Tissue-Dependent Degradation of Monensin Residues in Chicken Tissues with Prolonged Freezer Storage

Abstract

Monensin, a monocarboxylic acid ionophore, is widely used in the poultry, cattle, and swine industries? Concern over its toxicity has risen in recent years with several reports of poisoning outbreaks.’ Monensin is known to be readily absorbed through the gastrointestinal tract of most animals. Residue concentrations, however, do not reach high levels, even in severely intoxicated animals. 4 This produces a diagnostic problem, especially if a history of clinical signs that could implicate monensin is not presented with the case upon postmortem examination. Because of the likelihood of low residue concentrations and the possibility of residue degradation while in freezer storage, it is desirable to know which tissue to select for monensin testing. The purpose of this study was to determine a suitable marker organ by testing poultry tissues using a sensitive thin-layer chromatography/ bioautographic detection method for monensin. A marker organ as defined for this study is that tissue in which monensin can be detected in greatest quantities after a specified period of freezer storage. The animals in this study were cared for in accordance with the standards set by the Canadian Council on Animal Care. 2 Four 7-week-old male broilers (Hubbards) a were given an oral dose (1,000 mg/kg body weight) of monensin- sodium salt b via direct intubation to the crop. Samples of cardiac muscle, skeletal muscle, liver, and kidney were taken immediately after death. The tissues of the 4 birds were pooled and homogenized. c The samples were then placed in air-tight plastic d bags and stored in a freezer at -20 C. At