guernseys (4-97 and 8-64 mg./L). For vitamin A, Jerseys were bottom of the four breeds on both occasions (2-18 and 1-44 mg./L), but Ayrshires led in the first study with 2-94 mg./l. and Guernseys in the second with 2-79 mg./l. The values for the Brown Swiss were 4-97 mg./l. for carotene and 3-48 mg./l. for vitamin A. It is noteworthy that the colostrum of the cows which calved in winter was relatively poorer in carotene and richer in vitamin A than that of the cows on pasture. The differences were much less marked in later samples. An interesting feature of these findings was that, on both occasions, the concentration of carotene in the Jersey colostrum was at first much less than for Guernseys, and even less than for Ayrshires, but the concentration declined more slowly, and the Jerseys were leading, for example, from the fourth to the seventh milking in the second experiment. The results indicate a marked individual variation in the concentration of vitamin A and carotene in colostrum, a fact emphasized by the findings of most other authors. In the first 3 days after calving some 50 mg. of vitamin A and 60 mg. of carotene were secreted in colostrum (80).Hansen, Phillips & Smith (82) followed the vitamin A and carotene content of the colostrum, and its change with the progress of lactation and method of milking, of eighteen Friesian cows which were uniformly fed indoors throughout their first ...
