Plant Toxins in Myopathies of Ruminants and Pigs
A variety of plant toxicities affecting both cardiac and skeletal muscle occur worldwide. Clinical signs are not specific for the toxin and include anorexia, cardiac failure with tachycardia, dyspnea, diarrhea, stiffness, muscular weakness, recumbency, and myoglobinuria.
Myonecrosis can occur when gossypol is fed as a protein supplement. In pigs, clinical signs appear when cottonseed supplements are fed at > 10% of rations but can take up to a month to develop (1). Monogastrics, including preruminant calves, should not ingest feed containing > 200 ppm gossypol (2), whereas some mature ruminants can tolerate 20 g of gossypol/head/day for at least 84 days (3).
Senna obtusifolia (sicklepod) is prevalent in the southeastern US, and ingestion of its seeds by swine or ruminants can cause a degenerative skeletal and/or cardiac myopathy.
Trematone is a toxic component of white snakeroot (Eupatorium rugosum), which grows in shaded areas of the eastern and central US, and of rayless goldenrod (Isocoma wrightii), which is common in the Southwest on open pastures. Ingestion of these plants in quantities of approximately 2% of body weight can cause a fatal cardiomyopathy and severe skeletal muscle degeneration (4). Trematone remains active in hay and in the stalks of the dead plants on pasture.
Ionophores in Myopathies of Ruminants and Pigs
Ionophores are fed in diets for control of coccidiosis and to improve feed utilization in ruminants. Ionophores added to feeds in excess of recommended levels can cause cardiac and skeletal muscle necrosis. Experimental studies have indicated that LD50 values for monensin are 12, 16.7, 26.4, and 26–80 mg/kg body weight, for sheep, pigs, goats, and cattle, respectively (5, 6, 7, 8). Feed concentrations of 100 g/ton and 400 g/ton have been fatal to sheep and cattle, respectively. Newborn calves dosed with 100 mg lasalocid 3 times a day for cryptosporidiosis experience muscle necrosis (9). Ionophores such as maduramicin and semduramicin, which are used in poultry, are not approved in cattle. Accidental exposure of maduramicin in cattle reportedly induced acute fatal cardiomyopathy (10, 11). Other ionophores include naracin, salinomycin, and laidlomycin.
At necropsy, pale areas of myocardial necrosis and pulmonary congestion are usually prominent in cattle. Pigs and sheep tend to have mainly skeletal muscle lesions that appear quite similar grossly and histologically to those of nutritional myodegeneration. Diagnosis requires history of exposure with development of characteristic clinical and pathological alterations.
Muscle Crush Syndrome of Cattle
Muscle damage commonly accompanies bovine secondary recumbency. Tearing of adductor or semitendinosus/membranosus muscles can arise as animals weakened by hypocalcemia attempt to rise. Additionally, the weight of a recumbent animal on dependent muscle groups creates substantial increases in intramuscular pressure, resulting in decreased perfusion and ischemia of muscle and nerve. Muscle trauma leads to edema and inflammation, both of which can exacerbate local tissue degenerative changes. Mild increases in serum CK can be expected in recumbent cows; however, increases > 5,000 U/L usually indicate traumatic muscle damage.Treatment requires correcting the underlying cause of recumbency, fluid therapy if renal damage is evident, NSAID administration, good nursing care, adequate footing and bedding, and lifting or rolling the animal several times a day.Aquatherapy using float tanks for cattle also appears to help relieve pressure on muscle groups.
For More Information
Ekinci AB, Chlodowska A, Olejnik M. Ionophore toxicity in animals: a review of clinical and molecular aspects. Int J Mol Sci. 2023;24(2):1696.
References
Haschek WM, Beasley VR, Buck WB, Finnell JH. Cottonseed meal (gossypol) toxicosis in a swine herd. J Am Vet Med Assoc. 1989;195(5):613-615. doi:10.2460/javma.1989.195.05.613
Zelski RZ, Rothwell JT, Moore RE, Kennedy DJ. Gossypol toxicity in preruminant calves. Aust Vet J. 1995;72(10):394-398. doi:10.1111/j.1751-0813.1995.tb06180.x
Mena H, Santos JE, Huber JT, Tarazon M, Calhoun MC. The effects of varying gossypol intake from whole cottonseed and cottonseed meal on lactation and blood parameters in lactating dairy cows. J Dairy Sci. 2004;87(8):2506-2518. doi:10.3168/jds.S0022-0302(04)73375-5
Davis TZ, Stegelmeier BL, Lee ST, Green BT, Chitko-McKown CG. Effect of grinding and long-term storage on the toxicity of white snakeroot (Ageratina altissima) in goats. Res Vet Sci. 2018;118:419-422, doi:10.1016/j.rvsc.2018.04.006
Anderson TD, Van Alstine WG, Ficken MD, Miskimins DW, Carson TL, Osweiler GD. Acute monensin toxicosis in sheep: light and electron microscopic changes. Am J Vet Res. 1984;45(6):1142-1147. https://pubmed.ncbi.nlm.nih.gov/6742573/
Novilla MN. Ionophores. In: Gupta RC, ed. Veterinary Toxicology: Basic and Clinical Principles. 3rd ed. 2018, Academic Press; 1073-1092. doi:10.1016/B978-0-12-811410-0.00078-7
Potter EL, Van Duyn RL, Cooley CO. Monensin toxicity in cattle. J Anim Sci. 1984;58(6):1499-1511. doi:10.2527/jas1984.5861499x
Nebbia C, Ceppa L, Dacasto M, Nachtmann C, Carletti M. Oxidative monensin metabolism and cytochrome P450 3A content and functions in liver microsomes from horses, pigs, broiler chicks, cattle and rats. J Vet Pharmacol Ther. 2001;24(6):399-403. doi:10.1046/j.1365-2885.2001.00362.x
Galitzer SJ, Oehme FW, Bartley EE, Dayton AD. Lasalocid toxicity in cattle: acute clinicopathological changes. J Anim Sci, 1986;62(5):1308-1316. doi:10.2527/jas1986.6251308x
Shlosberg A, Perl S, Harmelin A, et al. Acute maduramicin toxicity in calves. Vet Rec. 1997;140(25):643-646. doi:10.1136/vr.140.25.643
Di Paolo LA, Sosa PS, Ancinas MD, Muñoz Al, Travería GE. Maduramicin poisoning in prepartum dairy cows due to cross-contamination of anionic salts. Vet Rec Case Rep. 2025;13(3):e70077. doi:10.1002/vrc2.70077
