This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
There have been very severe losses from forage poisoning in various parts of this continent, but although much painstaking work has been done to determine the cause of the disease, the results have been conflicting and unsatisfactory. Horses and mules are the animals chiefly attacked, the disease following the feeding of mouldy silage, spoiled hay, or immature mouldy corn. Cattle, sheep, pigs and poultry are apparently very resistant if not immune.
Many have considered that the disease is due to poisons secreted by moulds on the feed. Several species of mould grow commonly on corn and hay and a great deal of work has been done with a view to determining the particular one responsible. Efforts toward this end have not been successful. From experience with numerous cases of poisoning, evidence against a certain mould or group of moulds has been built up. Later, samples have been found which, though they contained these moulds, were harmless. Such differential action might possibly be accounted for by assuming the presence of different strains of the same species. An analogous case has been described by Dr. M. Otto, who found that while a strain of Aspergillus fumigatus from Italy was markedly poisonous, another from Germany was not at all, or only slightly so. The existence of similar strains of other common moulds has not, however, been demonstrated.
A more promising line of attack has been from the bacteriological standpoint. The work was carried out at the Kentucky Agricultural Experimental Station by Graham, Bruechner and Pontius. They isolated from mouldy hay that had caused typical cases of forage poisoning, a bacillus resembling B. botulimis, the organism of botulism. Like the latter it is an anaerobic bacillus but grows in air when accompanied by certain of the moulds usually found on forage. Pure cultures of the bacillus, fed to horses, mules and guinea pigs, produced typical cases of forage poisoning, similar to those caused by the hay from which it had been obtained. The disease is apparently caused by toxins produced for the most part, before the forage is eaten. In their experiments animals were poisoned from a single barrel of the hay, by water which had been poured over the forage and had dissolved some of the toxin. Since the bacillus in question closely resembled B. botidinus in appearance, anaerobic characters, and physiological effects, these investigators made further tests to determine, if possible, whether the two were identical. Antitoxic serum prepared from B. botulinus was procured and was found to produce immunity from the effects of the bacillus cultured from the poisonous hay. It was further found that the hay itself, or rather the water in which it had been steeped, was incapable of producing forage poisoning in animals protected by the B. botulinus antitoxic serum. Samples of food which had produced forage poisoning in two other widely separated parts of the country were found to contain the same bacillus. It has thus been proved that one cause of forage poisoning is a bacillus, and that this bacillus, if not B. botulinus, resembles it so closely that morphological investigation has thus far disclosed no differential charac-istics. Although the investigators hardly feel yet in a position to state that it is the only cause, the results are most promising and would appear to indicate the final solution of this perplexing problem.
The first symptom noticed is usually weakness and staggering, with a tendency to stumble over ordinary low objects. The muscles of the tongue and throat become paralysed, and saliva drips from the mouth owing to difficulty in swallowing. The animal may become violent, rushing about, usually in a circle, and crashing into objects that come in his way. He soon becomes stupid and sleepy, and gradually loses control of his muscles, leaning against the stall or standing with feet spread apart. Paralysis increases, and after some time he is unable to stand. Bladder and bowels become partly paralysed and do not function unless artificially stimulated. The animal may live from one to two weeks, but in some cases death may take place within a day or so from the time symptoms become noticeable. Dr. Mc-Gilvray even states that animals may drop dead when taken from the harness, without showing any previous symptoms.
If treatment is begun soon enough, some of the animals may be saved. It is important to remove all traces of the poison as quickly as possible from the alimentary canal and to prevent access to mouldy or spoiled feed of any kind. It is necessary also to discontinue immediately the feed-stuffs in use and provide an entire change of feed, to avoid a further ingestion of poisonous substance. A purge and nerve stimulants as well as atropin for the circulation are recommended. Haslam prescribes injections of arecolin or eserin and pilocarpin followed by an antiferment and possibly an aloes bolus. Where paralysis of the throat has begun medicine cannot be given by mouth except by means of the stomach tube, as it is almost sure to enter the air passages and cause suffocation.