A manager took over a new property last year and bought on an entire new herd of 3-6 year old, in-calf Angus beef cows, with a supposed planned start of calving of mid august.

The cows were rotationally grazed until they were set stocked in mid July with the sheep. On the 20th of July (nearly a month earlier than expected) calving began, with the first cow found dead. Over the next two weeks they lost another two or three and had a total of 8 cattle down over four paddocks.

One of our vets arrived to find a down cow on her side with her neck stretched out and her eyes rolling in her head- classic signs of magnesium deficiency. She took a blood sample and treated her with Calcium and Magnesium intravenously and under the skin and then backed away quickly- magnesium deficient cows can be very aggressive!

Blood testing confirmed hypomagnesaemia and later soil testing confirmed that the property was low in calcium and magnesium…

In Dairy cattle we often see a down cow syndrome that is due to both magnesium and calcium deficiency, so they are supplemented with magnesium in the lead up to calving and often given a starter drench containing calcium in the first 24 hours post-calving. Of course in our beef cattle this can be a little more difficult!

In this case, the manager bought in the entire herd and separated them into pre and post calving cows. The post calving cows were fed bailage dusted in mag oxide while the pre calvers were break fed dusted grass and bailage. This year he plans to supplement the cows with dusted bailage and break feed as needed. Another option is trough feeding mag in the water, or long acting magnesium boluses given two to three weeks before planned start of calving.

Often we get the question of whether mag supplementation is really needed in your system, and the best way to be sure is to blood test cows post calving. Testing three to five cows calved within the last 24 hours is the best option to ensure we have the best idea of their magnesium levels.

Have you had experience with losing cows around calving? Give us a call to discuss any concerns or questions you might have.