By Dwayne Summach, MSc, PAg, Kindersley, Regional Services Branch
Significant amounts of annual cereal crops are used for forage this winter. Barley, corn, oats, triticale and other cereal crops typically have adequate protein and excess energy for maintaining mature cows in mid to late-gestation. Use of these cereal greenfeeds and silages requires attention to balance the macromineral supplementation in order to achieve optimum performance. The most common concern is maintaining a calcium to phosphorus ratio. The natural mineral profile of annual cereals supplies the amount of calcium and phosphorus required, but not in a ratio that is appropriate. Provision of 100 grams of a 3:1 mineral often addresses the ratio concern. Other minerals to pay attention to, especially if diluting the greenfeed with cereal straw, are the amounts of potassium and magnesium. High potassium levels, when combined with low magnesium and limited calcium content, will set up cows for low magnesium induced paralysis (hypomagnesaemia) – or downer cows prior to or at calving. Minerals that contain magnesium at one per cent to three per cent usually minimize this risk. Be aware that the ingredients used to supply magnesium are not very palatable and may reduce intake, or cause complete refusal.
Grazing standing corn is another method for feeding cattle during the winter. When the whole plant is consumed, the resulting nutrient intake would typically have excess energy; adequate to marginal protein levels, depending on the stage of production and a calcium to phosphorus ratio that approaches 1:1. A significant amount of calcium, 100 grams of 3:1 mineral plus an additional 50 grams of limestone is required in order to address the calcium to phosphorus ratio. This rather chalky mixture is highly unlikely to be consumed voluntarily, so some form of inducement is usually required. Some ideas that have had limited success include mixing dried molasses or dried distiller grains to dilute mineral content and improve palatability; providing a limited amount of ground grain mixed with the mineral on a daily basis; provision of a partial total mixed ration – mixing the mineral or pelleted supplement with a limited amount of silage. Unfortunately, this means incurring feed and yardage costs that grazing is supposed to minimize. Another option to address the mineral ratio imbalance includes planting a legume – peas, hairy, vetch or lentils – with the corn. These legumes naturally have a higher calcium to phosphorus ratio and consuming even a limited amount moves the ratio in a favorable direction. The same thing can also be done by limiting the feeding of alfalfa hay to every second or third day.
Regardless of the situation, monitoring intake of the mineral provided is the first step in calculating overall nutrition provided. A 25 kg bag of mineral supplies 250 cows with 100 grams each for one day, or 125 cows with 100 grams each for two days. Yes, it adds up to a lot of mineral if the cows are eating the amount of mineral intended.
Avoid nutrition related problems in your operation, test your feed sources, determine what is missing or not balanced by consulting a livestock nutritionist and then provide the correct nutrients for your livestock. For assistance balancing your herds nutrition, contact your local livestock and feed extension specialist or contact the Agriculture Knowledge Centre.