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Evaluation of sodium monensin potential in the predisposition of liver copper accumulation in sheep

Abstract

Sheep farming grew considerable in the last decade in the south, southeast and northeast regions of Brazil. Many sheep farmers have been improving sheep husbandry with the use of new sheep breeds and nutritional strategies in order to reduce the age of slaugther. The intensive sheep farming system leads to the manifestation of several illness, like copper toxicity, which is a result a long-term accumulation of copper in the organism, mainly in the liver. The frequency of copper poisoning in sheep is high in Brazil, and keeps rising in the last two decades due to the intensive husbandy system. Cummulative copper poisoning is the said to be the 2nd main cause of death in sheep with 15,5% from all deaths. Normally there is a large economic loss because mostly of the animals with CCP are valuable and with a great zootechnical potential. With the intensive sheep husbandry system, the use of ionophores was introduced in sheep farming. Ionophores prevent coccidiosis, and also modifies the ruminal flora, which increases the gain of body weight and feed conversion. Monensin and lasalocid are the most used ionophores. Several studies in cattle and sheep showed that animals supplemented with monensin had a higher copper concentration in liver and serum. Higher copper retention has a great importance when deciding wether or not supplement sheep with ionophores, because sheep has a low toxic threasehold. Recently, a mineral salt containing 1300 ppm of sodium monensin was released on brazilian market. This study will verify the influence of a mineral salt with sodium monensin in liver copper accumulation and in the probability of occuring CCP in sheep that receive high ammounts of dietetic copper. Thirty two ovines distributed in four distinct groups will receive different diets (supplemented or not monensin, and supplemented or not with copper) during 90 days, and compare the copper metabolism, its hepatic accumulation, and the laboratorial and clinical picture dias among the groups. This study will be evaluated whole blood and serum values of copper and zinc, and serum values of urea, creatinine, and activities of CK, GLDH, AST and GGT; urine exam (colouration, odor, density and pH); copper and zinc concentration in the liver; and the clinical picture. (AU)