Maria Villagrasa & Fernando Diaz
Vitamin E is an essential nutrient for cows, but the effects of its supplementation are often controversial in the scientific literature. The goal of a recent meta-analysis published in Journal of Dairy Science was to evaluate the effects of vitamin E supplementation and serum vitamin E levels on productive and reproductive variables of dairy cows in transition.
Alvaro Garcia
Diet formulation for lactating dairy cows requires a thorough understanding of ruminant biology. Their unique digestive system makes them susceptible to disfunctions of the pre-stomachs when departing from their requirements. Successful nutritionist understand that they need to feed two interdependent systems, the host itself (the cow), and the microorganisms populating the rumen.
Supplying the reticulum and rumen with energy, nitrogen/protein, minerals and even vitamins, maximizes the growth of the microbial population and allows the fine-tuning of this symbiotic relationship. Different microbial groups within this population have specific needs and are specialized in their ability to degrade different substrates.
Recent studies for example have indicated that folic acid (FA) addition to the diet stimulated DNA synthesis in dairy cows and upregulated the gene expression related to protein synthesis in the mammary gland. Folic acid is reduced to tetrahydrofolate which is essential for the growth of Ruminococcus (R.) flavefaciens.
Dietary rumen-protected folic acid addition has increased cellulolytic bacteria population and the activity of its enzymes, α-amylase and protease. It has also had a positive effect on milk and milk protein yields. Betaine, the trimethyl derivative of glycine, arises from choline oxidation and is used in osmoregulation and transmethylation reactions.
Betaine donates a methyl group to regenerate methionine from homocysteine and is then converted to dimethylglycine. The methyl groups of the latter are split-off through oxidation and transferred to tetrahydrofolate to generate 5,10-methylene- tetrahydrofolate. Dietary betaine supplementation has been shown to increase intestinal microbes, digestive enzyme activities and nutrient digestibility in single-stomached animals and helped maintain the structure and activity of the mammary gland cells in dairy cows.
Alvaro Garcia
Early lactation is a challenging and stressful period for dairy cows. Several metabolic diseases happen during this period, which is characterized by a negative energy balance and metabolic imbalance. Most of these issues start as close-ups and result from faulty management and/or feeding practices. Over-conditioning cows during the dry period allows them to mobilize more fat after calving and make them prone to metabolic diseases early in the lactation.
Recently calved cows have reduced appetite and greater energy demands due to the sudden increased milk production. This results in greater fat mobilization and increased hepatic triacylglycerol deposits predisposing to what is known as fatty liver and even ketosis. There are also negative effects of excessive fat mobilization on the metabolism and the immune system (neutrophils). Blood neutrophil phagocytosis has been shown to decrease 14 days post calving in cows overfed during the dry period. Choline helps with lipid transport from the liver in very low-density lipoproteins (VLDL).
Alvaro Garcia
Reducing the use of antimicrobial drugs is a concern in modern animal production. As a result, successful health interventions through the use of natural feed additives are currently explored. Vitamin dietary fortification has shown promise as potential to improve health and prevent disease. Vitamin D, for example, has shown effects from this perspective against both mastitis and metritis.
Aside from role of vitamin D in Ca and P homeostasis there are other effects however, such as its immunomodulatory role in cattle innate immune cells and mammary gland. This vitamin intervenes in physiological functions regulated by enzymatic activation and intracellular vitamin D receptors. The form supplemented however is important. Cows fed 25(OH)D3 have shown improved neutrophil function, mastitis reduction, reduced risk of retained placenta, metritis, and increased milk yield compared with cows fed just vitamin D3.
Fernando Diaz
Biotin is a water-soluble vitamin that is synthesized by ruminal bacteria. It is a vital enzyme cofactor involved in several metabolic processes including fat and carbohydrate metabolism, and protein synthesis. Because newborn calves do not have a functional rumen, they rely on biotin acquired in utero and by colostrum intake.
Providing a colostrum with optimized concentrations of biotin could be beneficial for the pre-ruminant calf growth and health. A recent study conducted at the Agriculture and Agri-Food Canada Research Centre, Quebec, Canada evaluated the effect of maternal biotin supplementation before calving on colostral and plasma concentrations in this vitamin in both the cow and the newborn calf.
Fernando Díaz
Folic acid or folate is a B-complex vitamin that works as a donor and acceptor of one‐carbon units. Thus, it is involved in the synthesis of nucleic acids (DNA) and amino acids (methionine). The name folic acid is deduced from folium (leaf in Latin), because this vitamin was originally isolated from spinach leaves.
Ruminal microorganisms from healthy cows produce enough amounts of folic acid to avoid deficiency. However, previous studies in dairy cows demonstrated that dietary supplementation of folic acid increases milk and milk protein yields. Since microbial degradation of supplemental folic acid is very extensive (more than 95%), rumen‐protected folic acid is usually used for feeding lactating cows.
