Acidosis

Grain poisoning or ‘acidosis’ is a common health risk when feeding cereal grains or high-grain based pellets or rations. 

What causes acidosis

Acidosis is caused by ingestion of excessive amounts of carbohydrates or rapidly fermentable feed. Once ingested, this feed is broken down in the rumen resulting in the explosive formation of lactic acid-producing microbes. This creates an acidic environment within the rumen.

Once the rumen pH is less than 5, several things happen: 

1. rumen motility and function reduces affecting the animal's ability to digest and absorb nutrients.
2. Lactic acid is absorbed across the rumen wall, making the blood more acidic. This can cause circulatory failure and laminitis.
3. The high osmolarity of the lactic acid causes water from the blood to be drawn back into the rumen. Rumen contents become watery (presents as scours) and the animal quickly becomes dehydrated.
4. The low pH degrades the integrity of the rumen wall which then allows pathogens to pass through. These pathogens can then spread to other organs causing sepsis.

Acidosis can be acute, subacute, chronic or be the catalyst to other secondary issues – and is mostly dependent on the magnitude and persistence of an acidic rumen environment. 

Clinical signs of acidosis

Acutely acidotic animals quickly succumb to the effect of shock and dehydration and are either found dead or are showing signs of severe colic. 

Sheep with a chronic or subclinical acidosis often have more subtle signs:

• varying severities of weight loss or production losses
• lethargy
• scouring
• colic. 

These animals often recover after a period of adaptation or intervention.

How to prevent acidosis

• Limit time off feed: when stock go for extended periods without feed, their normal microbial population within their digestive tract or ‘gut flora’ decline. This provides the opportunity for the overgrowth of diseasecausing bacteria within their gut.
• Provide safe feed source on arrival: when stock arrive on farm ensure they are provided good quality hay before introducing new feed or putting them out to pasture. Hay is a relatively safe feed source that will provide adequate gut fill and ‘kick start’ the rumen bugs into functioning properly again.
• Introduce grain diets slowly: to minimise the chances of developing acidosis, livestock should be acclimatised to the grain before being put onto ungrazed cereal stubbles. Hungry stock should not be introduced to grain.