ON THE LAND

Taranaki Daily News, 30 January 1929, Page 16

ON THE LAND

DAIRY COW DISEASES.

RESEARCH WORK IN DOMINION.

DEPARTMENTAL INVEST IG AT lONS

A paper was read at Auckland on the 25th instant before the Agricultural Section of the Science Congress by Mr. C. S. Hopkirk, officer, in charge of the veterinary research laboratory at Wallaceville, which proved of very great interest to farmers. The paper gives the result of laboratory and field work in dairy cow diseases, and is in reality a progress report of the team of veterinarians, Messrs. Dayus, of Waikato, Webster, of Taranaki, and Hopkirk and Gill, of Wallaceville, who are investigating cattle trouble. Naturally much of the work is negative in character, but is none the less valuable on that account.

Three diseases ■were dealt with, mastitis, abortion and sterility, in that sequence. STREPTOCOCCIC "MASTITIS This was at the outset stressed as a contagious disease with no differentiation at ’far as the farmer was concerned into a non-contagious and contagious form. A description of the causative organism showed that the New Zealand differed.from the American form by its action on blood, probably quite a minor point, and stress was also laid on the difficulty of classifying organisms of the group to which the mammitis germ belonged. Investigational work was proceeding on three lines: (1) Diagnosis of the disease; (2) paths of infection; (3) treatment and prevention. Diagnosis was necessary in order to free herds from the disease. Various

methods had been given a trial, including indicator test papers, and blood tests, but the method par excellence was that of microscopical examination of a sample. By examination of a sample of milk from the quarter, the observer could say whether tho condition was acute, subacute or chronic. It had been found that only a very few quarters were ever free from all germs normally, and that the usual inhabitant was a harmless one, but one which if inflamation occurred, was liable to increase in numbers. Many workers were prone to think this saprophytic organism one of the chief factors in mammitis, but the present workers thought otherwise. One point was of special interest, and that was once a cow had been infected with mammitis she usually remained infected in a chronic state with a return ,to acute or subacute condition at intervals. Therefore a large percentage of cows were infected in New Zealand sheds.

PATHS OF INFECTION. Setting up the disease experimentally was* found possible in only one way of many attempted, and that by inoculation of the causative germ into the teat sinus. The best material to use was infected milk from chronic or acute cases and not cultures of the organism. If few organisms were injected the disease appeared in five days, if many, 12 hours were sufficient. A"theory was put forward to show the way in which the udder became infected, and this, in short, was the necessity for two factors, the injury of the quarter and the presence of the streptococcus. The peculiarities of the organism in media of alkaline reaction were considered to have 'a distinct bearing on the problem, as the injury, .whatever it might be, was the cause of an acidity which raised the pathogenicity of the ’streptococcus. Milking machines were considered to be a helpful means of spreading the disease if wrongly used, not only because of the injury caused to a quarter, but because of the possiorrrey of the cups' actually sowing the germ into tho quarter from chronic cases in the herd.

The possibility of the sour milk streptococcus setting up mammitis was discussed, and also the reaction of the' udder tissue to introduce fluids, or to filtrate from cases of mastitis alone. Filtrates were states to contain poisonous bodies, but these were insufficient to injure anything but udder tissue.

POSSIBLE TREATMENT. Treatment with a number of named materials had proved useless. The description of prevention, however, was of interest because of the experiments tried out on herds with vaccines made from the streptococcus prevalent in those particular herds. Segregation of affected animals was considered to be the best way to set about prevention at present. By microscopical test, over five herds comprising 155 vaccinated and 64 control cows gave the following results: — First examination before vaccination, 15.5 per cent, mammitis vaccinated, 15’.6 per cent, mammitis control. Second examination immediately after vaccination, 21.6 per cent, mammitis vaccinated, 18.8 per cent, mammitis control. Third examination after vaccination, 14.4 per cent, mammitis vaccinated, 13,3 per cent, mammitis control. Fourth examination after vaccination, 15.7 per-cent, mammitis vaccinated, 17.5 per cent, mammitis control. Therefore there had been in five herds no suggestion of betterment of the conditions through vaccination, nor had controls shown any inclination to a higher incidence of disease than vaccinated following vaccination.

A further instance was given together with a graph showing how a proprietary vaccine used repeatedly was unable to stop the spread of inammitis in the herd quoted, the figures being:— First examination 31.2 per cent mamrnitis at time of vaccination. .Second examination 30 per cent, mainniitis after vaccination. Third examination 30.7 per cent, mammitis seen months later. Fourth . examination’ 31.1 per cent, inammitis one month later. Fifth examination 4.1.7 per cent mam* initio’ seven months later. CONTAGIOUS ABORTION. A statement was made that abortion in New Zealand was definitely due to bacillus abortus and that in a large dairying district where investigations had been intensive 4.1 per cent of cows aborted, and 11 per cent of heifers. Thera was found to be no general linking up of inammitis and abortion even though the

abortion organism would cause mam 1 .mitis.

The reason for the predilection of the abortion bacillus for the uterus and udder was because of the acid reaction of ' these two tissues compared with the rest of the body. Methods of spread were discussed by other means than contaminated pastures, by means of milkers’ hands and by means of the bull. An interesting experiment was said to be in progress at Wallaceville where the bull appeared to bo carrying infection, following infection by inoculation. Diagnostic methods wore being perfected, and four tests were discussed, three of them blood tests, and the fourth a skin test which was proving to be fairly delicate and probably better than the blood tests.

Vaccination in New Zealand had apparently from figures quoted proved a complete failure, though a second trial over a large number of heifers was in progress. TEMPORARY STERILITY. Temporary sterility was considered, and the possibilities of its being physiological or bacterial. Active work was stated to be in progress in collection of data and trial of definite methods of treatment—'(a) .-from the dietetic point of view, where a deficiency 'may exist; (b) from the physiological point of view considering the relationship of milk production to sterility; ftnfi (c) from the germ invasion of the uterus viewpoint. Analysis of pastures was being undertaken on selected farms to see whether that would throw light on the trouble.

The condition at present was complicated, but the essayist felt confident that more would be accomplished shortly with sterility than with mammitis and abortion.