At the recent Ruminant Nutrition Symposium, dairy nutritionist and allied industry got an update on recommendations for trace minerals and vitamins for dairy cows. While nutritionist are still operating with information from the 2001 NRC (7th edition Nutrient Requirement of Dairy Cattle), an updated version will likely have some updated recommendation for vitamins and minerals. Dr. Weiss, Department of Animal Science, The Ohio State University discussed some of these changes at the symposium. One of his key point was to look at the actual needs of the cow in mg/day instead of ppm in the diet. This is important because with high producing cows eating much larger quantities of feed, the ppm is decreased as the amount of feed increases. Another key point was not to ignore the minerals and vitamins found in basal feeds. While this amount might be highly variable, it should not be ignored completely. He recommended taking multiple samples to improve accuracy or using the reliable values from a current feed library or your testing lab. Furthermore, a portion of basal feed minerals and vitamins may be more available than the inorganic or organic sources, so they should be counted in the formulation.
Some important minerals and their interactions were also discussed. Dr. Weiss noted that while overfeeding some minerals can cause toxicity problems, underfeeding is more of an issue. For example, Copper (Cu) has been proven to decrease the cases of mastitis and metritis in dairy cattle. Underfeeding and excessive overfeeding of all minerals should be avoided.
The interaction of Sulfur (S) with other minerals was discussed. Sulfur can cause the Copper (Cu) and Selenium (Se) in the diet to be less available. Dr. Weiss recommended testing your water to determine the level of Sulfur (S).
Dr. Weiss also noted that not all mineral sources were equal. For example, organic Zinc (Zn) has been show to decrease fecal excretion of one pathogen associated with digital dermatitis. However, feeding the same level of Zinc (Zn) from an inorganic source did not have this benefit. Because this effect happens within either the rumen or intestine, the response is not related to differences in bioavailability.
Dairy farmers and their nutritionist use research based information to provide the best diets for healthy cows. These diets provide their exact nutrient needs, promote healthy immune function, and promote environmental stewardship.