As the autumn season progresses, sheep farmers across Ireland face critical management decisions, particularly around weaning and moving lambs onto lush aftermath grazing, or into housing for intensive meal feeding.
These changes, while necessary for maintaining growth rates, can present significant animal health risks. Some common causes of sudden death in lambs during this high-risk period are systemic pasteurellosis, pulpy kidney disease, ruminal acidosis and parasitic gastroenteritis.
Systemic pasteurellosis, caused by the bacterium Bibersteinia trehalosi (formerly Pasteurella trehalosi), is a frequent diagnosis in Regional Veterinary Laboratories (RVLs) between September and December. The bacteria typically reside harmlessly in the tonsils of healthy sheep.
However, periods of stress – such as weaning, transport, handling, inclement weather, heavy worm burdens or sudden movement to lush grazing or rapid dietary change – can trigger the bacteria to multiply rapidly and enter the bloodstream, leading to severe septicaemia and sudden death.
Affected lambs are often found dead without prior clinical signs.
Prevention relies heavily on a robust vaccination protocol, using multivalent vaccines, ensuring lambs receive their primary courses and timely boosters according to manufacturer guidelines. Minimising handling stress, controlling gastrointestinal nematodes and managing dietary shifts gradually are equally essential.
Ruminal acidosis, or “grain overload”, occurs when lambs ingest excessive amounts of rapidly fermentable carbohydrates, such as intensive cereal concentrates, or lush, sugar-rich autumn pastures.
This results in a sharp drop in rumen pH as lactic acid accumulates, damaging the rumen epithelium and compromising overall metabolic health.
Crucially, when unfermented or excess starches escape the rumen and flood the small intestine, they create an ideal environment for the rapid proliferation of Clostridium perfringens type D. This overgrowth triggers pulpy kidney disease (enterotoxemia), a rapidly fatal condition caused by toxin absorption.
Consequently, maintaining adequate forage and fibre intake, and implementing a rigorous clostridial vaccination programme, are vital preventive measures.
Concentrates must be introduced slowly, starting at low levels and increasing gradually. Access to a clean water source must be maintained.
The recent rainfall, following a hot dry summer, has rehydrated faecal pellets and grass, allowing infective larvae to move rapidly up the plant – which can result in acute outbreaks of parasitic gastroenteritis in lambs.
Closely monitor lamb performance and watch for scouring and poor weight gain. Devising a safe grazing strategy for susceptible lambs is also an essential part of any parasite control programme.
Management of these conditions emphasises the importance of attentive husbandry measures, with careful nutritional and stress management during dietary changes.
In indoor systems, particular attention needs to be paid to additional potential stressors, such as air quality, stocking rates and ectoparasite management.
Farmers are encouraged to consult private veterinary practitioners to establish preventative health plans.
In cases of sudden death, prompt post-mortem examinations at an RVL remain invaluable for confirming diagnoses and safeguarding flock health.