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It will be seen that there is a very respectable assemblage of elements within us and indeed within all animals, but not all are admitted to be necessary to life. Some of these elements may be there by accident, such as aluminium and silicon, but even those which are present in the rarest quantity may have a useful function to perform. Iron we know is indispensable, although only present to the extent of 0.004 per cent:, and iodine occurs in even smaller proportions but that also is necessary to life. An omission from this list is that of zinc and copper, both being present in traces, and since boron has been found to be necessary for the growth of some plants possibly this also should be added. In this address consideration will be confined to those mineral elements usually held to be necessary to animal life. Researches concerning mineral foods have been forced into prominence in the agricultural world owing to very puzzling troubles which affected some farming communities, both in old pastures in the old world, and in new pastures in recently settled areas in the New World of America, and in the newest settled world of South Africa, Australia and New Zealand. Animals ultimately failed to thrive when pastured on land where there was apparently plenty to eat, yet when they were removed to land where no such trouble exists the same animals not only recovered but often soon out-distanced in condition the animals native to that farm. These troubles are now generally referred to as “deficiency diseases.” The word “ultimately” is used advisedly, as imported stock do thrive, for periods extending over months, upon the same pasture on which, in time, they will become emaciated and eventually die of starvation. The reason that an imported animal may thrive for a time or may even fatten on “affected” country is that every animal possesses a store of each mineral element likely to be deficient, and while it is thriving it is using up that store, although it may take months to deplete it. In some forms of these mysterious troubles there were definite clinical symptoms, such as obvious deterioration in the bone texture, swellings in the bones and joints, and more or less lameness, and the cause of these was at once referred to extreme phosphorus deficiency in the diet. In other forms there was little to guide the veterinary pathologist as to the cause. Other characters of this class of trouble in stock were that the ailment did not spread but was restricted to definite areas, and in one deficiency disease blood from an affected animal could be transfused into the veins of a healthy animal without ill effect to it. The obvious conclusion, where wasting in numbers of stock occurs on pasture apparently sufficient in quality and quantity, and where pathologists cannot detect any ordinary disease or adequate parasitic trouble to account for the wasting, and where the pastures contain no mineral poison or poisonous weeds, is that there is some deficiency in the mineral foods,

which, although they are present in the soil in amounts sufficient for the growth of normal pasture plants, are not present in an amount sufficient to produce healthy stock. To prove the truth of this it should only be necessary to analyse the pasture, compare it with normal pasture on which the flocks and herds are healthy and develop normally, determine which elements are deficient, and give the deficient element or elements in pure form as a drench to the animal. Then if the animal always recovers under the treatment while still grazing on the pasture upon which it becomes sick, it should go a long way to prove what element is deficient. The recovery of the animal under the administration of a pure mineral food necessarily banishes the possibility of a vitamin being deficient in the food supply.

That the presence, in pasture, of an ordinary mineral element in unusually high amounts, or in other words that some want of balance of the mineral constituents might be a possible cause of mal-nutrition, has not been forgotten. Long continued experiments on ruminants at the Wallaceville Laboratory have shown that no ill effects attend the ingestion of soluble silica, or silicate of soda, or soluble copper, or copper acetate. The necessity for a proper balance in the diet of the various mineral foods does not seem to be well proved, and it is not accepted by Theiler who argues that so long as the essential elements are present in sufficient quantity, the animals probably have the power to eliminate any excess of them, which seems a most reasonable view. (“Minimal Mineral Requirements in Cattle” Journ Ag. Sc., July, 1927, vol. 17, p. 202).

The investigation of what is called a deficiency disease may therefore appear from this to be a comparatively easy matter, but on the contrary it is one of the most difficult cases submitted to the chemist.

In the case of the wasting herbivorae grazing on pasture, after the veterinarian has diagnosed the matter as beyond his scope, as more a matter for the chemist than the veterinarian, the collection of samples of the food will be the chemist's first duty. This is not nearly such an easy matter as it looks. For the material must be selected most carefully from bitten pasture, otherwise there is no security that a fair sample of what the animal has consumed is being collected, and Godden (Journ. Agric. Science, vol. 16, 1926, pp. 78–88) has shown that great difference in composition may exist between the “eaten” and the “not eaten” pasture in the same field at the same time. The samples must be collected over the whole range of the animal's grazing, and in the case where mineral foods like iron, calcium, manganese, silicon and iodine are suspected of being deficient the utmost care must be taken to guard against contamination by soil. The reason for this is that in some cases (e.g. iron) the element has to be in a special state of combination for the animal to utilize it as food, and in other cases the method of analysis cannot imitate the digestive process of the animal, and probably more element is dissolved from the contaminating soil in the laboratory than would be digested by the animal. In the case of iron and iodine the soil contains such a large

amount of these elements compared with that in the plant that completely misleading results may be obtained. Neither is it possible to wash or remove the adhering dust or earth by mechanical means, since in washing with water there is danger of dissolving out some of the more soluble minerals from the plant tissues. But even washing with water will not remove fine dust. I feel sure that many of the results which are stated in the standard literature, dealing with the analysis of fodders for iron, are misleading, and that the high amounts of iron recorded in many cases are the result of contamination by soil. This seems to have been partially realised by some workers and not by others (Robinson et al., “The Relation of some of the rarer Elements in Soils and Plants,” Bull. U.S. Dept. Agr., No. 600, 1917).

Seeking for a way of discriminating between contaminated and uncontaminated samples, I have introduced the method of using the alumina present as a guide. Alumina is always present with iron in soil, but is only taken up in traces in the tissues of the higher plants to which pasture plants belong. Hence if alumina is found in comparatively large quantity, the sample is probably contaminated with earthy matters. Diseased maize plants may apparently take up quantities of alumina, but the possibility of contamination by soil has not apparently been considered. (Hoffer and Carr: “Accumulation of Aluminium and Iron Compounds in Corn Plants and its probable relation to root rot,” 1923 J. Agric. Res. vol 23, p. 801). The accurate determination of alumina in small quantities in plants is not easy. Nevertheless it must be attempted.

I would like to lay particular stress on the difficulties of sampling pastures, and the need for overcoming them. Results obtained by analysis in my laboratory have shown that great divergence may be found in the composition of samples taken in the same field on the same day by different collectors, one skilled, the other untrained. Where the sampling is faulty, all the time and money spent in analysis is not only thrown away, but the information obtained may be misleading, and lead to additional loss. An eminent English authority who recently visited New Zealand was most emphatic that the chemist should obtain his own samples, and I was very glad to obtain his confirmation of what I believed to be an essential practice.

When suitable samples of pasture have been obtained they must be carefully dried to a state in which they will carry through the post without becoming mouldy, then, on arrival at the laboratory, botanically analysed, picked over, ground to a very fine powder in a mill especially imported for the purpose, and finally bottled up. They are then analysed in duplicate by the workers independently of each other, using—when possible—different methods which have been found to give comparable results.

Time will not permit the discussion of the methods and difficulties met with in sampling and in determining small quantities of mineral elements in large quantities of organised matter. All the resources of the inorganic chemist will be required to carry out successfully a complete mineral analysis of pasture. It should be

remembered also that living matter is ever changing in composition, and that in the case of pasture there are variations due to:—

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of which factors 1 and 2 are undoubtedly the most important.

The proper study of any widely spread mal-nutrition disease in herbivores should be investigated from every angle, embracing thorough research into:—

• (1) The soil which grows the pasture,

• (2) The pasture on which the animals feed, and any supplementary diet,

• (3) The animals themselves.

Let us consider first the two mineral food elements which are evidently economically the most important since they are the only ones mentioned by the Fertilizers Act, 1927, phosphorus and potassium.

This country is now importing, making and using every year mineral manures which are costing the farmers about two millions sterling, a large sum for a population of a million and a half to pay. The predominant element, for which about 95 per cent, of this large sum is paid, is phosphorus and it is this element which the chemical analysis of soils in the North Island shows to be most deficient. About one half of all the money spent on fertilizers goes for superphosphate. This is a most valuable substance, because almost all the phosphorus in it is soluble in water. This enables the ready distribution of phosphate in the soil water, where it is precipitated in the first few inches of soil by being fixed in combination with some base. When this base is calcium all goes well, but when it is iron, aluminium, manganese, or titanium, chemists are inclined to think that the resultant compound is not readily available as plant food. Hence the normal soil should always contain free calcium carbonate, for this will afford a base with which the soluble phosphate will in preference combine and become less soluble, but not so insoluble that it will be unavailable to the plant roots. Calcium carbonate is rarely naturally present in New Zealand soils and is too little used in New Zealand agriculture.

There is no doubt that the element most deficient in New Zealand soils and pastures is phosphorus. The proof of this is:—

• (a) The analysis of the soils (N.Z. Journal of Agriculture, 1913, vol. 7, No. 2, page 122-3), which shows that phosphorus is the most deficient element of any.

• (b) Analysis of pastures, which show, in unmanured lands, deficiency of phosphorus in the plant.

• (c) The universal experience of the beneficial results of phosphate manuring in New Zealand, manifested by the enormous disproportion

• in the fertilizers used (95 per cent. of the value of imported manures being for phosphates, and 5 per cent. for the other two constituents of artificial fertilizers, nitrogen and potash). The need for phosphates is more strikingly shown in the North Island than in the South Island where there is more phosphorus in the soil and where the consumption per acre of phosphate is far less than in the North. There are no great deposits of mineral phosphates in New Zealand, consequently under the present system of manuring external sources of supply have to be relied upon to continue and increase New Zealand's productiveness. When animals are grazed on pasture very deficient in phosphorus, especially when those animals are high-yielding milking cows or quickly growing young sheep, symptoms readily distinguishable by the expert veterinarian appear. These symptoms consist of abnormalities of the bones, which in sheep may become so fragile as to break readily on handling the animal. This indicates that the phosphates in the bones are being reabsorbed, and the animal is drawing on the store of phosphates contained in the bones, for these in addition to being the skeleton or framework upon which the animal is built, have the important faculty of acting as a storehouse of phosphates to be drawn upon if required. Forbes (“Evidence of deficiency of Mineral Nutrients in the Rations of Milk Cows” 1924, Washington), states that under certain conditions it was clear that the calcium of the skeleton was more readily available for milk formation than was even the water-soluble calcium of the ration. The largest land animals are herbivores. This is possibly connected with the fact that the phosphate in the food supply varies with the season and necessitates the building up of a substantial balance in their bank of phosphates to tide over periods of depression in the supply. Whereas the smaller carnivores, in the flesh foods, blood and bones which they eat, obtain a regular daily supply of phosphates. The largest birds are purely vegetable feeders, the moa and the ostrich being outstanding examples. One would like to follow up this interesting theme and learn why some New Zealand aquatic or semi-aquatic animals, the whales, sea elephants and sea lions, have developed such great skeletons and of what their food consists from season to season, but we must return to the domestic breeds.

“Waihi Disease,” or bone mal-nutrition trouble, so called because it first appeared in cattle at Waihi, in Taranaki, is often very prevalent in many parts of the North Island, especially in droughty seasons. Abnormal dryness in the soil has apparently a greater influence in hindering the absorption of phosphorus than of other mineral elements by the pasture. South African experience indicates that as the season and soil become drier there is a corresponding decrease in the phosphorus content of the herbage (Theiler et al., 11th and 12th Report Director Vet. Ed. and Research, 1927), the P₂O₅ gradually decreasing from 0.6 per cent. in November to 0.09 per cent. in June, without any corresponding change in the calcium content.

The cure of the ruminant animal acutely suffering from a phosphate deficiency is medicinally effected by administering a soluble

phosphate, either through the drinking water, or by drenching the animal. Good results also follow bone dust, when supplied to the animal as a lick, and as concentrated food stuffs rich in phosphate, such as bran. Other treatments are the removal to better pasturage, or top-dressing the deficient pasture with an available phosphate. In droughty seasons the top-dressing cannot be expected to, and in fact does not, take effect until sufficient rain has fallen to carry the fertilizer to the plant roots. The recognition of the cause of the “Waihi Disease” and the appropriate remedies to apply have been so easy, and the results of treatment have been so successful, that it has not been necessary to call in the chemist to advise on the composition of the soil or the pasture, and opportunity for acquiring much valuable data has been lost. It is, of course, highly desirable that such cases should be thoroughly investigated, even though the remedy is perfectly well known and a cure certain if directions are followed. A thorough knowledge of one deficiency disease may help in understanding other similar troubles in which the cause is uncertain. That lack of phosphorus in the food supply is the cause of malnutrition of the bones is always the accepted theory, since the animal recovers when phosphates are supplied, and, under favourable conditions, when the land is top-dressed with phosphates. Sir Arnold Theiler (Journ. Ag. Science, vol. 17, 1927, p. 305) in his South African experiments was not able to produce the typical symptoms of aphosphorosis (as phosphate deficiency in the animal is called) by feeding heifers on a diet deficient in calcium but adequate in phosphorus. For the reasons stated exact information regarding the soil and pasture composition on farms where “Waihi Disease” occurs is still very meagre. It has been recorded from several differing soil types, ranging from swamp soils to loams, but, to my knowledge, no case has been observed on any pumice type of soil. In one Wairarapa farm where the trouble was prevalent the pasture showed a lower phosphorus content than any hitherto met with in New Zealand, a figure which compares very unfavourably with those found in the dry pastures of South Africa. It is hardly to be wondered at that some pastures, which the owners have not yet learned to top-dress, show a great deficiency of phosphorus, when it is remembered that as much as 20 lbs. of phosphoric acid (equal to say 1 cwt. of ordinary superphosphate) may be taken off each acre yearly in the milk alone.

Deficiency of the one other mineral ingredient of fertilizers recognised by the Fertilizers Act, potash, when it ever occurs in New Zealand normal soils other than those humus lands resulting from drained swamps, does not and is not likely to affect the herbivorae, but excess of potash may cause mal-nutrition in cattle and horses (Zuntz, 1912, quoted by Armsby “Nutrition of Farm Animals,” 1917). This group of animals has indeed the difficulty of getting rid of the excess of potash which they always ingest with their food, requiring, as a rule, to be provided with a salt lick, the sodium of which assists them to eliminate the potash. Here is another great difference between the herbivores and the carnivores in their respective mineral food requirements. The herbivores require common salt (sodium chloride) and if they do not get sufficient become unthrifty. The

carnivores require no salt to be added to their diet, for any sodium chloride required is obtained from the animal matter which provides their daily food. Bunge has shown that this is true of races of men whose food is chiefly the proceeds of the chase and consists of animal flesh with little or no vegetables, whereas those races whose diet is mainly vegetables crave for salt. Bunge first suggested that this extra sodium supply is necessary to assist in elimination of the potash excess in the vegetable feeding races.

There are many other mineral plant foods which are not recognised by the Fertilizers Act, as they are supposed to occur in sufficient quantities in all soils and are not required, or, if required, are so cheap as not to need the protection of the Act. The one other which might possibly be inserted is calcium, or, as the compounds of it are called, lime or limestone. Calcium occurs in all normal soils in sufficient amounts for plant foods, but the addition of one of the salts or the oxide effects such an amelioration of many soils that liming has become a fixed practice in agriculture. Lime and calcium salts encourage the growth of clovers, a genus of plants which, besides being highly nutritive as stock food, contains about twice as much calcium as the ordinary grasses—a boon to sheep which are especially liable to suffer from calcium deficiency. The great value of an abundance of calcium in the food supply of domestic stock is the wonderful effect it has on the health and fecundity of the animal. One cannot but be struck with the fact, even in New Zealand, that in travelling across unsettled country the limestone areas stand out prominently from the abundance of wild herbivores these areas support, compared with adjacent non-calcareous types of country. Theiler's experiments in South Africa (J. Agric. Sci., vol. 17, July, 1927, p. 305) indicate that where very low calcium rations are fed to heifers they in consequence lost their calves.

Hart et al. (“Influence of rations restricted to the oat plant on reproduction in cattle” Wisconsin Agr. Bull. 49, 1920. See also Lindsay and Archibald, Journ. Ag. Research, vol. 33, 1925, p. 771) found that when cows are fed entirely on oat plant products, reproduction in cows was a failure, calves being either born dead or too weak to rear. When calcium salts were added to the ration a marked improvement in reproductive function was noted.

Unfortunately calcium is a difficult element to apply to poor pasture lands; the form which is available in New Zealand—ground limestone, sold as carbonate of lime—must be distributed on deficient lands at the rate of at least half-a-ton to a ton per acre, a laborious undertaking and an expensive one, owing to the high cost of road transport and bagging. The pellet method of feeding calcium to sheep may provide an alternative for liming hilly country of low value. This method was first introduced by Dr. J. B. Orr and his associates at the Rowett Institute, Aberdeen. Dr. Orr explained the method fully to me when he visited New Zealand last year. The method has been successfully applied to “Bush Sick” sheep and lambs in the Rotorua district (N.Z. Journal of Agriculture, vol. 38, Jan. 1929).

A paste is made off various oily and starchy meals, together with suitable oil and the mineral foods, the thoroughly mixed materials are steamed, forced through a perforated iron plate, and the cube-shaped pellets dried and baked to a dry, hard, tough waterproof state, which will carry well without breaking down to a powder or becoming mouldy. The Scottish experience is that by training a number of sheep to eat the pellets they will eventually, in the course of a year or so, teach all the sheep on the run to eat them, so that in time fifty pounds of pellets may be scattered on the grass, and the whole of the flocks on the hills, having acquired a taste for the pellets, quickly assemble and will eat the whole batch in less than half-an-hour. It will be obvious that the easy periodical mustering of a flock from a large area of broken or hilly country has its advantages to the shepherd, in addition to the attainment of the main objective. There is here, therefore, a new and cheap method of supplementing the mineral ration for sheep afforded by poor pastures, which is well worth extensive trial by the great run-holders.

It must not be forgotten that superphosphate contains more calcium than phosphorus, and that it also contains a good percentage of sulphur as calcium sulphate. It is therefore a phosphorus, calcium and sulphur manure, but although valued only on phosphorus content some of the good effects may be due to the sulphur or calcium which it contains. Where these two latter are proved to be deficient, it would of course be far cheaper to supply them to the soil as ground limestone or gypsum. Although not recognised by the Fertilizers Act, sulphur, sodium, magnesium and chlorine are elements necessary to life which are amply supplied for plant food in the rain which brings down from the air dried sea spray, the chief salts of which are sodium and magnesium chlorides and sulphates and calcium sulphate with smaller quantities of potassium salts. Sulphur has, however, been put on the market as a plant food, but, judging from the exact experiments reported, with no response in yield. The herbivorous animals' need of chlorine and sodium is far greater than that of the plants, so that this must always be supplied in lick form: ad libitum to ruminants and horses, but with great caution, and in the prescribed amounts, if fed to pigs and poultry. Analysis of some pastures in Canterbury has shown a deficiency of chlorine, and this is an additional reason why run-holders should not neglect to give rock salt or agricultural salt, supplying the most cheap and easily administered mineral food, sodium chloride.

I now come to an element on the list which is highly important, though present in such small proportions as 0.004 per cent. of the whole body—iron. For the last thirty years I have been endeavouring to learn something of a mysterious mortality in stock called variously “Tauranga Disease,” “Bush Sickness,” “Cattle Sickness,” or “the Skinnies,” a wasting, characterised by progressive anaemia and a typical deficiency disease, where the mortality was 100 per cent.

This serious trouble in stock was proved by Gilruth, in 1903, to be non-transmissable, even by transfusion of blood tests (1928 Aston

N. Z. Inst. Transactions, vol. 58, page 540), that it was not due to any micro-organism, that the disease in cattle and sheep was similar, that the water drunk by stock was not responsible, that to the naked eye and under the microscope the tissues and blood presented no diseased condition, that everything points to a deficiency of some most important constituent in the food supply, and that contrary to what one would expect from the rich looking pasture at Kaharoa, animals become most readily affected at Kaharoa, next at Lichfield and least readily at Tauranga. The truth of these opinions has been fully substantiated by much research work carried out since 1903. This has been summarised by Reid (“The Diseases of Farm Animals in New Zealand,” Wellington, 1923, page 481) who states “This is not a disease in the ordinary sense of the term but a state of mal-nutrition resulting from some hitherto unascertained cause. All attempts to artificially infect animals with products from pre-existing cases have consequently failed and the elucidation of the problem has resolved itself more into a question for the physiological chemist than the veterinarian.”

Gilruth early recognised the importance of chemical research in this matter, and one of the first requests I received on entering his laboratory as chemist to the Department of Agriculture in 1899 was to ascertain whether there was any poison in grass from the affected country, since poison would be capable of causing the anaemia. On reporting that there was no poison in the grass (1900 Ann. Report of Dept. of Agriculture, page 136), nor, as was afterwards proved, in the livers of dying animals, the investigation was naturally directed into another channel, the search for a deficient element in the food supply.

The first three local names of the disease “Tauranga disease,” “Bush Sickness” and “Cattle Sickness,” are misleading. Tauranga is not a typically affected district, the trouble does not invariably occur in “Bush” or forest country, and sheep are more susceptible than cattle to the ailment. As a descriptive title “the Skinnies” is much more appropriate and quite descriptive. Affected cattle become so thin that their bones, which are large, perfectly sound, well-formed and of normal composition, stand out conspicuously, and the animal appears like nothing so much as a walking skeleton. Since I have shown that deficient phosphorus in the diet produces a diseased condition of the bones, the excellence of the bones of “Bush Sick” animals is evidence that phosphorus is not a deficient element in this disease. Clovers thrive remarkably well on pumice lands of all types, and are a prominent feature of the pasture, so that lime can be ruled out as a possible deficiency. If sulphur were the deficient element, one would expect that the application of superphosphate—which contains a good deal of available calcium sulphate—to the pasture, would cure the disease, but superphosphate does not have this effect.

Lime applied, in amounts from one to two tons per acre, to the pasture growing on sandy silt soils of the pumice type has given deleterious results to the stock. In fact stock lost condition more quickly on the limed land than on paddocks to which no treatment had been applied. This was confirmed by several experiments at

Mamaku and Lichfield (N.Z. Jour. Agri. vol. 6, June 1913, p. 616). It is a well known fact in agricultural science that amelioration of sandy lands is better effected by the addition of organic manures than by liming. In King Island, off the coast of Tasmania, cattle are affected with a complaint which is undoubtedly the same as “Bush Sickness” and are curable by the same treatment which has been successful for “Bush Sick” animals, namely, removal to healthy country and treatment with iron medicines. The soil on which this occurs is a dune sand containing 50 per cent. of carbonate of lime. (Dickinson, Australian Veterinary Journal, September, 1927).

Potassium is present in abundance in the pasture, as one would expect from the fact that pumice contains more than 3 per cent. of potash. Magnesium is also present in the usual amount in the pasture. Sodium and chlorine given as a salt lick do not prevent the disease from appearing in flocks or herds. Iodine has been administered to a sick animal without effecting any improvement. There is no evidence that would lead one to suppose that any of the other elements mentioned, save one, are present in deficient amounts. Our knowledge of whether fluorine, arsenic, aluminium and boron are necessary is too remote to warrant further enquiry. Copper, silicon and manganese are present in excess in the food supply compared with normal pastures but long continued experiments with copper and silicon compounds on ruminants have failed to show any injurious effects. There is only one element left to consider, that is iron. It should be mentioned that Gilruth's predecessor, A. Park, the first Veterinarian appointed by the New Zealand Government, had suggested as early as 1898, on theoretical grounds, that anaemia should be curable by iron remedies and had actually tried Parrish's Chemical Food (compound syrup of phosphate of iron) without success. He thought the cause was something wanting in the soil, and recommended the settlers to try iron remedies on their stock (Report Dept. Agric., 1898, pages 88 and 92). Park's failure may have discouraged the use of iron remedies, at all events no steps were taken until chemical analysis of the pasture, and of blood from beasts dying of the disease, showed deficiency of iron (Aston, Trans. N.Z. Inst., vol. 44, 1911, p. 288), and iron sulphate top-dressings of pasture, suggested by these analyses, proved highly beneficial to the sheep pastured on them (Reakes and Aston; 1913, N.Z. Journ. Agr. Vol 6, p. 623). Then Park's cure, syrup of phosphate of iron, was again tried and proved to be curative if the treatment was continued long enough. Later in 1918, I suggested the use of ferric ammonium citrate as a more convenient compound and this was found to be equally efficacious, subsequently completely displacing the syrup.

It can be confidently stated that this compound, the double citrate of iron and ammonium, if given daily to a “Bush Sick” beast as a drench, will effect a recovery, provided the animal can be kept alive for a fortnight after the dosing starts. The Department of Agriculture now imports the drug regularly and supplies it at cost price to bona fide farmers in the affected districts. Last year 4 cwt. was thus disposed of in small lots of a pound or so each, the total sold being enough for 58,000 cattle doses. The necessary duration

of treatment for a beast obviously sick is a matter of weeks rather than of days. For sheep the pellet method seems to provide the most hopeful results, for cattle drenching, and for calves administering the drug with the milk food. The compound is finding its greatest use as a preventive and as an intermittent adjunct to the usual ration of dairy cows in the border line districts, where previously the stock could not permanently be kept healthy on pasture alone without changing to healthier districts. It is found that the iron compound not only keeps cows healthy, but increases their yield. For instance, a farmer milking 130 cows on 200 acres, as the result of putting the drug in the drinking water finds his cows now give 8 lbs. more butter-fat a month than do those of his neighbours, milking under similar conditions. Testimony by farmers as to the efficacy of the iron treatment whose farms are distributed over some millions of acres may be found in the official reports. (See 1928 N.Z. Journal of Agriculture, vol. 36, pp. 306, 302 and 1929, vol. 38).

Seeing that the effect of artificially supplying the deficiency of one important mineral in the diet has so beneficially affected the yield of butter-fat, it is probable that similar results will follow the same treatment, when other deficiencies such as calcium and phosphorus are concerned.

Another aspect is the pre-disposition to infectious disease, which any form of mal-nutrition due to faulty diet entails on the animal. Orr (“Mineral Metabolism and Disease,” Practitioner, January, 1925), having noted that such diseases, especially those affecting the respiratory tract, more frequently occurred in laboratory animals with intentionally badly balanced mineral diets than in the control animals, suggests the possibility that lower resistance to certain infectious diseases may be due to defects in the mineral diet.

It is necessary to keep in view the fact that the same mineral nutrients are required in very different proportions, by the plant on the one hand and by the animal on the other. The text books say that traces of iron in the soil are sufficient for the plant, forgetting that the plant is grown for the animal. The amount of iron required in the daily food of a man is variously computed by Sherman at 10 milligrams and by Albu and Neuberg at 60 milligrams. One would surmise that the larger ruminants, owing to their more rapid rate of growth and greater weight, would require iron in a much greater proportion. A cow is eight times the weight of a man and at the maximum rate of growth grows four times as fast as a man. Ewes and sows are about 1 ½ times the weight of a man and grow 12 to 16 times as fast. In one experiment at the Rowett Institute a sow's piglets suffered from anaemia when the mother was receiving a gram of food iron daily, but the mother remained healthy. This indicates a figure less than but somewhat near the minimum requirement for the sow, viz. 1,000 milligrams.

If one might be allowed to theorise from very limited data, one might put 1,440 milligrams of food iron as the daily requirement of that sow, which, however, is not a ruminant and is able no doubt to utilise sources of iron not available to the cow. As the latter takes

about six months to begin to show signs of wasting from iron starvation, when the pasture only provides a gram of food iron per day, on the figures given, it looks as if 2 grams would be necessary. Now this means .015 per cent. iron on the dry matter, which is something more than the merest trace said to be sufficient for plants.

The composition of the milk of animals has been stated to be the best guide to the mineral requirement of animals, but this is not true of iron, for milk is deficient in this important element, the young animal being, in most species, born with a store of iron. However, some indication of the order in which animals require iron may reasonably be deduced from the iron content of milk from different species. According to Alderhalden (Journal Physiological Chemistry, vol. 27, p. 594) ewe's and sow's milk contains four times as much iron as cow's milk and over fifteen times as much as human milk. I think these figures point to the probability of the more rapidly growing animal requiring a much larger proportion of food iron and that so large an amount as 1,000 milligrams may reasonably be held to be insufficient without invoking the aid of the interaction of other elements, especially manganese, in rendering the iron unavailable. With regard to this element I consider that the evidence which we have at present points to any excess being beneficial rather than the reverse. Godden and Grimmett (1928, Journal Ag. Science, vol. 18, p. 363) have shown that manganese is absorbed by plants in much greater amounts under conditions where the soil was saturated with stagnant water, and it is under these conditions that cattle, brought from sick areas, rapidly recover when pastured at lakeside paddocks Rotorua. Analysis of the herbage there shows a high manganese content. Titus et al. (1928 Journal Biolog. Chem., vol. 80, p. 570) following the experiments of Hart et al. (1928 Journal Biological Chemistry, vol. 77 p. 769) show that manganese, both when added to iron diet, and to copper-iron diets of rats, seemed to give almost as good results as copper in the building of haemoglobin, but when these elements were given together better results were obtained than when given singly with iron. They suggest the existence of a group of substances rather than one, which are active in haemoglobin building. Copper was found to be present in “Bush Sick” samples (soil, plants and animals), in rather high amounts (Aston, Trans. N.Z. Inst., vol. 44, 1911, p. 288). Following this up, H. A. Reid in 1910-11, carried out at the Wallaceville Veterinary Laboratory a series of experiments on calves and sheep extending over a year in which he dosed them with copper salts. The calves were strongly stimulated at first. The liver of one, which was killed, after the treatment had been going on for a year, contained 0.42 per cent. of copper in the dried material. The results obtained by Hart and his fellow workers, showing the important effect of copper on the growth of small laboratory animals, therefore bear out some unpublished results obtained by H. A. Reid, working in conjunction with myself in experiments with pure copper salts on ruminants, in the years 1910 and 1911.

It may be here stated that a careful perusal of the literature available, and correspondence with and visits to other countries,

including two trips round the world, and consultations with many authorities, failed during the first twenty years of the investigation to reveal the occurrence of anything similar to “Bush Sickness” in other countries than New Zealand, except the following statement reprinted in the second edition of Kellner's “The Scientific Feeding of Animals,” (1926, translated by Goodwin, p. 65).

“Lack of iron compounds in the food leads to anaemia, a disease, however, very seldom met with in domestic animals. It has been noticed in sheep and in pregnant animals, but ordinary foods contain more iron than an animal requires.”

This is the kind of statement calculated to put one off the track, for what can be more ordinary food than pasture for ruminants? Analysis of the pasture from affected country, however, showed a great deficiency in the iron compared with what was found in non-pumice districts, where the stock developed normally. In 1924, the theory which had tentatively been advanced twelve years previously (1912, Dept. of Agricultural Journal, vol. 5, p. 125), that iron deficiency in the pasture was the cause of “Bush Sickness,” was finally adopted in a series of articles (see 1924, N.Z. Journal of Agriculture, vol. 29, p. 87).

Owing to publicity of the matter in New Zealand, two other instances of similar disease had by now come to light, in widely separated countries, one in Kenya Colony, and the other in King Island, Tasmania. These two were brought under my notice by the Veterinarians in charge, and they subsequently, with success followed the advice to give iron remedies. Another most extraordinary case was that which has always been known in the Scottish Hills as “Pining.” On reading an account of this, which was first described by Hogg, the “Ettrick Shepherd,” in 1807 (McGowan and Smith, 1922, Scottish Journal of Agriculture, vol. 5, No. 3), I decided that it was the same as “Bush Sickness” in sheep, as the symptoms were exactly similar. On bringing the matter before Dr. Orr he at once admitted the similarity, and it is satisfactory to learn that the iron remedy, first discovered in New Zealand, has now been successfully applied to the curing of affected stock in each of these three countries. A curious fact in connection with all three cases is that the soils upon which the deficient pasture is growing are of coarse texture, being technically either dune sands or sandy silts. From Papua, quite recently, similar trouble in cattle on pasture on a coarse sandy volcanic silt, similar to pumice, has come to light. It was early recognised as a diagnostic point in “Bush Sick” lands that the finer textured soils were immune from the disease. A soil survey of the Rotorua county has been carried out, based entirely on textural differences, and a survey which has proved of great value in classifying the different types of soil and correlating the incidence of “Bush Sickness” with these types. It is an interesting ecological fact that, in addition to texture of soil, the change in botanical composition of the natural forest in one area provides an additional method of distinguishing healthy from sick land (Journ. N.Z. Dept. Agric., June, 1926 and August, 1927).

There is, therefore, available information, extensive but incomplete, regarding two deficiency diseases, which are undoubtedly due

to deficiency of essential mineral foods in the pasture, and it may be advisable to tabulate the facts so that they may be seen at a glance.

There are two other deficiency diseases in the North Island which are the subject of intensive experiment in field and laboratory, one in which lack of calcium is suspected of causing trouble in sheep, and another in which iodine is the deficient element, the latter resting at present solely on clinical evidence—hairlessness in young cattle. It is dangerous to any investigation to shut one's eyes to the fact that a given trouble may be resulting from two or more distinct causes. The work of Theiler in South Africa on a very extensively distributed deficiency disease, in which lack of phosphorus was combined with a micro-organism in producing the result, will become a classic instance. Where theory can suggest a treatment, which subsequently proved to be 100 per cent. curative for affected animals as in “Bush Sickness,” I think we may not unjustly claim to be on the right track to the discovery of an economic remedy, and one which when completely adopted into farming practice will greatly increase the revenue from millions of acres of pumice lands, now either not up to average production, unimproved or abandoned.

Although it is not a mineral element, a few words about nitrogen may be of interest. North Island soils are usually well provided with this valuable fertiliser constituent, and this is reflected in the better pastures, where extraordinarily high figures for nitrogen, and consequently protein content, have been recorded in the lower Wairarapa, Waikato and Nelson districts, the last by Mr. T. Rigg of the Cawthron Institute. This would not warrant mention if at the same time there were not appearing in New Zealand troubles in stock, which may possibly be referred to an excess of nitrogenous constituents in the diet. Many years ago, at Waitotara, nitrates or nitrites in mangels were held responsible for the deaths of many cattle and pigs when fed on mangels growing in the field. (Journal of N.Z. Dept. of Ag., 1911, vol. 3, p. 311). This will show the high percenatage of nitrates which may occur in New Zealand soils under favourable conditions. The pulpy kidney in lambs, reported from Central Otago, has been attributed to the excessive proportion of amines in the spring grass, and this has been suggested as a cause of the mortality (N.Z. Journal of Agriculture, 1927, vol. 34, p. 231). Bulletin 417 of the Ohio Agricultural Experiment Station, page 59