Dealing with a lack of calcium in pregnant cows

Beef and forage specialist Barry Yaremcio does the math on providing this mineral 
to pregnant cows

When feeding cereal silage, greenfeed or swath grazing to pregnant cows, there can be a concern with a lack of calcium and magnesium. An added product can often be the solution.

“In this situation, an added product should have more calcium than phosphorus,” said Barry Yaremcio, beef and forage specialist, with the Ag-Info Centre in Stettler.

“Most block and tub products along with some minerals have equal amounts of calcium and phosphorus or generally 2:1 calcium-to-phosphorus ratio. In many situations, the calcium-to-phosphorus ratio in a mineral product may need to be 8:1 or higher (similar to a feedlot-type mineral) to bring calcium and phosphorus levels into line.

“Tub or block products have lower calcium and phosphorus levels compared to a dry mineral. It’s difficult to have minerals stay in suspension during the manufacturing process.”

To successfully register a feed product, the Canadian Food Inspection Agency requires the nutrient content in the first block must be the same as what is found in the last block in a batch. Calcium and phosphorus are difficult to keep in solution during the mixing and manufacturing phase; thus, the lower concentration in the final product.

“It’s generally more efficient and more economical to feed a dry mineral to provide calcium or phosphorus in a ration rather than using a tub or block,” said Yaremcio.

In a swath-grazing situation where the feed contains 0.32 per cent calcium and 0.2 per cent phosphorus and the calcium content in the tub or block is 4.7 per cent calcium and 1.75 per cent phosphorus, it would require 3.9 pounds of the block product to achieve 2:1 calcium-to-phosphorus ratio in the final feeding program. Cost would be $0.63 per head per day (at 17.5 cents a pound).

“There would be other nutritional problems if this feeding program was followed,” said Yaremcio. “Some nutrients would be excessive and it could cause a reduction in performance. A second option would be to feed 0.067 pounds (30 grams) of limestone (38 per cent calcium) to achieve the 2:1 ratio. The cost would be one to two cents per head per day. If a feedlot-type mineral with 24 per cent calcium and eight per cent phosphorus is used and fed at 0.25 pounds a day, the cost would be roughly eight cents per head per day. The key is to minimize expense but provide a proper ration.”

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