Mouldy or musty oats, or other grain or fodder have long been notorious for producing diuresis in horses with excessive elimination of phosphates, extreme emaciation, weakness and death. In other seasons, and probably because of a difference in the fungi or their products they have caused widespread enzootics of indigestion with paresis of stomach and bowels, and of the systemic muscles. Paraplegia is a common manifestation, suggesting lesions of the spinal cord, and in other cases there are general paresis, somnolence and delirium suggesting cerebral lesions, (Staggers).
Gillespie records an enzootic of gastro-intestinal indigestion and tympany among the horses of a battery of artillery in Afghanistan from eating mouldy grass. Fröhner, Martin and Varnell have seen cases of poisoning by moulds without digestive, urinary or febrile troubles.
Of rusts growing on grain crops there are two chief varieties; the spring rust (uredo rubigo vera) which commences as light yellow patches on the leaves and stems, which change to black as the fungus approaches maturity; and the summer rust (uredo linearis) which grows to a larger size and assumes a browner color. Each of these passes through an evolutionary cycle, the small preliminary patches (uredo) passing into the mature fungus (puccinia rubigo vera and puccinia graminis.) Then it must pass through an alternate generation on another family of plants before it can again grow on the gramineæ.
Bunt produced by the tilletia caries attacks the grasses and small grains. The growing seed (wheat especially) is changed into a black or olive colored powder, having a fishy odor. If the stems are attacked the leaves become pale, withered and dry. It can only be detected by carefully examining the individual seeds.
Other forms of smut are the ustilago carbo and ustilago maidis the familiar black smuts of small grains and maize. These develop by preference in the growing seeds, but also in the stem and leaves. The tilletia caries is as a rule more poisonous than the ustilago the effects being mainly hyperthermia and paralysis. There is, however, a tendency to spasmodic contractions, and abortions, and dry gangrene will occur from smut. The author has seen a large herd of cattle attacked with gangrenous sores around the coronet, which were promptly stopped when the light, smutty ears of corn were no longer given. In other cases the hoof was in part separated from the quick and creaked when the animal walked.
In connection with the gangrenous ergotism of cattle, the author has found on the same farms and feed, horses with ulcers on the buccal mucosa and gastro-intestinal indigestion. Ergot affects the seeds in nearly all the small graminaeæ and is produced by the claviceps purpurea which first attacks the ovary of the seed (sphacelia stage), then it invades the whole seed which grows out from the glumes as a hard, dark or purple spur-like process (ergot stage), then falling on the ground it grows up as a minute stalk with rounded head containing spores.
Honey dew growing on leguminous plants is reputed to cause skin disease in white horses and on the white spots of dark horses, from which those not eating the diseased plants escaped.
Bacterial ferments have an equally bad reputation. Bastin records the poisoning of five foals by fermented rye; Dieckerhoff describes an acute gastro-enteritis with congestion and swelling of liver, spleen and kidneys, as the result of microbes and their products in the fodders. Galtier traced a pneumoenteritis in the horse to two cocci, a motile diplococcus and non-motile streptococcus. Both stained in aniline colors, and were bleached by iodine. They grew in ordinary culture media above 50° F. but most freely at 98° F. The animals were infected by drinking putrid water or spoiled fodders in which the microbes were contained. The change to boiled water in the former case led to their prompt disappearance. Reynal, Cailleux and Foucher have also adduced instances of severe enteritis in the horse from drinking putrid water. These animals showed active congestion of the intestinal mucosa with abundant infiltration of the submucosa.
Bouley found 14 cases in one stable, the owner of which had marketed the good fodder and kept the spoiled for home use. Barthelemy, Alasonniere, Lombroso and Hausmann, Clichy, Rey, Gamgee and others give similar examples.
A large number of observations show the dangerous results on the horse of mouldy bread, inducing colics, vertigo, profuse sweating.