DAIRY-COW DISEASES IN NEW ZEALAND.

New Zealand Journal of Agriculture, Volume XXXVIII, Issue 2, 20 February 1929, Page 75

DAIRY-COW DISEASES IN NEW ZEALAND.

RECENT RESEARCH WORK BY DEPARTMENT OF AGRICULTURE.

Paper read by

C. S. M. Hopkirk,

B.V.Sc., Officer in Charge, Wallaceville

Veterinary Laboratory, at the New Zealand Institute Science Congress,

Auckland, January, 1929.

Three diseases are to be discussed in this paper. Two of these have been well known all over the world for many years —namely, contagious abortion and mastitis (mammitis), while the third, a more recent arrival, has become noticeable in the last twelve years and is known as “ temporary sterility ” or “ return to the bull.”

Dr. J. A. Gilruth, and associated with him Dr. C. J. Reakes and Mr. H. A. Reid, have all done considerable work here on contagious abortion and on mastitis, but, although they have helped to throw more light on these diseases, they have not had better results with treatment than European workers. On account of the great economic losses associated with dairy-cow diseases in this country, a further effort by a team of workers has been for some time in progress in an attempt to find definite curative and preventive measures for combating the three major diseases. The team is composed of four veterinarians of the Department of Agriculture—Messrs. C. V. Dayus and W. M. Webster in the field, and C. S. M. Hopkirk and D. A. Gill in the laboratory—with the help of field officers of the Livestock Division in general and of the Department's Chemical Laboratory for the analysis of pastures. It is proposed in this paper to deal with our work up to date in the field and in the laboratory, and to incorporate some of the theories leading up to the lines of work attempted. At this stage it must be pointed out that a knowledge of the causative organism of any one disease does not necessarily mean that the disease can be easily cured or protected against. The diseases will be dealt with in the order of mastitis, abortion, and temporary sterility.

MASTITIS.

Mastitis (inflammation of the udder) is known to the farmer as contagious mammitis, and was at one time differentiated from a non-contagious form. This differentiation no longer exists, and the

point requires stressing that all mastitis in the herd must be looked upon as contagious, even though it be not of streptococcic origin. Mastitis is a localized disease of one or more quarters of the udder, and it increased considerably after the introduction of the milking-machine. There is little doubt that the streptococci as a group are the organisms responsible for the enzootic forms of the disease in dairy cows. Acute cases of mastitis are found both culturally and microscopically to contain streptococci, often alone, but sometimes associated with other micrococci which may or may not increase the inflammation and resulting induration, but which are usually harmless saprophytes of the normal udder. At the present time we are not interested in other definite forms of ’mastitis, such as pure staphylococcic, or infection due to Bacillus coli, Bacillus aerogenes, or Bacillus ■pyogenes bovis. These are not uncommon forms, but do not compose | per cent, of the cases of mastitis examined at Wallaceville.

The streptococci have been placed in a group as causative of mastitis mainly because of the difficulty experienced in obtaining uniform reactions on media in the growth of organisms isolated from typical cases of the disease, and from the fact that occasionally strains have been isolated which • differ decisively from the majority and resemble in some cases Streptococcus lactis and in others a morphologically different streptococcus of faecal origin.

The organism mainly responsible gives the following reactions to media as a general rule : —

Morphology : Palisade growth in long, winding chains, in samples from acute cases. The length of the chains may alter considerably and in less acute cases they may be difficult to find, may be phagocyted, and, if found, are in chains of four to six individual spherical cocci. Cultural growth : The optimum temperature is that of body-heat, but no growth occurs at io° centigrade in milk as in Streptococcus lactis. Sugar broth cultures (broth alone is not conducive to growth) of pH 7-2* gives a flocculent deposit, except in rare cases where turbidity is produced, in which case streptococci are present in very short chains. Sugars are not uniformly broken down, but there is usually acid and no gas production in glucose, lactose,‘ saccharose, and salacin. No reaction occurs in inulin, nor usually in raffinose or mannite. Lactose litmus agar pH 7-2 gives an acid reaction to growth in twenty-four hours, and colonies may vary. Often one finds a smooth, entire, dome-shaped colony in twenty-four hours, which at forty-eight hours may give place to a flat, slightly ragged, rough, concentrically ringed colony, which resembles the rough type as opposed to the first smooth. Dissociation from smooth to rough is now a feature in streptococcal work and will be referred to later. Serum : Non-liquefying colonies similar to lactose litmus agar. Blood agar : Usually non-haemolytic (no action on blood), yet on occasion green-tinged colonies have been noticed. Milk : Is coagulated in twenty-four hours usually, but sometimes takes fortyeight ; acidity about 0-62 to normal sodium hydroxide with indicator phenol-phthalein. Methylene blue : Inhibits growth in milk. Rats or mice are not affected by intra.-peritoneal injections.

The main lines of work which are being pursued with regard to mastitis are (i) diagnosis of the . disease, (2) path of infection, (3) treatment and prevention.

(1) Diagnosis.

In order that the incidence of mastitis in herds may be correctly judged, so that the owner may eliminate the disease, reliable diagnostic methods must first be obtained. . Manipulation of the udder is not reliable, as it fails to pick out many intermediate and other cases. A fine gauze strainer used for the fore milk is helpful in the more acute or in subacute cases.

The method of employing delicate indicator fluids soaked up and dried on blotting-paper has been attempted, the indicators being methyl red, neutral red, azolitmin, phenolphthalein, brom thymol blue, brom cresol purple, and Andrade’s indicator. A slight reaction may be obtained with methyl red in acute cases, and a definite purple reaction with brom cresol purple, but the others are of little use. Brom cresol purple is at present being tried out on known herds, but is not likely to be entirely successful, because the chronic types of disease are not readily picked out by it.

Agglutination tests have been to some extent successful in the few attempted, and the records show the only sound cow in twelve to have been picked out ; but the method is cumbersome, the antigen not stable, and antibody in the sera weak. The results, too, do not give one the picture which the microscopical test can. There is a recently perfected rapid agglutination method which is yet to be tried as opportunity offers.

The microscopical test is made after the milk-sample, which comprises the first strippings from the quarter, has been allowed to stand about one or two hours, the optimum being two hours. A loopful of the top layer, be it cream or other floating material, is then smeared over a glass slide, dried, and stained with Loeffler’s methylene blue. Carbol thionine blue is unsatisfactory, and the gram stain shows only the organisms and not the leucocytes, besides taking up considerable time in preparation. An oil-immersion one-twelfth lens then shows the number of leucocytes in the secretion, and, if present in numbers, the causative organism. The examiner may then state the condition of the quarterwhether affected acutely, subacutely, or chronically. Because of the large number of milk-samples which one has to examine microscopically, no time can be devoted to an accurate count of the numbers of leucocytes to the cubic centimetre of milk. Therefore a practical method was required for comparison, and that was supplied by the symbols L x , L 2 , L 3 . Later intermediate signs,were added — L, L x + , L 2 —giving, in all, six headings for comparison.

The correlation of results of many hundred milk-samples examined repeatedly shows that with experience the examiner is remarkably accurate in classifying the samples. The incidence of mastitis in herds in this country varies considerably, the numbers of cows affected being at present worked out in data from many experimental herds.

The microscopical test cannot be doubted after following histories of known cows for several years and of herds of cows for upwards of two years, except possibly where there is a fresh attack with Bacillus

abortus or where vaccinia is present on the udder-surface. Speaking of abortion infection, it may be dismissed at this stage by saying that little evidence can be produced, as certain workers in America claim, to show any connection between abortion and streptococcic mastitis, though Bacillus abortus may possibly set up acute inflammation of the quarter for some days, but with little or no induration. This statement is made after examination of herds throughout the country for both diseases.

Many cows during their milking career are at some time affected with streptococcic mastitis in an acute or chronic form, whether it be for a few days’ or a few weeks’ duration. This acute form subsides into a subacute and then into a chronic type, where the streptococcus is present in very small numbers but where some, induration of the quarter may possibly be noticed. The streptococci themselves, however, do not wholly leave the udder tissue, but may persist for years. Cultural examination of milk in acute cases usually shows a pure streptococcic infection. From subacute cases streptococci and staphylococci—some 50 per cent, of eachare obtained. In chronic cases only a few streptococci are found, but an increase of staphylococci. These latter persist in great numbers in injured quarters, but during exacerbation of the acute inflammation— streptococci, &c., appear in greater numbers for the time being —they disappear almost entirely. Examination of a number of normal cows of known history has been undertaken to show that no streptococci are ever found in the quarters in which leucocytes are not present and which are known to have been normal always ; but in the majority of such quarters the coccus present in chronic cases is found to be living quite harmlessly and saprophytically. Very few normal quarters are actually sterile. However, if a culture of this saprophytic coccus is injected into the udder, and the balance between the body cells and organism is thus upset, then a violent mastitis will result, the cow being obviously unwell, and running a temperature, and the quarter much swollen, hot, and painful, with an inclination to abscess - formation. This form of mastitis is apparently staphylococcic, and may exacerbate when the cow is dry, producing a large, swollen, fleshy gland before milk is produced in the udder, and is totally different from streptococcic mastitis.

(2) Path of Infection.

This is the biggest problem which we are up against in streptococcic mastitis. How, when, and why does the streptococcus reach and attack the udder tissue ?

So far the setting-up of mastitis by various means has been, except when the organism is directly introduced into the quarter, of a negative nature. No mastitis occurs with intravenous injection of culture ; drenching of the lactating cow with large quantities of affected milk does not produce the disease, but may set up scouring ; inoculation through the mucous membrane of the mouth and instillation of culture into the eye are ineffective. No, results have been obtained by milking with hands washed in affected milk, or by leaving affected udder secretion on the ends of the teats, over a period of a week, on a number of cows. Injection of streptococci into the

uterus of a recently calved cow proved ineffective ; yet one cow given acute strep, mastitis by injection of streptococci into a quarter later aborted a foetus through streptococcic metritis, an unusual occurrence at Wallaceville, where no such case had previously occurred. This incident gives food for thought, but has not recurred.

The only method left to produce mastitis experimentally is to introduce the organism into the teat-sinus. Not only must the organism be introduced, but it is also required that the organism be of a definite type or that injury of the quarter also exists, to produce a lasting inflammation. On several occasions flocculating lactose broth cultures have produced an acute inflammation for a few days, but this has disappeared, leaving, as far as can be judged, no permanent impairment.- If, however, we give udder secretion containing the streptococci as found in acute strep, mastitis, then acute mastitis follows, and the animal has typical acute streptococcic mastitis, known to the farmer as contagious mammitis. The disease does not require secretion from the acute stage of the disease only to be passed on to a cow, but milk from chronic cases which are macroscopically normal may set up inflammation. In one recent case, where a chronic milk was inoculated into a normal quarter of a clean cow, the result was a chronic type of inflammation, which took four days to show up macroscopically, but which on the third day showed a pure culture of streptococci. A second case was to some extent accidental, but this also took five days to show up, as follows : The effect of acid solution was being tried on a cow in quarters showing chronic mastitis and in those apparently normal. Normal saline solution of pH 6-5 was used, 100 cc. being introduced. The affected quarter was injected first, and then, after rinsing the teat-tube only in boiled water, a second normal quarter was injected. A third quarter, also normal, was then injected by means of a sterile teat-tube as a control. Mastitis showed up acutely on the fifth day in the second quarter, but subsided quickly to a subacute stage. In the affected quarter, however, acute mastitis became evident in a few hours, while the third normal quarter remained normal. There could have been very few streptococci placed in the second quarter; but they were able, nevertheless, to produce mastitis, and were helped, possibly, by the acid solution. Although streptococci were originally present in large numbers in the acute stage of the accidental case of ...mastitis, yet later staphylococci developed in large numbers, with only a few streptococci to be seen in culture amongst them.

The acid experiment was carried out because of recent work on dissociation of organisms into rough and smooth and intermediate types, and this dissociation has recently been shown to exist, in the streptococcic group by an American worker. The rough type is a resistant organism, not nearly as pathogenic as the smooth type. The rough prefers more alkaline fluids, while the smooth prefers the acid range. Therefore on the introduction of acid to a chronic case it is possible that there was a change from rough to smooth in the quarter, with consequent acute inflammation. There is such an outpouring of alkaline fluid into an acutely infected quarter from the body that one would expect the smooth to give place after , a while to the rough type, and thus acute mastitis would become chronic and the organism resistant.

If this theory is correct, it fully explains the method of attack of this organism and the reason for chronicity in the affected quarter. For some time it has been recognized that some other factor than the streptococcus itself existed. This factor was postulated as injury. We may in theory look upon injury, by whatever means it occurs in the udderchill, knocks, milking-machines, hand-stripping, cow-pox, digestive disturbances, &c. —as causing an excess of lactic-acid production in the tissue of the part; and by this means smooth types are able to take hold and set up an acute inflammation of a part which at the time of invasion was debilitated by an acidosis and not actually inflamed. The exacerbation from the chronic type differs only in that, the organism is present and requires the acidosis for setting up a more toxic condition. It is believed that milking-machines may become a serious source of injury when they are employed for too long a time, on individual cows or at too high a pressure, and field reports confirm this. In our attempt to establish further this acidosis theory, a - cow at Wallaceville has recently been fed on ammonium chloride in large doses to set up a general systematic acidosis. This cow was infected with mastitis four years ago during vaccine experiments, and has remained more or less chronic, with temporary exacerbation, ever since. At the time of the experiment two quarters were affected in a chronic form. Towards the end of three days’ feeding one of the quarters showed a subacute mastitis which existed for a week after the finish of the feeding. The case did not become acute, but in becoming subacute showed possibilities, and the experiment will be repeated.

How infection takes place cannot be said at present. It may under exceptional circumstances be blood-borne in septicemic conditions, but such cases must be rare. Infection apparently is usual through the teat-orifice. Experiments show that if only a very small number of organisms gain entrance it may take five days to show up. On the other hand, a massive infection or an infection with a more virulent type may show up in a few hours. Assuming the quarter is in a fit state of debilitation to become infected, what chance has the organism of gaining entrance through a tight sphincter-muscle opening, particularly in a hand-milked herd and with a non-motile streptococcus ? With milkingmachines there is very possibly a tendency, especially when the pressure is in the vicinity of 17 lb., for a slight back-suction into the teat to take place, and if this occurs one can understand why machines are so great a danger where mastitis exists in a herd. Experimentally this point is difficult to prove, though at the first opportunity a trial will be made. With high machine pressure it is known that.quite a number of cases may result in a herd. Frequently the Department’s officers will hear of some twenty cases occurring overnight when holidays, &c., have caused a careless use of the machines. Friction gives the injury ; the streptococci present in the machine from chronic cases provide the organism.

' On several occasions tests have been made to induce Streptococcus lactis to become pathogenic. Cultures in milk have been injected into the quarter, and when the resultant inflammation takes place a second quarter has been injected with material from the first. The second quarter shows slight inflammation, but the third quarter of the series does not respond, and the streptococcus is found in culture to have died

out. It is evident that the inflammation is set up in such cases from the acid formation of the Streptococcus lactis in the milk, and is not due to any toxin produced.

It is remarkable how quickly the udder tissue responds to any change of pH of fluids injected, or to any form of irritant fluid'; but as far as can be seen no permanent injury results from such injections unless they break down the secretory cells, even though the saprophytic coccus may be present at the time of injection. This fact rather obliterates the suggestion that saprophytic staphylococci are causative of enzootic mastitis. While acute inflammation exists the coccus almost disappears, but reappears at the first sign of return to health or chronicity of the part. Heavy saline solution, acid solution in the vicinity of a pH of 4-5 (the end point of sugar metabolism by Streptococcus mastitidis), and irritant such as weak formalin or ether, all produce a passing inflammation which is not harmful, provided the streptococci are absent. The streptococcus itself will produce a certain amount of toxin, which accumulates in the milk secretion of the udder, but does not cause a clinical reaction in the cow. When the secretion from an acute case of mastitis is filtered through a Seitz filter and reinoculated into a clean quarter intense inflammation results, which again is only temporary. Such a filtrate does not kill an experimental animal such as the guineapig or rat, nor cause them inconvenience.

It may be mentioned in passing that Streptococcus mastitidis is harmless to human beings in the city milk-supply, and does not( as one frequently hears, cause sore throat epidemics.

(3) Treatment and Prevention.

Although the matter of path of infection is exercising our minds, there is also the question of treatment and prevention, which we are fully conscious of and alive to.

Curative treatment falls into two groups — one chemical, either local or general; the other immunological, again local or general. In none have we been successful or even partially successful. Many chemicals were tried by workers before the present team began work in New Zealand ; those recently used were as follows : — General —

„ ,, / Potassium iodide. Permouth 1 Formalin. Intravenously . . . . . . . . Acriflavine. Local— T Brilliant green. i Acriflavine. ■ F tlrer Into udder sinuses .. .. • A Formalin. l Formalin. • - |. Ether-formalin mixture. ■I Selectan. Intraparenchymatously . . . . Selectan.

Immunological methods were tried in New Zealand in pre-war days by Mr. H. A. Reid, and consisted of the use of vaccine, and vaccine and sera combined. No beneficial results were obtained. Over thepast three years individuals in several herds have been given treatments with vaccine made from autogenous strains of organisms, but

no curative results have been obtained, either with mixed staphylococci and streptococci or with streptococci alone.

A trial was also given Besredka’s filtrate in several cases of acute mastitis. In this method the washing from the cells is said to contain a material inhibitive to streptococcal growth, and the filtrate is used in local injections or on pads in local infection in human work. Results, however, were entirely negative.

The prevention of mastitis is also difficult. The recent finding, mentioned earlier in this paper, that so many cows in dairy herds are affected, makes it practically impossible to dispose of those affected and retain clean animals as one would like to do. Until recently the cows at Wallaceville have never developed mastitis naturally, but within the last month two second-calf cows have shown infection in one and two quarters respectively. It may be that in this case a change of milkers has brought this about, and as some of the recent assistants have been inexperienced and heavy-handed men one might assume injury from that fact. The organism has been present for years in certain quarters of many of the cows, having .been introduced experimentally into the animals, but no effort has been made to segregate those affected. At the time of writing this paper abortion was not known to be present in the young cattle, but since then cultural work has shown that one of these heifers with leucocytes in the quarters shows only staphylococci in culture and no streptococci. Also, she now reacts to the abortion test, and an effort is being made to find whether Bacillus abortus is the causative organism in the mastitis or whether the staphylococcus is the original culprit. It would be unwise to generalize on this case, and the results of further work are now being awaited.

Segregation of animals showing subacute or acute infection is possible and helpful. ‘ Such is being attempted on farms where the farmer is willing or can split his herd, and with the elimination of affected cows, which often, inadvertently perhaps, were placed on machines, there has been a marked diminution in fresh cases. Hygienic sheds and apparatus are matters of common - sense and need not be discussed here.

Vaccination.

The question of vaccination must be somewhat specially dealt with in view of the extensive use of this material by private concerns throughout the country. Previous experiments in which vaccinated cows were submitted to infection by the only means in our power — that of udder inoculation with culture or secretion not, in our opinion, show that the vaccine was of value as a prophylactic. Data have since been collected over a number of herds vaccinated with herd-autogenous streptococcus vaccines killed with formalin or with heat, and they show absolutely no change between the vaccinated and control groups in the herd. A method of tabulating samples from such herds has been built up as follows : The cases are shown by microscopical examination to contain leucocytes in amounts Lj, L x , L 1+ , L 2 , L 2+ , or L 3 —that is, from chronic by grades to acute. Figures from I to 6 have been given these amounts, so that Lx equals I and L 3 equals 6. Then by counting the vaccinated and control cows in each herd and making a percentage of infection against possible normality — for

example, three at L 3 , five at L 1+ , six at L,, in twenty-eight cows gives (3 X 6) 5 X 3) (6x2)= forty-five in a possible of (28 x 6) = 168. ( X 100 ) = 26 per cent of infection. \i68 '

By this means the following figures have been evolved from five of the herds under trial following four examinations of the samples the first examination before vaccination, the others during or following vaccination. Vaccinated animals, 155 head. Controls, 64 head. Vaccinated. Control. Per Cent. Mastitis. Per Cent. Mastitis. First examination .. .. .. 15-5 15-6 Second examination . . . . . . 21-6* 18-8 Third examination . . . . . . 14-4 13-3 Fourth examination . . . . .. 18-7 17-5 . * A slight rise after vaccination. A point of interest is the rise in the fourth reading, which was due to bad weather conditions that arose prior to the taking of the samples of milk. , Examination will, of course, continue . over two seasons. In two vaccinated herds they have continued intermittently for two years already, but, we claim, with no results. Many opportunities for watching herds vaccinated by private concerns have not been taken advantage of, in view of the reports received from a large number of our field officers as to the inefficiency of the vaccine in different districts. One particular herd, however, was watched with considerable interest because of our long association ’with it. The percentages are striking, and are drawn by the same method of computing the results as previously mentioned. Each quarter of the thirty-eight cows has been examined five time's,commencing at vaccination and carried on since February, 1928, at intervals as follows : February, March, April, May, and December at which latter date all the cows were in full milk once more. It may also be stated here that the cows were repeatedly inoculated about the third examination, and later because of the unsatisfactory state of the herd.

The five examination figures showing the percentages of mastitis are as follows 15/2/28, 31-2 per cent, (at time of .vaccination) ; 16/3/28, 30 per cent. ; 4/4/28, 367 per cent. ; 17/5/28, 31-1 per cent.; 12/12/28, 417 per cent. (See graph, next page.) From both groups of the above figures it is therefore impossible to claim improvement. The latter herd had no control animals left for comparison. Prevention, therefore, cannot' be sought along. those lines unless the vaccination method is radically changed. At present segregation and hygienic precautions are our only stand-by. '

Trial was also made of a method of vaccination employed in anthrax —that of cuti vaccination with cultures of streptococcus. Injections were made in two cows, with one cow left as a control; then all three were given mastitis by quarter inoculation, but no difference in time of cleaning-up of the inflammation was noticed, nor was mastitis avoided in the vaccinated animals.

CONTAGIOUS ABORTION.

Data collected in New Zealand on the disease known as contagious abortion have shown that the endometritis causing the actual abortion in the calf or retention of membranes as common symptoms originated from the action of the organism known as Bacillus or Brucella abortus (Bang). This organism is at present assuming greater significance in Denmark and the United States of America, because of the number of cases of intermittent fever in man ascribed to its presence in the blood stream. So far no cases have been known in human beings in New Zealand, but the Health Department is keeping in touch with modern findings and is watching for such cases. Curiously enough, all recorded cases have been in men and in non-pregnant women, so that the effect of the organism on the human genital tract is not known. There are cases of abortion due to other organisms, a few cases having been known due to a streptococcus, but these are in a decided minority. Also some are due to mineral deficiency, such as iron deficiency in the Mamaku area, and unrelated to bacterial invasion.

In one of our large dairying districts where careful observations have been made the disease is present to the extent of 4-1 per cent, in herd cows, but 11 per cent, in first calvers. There is evidence to show that first calvers at two years of age are more subject to abortion than first calvers at three years of age. Also that in good limestone country there is less of this disease than on lime-deficient farms. Whether, as in mastitis, this has a bearing on the reaction of the tissue to the organism resulting in different types has still to be worked out, but the suggestion was made in England recently that such was a possibility. The predilection of the organism is for the pregnant uterus and lactating udder, but no information has been found dealing with the pH of these organs compared with the rest of the body tissues. One would expect, however, that there would be in the pregnant uterus a decided acid reaction due to foetal metabolism, more particularly at the cotyledons, where the disease organism • attacks most heavily. Abortion occurs more often in the later months of pregnancy, too, which may have a bearing on the theory that the reason for the persistence of the. organism in the uterus at pregnancy is because of the optimum conditions of that organ in acid requirements for Bacillus abortus. (Since writing that I have come across an article by an American group of workers showing that a decided increase in CO2 is present in those two organs.)

One of the problems exercising us at present is the mode of entry of Bacillus abortus. It has long been recognized that contaminated pastures are a source of danger, the organism being able to attack animals after injection. Is there, however, a possibility of the bacilli gaining entrance by other ways ? Recent experiments at Wallaceville show that the organism injected into the udder will set up acute mastitis, which lasts several days only but sets up an agglutination reaction in the cow. Such a reaction lasts at least three months, but it has not been decided whether actual abortion occurs as a result of this invasion of the udder. The cow affected is five months in calf. Will she abort ? Two days ago the seal of the os cervix was obviously degenerating, and we confidently expect abortion within the fortnight.

Another means by which infection may possibly be set up is by the bull. This at present is very much doubted by workers on the subject. At the present time one of our Laboratory bulls has been given an intravenous injection and shows a decided reaction. This bull is now being used with seven known clean heifers to find whether the disease may be transmitted by copulation. Two heifers out of the three served in December have already given a marked positive reaction to both the intradermal and agglutination tests.

Diagnostic Methods in Control.

Diagnostic methods play a very great part in control of abortion. Such methods must be accurate, because many dairy-farmers employ repeated tests to eradicate the disease and keep their herds clean. The test used at Wallaceville is that known as the macroscopical agglutination test, applied to blood serum taken from individual cows. Such a test shows a large percentage of reaction in nearly every herd tested, but not all such cases abort. Data are being collected to show just what percentage of abortion can be expected in cows reacting. Another point of interest in data collected from reacting herds is the fact that about I per cent, of heifers pick up or retain infection and react to the test before pregnancy occurs. This percentage, however, is small, and differs remarkably in herds.

The macroscopical test takes twenty-four hours to carry out in its entirety, and therefore attempts have been made to utilize a rapid slide agglutination test which takes two to five minutes. Considerable experience is required, but over a large number of bloods we have shown that the test is slightly more delicate than the longer method ; it does not, however, in our experimental work give the highest results which we require. Before Christmas last a test called the double intradermal test —employed in testing cattle for tuberculosis — applied for abortion, and, from the results obtained in the herd, the test is sufficiently satisfactory to try under field conditions, in fact, the suggestion is that it is even more delicate than the agglutination tests. The drawback in field-work is the necessity for repeated visits of the veterinarian and the keeping of accurate skin-measurements during the test.

Recently a field test known as Bevan’s abortoscope has been tried, but in our New Zealand climate the temperature is not high'enough to allow the use of this test without an incubator. However, a modification of the test may be useful. Modification gave results in half an hour, but the reading did not appear as easy as with other methods. It has been claimed in America that mastitis and abortion are correlated, but our New Zealand statistics do not prove this point, and we claim our results to be definite and correct so far as the agglutination test of blood-samples and microscopical examination of milk-samples can correlate the two diseases. Yet from one isolated case, in a heifer at Wallaceville (previously mentioned) 'we feel that there may be a relationship in occasional cases, and on that account we cannot be completely dogmatic.

Preventive Treatment

.■ Curative treatment for animals considered about to abort has not been attempted. The position of the organism as it exists in the

lesion in the udder and uterus makes the action of any drug on the organism impossible. Therefore reliance has to be, placed on preventive measures. For over two years the Wallaceville Laboratory, farm has been divided into two partsone side running affected stock, the other running clean heifers born oh the place from affected animals, but segregated and tested frequently to ensure their remaining clean. They have now calved twice, and neither abortion nor agglutination reaction has occurred among them. It is on these heifers that the infected bull is being given service. This method of dividing a farm is, then, a possibility where the farm lends itself to cutting up. One shed only is required, but two holding-yards, and the only precautions to take are to milk clean animals first, to see that the two herds do not mix, and to use separate bulls.

My latest returns, showing that three of these heifers have very recently indicated abortion, do not conflict with the statement that herds can be kept clean by segregation of infected animals. - They do show that the bull is carrying abortion to the heifers. Two of the heifers had been served early in December and a third not until after the reaction had shown up. An explanation is required in the third case. . Owing to error the services had not in all cases been performed on neutral ground, and in three instances the bull had run overnight with the heifers. It is a possibility that the heifer which showed a reaction may have been served with one of the others unnoticed, and this possibility is quite a sane one in that the heifer was noticed on one occasion to have a discharge on the tail, suggesting oestrum somewhere about six weeks after calving ; and because she calved at the 276th day she would probably return to the bull, making the known service on 12th January her second acceptance. Even though unserved, there is every chance of her having picked up infection from the pasture from the bull’s seminal discharge, if he is capable of transmitting the organism to the heifers.

Many countries have used one or another sort of vaccination for the purpose of preventing the disease. In England an extensive trial was given for some years to a vaccine made of live germs injected into the cows. The estimated lessening of abortion was only about 5 per cent, at the most, while the number of carriers made by this method was greatly increased. Dead vaccines were considered useless ; nevertheless a vaccine made by killing the organism with chloroform was tried in Rhodesia, and claims were made that abortion was much reduced in . native cattle. This method, being harmless, was given a trial in New Zealand last year in heifers, and, because of possibilities of errors in methods of inoculation, repeated this season. Figures and results are as follows for last year, and totals have been reduced considerably where herds were not kept as required by the experimental conditions imposed : —

Taranaki.

205 vaccinated heifers : slipped, 23 — n-2 per cent. 442 controlled heifers : slipped, 38 = 8-6 per cent.

Wairarapa.

149 vaccinated heifers : slipped, 4 = 2-7 per cent. 29 controlled heifers : no slip.

A number of farmers are at present using lime in larger quantities, particularly in the water-troughs, but it is too early to ascertain whether the treatment is actually effective. A note is being made of the incidence of the disease where such methods are employed. As Bacillus abortus is an inhabitant of the udder during pregnancy, it remains for a cure to be found for both it and mastitis together.

We in New Zealand believe that there is considerable so-called herd immunity to abortion, and that after years of this disease in the herds the majority of older animals remain immune after their heifer days. This herd immunity - probably arises from the udder infection, and is not a passive but an active immunity, and such immune cows are therefore dangerous to their pregnant daughters.

TEMPORARY STERILITY.

This problem, in which numbers of herds throughout the country contain a varying proportion of individuals which fail to conceive from the first two services, is causing far greater concern than other diseases which we know are infectious and contagious and which the causative organism is known. In temporary sterility there are many factors to be taken into consideration and many lines to work upon — much so that we find our present team in no way adequate to carry out the necessary work as fully as we should like.

The condition, briefly put, is this : In the first year a large proportion of the cows of a herd return after the first service, which is usually allowed in October. Some cows, however, hold, which rules, out total impotence of the bull. A large proportion of the affected cows continue returning regularly or irregularly, but will finally get in calf, often as late as in January or February. Many of these cows are slaughtered, and some are kept over the season and milked the following winter. At their first service in the following spring they hold. In an affected herd the second year finds many of the cows ' calving late-October, November, and December. The first oestrum following calving appears quickly, and the bull is allowed to mate. Such a service is usually unsuccessful, and we find a repetition of the first year’s experience. In such cases quite a considerable proportion of these cows fail to hold for some months, but if held over will easily be got in calf. Therefore one is inclined to say that a genital rest is required. As the condition has been getting more prevalent for the last fifteen years and the average butterfat-production has also increased during those years, one is also inclined to hold that sterility is physiological and caused by greater development of the lactating function to the detriment of reproduction.

’ The question then arises, How could this occur ? Is there an upset of balance among the endocrine glands, or has a mineral deficiency taken place due to the great quantities of lime and phosphate required to produce both milk and calf ? As dairy, herds in other countries are similarly affected, though largely fed on concentrates, we are rather inclined to think that diet is not the most general factor. However, work is being conducted on both the lines of research mentioned, (i) With minerals : Four farms have been top-dressed with lime and the necessary controls left for experimental purposes ; in addition to

this, herds are being fed on minerals. (2) With endocrine extracts : Anterior pituitary lobe to increase the activity of the ovary; follicular fluid to increase the tone of the uterus for the attachment of the fertilized ovum ; and in cases where oestrum is irregular but early the use of extract of corpus luteum.

In Denmark and in America it is the opinion of veterinarians that the condition is due to endometritis. Several reasons present themselves on the negative side, the first being the fact that on examination of many hundreds of cows at meat-works, following cull-cow drives in New Zealand, practically none of the animals showed endometritis or salpingitis. They did in many cases show cervicitis where the first fold is extruded through the cervical os, and many cows showed a cystic condition of the corpus luteum. Both these conditions might possibly be a result of endometritis, and possibly the original condition had disappeared, leaving the secondaries in its wake. But we have found all cystic corpora sterile, and have not found any one organism consistently present in the inflamed cervix. Another reason on the negative side is the fact that possibly' 90 per cent, of affected cows return after first service, following what was considered by the farmer to be a perfectly normal calving. Analysis of calving figures, however, shows, that in a large number of such cases the calving is a few days early. This fact is at present being demonstrated in heifers at Wallaceville. Three of the animals calved after 278, 276, and 274 days gestation. The other three calved at 283, 283, and 285 days. Two of the short-time group have returned more than once to the bull, while in the second group two have not returned. The remaining two have not yet had time to show up one way or the other.

This in itself suggests an endometritis present during gestation, but may also be physiological, due to an ovarian excess stimulation. That the endometritis if present is not due to Bacillus abortus has been amply proved over a series of several hundred cows. Should the condition be endometritis, to what organism is it due ? Uterine and vaginal discharges have been examined from many cases, but no consistent growth of any one organism has been obtained. There is often a streptococcic infection of the cervix and vagina in cows, and a streptococcus of the alpha haemolytic type has been isolated, frequently, but numbers of varieties of this type appear. A cow was slaughtered at the Laboratory farm a week ago after returning to a third service, but bacteriologically nothing could be found which could be suspected. .Histological results are not yet available, but macroscopically the uterus, tubes, and ovaries were normal. The cervix was slightly flushed and showed a minute flake of pus at the second fold, but as nothing but sporulating aerobes were found one cannot blame that portion of the genital organ. Ovulation had occurred normally, and a normal corpus luteum was being formed. The pH of the organs was also normal, giving a blue reaction to brom cresol purple papers.

Very serious consideration is being given to the position of the bull in sterility. Examination is now consistently made of the seminal fluid for its sperm content and for a possible flora. Clinical evidence frequently supports the theory that the bull is the chief infective agent, but if endometritis is present before calving we are examining the wrong bull or the right bull in the wrong season.

The. secondary conditions confuse the issue in the investigation of this disease. Granular vaginitis and vesicular vaginitis, for the treatment of which a number of preparations are placed on the market, are in no way connected with the trouble. They may aggravate it when present, and should be treated where a catarrhal state exists. There are occasions, too, where impotence in the bull is the fault, but such cases are not general. Also, where heifers fail to conceive for their first calf one frequently finds not temporary but permanent sterility, due to cystic oviducts. Some suspicion attaches to the bull where a number of such heifers are found on one farm, but there remains the hereditary tendency to genital defect- side which it is hoped to develop from the mass of data being collected wherever possible in the field.

Our principal experimental work lies then in—(1) Collection of all data for sifting in the light of further knowledge. • (2) Bacteriological and histopathological work in bulls and cows, at calving and before service. (3) Experimental infection „ of animals when suitable . suspected organisms are isolated. (4) A judicious use of post-mortem examination. (5) Trial of drugs and endocrine extracts for specific effects on various organs. (6) Experimental use of minerals.

(7) Chemical analysis of pastures. This work has only recently been commenced, and the few results to hand show an adequate supply of lime but a low phosphate content. Where the phosphate content drops to 0-20-0-24 per cent. P 2 O 5 we find a total retention of the corpus luteum, due to inactivity of the ovary and to a total lack of oestrum. Such cows are affected with Waihi disease or aphosphorosis. Where the phosphorus reaches -6 per cent., however, the ovaries act normally, and cows may or may not be affected by the temporary sterility.

Where analysis will not help us is in connection with the vitamin content of pastures. The recently found vitamin E may have a distinct bearing on temporary sterility. The absence of vitamin E does not inhibit conception, but causes the death of the foetus at varying intervals, which have not been worked out in larger animals than the rat. What we may have to consider, however, is not the lack of vitamin E, but the too great quantity of the material in the pasture. Vitamin E exists in the green luscious pastures, and it is in this state that the pasture is eaten by cows when the trouble is rife. As the grass dries and becomes shorter, then the cows conceive. That vitamin in excess as well as in too small quantity may have a bearing on disease is suggested by German workers, in particular where vitamins A and D have been used ; so that although the possibilities of excess of E are not actually grave, yet every theoretical avenue must be explored practically.

At this stage no exact and specific treatment can be suggested for general use by the farmer, for the etiology is entirely unknown and a matter for conjecture only. . Experimental treatment has been undertaken widely with very mixed results.

In early years much general washing out with a variety of stimulating, antiseptic, or astringent chemicals was tried regularly, but the irritation to which the cows were subjected sometimes became an act of cruelty. Later specific washing with drugs for special effects was tried, more particularly to reduce the inflammatory state of granules in a number of the cows where granular vaginitis occurred as a secondary characteristic, or to reduce the cervicitis found present very generally in such cases. One point noticed in connection with such washing was the intense straining caused by mild solutions, and this could only have' been due to the action of the fluid on the inflamed anterior vagina. Another point of interest noted at this time in the handling of cows was the fact that on going through a herd it was possible by the state of turgidity of the lips of the vulva to say with considerable degree of accuracy which cows were in calf, provided they were three weeks in gestation and not more than some nine weeks. This point was verified by three field veterinarians.

Recently washing was superseded by swabbing of the inflamed cervix through a speculum with soothing chemical agents, and at times some degree of benefit appeared to be derived by this treatment. However, results were not sufficiently good to make the method general. A number of farmers and some veterinarians now attempt a simple method of treatment which has been in vogue for a considerable time and at times seems to be effective. That method is the pushing of a finger into the cervical os in order to clean out the plug of mucus which occasionally lodges at the entrance. This mucoid material is likely to form with any inflammation of the cervical canal. A similar method is in use in human medicine by instrumentation, and beneficial results have been often obtained even though nothing abnormal could be found in the cervix. Apparently stimulation'alone may be useful.

The latest method is that practised by Professor Neilsen in Denmark, consisting in the passing of a catheter into the uterus for irrigation purposes, and this method is now under trial here. In the hands of a skilled veterinarian there is some risk of passing the catheter through the uterine wall, so that the method will not become a general one for use by farmers ; but it is required in order to ascertain whether we are dealing with an endometritis, or at the least some inflammatory state of the cervical canal which will respond to such treatment. Late advice from the field is that, although a number of cows have been tried, results do not appear satisfactory; but in the hands of a second field ''veterinarian results in eight hundred cases are said to be hopeful.

Properties of Superphosphate in Plant Husbandry.— Discussing papers presented at the recent Washington International Soil Congress in the Journal of Science, Mr. T. Rigg remarks : “ In a paper dealing with the growth of lucerne on acid soils it was shown that, in the particular cases examined, manuring with phosphate did not increase the percentage of phosphate in the lucerne-plants. In view of the well-known response of pastures, lucerne, and other crops in New Zealand to superphosphate, it is most important that careful study should be made of the exact part played by phosphorus, sulphur, and calcium, which are all contained in superphosphate, on both yield and quality of New Zealand crops. It does seem possible that in a number of cases greater benefit has been ascribed to the phosphate contained in superphosphate than actually occurs. Several workers both in California and in Tennessee pointed out the importance of small traces of such chemical elements as boron, manganese, and copper in plant-nutrition. ... ”

* pH refers to the hydrogen ion concentration of a substance, and is known as the “reaction.” Above the neutral 7’0 a fluid is alkaline, below 7’0 acid.