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.