Rape and Kale poisoning occurs when excessive amounts of these fodder crops are ingested by cattle and is characterised clinically by red blood stained urine.

PREVALENCE

The incidence is generally low but several cases may occur within an individual herd. Lactating cows, particularly those which are recently calved and lactating heavily, are usually affected but the condition has also been described in bullocks.

EPIDEMIOLOGY

Rape and kale are used as fodder crops during the autumn and early winter and thus the disease is seen at this time. Outbreaks of poisoning have been associated with frosting of the plants but this is probably related to an increase in the toxic factor (see below) in the plant as it ages. Wet, cold weather has also been suggested as a factor influencing occurrence of the disease.

Rape and kale contain a toxic compound, 5-methylcysteine sulphoxide (SMCO), which is metabolised by the rumen, absorbed and directly or indirectly causes breakdown of the blood cells. As the amount of SMCO in the plant increases with ageing, the plants are most toxic once flowering and secondary growth occurs. It should also be noted that different varieties of rape and kale contain varying amounts of SMCO.

CLINICAL SIGNS

These are very similar to the signs seen in post-parturient haemoglobinuria. There is red blood stained urine, inappetance and a marked drop in milk yield. Pallor and moderately severe jaundice develop. Other clinical signs of anaemia are evident. Diarrhoea is a common feature. Fever is rare. Deaths may occur.

Diagnosis is based on clinical signs and history. Blood tests may be of use.

TREATMENT

Cease feeding of rape or kale. Where considered necessary blood transfusion may be performed on individual animals. However the donor should be selected carefully as apparently normal animals may be in the early stages of the disease. Reintroduction to the rape or kale should be gradual and intake should be restricted.