Minerals are essential in dairy cow diets for normal lactation performance (milk yield, animal health, and reproduction). But, animal mineral requirements are variable and depend on the animal’s productivity. Also, concentration of minerals in forages and concentrate feeds are variable, and not all the minerals in the diet are available for absorption. Mineral absorption coefficients can be very low, variable, and for some feeds are not very well known. Moreover, interactions between dietary minerals in excess or deficit may affect the minerals’ absorption coefficients. The only solution to minimize and control this situation is to analyze feed mineral content and drinking water mineral composition, and use this information to supply minerals strictly according to the animal’s requirements. There are two main reasons to control mineral content in lactating dairy diets in California: economical and regulatory.
Excessive mineral intake wastes money and in many cases affects the animals’ productivity. For example, excess salts in the diet may affect rumen osmolarity and rumen dilution rate. High osmotic pressure in the rumen was associated with cessation of rumination and increased rate of passage. For high-yielding dairy animals fed highly concentrated diets, a reduction in rumination rates and rumen retention times may reduce rumen fiber fermentation and milk fat content, and increase both subclinical acidosis and laminitis problems. From the regulatory point of view, the Mineral Tolerance of Animals (NRC, 2005) identified 10 minerals that could be of concern because of their potential effects on crop yields or the environment: cadmium, copper, iron, mercury, phosphorus, potassium, sodium, selenium, sulfur, and zinc. In California, dairy producers are preparing waste management plans and nutrient management plans where nitrogen is currently the primary concern. In the near future, the minerals indicated previously might be considered. It is recommended to make a mineral content database of the feeds utilized on each dairy, including the drinking water. This database will allow each dairy to formulate diets according to the animals’ mineral requirements.
This will improve production efficiency, reduce feed cost, reduce mineral excretion, and help farms comply with environmental regulations.