StettlerLocal.com February 25, 2022
With limited hay supplies, many cows are fed straw grain rations before calving. This can be done successfully as long as nutrient requirements are met. The biggest challenge in these rations is providing adequate amounts of calcium and magnesium to the cattle to prevent downer cows.
As we get closer to calving, dietary requirements for calcium and magnesium increase because of higher requirements of the developing fetus and the production of colostrum. Three to four weeks prior to calving, calcium and magnesium move 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.
When there is a problem with a downer cow, talk to your veterinarian and have a diagnosis made during a farm visit. If the animal responds to intravenous treatment, it can indicate 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. Increasing the calcium and magnesium in the ration is recommended until the feed test results are back. For a 1400 pound cow in late pregnancy, adding 4 ounces of limestone and 1 ounce of magnesium oxide (per head per day) to the ration will help the situation. Fine-tuning can be done when the results have been received.
Mix the magnesium and calcium into silage or a grain mix. These two products are not appealing to cows and aren’t well consumed 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 should be added to the mix to improve consumption. A rough guideline is to include one of these products at 8 to 10% 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 of flavouring agent.
Barry Yaremcio
Ruminant Nutritionist
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