Haemorrhagic syndrome of cattle associated with the feeding of sweet vernal (Anthoxanthum odoratum) hay containing dicoumarol

Abstract

An outbreak of a haemorrhagic diathesis in cattle fed home produced hay is described. A similar syndrome was reproduced experimentally in calves by feeding them the hay. The experimental disease was characterised by increased prothrombin and partial thromboplastin times while the leucocyte and erythrocyte counts remained normal until the terminal haemorrhage. The calves ate well and grew well until the rapid onset of progressive weakness, stiff gait, mucosal pallor, tachycardia, tachypnoea and haematomata ending in sudden death. The absence of blood coagulation was seen at necropsy while petechial, ecchymotic and free haemorrhages were found in most organs. Particularly striking were massive ecchymotic haemorrhages on the peritoneal surface of the rumen, a bloody, gelatinous mass enveloping each kidney and extensive bruising, haemorrhage and haematomata in the subcutis of the limbs. In a second feeding trial the effects of various preparations of vitamin K1 and vitamin K3 were investigated. Oral administration of large quantities of vitamin K1 reduced the elevated prothrombin time; vitamin K3 acted less consistently. Analysis of the hay for trichothecene mycotoxins was negative but floral analysis revealed that sweet vernal grass (Anthoxanthum odoratum) comprised about 80 per cent of the hay. Dicoumarol was detected in the hay and in the serum and ruminal contents of the experimental calves. The diagnosis, treatment, control and importance of this syndrome in the United Kingdom are discussed.

Experimental Ferula communis (giant fennel) Toxicosis in Sheep

“…In contrast to the 2 other plants, Melilotus alba (sweet clover) and Anthoxanthum odoratum (sweet vernal grass), which can cause a specific anti-coagulant effect, and whose anti-coagulant properties are instigated by fungal infestation ("spoilage") (GOPLEN et al, 1964;PRITCHARD et al, 1983), F C appears to be unique in containing the toxic principle(s) in fresh, uncontaminated plant material. Furthermore, whereas the other 2 plants are usually fed as hay, with which the matter of choice is not applicable, F C is only encountered by grazing natural pastures.…”

Dicoumarol toxicity in neonatal calves associated with the feeding of sweet vernal(Anthoxanthum odoratum)hay

“…The disease syndrome is common in Northern America and Canada and has been reported in England. 3,4,9 There have been only two cases of reported dicoumarol poisoning in Australia. 7,8 Adult cattle and sheep fed melilotus species based hay were diagnosed with dicoumarol poisoning in South Australia in 1961, and cattle in Victoria were diagnosed with dicoumarol poisoning in 2002 following the feeding of silage containing approximately 90% sweet vernal grass that constituted between 50% and 100% of their diet.…”

“…1,3,12 Epistaxis, dysentery and haematuria occur rarely. 3 Severe toxicity has been known to cause death within 24 to 48 h, 3,5,9,11 although it may be as long as 21 days following exposure to toxic material. 8 A positive association between the ingestion of dicoumarol and the incidence of retained foetal membranes has been reported 3 and is due to haemorrhages in the pelvic cavity and broad ligament causing delayed involution of the uterus.…”

“…Clinical signs have been seen in calves eating hay with toxin levels of only 15 ppm. 9 Toxicity occurs at dicoumarol levels of 20 to 30 ppm in feed if fed for more than 4 months, while levels of 50 ppm can cause toxicity within 17 days of feeding. 3 Levels of < 20 ppm are reported to be safe for feeding up to 100 days.…”

“…If the level is < 30 ppm then mixing the affected hay 1:3 with normal hay, or feeding the toxic hay for 2 weeks then the normal hay for 2 weeks, has been reported to minimise the risk. 9 Feeding affected hay to cows in the 3 weeks before calving is not recommended. 3 The paddock from which the hay was sourced had been neglected for a number of years.…”