As this column goes to press, the 2019 calving season will be starting for some while for others it will unfold over the next three to four months. In this column we have stressed the importance of proper nutrition during this period, both for the health of the cow and calf and for the success of the subsequent breeding season. While there are many aspects of nutrition to consider when developing a balanced ration, mineral nutrition is often neglected. With this column, I want to remind you of the importance of a mineral feeding program and try to answer some common questions producers have regarding this topic.
Perhaps the question I get most often from producers is which mineral is right for their operations. It’s not surprising that there are no simple answers when one looks at the multitude of choices (loose minerals, blocks, tubs, protein supplements) on the market, each with their own unique formulation in terms of macro (i.e. calcium, phosphorus, magnesium) and trace (i.e. copper, zinc, magnesium) minerals.
My approach to addressing this question is to ask the following series of questions. How well do you know your operation in terms of factors that influence forage mineral levels and availability? Have you had your forages tested for macro and trace mineral levels? What about testing your soil — soils deficient in specific minerals will lead to deficient forages. Also certain soil types can lead to either deficient forages or forages with specific minerals that are tied up and not available to the animal. As an example, grey wooded soils are known for their low selenium content while soils high in molybdenum can lead to induced deficiencies as they tie up copper and render it unavailable to the animal. Similarly, high-sulfate water — both surface and groundwater — can lead to a deficiency, as sulfate acts alone or in combination with high molybdenum levels in forages to tie up copper and render it unavailable to the animal.
Answers to these questions will go a long way to determining the type of mineral required, as well as the need to feed chelated minerals. For example, if your operation is in an area that is known to be deficient in copper or another trace mineral, then feeding a chelated mineral pre- and post-calving can be a strategy to help ensure adequate trace mineral status. Most inorganic minerals are poorly absorbed in the rumen. In fact, other than newborn calves, cattle poorly absorb copper and some of the other trace minerals. Chelated minerals are manufactured to be more available to the animal and thus can help to prevent deficiencies when feeding situations as discussed above arise. Answers to the above questions can also help your veterinarian diagnose and treat diseases such as white muscle disease in calves or retained placentas with vitamin E or selenium injections.
While one can purchase trace minerals on their own as either blocks or loose mineral, most commercial minerals are combinations of the macro and trace minerals and are often sold based on their calcium and phosphorus content. For example, there are numerous 1:1, 2:1 and 3:1 minerals on the market. These designations refer to the calcium and phosphorus ratio in the mineral. A 1:1 mineral has equal parts calcium and phosphorus, while a 2:1 mineral has twice as much calcium as phosphorus. The exact levels will be indicated on the mineral tag. For example, the tag of a 2:1 mineral might indicate that it contains 18 per cent calcium and nine per cent phosphorus, while a 3:1 tag might indicate 18 per cent calcium and six per cent phosphorus.
The choice of which macro mineral ratio best suits your operation often depends on the type of forage being fed. For example, legume and grass/legume hay will typically be high in calcium and marginal in phosphorus. In such situations a 1:1 mineral is most likely appropriate. For those grazing whole plant corn, calcium intake becomes a concern and a 3:1 mineral is justified.
Another area of confusion is the mineral tag itself. It contains information that points to both its nutritional value and its economic value. For example, the tag will indicate expected consumption such as 90 or 125 grams per head per day. It will also give the level of specific minerals in the mix, either as a percentage, as in the case of macro minerals, or as milligrams per kilogram (mg/kg) for trace minerals. Together, these two pieces of information can be used to evaluate the value of the mineral.
For example, an animal that consumes 90 grams of a mineral that contains 900 mg/kg of copper actually consumes (0.090 kg*900 mg/kg) 81 mg of copper. If that same animal consumes 125 grams of a mineral that contains 1,500 mg/kg of copper, it consumes (0.125 kg*1,500 mg/kg) 188 mg of copper.
For a 1,400-pound cow eating two per cent of her body weight on a dry matter basis, the first mineral is deficient in copper while the second will typically meet her needs. It pays to read and understand the tag before selecting a mineral — don’t just focus on price!
In next month’s column, we will focus on managing the mineral program.