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White muscle disease in Western Australia appears to be a sporadic disease, fundamentally related to selenium deficiency but in the main limited to young sheep subjected to other concurrent stresses. Whether the complicating stress condition acts primarily at a nutritional level or whether if affects associated endocrine or metabolic pathway is uncertain from present evidence, although it is possible that both mechanisms may be involved. The disease is restricted to the southwestern agricultural districts, having rainfalls of greater than 20 inches. A much greater than average rainfall during the early winter growth stages of subterranean clover, followed a dry August and September, was common to both years (1960 and 1961) during which WMD was first widely recognized and may be ecologically significant in winter outbreaks. There are two peaks of incidence--one in late winter and early spring, affecting young lambs running mainly on subclover pastures, and the other in the summer, affecting weaners and hoggets fed cereal stubble, hay and grain. A survey of these feeds suggests that tehy are very often low in selenium, and may frequently contain less than 0.03 p.p.m. (dry matter) which is proposed as a critical level. However, many flocks grazing pastures containing less than this amount of selenium appear healthy. Ten trials were carried out in the affected area in 1960-61 to test the effect of selenium on lamb or weaner rate of growth Only one trial produced evidence of a significant response although one other suggested that an improvement had taken place. Five trials to determine the value of selenium in improving ewe fertility and early lamb survival were also conducted. The. results of two of them suggested that some improvement could be achieved. Vitamin E also appeared useful in the fertility trials. The soil and plant selenium backgrounds, insofar as thy are known in Western Australia, are discussed in relation to the pattern of outbreaks. Certain factors in the changing agricultural practices are mentioned as probable contributors, notably an increase in sheep stocking rates and heavier application of superphosphate.

A survey of plant selenium was carried out in the agricultural district of Western Australia in the spring of 1962. Pasture samples were collected from mid-August to mid-November during, or shortly after, the spring flush of growth in the different districts. Pastures were collected from both 'light' and 'heavy' country in each of the districts, and whenever possible, fertilizer history was recorded and botanical composition determined. Pasture samples from the 10-15 inch rainfall belt averaged 0.26 p.p.m. selenium ; from the 15-20 inch rainfall belt, 0.08 p.p.m., from the 21-30 inch rainfall belt, 0.056 3.p.m ; and from the higher than 30 inch belt, 0.036 p.p.m. If the critical level for selenium deficiency syndromes is placed at 0.05 p.p.m., then deficiency levels mg appear in all rainfall belts, the lower limit of which is the 15 inch isobyet. Regression analyses showed that there was a significant difference between the selenium contents of pastures from heavy and light soils in each rainfall area. The indicator condition of selenium levels of 0.05 p.p.m or less (white muscle disease) has not been seen in the northern range of the higher rainfall districts, although here, as elsewhere, plant selenium levels appear to be predicated on mean annual rainfall figures and on type of county. Grasses and cereals tended to dominate the pastures in the areas with less than 15 inches of rainfall a-year, while subterranean clover with admixtures of capeweed and grasses were chiefly found in the higher rainfall districts.

The chronic liver disease caused by the nuts of Macrozamia reidlei was studied experimentally in sheep given up to 4 kg over a period of 1-11 months. Similar degrees of liver damage were produced by this amount of powdered nut whether consumed in 3 or in 11 months. The liver pathology was similar in some respects to that caused by toxic lupins where a direct relationship to copper concentration in the liver has been established. The botanical and ecological aspects of M. reidlei in relation to other plants of the order Cycadales are considered.

The botanical description and distribution of a Western Australian species of Swainsona is reported in connection with investigations of the plant as a poison plant responsible for extensive losses of sheep and horses in the Goldfields station country. Feeding trials in sheep and rabbits confirmed the toxicity of Swainsona. Sheep exhibited depression, anxiety, "blind staggers", incordination, and emaciation. The central nervous system of both animal species was seriously affected, with chromatolytic and vacuolar degeneration of neurones and with oedematous changes. Renal cells showed hydropic degeneration and spleens were intensely haemosiderotic. These changes occurred after 4 or 5 weeks of chronic feeding and closely resembled those of locoweed poisoning of livestock in the western United States.

The distribution of the six species of Isotropis occurring in Western Australia has been delineated, with botanical descriptions of the four known to be toxic. Outbreaks of intoxication due to I. Cuneifolia or I. Drummondii, supplemented by feeding trials, were studied in detail and the basic pathological effects recorded. It is suggested that the toxic principle exerts its main effects on the glomerular capillary endothelium and the epithelium of the proximal convoluted tubules of the kidney, and on the centrilobular liver cells. Gastrointestinal and cardiovascular lesions may also contribute to acute deaths. The histopathological changes are described in detail.

Lupin components from 25 experimental paddocks in the Gingin-Dandaragan area were analysed for standard feed components and trace elements in 1961 and 1962-63. Lupinosis had occurred in all the experimental paddocks. Much of this area is deficient in trace elements and lupinosis appeared in 1948 soon after copper-ore topdressing was introduced and the use of superphosphate greatly expanded. The analyses were related to soil types, past dressings of copper and zinc, and compared with general lupin analyses in the district. Protein and calcium in the leaf and seed and calcium to phosphorus ratios in the leaf were high. Cobalt was often below the critical range for sheep health, iron was very high (815-2400 p.p.m. in leaves), organic sulphate was low (mean 0.2 per cent) and manganese was high (mean 326 p.p.m. in leaves). Molybdenum varied widely and was related to past copper and zinc topdressing. It was high in lupin seed where copper-ore topdressings were applied. Copper was marginal for sheep health (3-6 p.p.m.) in leaf and seed and deficient in stems and in associated grasses. Copper was lower and molybdenum higher on paddocks where lupinosis was severe.