Ag News

Managing mineral nutrition when grazing cereal crops

  • By: Farm Tender "Prime"
  • Oct 13, 2017

Our Australian sheep flocks are showing increasing calcium deficiency issues. We’ve moved from running a primarily Merino based system carrying single lambs, to one of larger framed ewes, often well fed and carrying multiples. That puts additional nutritional pressure on the ewe, especially as gestation advances and during early lactation. In addition, we are keeping older ewes in our flocks, in response to lower ewe numbers and a desire to produce more lambs with good lamb prices.

Early sown cereal crops such as wheat, barley, triticale and oats, grow rapidly and fill the winter feed gap with quality feed, supporting weight gain and increased stocking rates.

However, cereal crops contain potassium (K) levels excess to stock needs, adequate magnesium (Mg), adequate to low sodium (Na), and calcium (Ca) levels are low for animals with high calcium demands (eg. twin bearing ewes). A high ratio of K:Na lowers the absorption of Mg and Ca across the rumen. Other important ratios between these cations affect the blood and urine pH, blood levels of Ca and the ability of the kidney to make vitamin D3 which assists in Ca uptake. Together these mineral balance ratios can point to the risk posed by cereal crops, and the need for calcium and magnesium supplements.

Calcium issues in sheep
Several of the diseases seen more frequently now with sheep grazing cereal crops, particularly pregnant ewes, relate in part or fully to these mineral imbalances including hypocalcaemia (milk fever, low Ca), dystocia or lazy lambers (difficulty birthing), pregnancy toxaemia (low energy), hypomagnesaemia (low Mg), and uterine prolapse. This is also true for Autumn lambers, when ewes have been fed a lot of cereal...
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