As we approach winter, with grass quality decreasing, many of you will start feeding cake to help finish lambs not yet sold. This will speed up the finishing process significantly but must be fed carefully to prevent the development of ruminal acidosis.
Ruminal acidosis commonly occurs following the sudden ingestion of large amounts of carbohydrate rich feeds (cereals), such as when concentrate feeds are introduced too quickly or lambs are turned out onto grain stubbles. The increased acidity in the rumen kills the normal ‘resident’ bacteria. The bacteria which can handle this environment then produce even more acid. Acid is then drawn into the bloodstream resulting in metabolic acidosis. Water is also drawn into the rumen from the animal’s reserves resulting in dehydration. To make matters worse, the damage to the rumen caused by acidosis leads to bacteria and toxins entering the bloodstream.
The signs you will see in your animals vary in severity depending on amounts ingested, feed type, breed (hill breeds at increased risk) and the rate of introduction of the feed.
In mild cases of ruminal acidosis, lambs may show the following: dullness, reduced appetite, and diarrhoea. In more severe cases, animals will be depressed, refuse to eat, weak, reluctant to move/ unable to rise, teeth grinding (pain), scouring and may appear bloated due to an enlarged rumen. Severe cases will be seen panting to lower acid levels, which may easily be mistaken as a sign of pneumonia.
In mild cases, removing cake from the diet completely and providing good quality hay to stimulate rumen function may be sufficient. In more severe cases, veterinary advice should be sought. These cases tend to require oral fluids containing antacids, pain relief, antibiotics, and vitamin B1. Mortality can be high in such cases, even with treatment.
To prevent ruminal acidosis, cake should be introduced slowly. Lambs can be started on 50-100g per head/day. Feed rates can be increased by 50g every 3-4 days once all animals are seen eating and all cake is eaten within 5 minutes. Lambs must have constant access to good quality roughage (grass/hay etc), as this stimulates saliva production which helps neutralize acid.
Written By David Deane, Veterinary Surgeon