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 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 animals’ requirements. The two main reasons to control mineral content in lactating dairy diets are: economical and regulatory.
From an economical point of view, excesses and/or imbalances of dietary minerals may have the following effects: (a) increased feed price, (b) decreased animal performance, and (c) increased manure production. 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 with highly concentrated diets, reducing rumination rates and rumen retention times by increasing rates of passage may increase subclinical acidosis, reduce rumen fiber fermentation and milk fat contents, and increase laminitis problems. According to recent studies, an average dairy farm would be able to reduce about ½ pound mineral excretion per cow per day, representing a significant reduction of manure production, labor management and money.
From the regulatory point of view, the NRC 2005 (Mineral Tolerance of Animals) 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 concerned with waste management plans and nutrient management plans where nitrogen is currently the primary concern. In the near future, most of the minerals indicated previously might be considered.
Finally, it is recommended to make a mineral content database of the feeds utilized on each dairy, including the drinking water and the most commonly purchased concentrate feeds. In a few years, each dairy will have information to make correct mineral balances and to control mineral supplements strictly according to the animals’ requirements. This will improve production efficiency, reduce feed cost, reduce manure production and help farms comply with environmental regulations. ANM
Alejandro R. Castillo
Farm Adviser-Dairy Science at UCCE Merced County
arcastillo@ucdavis.edu
