288 Transactions. 



Art. XXX. — The Chemistry of Bush Sickness* 



By B. C. Aston, F.I.C., F.C.S. 



[Read before the Wellington Philosophical Society, 4th October, 1911.] 



The mysterious wasting condition locally known as ' bush sickness." 

 which always eventually appears in ruminating herbivora pastured on 

 certain areas of pumice country in the North Island situated near the inter- 

 section of the 38th parallel of E. latitude and the 176th meridian of S. 

 longitude has been the subject of much consideration for the past fourteen 

 years, though it is only within the last two years that any adequate provi- 

 sion has been made to submit the matter to systematic research. From 

 the references given at the end of this paper one may find the little that 

 is known regarding the veterinary aspect of the matter. It is desired 

 here, at the direction of the Minister of Agriculture, to record some facts 

 which have been elucidated through the chemical analysis of sundry 

 specimens which I from time to time have collected or received. The 

 reasons why the matter should be referred to a chemist to investigate are 

 given in an article in the " Journal of the New Zealand Department of 

 Agriculture " for November, 1911 (vol. 3, No. 5). 



An ordinary analysis of the soils of the affected district does not show 

 any reason why stock should not thrive on the herbage grown by these 

 soils. In Table 6 are given the total amounts of constituents of the soil 

 obtained by breaking up the silicates with hydrofluoric acid. The 

 manganese is perhaps high for New Zealand soils, but Hilgard quotes 

 analyses of American soils with a greater percentage (see p. 372, 

 " Soils "). Table 5 gives the chemical analysis as ordinarily stated for 

 agricultural purposes. Analyses of grass-ashes are given in Table 1. 

 In considering these results it must be remembered that they do not 

 give constituents which may be present in amounts less than one- 

 hundredth of 1 per cent., such as copper, barium, &c, and that it is 

 possible that some of these constituents if taken up by the herbage 

 might affect the health of beasts pastured thereon. To obtain a clue as 

 to what element may exist in soil and grass that would produce bush 

 sickness it is necessary to systematically examine many animal specimens, 

 and it is this work which is being given first place in the research. 



As the symptoms of bush sickness would accord with those produced 

 by chronic mineral poisoning, one of my first experiments was to examine 

 the liver of a sick animal for traces of heavy metals. To my astonishment, 

 I obtained a considerable quantity of copper from the ash of a liver from 

 a steer which was killed under veterinary supervision as being a typical 

 bush-sick animal. On consideration it appeared possible that copper 



* " Bush sickness" occurs in ruminants pastured on land which has been recently 

 reclaimed from forest, or on open country which has been laid down in English pasture 

 for over twenty years. Veterinarians can detect no abnormal micro-organisms or signs 

 of disease in the wasting animal. Affected animals recover as soon as they are moved 

 on to healthy country. The affection is confined to a definite area of pumice country, 

 outside of which it does not spread, but within the area the sickness always in time 

 (a few months in sheep, longer in cattle) develops in cattle and sheep. The affected 

 area grows an abundance of green pasture — English grasses and clovers — at all times 

 of the year, and yet the animals become emaciated, and eventually die if not removed. 

 Ruminants from other parts of the country on being placed on " sick " country experi- 

 ence decided benefit for the change and fatten for a time. Horses fed for years con- 

 tinuously and entirely on the affected pasture are not injuriously affected. 



