The aetiology of phalaris straggers in sheep. IV. The site of preventive action and its specificity to cobalt

The preventive activity of cobalt against phalaris staggers in the sheep is very probably restricted to the rumen. In this disease cobalt does not act within the tissue cells nor within the intestines; cobalt injected intravenously is without effect. The destruction of the toxic substance present in the phalaris does not depend on the production of vitamin B12 by the rumen flora. The probability that cobalt acts by ensuring the proliferation of microorganisms in the rumen which accomplish this detoxication is discussed. The preventive action is specific to cobalt administered orally; frequent doses of a supplement that provide the daily equivalent of 10 mg each of boron, copper, iron, magnesium, manganese, molybdenum, nickel, titanium, and zinc fail to prevent the malady.

The aetiology of phalaris straggers in sheep. III. The preventive effect of various oral dose rates of cobalt

The earlier finding that cobalt administered orally in adequate amounts completely prevents phalaris staggers from developing in sheep that graze pastures containing a preponderance of Phalaris tuberosa L. has been confirmed. Weekly doses of 7 mg cobalt did not always afford protection but supplements of 28 mg (or more) at weekly (or more frequent) intervals were invariably effective. Extremely small supplements (0.05 mg) were effective when administered twice daily, but when the interval between doses was 4 weeks even very large amounts (280 mg) did not prevent staggers. The principles that govern the preventive administration of cobalt are discussed and relevant analytical data are presented.

The aetiology of Phalaris staggers in sheep. II. The toxicity to sheep of three types of pasture containing Phalaris tuberosa

The seasonal occurrence of phalaris staggers In sheep on three types of pasture containing Phalaris tuberosa L., during periods of 3 years, 2 years, and 1 year respectively, is described. A relatively pure stand of phalaris proved toxic to sheep for almost 6 consecutive months of its growing period. The consumption of appreciable quantities of lucerne, subterranean clover, or other plants, along with the phalaris, reduced the hazard very considerably. Neither the dormant tubers nor the standing straw of phalaris proved to be toxic. The widespread occurrence of phalaris staggers on a diversity of sol1 types is reported and the possibilities that the toxicity of phalaris may fluctuate according to climate and terrain are discussed. The view is advanced that actively growing phalaris is potentially toxic to sheep under most, if not all, circumstances.

The aetiology of Phalaris staggers in sheep. I. Preliminary observations on the preventive role of cobalt

During the course of an experiment, a "staggers" syndrome developed in Merino ewes which selectively grazed freshly growing Phalaris tuberosa. The symptoms and progress of the disease are described and the toxicity of phalaris is discussed. There was no incidence of staggers amongst 10 ewes which were dosed each week with 7 mg. cobalt, while 11 of 15 untreated ewes were affected, six of them fatally. This response to cobalt is highly significant ( P = 0.00054). In the light of these observations, earlier work relating to "phalaris staggers" is reviewed.