Prices of vitamin A (along with vitamins D and E) have increased to 10 times their former costs from just a few months ago. This skyrocketing price is due to a recent fire at a new manufacturing facility in Germany as well as several vitamin ADE plants that are down for maintenance in China. Together, these events have caused a worldwide shortage of these essential vitamins for both human and livestock nutrition, including the well-balanced diets put down in front of dairy cows and calves every day.
As a dairy nutritionist, I strongly believe that vitamin A is a primary nutrient for dairy cattle. Therefore, with the possibility of further price increases and limited availability, I recommend that dairy producers review their dairy diets of baby calf, replacement heifer, dry and lactation cows. Make sure that each group is fed their basic dietary requirement for vitamin A without anymore fed than needed.
University and commercial suggestions for providing vitamin A in dairy diets are significantly higher than guidelines set forth by the National Research Council (NRC). Many non-NRC references state non-lactating dairy cattle require between 50,000 – 75,000 iu/head/d of vitamin A, while their lactating counterparts need between 100,000 – 150,000 iu/head/d. All of which depends upon the animals’ stress and health status.
Regardless of what set of recommendations are followed, I know of no substitute for vitamin A. However, most people don’t realize that vitamin A is a generic term (like no-name products) that science uses to cover a number of compounds with similar chemical structures and specific biological activities to a compound called retinol.
There are three major functions for vitamin A in dairy cattle. First, vitamin A plays an active role in the maintenance and health of epithelial tissue, which in turn plays an indirect role in the first line defense against invading organisms. This tissue includes all outer skin surfaces and the cellular linings of the respiratory, digestive, and reproductive and urinary tracts. Other similar functions include healthy bone formation, a regular estrus cycle in female cattle and sperm production in bulls.
A second major function of vitamin A is in a compound called rhodopsin found in the retina of the eye. This chemical allows the animals’ sight to adjust from light to dark conditions (i.e.: prevents “night-blindness”). Although it is rare, a severely vitamin A deficient cow may give birth to a blind calf.
Closer to home, vitamin A’s last major function involves immune response, where it is required for the production of white blood cells to fight disease. We might see it as a marginal deficiency in post-partum dairy cows with a higher incidence of health problems such mastitis. It is believed pre-fresh cows transfer a large portion of vitamin A from their own bodies into colostrum for their newborn calf and literarily drain themselves of vitamin A, which lasts for few weeks into early lactation.
University of Guelph (2004) quantitated this risk of clinical mastitis as it relates to the post-partum cows’ blood level of vitamin A. The researchers collected blood samples in dairy cows; just prior to calving and posted them against clinical cases in the first 30 days of lactation. As a result, a majority of the mastitis cases occurred after calving and mastitis-positive cows had on comparison a much lower level of vitamin A in their blood (difference > 100 ng/ml) than mastitis-negative cows. It was concluded from this study that cows with high blood levels of vitamin A have a much lower chance of developing mastitis in early lactation.
This study demonstrates to me essential levels of vitamin A should be fed to dairy cattle including lactating dairy cows at all times. Other related studies also impress upon me to use only reliable commercial stores of vitamin A when I formulate these dairy diets. Some manufacturers use vitamin A precursors, reacted with gelatin and different sugars, to form insoluble (water) vitamin A beads, which gives them greater stability and shelf-life, yet retains high bio-availability in dairy cattle.
Despite the recent sticker-shock price of commercial vitamin A, it should never deter anyone from meeting these vitamin A requirements in dairy cattle. Besides, vitamin A is still available at these high prices and its price increase still amounts to pennies per dairy animal. I believe that it’s a still a small price to pay to keep dairy cattle healthy and strong performers.