Polioencephalomalacia in lot fed lambs.

Abstract

Proc. Aust. Soc. Anim. Prod. (1978) 12: 280 POLIOENCEPHALOMALACIA IN LOT FED LAMBS T.M. YOUNG* and L.W. McLAUGHLIN* The expansion of export demand for sheep meats has led to a resurgance of interest by producers in short term feedlot systems of fattening for sheep and lambs. Apart from the cost of rations, the incidence of disease and metabolic disorders is an important determinant of profitability. This paper describes a feedlot experiment at Hamilton during which an outbreak of polioencephalomalacia (PEM) occurred. Eighteen groups of eight 6-month old crossbred lambs were taken from pasture in March 1975 and confined to feedlots where they were fed rations of oat/barley grain, linseed meal and pasture hay ad Zibitwn (Table 1). After a progressive lo-day introduction to their ration the lambs remained in the feedlot for 120 days until slaughter. The first evidence of PEM occurred after 8 weeks in the feedlot. In the following 6 weeks, 11 lambs died between daily feedings without symptoms being observed. PEM was identified at post mortem as the source of death. Nine lambs observed at various stages of the disease before death were treated intravenously (200 mg) and intramuscularly (200 mg) with thiamine. Of these only two recovered. A total of 18 lambs died from PEM in this experiment. It is not possible to determine whether the occurrence of PEM was related to the influence of dietary factors on the ruminal concentration of thiamine or to specific thiaminase activity. However, the occurrence of PEM in only those groups on low grain diets may be significant. Phillipson and Reid (1957) reported lower ruminal thiamine concentrations in animals on hay diets than in those on concentrate diets. Severe economic losses may result from mortalities, impaired feed use efficiency, prolongation of fattening and cost of treatment, and producers contemplating a feedlot system of fattening should be aware of the disease, its recognizable symptoms and current methods of treatment. PHILLIPSON, A.T. and REID,\R.S. (1957). Br. J. Nutr. 11:27-41. x * Pastoral Research Institute, P.O. Box 180, Hamilton, Vic. 3300. 280.