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Farmers can reduce this risk in several ways.
Monitor the herd carefully and keep an eye out for sick cows or those not keen to feed when the rest of the herd is feeding.
Treat sick cows promptly, especially in poor weather, and call your vet as soon as possible.
To speed up a sick cow’s recovery, provide a suitable recovery site such as a grass paddock with good shelter, a low stocking rate and extra, highly palatable feed and water.
Your vet will advise you on the best recovery plan for your stock.
Think carefully about weather when wintering cows on crops.
Cattle tolerate cold conditions by making physical changes, i.e. thickening their skins and coats and drawing on their fat reserves.
If a cow is clean and dry and there is little wind or rain, cold stress is rare until ambient temperature falls below -10°C.
The factors that increase the risk of cold stress are very low temperature, wind, rain and mud, low condition scores and low feeding levels.
During periods of cold and wet, the energy required by cows can increase by at least 12 MJ ME/day depending on the severity of the conditions. Also, cows’ feed utilisation may decline, increasing the gap between energy intake and requirement. To keep cattle in the right condition during extreme winter weather offer additional feed.
For a typical crop-based wintering diet aimed at gaining 0.5 BCS units during a dry period, during mild weather a 500kg cow needs to eat about 124 MJ ME/day. Typical diets to provide this include:
9.5kg kale and 4kg average quality pasture baleage (assuming 80% utilisation of the crop and 85% utilisation of the baleage)
9.8kg DM swede and 4kg average quality pasture baleage (assuming 80% utilisation of the crop and 85% utilisation of the baleage)
8.3kg fodder beet and 3.5kg average quality pasture baleage (assuming 90% utilisation of the crop and 85% utilisation of the baleage).
If this same cow were exposed to prolonged cold and wet conditions, then her energy requirement would increase to at least 136 MJ ME/day. To achieve this increased energy requirement, assuming the same feed utilisation, either provide more crop or more supplement.
For a herd of 160 cows this extra energy could be provided by an extra bale/day of average quality pasture silage (220kg DM equivalent, 10 ME) or additional crop:
Kale: 160m2 for 160 cows grazing a 12t crop (1.2kg DM/cow)
Swedes: 120m2 for 160 cows grazing a 16t crop (1.2kg DM swedes)
Fodder beet: not recommended because it requires at least an additional 1kg DM/cow/day which could result in digestive upsets in some animals even when they were fully transitioned.
Depending on the BCS of the herd, and the weather, wet and windy conditions require an additional 0.5 - 3kg DM/cow/day.
For more information visit https://www.dairynz.co.nz/feed/crops/wintering-cows-on-crops/winter-crop-management/