PATHOLOGIC AND CLINICOPATHOLOGIC EVALUATION OF TOXIC MYOPATHY INDUCED BY SOME IONOPHORES IN BROILER

Abstract

Intensive broiler production which has been started in Egypt from more than 30 years still represents a major source of high quality and relatively cheap protein. This industry withstands many disease problems usually due to infectious agents and low management standards. Coccidiosis is one of the most important diseases which could be observed whenever chickens are raised. Now, it is widely recognized that coccidiosis continues to be one of the serious and economically devastating diseases of the intensive poultry production of all size and worldwide. Rough estimates of the animal losses to the world's poultry industry exceed billion dollars due to increased food conversion, decreased growth, mortalities besides the costs being spent on chemotherapeutics for treatment and control of the disease (Dalloul and Lillehoj, 2006).

Ionophores are polyether compounds used in the poultry industry for their anticoccidial activity. They include many compounds arranged in the historical approval by Food and Drug Administration (McDougald and Reid, 1997) as monensin (1971), lasalocid (1976), salinomycin (1983), narasin (1988), maduramicin (1989) and finally semaduramicin (1995). Nowadays and for the foreseeable future, ionophores are the predominant means of the chemical control of the coccidiosis in chicken because of their efficacy and the slow development of resistant strains to them relative to other anticoccidial drugs (McDougald and Reid, 1997).

Salinomycin, a monocarboxylic acid polyether antibiotic produced as a metabolic product of the fungus Streptomyces albus, was first described by Kinashi et al. (1973).

Maduramicin, a new ionophore produced as a metabolic product during the fermentation process of the fungus Actiomadura roseorula (Kantore et al, 1984). Singh and Gupta (2003) reported that they carried out clinico-hematologic and mineral studies on maduramicin toxicity in chicken because of the rarity of the literature concerning this ionophore toxicity.

Ionophores have the ability to form loose complexes with certain ions then transport them across biological membranes, and this disturbance of normal ionic gradients seems to be basis of both biological activity and toxicity (Todd et aL, 1970 and Whitlock et al, 1979).

Members of the ionophores group are classified as either monovalent or divalent on the basis of their affinity for particular cations. The monovalent ionophores as monensin, salinomycin and maduramicin tend to combine more readily with sodium and potassium, whereas divalent ionophores as lasalocid combine with sodium and potassium, as well as calcium and magnesium (McQueen, 1987). This effect may account for the activity of ionophores against some infectiOUS agents as COCCidia, Gram-positive bacteria, mycobacteria and some filamentous fungi (Miyazaki et al., 1974 and Danforth et al, 1977).

Unfortunately, the toxic effects of ionophores cause concern because of their narrow safety margin. Toxicity almost exclusively results from the difficulty of ensuring an even distribution of the drug throughout the feed resulting in improper feed formulation and feed mixing errors. Improper mixing could easily produce feeds varying in drug concentration so that some birds would receive 0.5X the recommended dose of a drug and