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When ruminants suddenly over-consume low-fibre carbohydrates such as grains, without them having been adapted to it beforehand, it can lead to acidosis and even death.
Dr Bennie Grobler, a veterinarian at the Beaufort Animal Clinic in Beaufort West, says sheep that develop acidosis and die is a regular occurrence in drought-stricken areas. This is because producers are forced to turn to kraal-bound grain feeding, as the arid veld is no longer a good grazing option for animals.
In the case of a grazing maize system or where crop residues are used as winter grazing, the high energy content of the maize also carries a risk of acidosis for sheep. However, if sheep are pre-adapted to the grazing maize or crop residues before they are given access to it, the problem can be controlled.
According to Dr Grobler, livestock producers need to realise that they are in fact farming the organisms in the ruminants’ stomachs. The stomach is literally the ‘engine’ that keeps the animal running, and its health must be monitored continuously.
Carbohydrates in the rumen
The rumen normally has a pH of between 6,4 and 6,8, says Dr Grobler. There is a high risk of developing acidosis if low-fibre carbohydrates such as maize, wheat, low-fibre molasses, oats, rye and grain sorghum are not consumed in the correct ratio to other feeds (especially roughage), or when consumed in excess.
These carbohydrates are fermented in the rumen where it forms lactic acid, which lowers the pH in the rumen, as well as the pH in the blood. This makes the organs less efficient.
“The big problem with carbohydrate fermentation is that it alters the ratio of rumen organisms, with harmful organisms now gaining the upper hand,” he says. The proliferation of these organisms aggravates the situation, the result being that a vicious cycle now develops in the rumen.
According to Dr Grobler, it is vital to adapt the rumen microbes to an energy-rich feed source. This applies to feedlot animals as well as animals that utilise maize as a feed source. It takes the rumen microbiome up to three weeks to adjust to a new ration, and only three days for this adjustment to be undone if the same energy source is not fed consistently.
Hence, sheep must be adjusted systematically and at regular intervals to a new feed source, especially energy-rich sources and urea. He suggests feeding kraaled sheep 50g of maize per animal every other day in week one, 100g every second day in week two, and 150g every second day in week three, for example.
Feed and grazing management
There should be ample feeding space so that all animals can feed simultaneously, he explains. This helps to prevent some animals from gorging themselves and then developing acidosis. Dominant animals are normally more prone to acidosis because they push away the weaker animals in order to consume their portion as well.
There should also be enough roughage. In the case of grazing maize, sheep must first be allowed to graze for short intervals at specific times, after which the intervals must be systematically extended over a period of three weeks.
“Acidosis is the result of a management issue. It is critical that the producer, veterinarian and nutritionist or livestock expert join forces to assess and evaluate the system in a holistic manner, so as to finally arrive at the best management system possible.”
Dr Grobler says as soon as producers notice discomfort or a bloated abdomen, the symptoms should be treated immediately so that rumen pH can return to normal. Magnesium oxide, aluminium hydroxide, magnesium hydroxide or calcium hydroxide can be used to stabilise the rumen’s pH.
Feed lime and sodium bicarbonate (baking soda) can also be used. Baking soda, however, releases large amounts of carbon dioxide that can contribute to bloating. Rather consult your local veterinarian for the correct treatment of acidosis.
For more information, contact Dr Bennie Grobler on 023 415 2266 or firstname.lastname@example.org.