Vitamin Supplementation Strategies for Transition Dairy Cows.

Even though clinical vitamin deficiencies are rarely observed in lactating dairy cows, we know that inadequate vitamin status can produce a wide range of more general and often subtle problems. Vitamin supplementation is critical for transition dairy cows, as supplementation of several vitamins diminishes the risk or attenuates the severity of metabolic diseases, infectious diseases, or both. Milk production generally has not responded to vitamin A supplementation but some studies showed that cows with lower concentrations of retinol in plasma are at higher risk for retained placenta, mastitis, and lameness. Several studies reported enhanced immune function, reduced prevalence of mastitis and retained placenta, and improvements in various measures of reproduction efficiency, when cows fed adequate vitamin A were also supplemented with β-carotene; although several studies showed no response to supplemental β-carotene. Vitamin D, which is known for its regulation of calcium homeostasis, has been related to improvements in innate and adaptive immunity, and reductions of the severity of mastitis. A preponderance of studies has shown that adequate supplementation of vitamin E improves measures of immune function and reduces the prevalence of retained placenta, metritis, and clinical and subclinical mastitis. Vitamin E also can reduce the severity of clinical mastitis. Clinical deficiencies of B-vitamins are unlikely in functional ruminants, as they are synthesized in the gastrointestinal tract. On the contrary, vitamin degradation can also occur within the gastrointestinal tract, therefore limiting vitamin availability for absorption. The balance between synthesis and degradation within the gastrointestinal tract is not conclusive for most B-vitamins, likely due to difficulties in vitamin quantification. Overall, several studies showed that supplementation of certain B-vitamins can enhance animal production, animal health, or both. Biotin, choline, and niacin are the only water-soluble vitamins commonly supplemented to dairy cows. These three B-vitamins can have major benefits when feeding transition cows. Biotin supplementation has been related to improvements in foot health, increased milk production, and effects on gluconeogenic pathways. Niacin has been related to anti-lipolytic and thermoregulatory effects, although results for these affects are not conclusive. Choline supplementation has been beneficial attenuating metabolic disorders related to fatty acid metabolism, with beneficial effects in milk production during the transition period.