printStock Journal Feature - February 2025
Author: Emma Shattock, Elders Livestock Production
In most grazing enterprises in South Australia, summer consistently represents a gap in both the quality and quantity of feed available. At this time, it is also common for vitamin and mineral supply to be below that required by stock, emphasising the need for supplementation. Feeding out grain and roughages rations can further complicate the issue by exacerbating nutrient imbalances.
A prime example of such an imbalance is calcium, as ewes reach lambing and lactation, her calcium requirements increase significantly. If this need cannot be met by daily intake alone, reserves are mobilised from the bones to help meet demand. Autumn lambing ewes will often be fed cereal grains in the lead up to lambing to help meet energy requirements, a feed that is notoriously low in calcium. If we have been undersupplying calcium to the ewes throughout their pregnancy, they will not have the reserves required to meet peak demand. The result is hypocalcaemia, otherwise known as milk fever, and can lead to ewe and lamb loss.
This effect is exacerbated in containment situations where the lack of access to grazing and reliance on grain further amplifies the deficiency. Calcium supplementation is a must in these situations.
The low calcium levels of cereal grain relative to phosphorus can also lead to urinary calculi in wethers and rams. Over time, excess phosphorus forms deposits in the bladder, developing into stones that can block the flow of urine and lead to the death of the animal.
Vitamin A is another good example a nutrient that can be in short supply over summer. This vitamin is found in good levels in green pasture but is generally deficient in dry feed. Stores from the liver can help meet the animal’s demand initially, but as time progresses supplementation becomes important. With important roles in immunity, fertility and growth, deficient animals become a lot more susceptible to disease.
While disease prevention is important, well-matched supplementation can also help to improve digestion and production. Dry pasture can be very high in fibre and low in energy and protein. Supplementation with a nitrogen source, such as a protein meal or urea, can help to improve appetite and the digestion of this feed in the rumen. This improves daily nutrient supply from the feed the animal is ingesting. Sulphur is also needed to help with this process.
Urea must be fed with caution as toxicity can occur in some situations. Do not allow water to pool on or around supplements containing urea and avoid feeding it to starving or thirsty sheep. Other restrictions exist so it is recommended to seek advice for the safest ways to provide urea.
Supplementation with essential vitamins and minerals can improve the health, digestion and production of sheep on dry feed. The examples given above are only a few of many of the vitamins and minerals to consider. Some of these can be quite region specific while others extend to most situations. The best advice is to speak with your sheep production consultant or nutritionist to find the supplement but suited to your and production goals.