Vitamins are essential nutrients that are required for normal development and functioning of the body. Vitamins are provided to the animal in two different ways: synthesized by microorganisms in the digestive tract of animals and provided in the diet through feed ingredients and supplementation when feeds are lacking in vitamin nutritive value.
In order for an animal to reach optimal health and performance, we must first understand the nutritional requirements of the animal, depending on their age and stage of production. Then, we need to evaluate their diet and supplemental program to identify if the appropriate vitamins are being supplemented and at what levels.
Most often, dairy cows are supplemented with vitamins A and E to prevent clinical deficiencies that can impair health and production. However, it is good to consider and evaluate research-supported benefits of other vitamins and levels not only to prevent deficiencies, but to also target optimal health and performance, including supplemental vitamin D, biotin, niacin and beta carotene.
Vitamin A
Vitamin A is derived from carotenoids found in plants and serves a wide range of functions to the animal, including playing a key role in bone, teeth and nervous tissue development, gene regulation, reproduction, growth, vision, kidney function and immune function. It is well understood and accepted that vitamin A has an absolute dietary requirement for dairy cows to prevent clinical deficiencies.
Vitamin E
Vitamin E is essential for optimum functioning of many biological systems in animals. It has important functions in the muscular, nervous, circulatory, reproductive and immune system. Vitamin E is also one of the most potent biological antioxidants and a free radical scavenger – functions that are well established and described in the scientific literature. Sufficient vitamin E and selenium levels have been shown to improve lactation and milk yield and reduce incidence of mastitis.
Vitamin A and E content in feeds is highly variable and unstable with exposure to oxygen, light, temperature and humidity. Supplementation is required in most cases when vitamin concentration is unknown and harvested feeds or poor-quality forages are fed. When including supplemental vitamins in diets, it is important to consider the quality to ensure stability and bioavailability of the nutrients.
Vitamin D
Vitamin D is known as the “sunshine vitamin” since vitamin D3 is synthesized in the skin from UVB light from the sun. However, there are certain times of year, depending on geographical location and feeding environments, where blood serum 25-OH-D3 levels have reached deficient levels and could compromise the many functions that vitamin D serves, including Ca:P homeostasis, immune function and reproduction.
In recent developments, an option to supplement vitamin D in the form of calcidiol, also known as 25-hydroxyvitamin D3, is available. This form of vitamin D, produced in the liver, supports skeletal development in cows and calves and will help in calcium metabolism before and after parturition for prevention of hypocalcemia.
Supplemental B vitamins: biotin and niacin
Rumen microbes are able to synthesize many of the B-complex vitamins cows need for optimal health and production; however, recent research suggests that microbial production of biotin and niacin may not be sufficient to meet the nutritional requirements of high-producing cows.
Biotin plays a role in gluconeogenesis, lipogenesis and protein synthesis and increased glucose production by the cow. Research supports improved milk production and improved fertility in cows supplemented biotin. It also is an essential factor in intracellular bonding the keratin leaflets of the hoof horn, supporting horn formation, horn quality and prevention, and improved healing of hoof lesions.
Niacin is a component of NAD and NADP, essential coenzymes in ATP production, also having a central role in DNA repair and skin homeostasis. It has been shown to reduce the concentration of ketones in blood, increase blood glucose levels, increase ruminal microbial protein synthesis and improve milk yield (3% to 4%) during first lactation.
Benefits of supplemental beta carotene
Beta carotene is the most common type of carotene in plants and considered a provitamin A, or a substance the animal needs to produce vitamin A. It also serves as a powerful antioxidant to reduce the effects of oxidative stress that can negatively affect fertility and performance of dairy cows.
More specifically, beta carotene has biological effects independent of producing vitamin A. It serves an important role in protecting the corpus luteum and promotes the synthesis of the pregnancy hormone progesterone, which supports stronger heats and greater success of implantation of the fertilized egg. In addition, reduced incidence of reproductive disorders and improved colostrum quality are other research-supported benefits of ensuring adequate beta carotene levels in cow diets.
In conclusion, considerable progress has been made in our understanding of vitamin nutrition of dairy cows during the last 15 years. The Optimum Vitamin Nutrition (OVN) recommendations have been compiled based on NRC guidelines and published data. The response benefit of the vitamins previously mentioned helps to optimize not only performance and milk quality, but also cow health and welfare. Healthy cows are important for saving costs, thus increasing profits, and ensuring longer and more productive milking lifetimes.
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