Acute photosensitisation and mortality in a herd of dairy cattle in Tasmania.
METHODS
A herd of Holstein, Jersey, or Holstein-Jersey cross lactating cattle of mixed ages presented with a sudden drop in milk yield in 94/678 cows on 3 October 2014 (Day 0). The herd was located in Gretna in the Derwent Valley (Tasmania, Australia) and had been grazing dryland pasture.


RESULTS
On Day 0 the cows variably showed recumbency, peracute photosensitisation, inflamed coronary bands, conjunctival erythema, periauricular oedema, distress indicated by kicking at the flank, bruxism, discomfort, weight shifting, vocalisation indicating pain and depression. Blood samples collected on Day 4 from five clinically affected cows showed high activities of aspartate aminotransferase, glutamate dehydrogenase and gamma-glutamyl transferase. Morbidity, based on the number of treated cases within 72 hours of clinical onset, was estimated at 165/678 cows (24.3%). Mortality over the first 30 days was 19/678 cows (2.8%).


RESULTS
Necropsies of two cows on Day 4 showed marked distension of the gall bladder and extensive icterus. Necropsies of another two cows on Day 5 showed enlarged livers with severe damage and oedema of the distal abomasum. Severe ulcerative abomasal gastritis was present in both cows. Hepatic histopathology was consistent with chronic cholangiohepatitis.
Fifty-five different mycotoxins were detected from a barley grass (Hordeum murinum) sample from the presumably contaminated pasture. Concentrations of B-trichothecenes, fumonisins, and zearalenone metabolites from this sample were remarkably high. The leaf smut, Jamesdicksonia dactylidis, that has not been previously reported in Tasmania, was identified from the sample of barley grass, but it is not known whether the smut can produce toxins.


METHODS
Probably an undescribed peracute mycotoxicosis associated with the ingestion of contaminated dryland pasture.


CONCLUSIONS
A definitive diagnosis could not be reached in this case of acute photosensitisation and mortality in dairy cattle grazing possibly contaminated dryland pasture. The findings differed from both facial eczema and acute bovine liver disease, suggesting an undescribed mycotoxicosis.
a Scibus , 2 Broughton St, PO Box 660, Camden , NSW 2570 , Australia.
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HM
Golder
a Scibus , 2 Broughton St, PO Box 660, Camden , NSW 2570 , Australia.
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Moss
b Dairy Systems , 6745 Lyell Highway, Ouse 7140 , TAS , Australia.
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Rogers
c Department of Primary Industries Parks Water and Environment , Biosecurity Tasmania , PO Box 46, Kings Meadows , TAS , Australia.
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B
Jackson
d Biomin Australia Pty Ltd , Level 4, 56 Clarence St, Sydney 2000 , NSW , Australia.
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N
Gannon
e Plant Breeding Institute , The University of Sydney , 107 Cobbitty Rd, Cobbitty 2570 , NSW , Australia.
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Wong
a Scibus , 2 Broughton St, PO Box 660, Camden , NSW 2570 , Australia.
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IJ
Lean
D000208:Acute Disease; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology* / Q000209:etiology / Q000401:mortality / Q000473:pathology; D005260:Female; D005704:Gallbladder / Q000473:pathology; D001467:Hordeum / Q000737:chemistry / Q000382:microbiology; D008099:Liver / Q000473:pathology; D015651:Mycotoxicosis / Q000453:epidemiology / Q000401:mortality / Q000473:pathology / Q000662:veterinary*; D009183:Mycotoxins / Q000032:analysis / Q000506:poisoning; D010787:Photosensitivity Disorders / Q000453:epidemiology / Q000401:mortality / Q000473:pathology / Q000662:veterinary*; D013648:Tasmania / Q000453:epidemiology
D009183:Mycotoxins
Acute bovine liver disease; Jamesdicksonia dactylidis; cattle; hepatic; mycotoxicosis; photosensitisation