Feeding of corn co-products like distillers grains and corn gluten has changed the mineral balance in winter cattle diets, said Dennis Bauer, Brown County Extension Educator.
Those products are really high in phosphorus, Bauer said. When ranchers begin feeding two to three pounds of these co-products, they can discontinue phosphorus supplementation completely and just feed salt with a little bit of copper and zinc.
Deficiencies of phosphorus, copper and zinc are of primary concern, he said, as is the ratio between phosphorus and calcium. Without these minerals and several others, cattle don't perform as well as producers might expect. More severe shortages of these minerals can disrupt reproductive health, Bauer said.
During a three-year study conducted between 2001 and 2003, UNL researchers tested about 1,000 samples of winter forages, including a lot of meadow hay. For the most part, meadow hay proved to be a good source of calcium, although it was a bit deficient in phosphorus, copper and zinc. Other minerals such as magnesium, manganese, potassium and sulfur were found in sufficient concentrations to meet the animals' requirements 90 to 100% of the time.
Forages such as millet (foxtail and pearl), oat hay, and forage sorghums contain most of these minerals in concentrations that will meet the cow's requirements in most situations.
Alfalfa is the best source of all the minerals. Copper and zinc were the only minerals found to be in concentrations below the cow's requirements. But, Bauer said, most producers don't provide a full feed of alfalfa, so the cow's requirements still may not be met. He did not recommend a full feeding of alfalfa because that would mean overfeeding protein.
Instead, he encouraged ranchers to test their forage. Find out what minerals are in the forages during the winter. They can give credit for the minerals those forages contribute and balance the ration with a custom-mixed mineral package.
Mineral balance in a cow's winter ration can make the difference between good and substandard performance.