A California barn operator is seeking a settlement from a feed producer on grounds that 13 of her horses died after consuming horse feed suspected of being tainted with an antibiotic.

Monensin is an ionophore antibiotic sometimes included in ruminant, swine, and poultry feed that is toxic to horses.

In September, Western Milling LLC voluntarily recalled some batches of Western Blend horse feed after learning that several horses reported to have consumed the feed either became ill or died. The suspect feed was distributed in California and Arizona. A written statement from Western Milling indicated that all but 67 of the 1,100 recalled feed bags were claimed by the company.

On Dec. 3, California barn operator and horse trainer Katie Flanigan alleged that 13 of her horses had died and another 49 had sustained long-term complications after ingesting the allegedly tainted feed