Adrenal-associated changes in experimental sporidesmin poisoning of sheep

Sporidesmin-dosed hoggets which developed photosensitisation were shown to have enlarged adrenal glands and premature involution of the thymus. These sheep also developed high concentrations of plasma cortisol after the onset of photosensitisation. Sporidesmin-dosed sheep which did not show photosensitisation showed less or no adrenal associated changes.     

Facial eczema in goats: the toxicity of sporidesmin in goats and its pathology

Groups of six goats were orally dosed with sporidesmin at rates of 0.3, 0.6, 1.2 and 2.4 mg of sporidesmin per kg body weight and their responses up to 6 weeks later compared with those of sheep dosed at the same time. Clinical facial eczema and pathological lesions similar to those found in sheep were found in all the goat breeds, but at higher dose rates of sporidesmin than those which caused equivalent lesions in sheep. Saanens were the most susceptible goat breed, requiring 2-4 times as much sporidesmin as sheep to achieve similar effects. G4 and feral goats required 4-8 times the sheep dose of sporidesmin to obtain similar responses. Gamma-glutamyltransferase reached its highest serum levels after 20 days while glutamate dehydrogenase and aspartate aminotransferase reached their highest levels between 10 and 20 days. Alkaline phosphatase did not rise consistently to high levels in affected goats. The elevation in aspartate aminotransferase levels tended to be early and transient; glutamate dehydrogenase early and prolonged; gamma-glutamyltransferase late and prolonged, and'alkaline phosphatase late and minor. There was considerable individual variation in the time at which elevations occurred and the levels which enzymes reached. Cholesterol and bilirubin levels were high if liver injury was severe.     

Guttural pouch hemorrhage associated with lesions of the maxillary artery in two horses

A two year old Thoroughbred gelding, presented with guttural pouch hemorrhage, had the internal and external carotid arteries ligated. Guttural pouch mycosis was detected on endoscopic examination. After one month of topical antifungal therapy, the horse was returned and euthanized because of recurrent epistaxis. A bacterial infection of the guttural pouch with associated ulceration and hemorrhage from the maxillary artery was found at necropsy.

A two year old grade gelding had ulceration and hemorrhage from the external carotid artery. Utilizing balloon-tipped catheters and arterial ligation, hemestasis was achieved in the internal carotid artery and the external carotid artery and its branches. Mycotic ulceration of the internal carotid artery was detected endoscopically and treated with local antifungal therapy for one month. Thirty-three days postoperatively the horse returned, bleeding from a lesion in the maxillary artery. The rationale for surgical intervention to prevent epistaxis associated with guttural pouch mycosis and possible etiologies for postsurgical epistaxis are discussed.

     

Hypocalcaemia associated with high dose rates of zinc oxide to lactating dairy cows

Clinical hypocalcaemia was associated with single doses of three oi more days; supply of zinc oxide to dairy cows for facial eczema control. Experimental hand dosing of a single dose of zinc oxide (40 and 120 mg Zn/kg b wt) to Jersey cows caused a significant drop in serum calcium concentration at 24 h followed by a rise to concentrations higher than controls at subsequent samplings over four days. At the highest zinc dose rate, 78% of serum calcium values were equal to or lower than the lowest control value at 24 h post dosing. Serum magnesium concentrations had a reciprocal relationship to the calcium levels at all samplings. Serum zinc concentrations were most elevated over the 48 h post dosing, returning to normal levels at the fifth day. Following the highest zinc dose milk yields were reduced by approximately 1.5 kg milk/cow/day for 48 h. Similar results were obtained when cows grazed pasture on which large amounts of zinc oxide had been sprayed.