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Long‐term assessment of horses and ponies post exposure to monensin sodium in commercial feed
Author(s) -
Hughes K. J.,
Hoffmann K. L.,
Hodgson D. R.
Publication year - 2009
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.2746/042516408x330428
Subject(s) - monensin , medicine , horse , treadmill , electrocardiography , cardiology , zoology , biology , paleontology
Summary Reasons for performing study : Acute monensin intoxication in equids is well described; however, the long‐term effects of sublethal intoxication and ability to return to previous use are less well understood. Long‐term observations may allow improved estimation of prognosis in cases of sublethal intoxication. Objectives : To assess horses and ponies exposed to sublethal amounts of monensin for evidence of chronic sequelae and ability to return to prior/intended use. Methods : Twenty‐nine horses and 8 ponies were assessed utilising serum biochemistry, treadmill exercise stress testing, electrocardiography, and pre‐ and post exercise echocardiography ≥6 weeks after ingestion of monensin‐contaminated feed. Animals with evidence of monensin‐induced cardiomyopathy were re‐examined after a period of rest of ≥11 months. Follow‐up information was obtained by owner telephone interview ≥52 months after exposure. Results : During resting echocardiography, 11 animals had reduced/low‐normal left ventricular fractional shortening (FS); an increase in FS in 8 of these animals was measured ≥11 months later. Six animals had reduced or low‐normal FS during post exercise echocardiography. Two horses had ventricular premature depolarisations during exercise. Follow‐up information was available for 35 animals: 21 returned to athletic/reproductive use, 13 were retired immediately and one died. Mean FS increased significantly (P<0.001) between initial and second examination in 15 animals that underwent resting echocardiography on 2 occasions. Conclusions : Some equids exposed to sublethal doses of monensin may not develop permanent myocardial disease and a return to athletic/reproductive use is possible. Potential relevance : Exercise stress testing, echocardiography and electrocardiography may be useful for detection and monitoring of cardiac dysfunction in equids exposed to monensin and determining whether a return to athletic/reproductive use is possible.