Vitamins

• The alveolar cells do not posses the ability to synthesize vitamins. Therefore the vitamins present in milk are transferred from blood generally in proportion to their presence in the blood.
• Increasing the carotene or vitamin A content of the diet, as occurs during grazing can cause a 10 fold increase in vitamin A content of milk.
• Similarly, exposing cows to sunlight can increase the vitamin D content of milk. Since rumen micro flora synthesize all the B-vitamins, their concentration in the diet does not change that in milk. The only exception to this is riboflavin.
• By changing from a straw and concentrate diet to predominantly green, forage feeding regime the riboflavin content of milk increases.