COBALT EXPERIMENTS

Timaru Herald, Volume CXLV, Issue 21280, 25 February 1939, Page 15

COBALT EXPERIMENTS

ROMANTIC HISTORY OF MINERAL RESEARCH SCIENTIFIC INQUIRY Much interest attaches to the cobalt experiments which are now being carried out in the Waikaremoana district under- the direction of Mr A. D. M. G. Laing, M.R.C.V.S., Government Veterinarian for the province. The story of how cobalt deficiency was traced is regarded as one of the most romantic developments of modern agricultural science and a review of this history will be of»interest. In New Zealand the three recognised forms of this wasting disease due to a deficiency of cobalt are bush sickness, which occurs on certain pumiceous areas in the North Island; Morton Mains disease in Southland; and Glenhope ailment in Nelson. In each of these forms it has been found that normal health is maintained, or returned to affected animals, by drenching with cobalt salts, the provision of licks containing cobalt or the top-dressing of pastures with cobaltised superphosphate. Many Workers Involved The story of how the deficiency was tracked down is one of the most romantic in recent agricultural scientific research. To no one person and to no one institution or department can the ultimate credit be given, because so many workers have made their contributions to the elucidation of the problem. The initial work on bush sickness in New Zealand was carried out by Mr B. C. Aston, until lately chief chemist to the Department of Agriculture. He believed the disease to be due to a deficiency of iron, and met with considerable success in combating it by the administration of commercial ferrio ammonium citrate. Later work showed that certain deposits of limonite, an iron ore, gave an effective cure, but other limonites and other iron salts were ineffective. Furthermore, animal physiologists were not satisfied that the iron intake of animals on affected areas was insufficient for the minimal requirements of the body. However, Mr Aston hau found a practical means of combating the disease, although there could be no absolute confidence in the quality of limonite for this purpose.

Assistance from England

Meanwhile it had been recognised that there were a number of areas in New Zealand, apart from volcanic soils, where the stock were more or • less unthrifty, and the pasture and soli analyses had shown a somewhat abnormal content of minerals at various times in the year, particularly in respect of lime, phosphates and iron. With the knowledge of these conditions, the Council of Scientific and Industrial Research secured from the Empire Marketing Board a grant of £2OOO per annum for a period of five years for the purpose of extending the work already proceeding on the mineral contents of pastures. This grant was subsidised by the Government, and work was undertaken by the Cawthron Institute and the chemical sec lon of the Department of Agriculture under the supervision of an advisory committee of the Council of the Scientific and Industrial Research. It was from these mineral content of pastures investigations and associated soil studies that the final solution of bush ..i :kness and kindred diseases was reached. Studies were carried on simultaneously on the volcanic soris of Mamaku, Mairoa and opaki and in th eTaranaki and Wairarapa districts by the Department of Agriculture and on the Glenhope and Moutere soils by the Cawthron Institute. Later an officer of the Department of Scientific and Industrial Research worked with the c-iwthron Institute and the Southland Frozen Meat Company to establish the cause of Morton Mains disease.

Pumiceous Showers An important step in the solution of the problem was achieved by two members of the Soil Survey Division in the course of a reconnaissance survey. They found that there were eight distinct pumiceous showers concerned in the soil formation of the central volcanic area of the North Island. Bush sickness was found to be associated with the area covered by two of these showers. The Taupo and Kaharoa showers, which had a wide distribution in the Bay of Plenty, Rotorua and Taupo districts. Recently a third shower, the Gisborne shower, has been known to be associated with bush sickness. At the Cawthron Institute it was found that the iron content of pasture from healthy country did not differ materially from that of unhealthy country. It was believed that there might have been some influence through direct ingestion of soil by the animal, for it was found that there was a considerable difference in the amount of soluble iron compounds in healthy and unhealthy soils. Drenching with soils high in soluble iron produced remarkable results in controlling and curing the disease, and confirmatory evidence of the value of certain soil extracts was obtained at Morton Mains to establish the wide geographical range of the ailment akin to bush sickness. Original Theories Revised “Tire varying results obtained in all three areas in New Zealand with different iron compounds, and the accumulation of evidence of the nonrecurrence of bush sickness on soils of remarkably low iron content led the research workers to revise their original suggestion that iron was the sole or major deficiency or factor involved in bush sickness and its allied diseases. The Cawthron Institute and the Department of Scientific and Industrial

Research worked in conjunction in the South Island experimental work to determine the potent principle, and a programme of elimination of the various trace elements was undertaken.

Towards the end of 1935, selected soil samples from New Zealand were spectroscopically examined in England by Mr H. Ramage, who found cobalt and nickel in two healthy soils from Nelson and Bluff, but was unable to detect a trace of either metal in a soil from Morton Mains, where sheep suffered from deficiency disease. Work on wasting diseases has been proceeding simultaneously in Australia, and in 1935 workers in South Australia and Western Australia reported beneficial results from the administration of minute amounts of cobalt to stock. These announcements focused attention on the part that cobalt might play in the cure of deficiency diseases in New Zealand, and it was found that ironfree extracts of soils and limonites which were particularly valuable in combating these ailments were appreciably higher in cobalt than extracts from ineffective materials.

When it is realised that 0.1 part per million of cobalt in dry matter in the herbage consumed by an animal is associated with normality and 0.04 part per million with wasting and death, it will be realised how complex this matter of defining deficient areas must be. Certain localities have long been recognised as deficient areas, but little is known of the marginal areas where the stock may be unthrifty but not to such a degree as to associate the unthriftiness with cobalt deficiency.

Survey of Pastures

The administration of cobalt to lambs in Southland in the summer, 1936-37, a bad one for lambs, on farms not generally recognised as suffering from cobalt deficiency produced amazing results. The implications of this are obvious. For every acre which was formerly recognised as definitely sick country, there may be 10 acres which show a marginal deficiency—i.e., the effect of the deficiency may not be so great as to be immediately obvious, or may appear under certain unfavourable seasonal conditions.

A survey of the cobalt content of pastures throughout New Zealand, particularly in suspect areas, is being undertaken. In the North Island the work is being done by officers of the Department of Agriculture and in the South Island by the Cawthron Institute in association with officers of the Department of Industrial and Scientific Research. The work is being financed by the New Zealand wool publicity committee and the New Zealand Meat Board.