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- Acidosis can give rise to livestock mortalities and impair a ruminant’s production potential.
- Besides animal deaths, the condition can also lead to diarrhoea and laminitis.
- Animals with acidosis must be identified timeously in order to limit mortalities and production losses.
- Any change requires the animals to adapt anew in order to prevent rumen and digestive tract disruptions.
- It is possible to curb the risk by stepping up management and applying the correct aids.
Acidosis can give rise to livestock mortalities and impair a ruminant’s production potential. According to Johan Mouton, manager of research and product development at Molatek, acidosis might well be the disease most to blame for a decrease in ruminant production, especially in cattle, sheep, goats, and game. Animals develop the condition when they consume an excess of concentrated, starchy feed such as drought pellets and/or grains such as maize, oats, wheat, barley, and triticale without having been adapted to it.
Gradual adaptation is vital
Besides animal deaths, the condition can also lead to diarrhoea and laminitis. It can damage the walls of the rumen to such an extent that even after recovering from the disease, animals will no longer be able to optimally utilise nutrients for growth. They can also become vitamin B1 deficient. This vitamin is produced by certain organisms in the rumen, and acidosis can have a negative impact on them. A deficiency can give rise to nervous symptoms, resulting in reduced production and even death.
Crop residues and grain crops used as standing hay are attractive and effective aids that producers commonly utilise to get their livestock through the winter. However, if the livestock are not systematically adapted to it, the chances of developing acidosis are good.
The pH of ruminants grazing natural veld normally ranges from 6 to 7,5. The pH of their saliva is typically 8,2 or higher, and serves as a natural buffer in the rumen. If the animals were to suddenly consume an excess of concentrated feed or grain, saliva flow will decrease and the buffering capacity of the rumen will also decrease. The starch will ferment in the rumen, resulting in increased lactic acid.
This causes the rumen pH to drop to between 5,8 and 6,5 at which point the rumen organisms become unable to utilise the excess lactic acid and digest the starch. These lactic acid-utilising organisms must be systematically increased over a period of two to three weeks in order to utilise the lactic acid.
Liver damage and abscesses
The reduction in saliva causes the animal’s body to channel moisture to the rumen, leading to dehydration. The harmful fatty acids damage the rumen wall and liver, as some of the organisms that end up in the liver can cause abscesses.
Animals with acidosis must be identified timeously in order to limit mortalities and production losses. The producer and his/her farm workers must be especially vigilant when animals are moved onto grain fields, crop residues, or when the ration is changed.
One of the signs of acidosis is animals that chew or ruminate less. Animals should start ruminating approximately two hours after having consumed feed. The time they spend chewing the cud is an indication of its fibre content. Cattle produce some 280ℓ of saliva per day which contains 3 to 4kg of sodium carbonate. The latter acts as a buffer against the acids formed in the rumen.
Other signs of acidosis are animals limping or standing with crooked backs. Although lameness can be attributed to several causes, acidosis is a known cause of laminitis as the damage to the rumen wall often results in an inflammatory reaction and subsequent laminitis. The initial lameness is due to the accumulation of lactic acid in the already acidic rumen and the resulting low rumen pH.
The composition of the manure can also change due to acidosis. Animals with acidosis usually excrete loose and watery manure, often with bubbles in it, and with a shape that does not resemble that of healthy cattle.
Adjusted rations
It is best not to change the composition of rations during a feeding period as any change requires the animals to adapt anew in order to prevent rumen and digestive tract disruptions.
The adaptation period can last two to three weeks. Specially formulated licks or buffer minerals such as magnesium oxide, baking soda, and commercial products can be given to stabilise the pH. Follow the instructions on the method of application and the correct quantity to give, as too much can cause alkalosis, which is an even bigger concern.
Starved animals should not be moved onto fields with grain crops or crop residues and they should not be given access to concentrated feed. They should first receive enough roughage which can be consumed in the mornings, after which they can be moved onto fields with grains or residues in the afternoon or be given concentrated feed.
During a drought, livestock should first be adapted on the drought ration and in the first week preferably receive only a small amount of concentrated feed together with enough hay. Double the amount can be given in week two and thereafter the feed can be given ad lib along with hay.
Buffers and small grains
The seeds of small grains such as wheat, which are often included in sheep rations, are high in energy. Nutritionists recommend that wheat should not constitute more than 50% of the energy source.
A good buffer should be provided if wheat grains, which should be fed whole, constitute a bigger portion of the ration. Sheep should have ad lib access to acidosis-preventing licks in the first two weeks. Such ready-mixed licks are specially developed and formulated to act as buffers, so that maize and crop residues that are high in seeds and grains can be used safely. These licks often contain other nutrients that livestock also require for optimal production.
Soya bean is a popular crop grown in the summer rainfall regions. They serve as valuable crop residues containing many of the essential nutrients animals need in winter. However, they bear a high risk of acidosis as well as blood alkalosis that can develop if animals consume too much too quickly.
A gradual process
Gradual adaptation is the best way to meet challenges head on. Fields with small quantities of soya bean kernels can be made available and the quantity increased gradually, so that sheep can adapt to utilising hay. Initially it can also make sense to limit their grazing time.
There is, however, no time limit for animals that are adapted to crop residues. Crop residues are an excellent source of fibre and roughage once the animals have adapted to also consuming grain. The utilisation of crop residues must be carefully managed. The longer the animals spend grazing, the fewer kernels are available. Animals that start to lose weight is a good indication that the crop residues are no longer meeting their nutritional requirements.
Given the greater emphasis on organic and no-till systems in crop production, it is also important to ensure that fields have ample organic matter available for improving soil quality.
In the feedlot
Feedlot profitability can also decline due to acidosis. Young animals entering feedlots usually come from farms where they used to graze natural veld. These animals are normally adapted before being given the full feedlot ration (backgrounding).
Rapid adaptation can lead to mortalities due to acidosis and even if an animal survives, the rumen might be so severely damaged that the animal will be unable to optimally utilise nutrients for growth. Substandard trough management and animals going long periods without enough feed is also a recipe for severe acidosis. When fresh feed is then provided, animals will engorge themselves on the concentrated feed, thus increasing the risk of disease and death.
Although acidosis is an everyday challenge that can lead to poor feed utilisation, impaired growth and other limiting conditions, it is possible to curb the risk by stepping up management and applying the correct aids. – Andries Gouws, Plaas Media
For more information, contact Johan Mouton at 083 278 7764 or johan.mouton@rclfoods.com.
