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Online Journal of Veterinary Research©
Volume 1:20-26, 1997
Experimental yellow-wood (Terminalia oblongata) intoxication in sheep
1Filippich LJ, 2Cao GR, 3Alsalami MT, 4English PB.
aSchool of Veterinary Science, The University of Queensland, Queensland 4072, Australia, b The Northwestern Agricultural University, Yangling, Shaanxi, Peoples Republic of China,c Royal North Shore Hospital, Department of Anatomical Pathology, St. Leonards, New South Wales 2065, Australia, 4Deceased
Filippich LJ, Cao GR, Alsalami MT, English PB., Experimental yellow-wood (Terminalia oblongata) intoxication in sheep, Online J Vet Res 1(3):23-42, 1997. Authors describe pathophysiology of chronic Terminalia oblongata (yellow-wood) intoxication in sheep. Yellow-wood leaf was air-dried, hammer milled and administered orally, as a drench, or intraruminally to sheep at various dose rates over several weeks. Chronic administration of yellow-wood leaf lead to reduced ruminal movements, inappetence or anorexia, body weight loss, reduced water intake and urine output. A normocytic, normochronic anaemia occurred in all sheep and blood gas and acid-base balance moved towards a metabolic acidosis as the study progressed. Plasma aspartate aminotransferase activity fluctuated while plasma alkaline phosphatase activity remained normal, except in one sheep which developed clinical jaundice. Plasma total protein levels remained normal or rose while plasma sodium concentration remained normal. Plasma potassium levels remained normal but decreased in one sheep to 2.8 mmol/l. Plasma urea and creatinine levels remained normal throughout the study and changes in plasma urea reflected changes in feed and water intake. Towards the end of the chronic yellow-wood intoxication study, renal mass in the sheep was reduced to 50% of normal by unilateral renal infarction so that the effect of chronic yellow-wood intoxication could be assessed in sheep with reduced renal function. After several more weeks of yellow-wood dosing, some of the sheep with reduced renal function showed neurological signs similar to those previously reported to occur in the field. However, none of the sheep showed a decrease in renal concentrating ability that could be attributed to chronic intoxication although one sheep went into acute renal failure. Evidence is presented to show that some sheep, not previously exposed to yellow-wood leaf, may have some degree of natural resistance to yellow-wood intoxication and that with continued exposure sheep can develop a tolerance to the yellow-wood toxin.
KEY WORDS: Terminalia, yellow-wood, tannins, sheep, intoxication.