As I write this article, we have just entered a new year and indeed a new decade. While we do not know what the next 10 years will hold for us, we do know that many of the production issues we faced in the last decade will still be with us as we move into 2020.
One of those issues is ensuring proper mineral nutrition of the breeding herd. As many of you will be calving in the next three to four months, it is a good time to review this important topic.
Whenever I give a presentation on mineral nutrition, I always stress that mineral supplementation should be a year-round initiative. While it is true that the last two to three months before calving and the time period from calving through breeding is most important, failure to supplement mineral during the summer or winter can leave cows deficient going into these two important periods. The key is to understand that mineral needs of the breeding herd change with the season and that the mineral you feed at one stage of production may not meet the needs at the next stage.
Let’s quickly review what minerals we are most concerned with. The first grouping is the macro-minerals — those that are required in relatively large amounts (i.e. grams per day). This grouping includes calcium, phosphorus, magnesium and potassium. Individually and as a group, they play a critical role in growth, health, pregnancy and lactation.
The trace minerals of concern include cobalt, iodine, copper, zinc, manganese and selenium. These minerals are required in minute amounts (i.e. milligrams per day) yet deficiencies result in severe production and health issues including infertility, reduced immunity, poor growth, white muscle disease and retained placentas.
Mineral deficiencies can be classified as a primary deficiency where soils and the resulting forages grown on them are lacking in a given mineral. They can also be classified as a secondary deficiency where mineral-to-mineral interactions in the feed and/or water result in a given mineral such as copper being tied up and unavailable to the animal.
With respect to the macro minerals, forage type and maturity have a large influence on the concentration of calcium, phosphorus and magnesium. For example, legumes and grass-legume mixes are typically high in calcium and relatively low in phosphorus. Cereal silages, cereal straws and various types of grass hay generally are intermediate in calcium and phosphorus concentration. Magnesium can be deficient in early spring pastures, potentially leading to issues with grass tetany. A pre-partum magnesium deficiency with symptoms similar to milk fever can also be induced by high dietary potassium levels.
Trace mineral deficiencies can also result from a primary deficiency in the soil or due to mineral-to-mineral interactions. A classic example of the former is that of a selenium deficiency in forages grown on grey wooded soils. Producers blessed with this type of land base are familiar with issues such as white muscle disease and retained placentas, both a result of a primary selenium deficiency.
Secondary trace mineral deficiencies are common across the country, particularly for copper. Copper deficiencies can result from excess dietary levels of iron, zinc, molybdenum and/or sulfur. In particular, high dietary molybdenum levels that result in dietary molybdenum/copper ratios less than 2:1 can result in a severe copper deficiency. Similarly, high dietary sulfate levels (greater than 0.4 per cent, including that from water sources) can act alone or in combination with high molybdenum levels to result in copper deficiency.
Most of the common minerals on the market are formulated using inorganic sources of the trace minerals. These include sulfate, chloride and oxide sources of copper, zinc and manganese. Bio-availability can be an issue with these inorganic sources. However, as long as there are no issues with primary or secondary deficiencies, these inorganic minerals work well when fed in a balanced, year-round program. In cases of obvious deficiency or known poor performance, chelated forms of copper, zinc and manganese can be included in the mineral formulation. While more expensive, chelated minerals have increased bio-availability as they are complexes of protein and the respective mineral.
When determining which mineral is right for your operation, there several factors to consider. First, make sure you have your forages tested for both the macro and trace minerals. This will give you a starting point for selecting which mineral program best matches your forage supply.
Next, realize that most feed companies market a line of minerals formulated to meet the needs of the cow as she moves through her reproductive calendar. These include products for summer grazing, early winter, late pregnancy as well as a breeding mineral. You need to ensure that the mineral you are feeding at any point in time aligns with the needs of your cattle.
It is also important to understand the soil type, soil nutrient concentration, water and forage quality that makes your land base unique. This knowledge will help you and your nutritionist select and/or design a mineral that overcomes any primary or secondary deficiencies that may influence the health and productivity of your cattle. Other factors to consider include mineral palatability, all-weather technology and price.
Finally, it nothing else sticks from reading this column, remember that mineral feeding is a year-round initiative.