AVA Conference Brisbane 2018

Neonatal and pre-weaning diarrhoea is a major cause of losses in young cattle. Likewise, parasitic gastro-enteritis can cause significant impairment of growth rate in rearing cattle. In older cattle, by contrast, diarrhoea is a less common presentation, and may often be a secondary sign associated with disorders of body systems other than the GI tract. The diagnosis of causes of diarrhoea is aided by looking at the pattern of age and incidence of cases: for example, acute diarrhoea in many animals is likely to have a different aetiology to chronic diarrhoea in sporadic cases. Many cases of diarrhoea can be diagnosed upon clinical signs alone: faecal culture or parasitology are generally best used only as a means of confirming a diagnosis. Most of the causes of diarrhoea in cattle have infectious or toxic aetiologies. Bacterial infections account for many acute cases (e.g. salmonellosis, yersiniosis), whilst Johne’s disease is undoubtedly the most important cause of diarrhoea in older cattle. Viruses and parasites are, generally, less common causes: BVD (despite its name) does not cause significant outbreaks of diarrhoea in adults, whilst parasitic infections of adults is largely limited to Type II ostertagiasis. On the other hand, there are a great many toxic causes of diarrhoea, and diarrhoea can also be associated with liver disorders, heart failure, rumen acidosis, a non-specific sign of toxaemia and, rarely, of renal amyloidosis. The faeces of cow change dramatically with feed and season, of course, so the faeces of cows on lush spring pasture can be exceedingly liquid. Treatment, where appropriate, is usually symptomatic; correcting fluid losses and giving antibiotics (anthelmintics) as required. A diagnosis of Johne’s disease in a naïve herd is of some importance, as it is notifiable in several states and may also result in movement restrictions being placed upon the herd.