In the fall Texas A&M Texas Dairy Matters newsletter, Kevin Lager, extension specialist with the Texas AgriLife Extension Service, offers the following comments on minerals in dairy cow rations:

Minerals comprise a small percentage of the diet, but can have huge consequences if supplements are removed or are supplied at inadequate levels in the ration. The major minerals, macrominerals, required by the cow include calcium, phosphorus, magnesium, potassium, sodium, chlorine and sulfur. Microminerals, minerals required in smaller quantities, include iodine, iron, cobalt, copper, manganese, zinc, and selenium.

Forages and concentrates provide a substantial portion of the mineral requirement, but supplemental mineral sources are required due to insufficient levels provided by the dietary ingredients and also due to the variability in bioavailability of the minerals from the forages and concentrates. It is necessary to test the dietary components for mineral content using approved methods of analysis.

Wet chemistry analysis most accurately measures mineral content for a greater number of minerals, followed by inductively coupled plasma (ICP) and near infrared reflectance spectroscopy (NIR). Samples analyzed by ICP and NIR are checked against samples analyzed through wet chemistry methods.

So if there is an ideal time to eliminate or reduce mineral supplementation, what stage of lactation allows for this adjustment? In early to peak lactation the cow is depleting her bodily stores of calcium and phosphorus and is at her greatest need for adequate mineral levels due to the body’s inability to store large quantities of available minerals. Selenium and zinc promote cow health during a time when her body is recovering from calving, maintaining a high level of production, and also preparing herself reproductively for pregnancy. Minerals, such as sulfur, copper and cobalt, promote gut health to assist with digestion of the large amount of feed being consumed that eventually ends up as milk. In mid to late lactation, the cow is still producing milk, but is also replenishing bodily mineral stores utilized in early to peak lactation to prepare herself for when she must draw on those stores when she freshens again. She also is supporting a growing fetus, which very well could be her replacement. The dry period also does not look good for inadequate mineral supply, since calf development is at its greatest during the later months of gestation. Sub-par nutrition in the dam significantly affects the health of the calf she is carrying.

The effects of inadequate mineral levels may not be realized for months after the ration adjustment. These effects may surface as lameness issues, since a weak point in hoof development today may take up to three months before the hoof will grow out to where she will display lameness. Reproduction may suffer with inadequate mineral supply leading to greater days in milk before conceiving and increased costs associated with breeding due to increases in the number of services per conception and drug costs for synchronization.

Poor economic times are an incentive to improve efficiency. Test for the mineral content of the dietary components and formulate rations to supply adequate mineral levels based on cow production. Knowing the mineral content of the dietary components may allow for a reduction in the level of mineral supplementation depending upon the lab test results. Continue to work with a nutritionist to find the proper balance. Cutting corners now may very well cut into profits down the road.

Source: Texas A&M