Sylvaine Lacrosse BVetMed MRCVS, Molecare Veterinary Services
Many farmers will have experience of a case of sudden death in growing lambs, but are these true acute sudden deaths? Lamb losses that appear to be sudden death, are sometimes not quite as acute as they seem, due to missed early signs of disease when checking large groups of animals.
For any case of sudden death, you should involve your vet as soon as possible. Early diagnosis and correct intervention reduces the number of future losses and targets prevention methods for the next season. A fresh carcase for post mortem is a must for the best chance of finding a diagnosis. There is no point opening up a decomposing carcase! Be ready to provide your vet with a detailed history as any minor detail or change in husbandry, which may seem insignificant, can hold the answer to the cause of death.
There are a multitude of causes which can lead to sudden death. This article will focus on the common causes in growing lambs, providing a brief overview of what to look for and how to intervene.
Husbandry and management
Grain overload is a common cause of sudden death affecting intensively fed lambs experiencing a ration change or lambs that have broken into a feed store. The grain ferments in the rumen, affecting the balance of rumen microbes, lactic acid content increases, which when absorbed into the circulation causes acidosis and death by endotoxic shock. Early signs to be vigilant for include profuse scour with undigested grains, lethargy, colic, staggering and blindness. It is important to spot these early signs as animals in the early stages have the potential to be saved by intensive supportive therapy.
Redgut occurs due to intestinal displacement or torsion which compromises intestinal circulation. This is usually seen in lambs which have been recently moved onto lush pasture, resulting in rapid passage of food (hypermotility) and these unstable intestinal conditions can lead to displacement. When moving lambs onto lush grass or leguminous crops, it would be advised to supply roughage to prevent intestinal hypermotility and the risk of twisted guts.
Systemic pasteurellosis is caused by Pasteurella trehalosi, a bacteria found in most healthy sheep. Under stressful conditions, the bacteria multiplies and spreads rapidly to the lungs and other organs. Clinical signs include dullness, recumbency and signs of respiratory distress. Once clinical signs are apparent, it is near-impossible to save the affected animal, but blanket treatment of the affected group with long acting antibiotics can save the remaining lambs. Prevention should include minimising nutritional stress and protecting lambs from wet weather stress alongside vaccination. Ensure that lambs receive a complete primary course, as the protection from a single dose of vaccine is only short lived.
Clostridia are a group of bacteria which cause a wide range of severe and often fatal diseases such as blackleg, tetanus, braxy, and pulpy kidney. These bacteria are present everywhere; in the soil, faeces and intestine of most animals, and disease is triggered by a combination of stress. Sudden deaths and a lack of appropriate vaccination will make your vet very suspicious of clostridial diseases. Treatment of affected animals is often futile, so we strongly advise vaccination against clostridia as the cost of dead animals soon outweigh vaccine costs!
Acute fluke. Autumn and early winter is the typical time of year where acute fluke can cause sudden death through mass migration of immature fluke through the liver parenchyma. A multitude of climatic conditions can affect the severity and time of year that flocks are affected by acute fluke. Flukicides have a range of efficacy against different stages of fluke, so it is important to have a parasite control plan tailored to your farm. Discuss this with your vet to ensure preventative treatments with the correct flukicide are carried out at the right times of year and in accordance with local parasite forecasts.
Nitrate poisoning occurs due to nitrates binding to haemoglobin in red blood cells, preventing oxygen being supplied to the tissues. Animals experiencing nitrate poisoning will be weak, lethargic and possibly cyanotic (blue). Treating animals is very hard because it requires rapid intravenous treatment with methylene blue, which is hard to get hold of. Once nitrate is determined as the cause of death, immediately remove remaining animals from any sources of nitrate.
Brassica poisoning. Brassicas, including turnips, broccoli, cabbage, kale, rapeseed and many more, can be part of a well-balanced diet. However, when animals are fed a brassica-rich diet, they can fail to thrive. Brassicas contain several toxic substances which cause a decreased appetite, hence a failure to grow well. One of the toxic substances in brassicas is nitrate, leading to death as it does in nitrate poisoning.
The above describes the most common causes of sudden death in growing lambs, however the list of causes of sudden death is near-endless. Other causes include anthrax, trauma, lightning strike, polioencephalitis, copper toxicities and many more.
The key is to look out for any subtle hints suggesting animals are going downhill, and if any sudden deaths occur, do not hesitate to get your vet involved as a post-mortem and a well detailed history will have the highest likelihood of finding the cause.