For a horse who suffered from fits, where he jerked his head and fell down but then got up again and seemed fine, the following remedy was offered in 1855:

“Give the animal two ounces of the tincture of asafoetida every morning for ten days. Tie the gum on his bit and wear it for six or eight days. He will never have a fit after the first dose.”

For a horse who suffered a chronic cough, it was recommended that the animal’s owner take:

“…powdered squills one ounce, ginger two ounces, cream of tartar one ounce, mix well, and give a spoonful every morning and evening in wet bran. This is good after hard riding or driving. It cures all coughs and colds, and will prevent the lungs from swelling.”

Source

The Horse. G.W. M’Coy’s catalogue of practical receipts, for curing the different diseases of the horse. Enered according to the Library of Congress, in the year of our Lord one thousand eight hundred and fifty-five by George W. McCoy…Indianapolis. Printed by Cameron & McNeely (1855). https://www.loc.gov/item/rbpe.019005ba/