Mineral losses Test showed feeding with a bale processor on snow can lose 30 per cent of calcium and 25 per cent of magnesium
Forage quality has been an issue this winter because of the weather conditions experienced last summer. Feed test results have shown that protein levels are down 20 to 25 per cent in many hay and silage samples compared to the long-term average. Delayed cutting has also increased the amount of fibre in the harvested forages, which results in reduced energy content as well.
There are other quality concerns with the forages grown last summer. “Test results are also indicating that potassium levels in mixed hays are almost twice as high as the long-term average,” says Barry Yaremcio, beef and forage specialist with Alberta Agriculture and Rural Development. “As we get closer to calving, dietary requirements for calcium and magnesium increase because of higher requirements of the calf and the production of colostrum.
“Three to four weeks prior to calving, calcium and magnesium is moving from the blood into the mammary tissue to produce milk. Older cows have a more difficult time mobilizing calcium from the bone and are more prone to be downer cows. High-milking cows are also at high risk because of the daily calcium and magnesium requirements. High potassium levels in the diet reduce the absorption of magnesium which can increase the number of downer cows.”
Feed test results provide a starting point to developing a balanced ration. What is recommended on paper can be quite different to what the cows actually consume. Research conducted at the Agriculture and Agri-Food Research Station at Lacombe found that feeding hay with a bale processor on snow can result in up to 30 per cent of the calcium reported on a feed test report being lost because of feed waste. The amount of magnesium lost can also be 25 per cent or higher. The loss of nutrients can result in downer cows, even when everything appears to be normal on the ration report.
“If there is a problem with a downer cow, talk to your veterinarian and have a diagnosis made when a farm call is done,” says Yaremcio. “If the animal responds to intravenous treatment, it can be an indication that calcium or magnesium, or both, could be borderline or deficient in the ration. Changes to the feeding program are needed.
“If the feeds have not been tested, do so. Until the feed tests results are back, increasing the calcium and magnesium in the ration is recommended. For a 1,400-pound cow in late-pregnancy or early lactation, the addition of four ounces of limestone and one ounce of magnesium oxide per head/per day, to the ration will help the situation. Fine tuning can be done when the results are back.”
If possible, mix the magnesium and calcium into silage or a grain mix. These two products are not tasty and cows tend not to consume much free choice. When including calcium and magnesium into a salt or salt/mineral mix, a flavouring agent or a product such as wheat shorts, dried molasses or dried distillers grains with solubles should be added to the mix to improve consumption. A rough guideline is to include one of these products at eight to 10 per cent of the total weight to improve intake. If intakes are still low, increase the inclusion rates of the flavouring agent, and if the intake is too high, reduce the amount.
Not all downer cows are caused by mineral imbalances. If experiencing downer cows or concerned about this situation in your herd, be sure to consult your herd veterinarian in order to obtain a proper diagnosis, treatment plan, and assessment of the situation. As well as consulting your veterinarian, if additional nutritional advice is needed, a feed company nutritionist or a provincial beef extension specialist can also be consulted. A team approach will yield the most favourable results.