Update on Vitamin Nutrition of Dairy Cows

Vitamins are organic compounds needed in minute amounts that are essential for life and must be absorbed from the gastro-intestinal tract. Either the vitamin must be in the diet (dietary essential) or be synthesized by microorganisms in the digestive system and absorbed by the host animal. Currently there are 14 recognized vitamins but not all animals require all 14 vitamins (Table 1). When an animal absorbs an inadequate quantity of a particular vitamin, various responses are observed depending on the vitamin and the degree and duration of deficiency. The most severe situation (seldom observed in the U.S. dairy herd) is a clinical deficiency. For example, rickets and scurvy result from a clinical deficiency of vitamin D and vitamin C, respectively. Marginal deficiencies of vitamins usually have more subtle and less defined signs. Unthriftiness, reduced growth rate, milk production, or fertility, and increased prevalence of infectious diseases can be observed when animals absorb inadequate amounts of vitamins.