Macro-Mineral Nutrition

Knowledge Nuggets

• There are seven macro-minerals (calcium, phosphorus, magnesium, sulfur, potassium, and sodium) required in relatively large amounts for proper animal nutrition. Macro minerals interact with each other and must be supplied in proper quantities and ratios to maintain animal function.

• Most legume forages, legume grass mixes, and brassica forages are good sources of calcium. Cereal forages (greenfeed or silage), corn silage, and cereal grains are poor sources of calcium.

• Grains are a good source of phosphorus while most forage is low in phosphorus. Phosphorus levels in forages drop rapidly after heading out.

• Calcium deficiency is not common in animals on high legume diet. If deficiencies occur, bone abnormalities, weakness or decalcification, swollen joints, stiffness, and reduced milk production are typical symptoms. Low dietary calcium impairs the absorption of phosphorus and Vitamin D.

• Phosphorus deficiency can cause irregular heat cycles and reduced fertility, reduced feed intake, depraved appetites, and in severe cases, bone fractures. The calcium-phosphorus ratio should not be less than 2 : 1 (i.e.: 2 parts calcium to 1 part phosphorus), and not greater than 7:1 in the final ration.

• Most forage in Western Canada contains adequate magnesium. High levels of calcium, phosphorus and potassium can interfere with magnesium utilization. Grass tetany and winter tetany are caused by magnesium deficiency, which occur when beef cattle are fed cereal straw, greenfeed or silage as a majority of the ration. Tetany can also occur when cattle are grazing lush, rapidly growing pasture.

• Forages normally contain adequate levels of potassium. Deficiency with high grain rations is more probable. Annual cereal crops grown for forage or silage are often high in potassium. Tetany problems can occur when animals are fed rations high in cereal forage because the high potassium levels can tie up calcium and magnesium resulting in an imbalance.

• Feeds generally contain adequate sulfur to meet the needs of growing and pregnant animals. High producing milk cows may require higher levels of sulfur. In areas where water is high in sulfates, excess sulfur may interfere with the absorption and utilization of copper and selenium, extra copper and/or selenium may be needed. Vitamin B1 deficiency causing Polio may also occur. Canola silage and other byproduct feed like corn gluten feed has high levels of sulfur and must be limit fed in rations.

• Salt must be available at all times. In most areas, feeds and water supplies do not contain enough salt (sodium chloride) to meet requirements. A prolonged deficiency can result in loss of appetite, unthriftiness, and reduced milk production.

• Use feed test results to determine which supplement, mineral or salt mineral mix is required to provide a balanced mineral package. A custom mixture may be required to meet specific needs or requirements.