Town Milk Producers’ Brucellosis Feat

Press, Volume CIV, Issue 30847, 4 September 1965, Page 10

Town Milk Producers’ Brucellosis Feat

There is a feeling of pride amongst Christchurch town milk producers who know that by their own unaided efforts Christchurch has become one of the few towns in the world to have a milk supply free from tuberculosis and brucellosis, says Dr. C. S. M. Hopkirk, veterinary research officer at Lincoln College, in an agricultural bulletin issued by the Canterbury Chamber of Commerce. ,

Dr. Hopkirk recalls that in 1943 a commission was set up to inquire into all aspects of the production, processing and distribution of town milk in New Zealand. In 1944 it made recommendations, among , which were two which are still of great importance—(l) to ensure that there was an adequate supply of pure, wholesome milk for consumption as liquid milk day by day throughout the entire year: and (2) to encourage and if necessary initiate research into all problems arising in achieving the aim just mentioned. With these recommendations in view, he said that the Christchurch milk suppliers had decided to produce milk disease free and wholesome. The first hurdle had been tuberculosis and this disease had been successfully eradicated. The next was brucellosis and that too had been successfully controlled. The third would be mastitis which was being intensively studied with a view to advising producers what must be done to prevent, if not cure, the disease. Both the co-operative companies producing milk—one with 62 herds and the other with 220 herds—had worked wholeheartedly at considerable cost to supplies in a voluntary scheme to eradicate brucellosis. The laboratory work had been carried out at Lincoln College from 1959 onwards, while the field and administrative work had been covered by the managers and staff of the companies, to whom a great deal of credit was due.

Having found a comparatively low percentage of infected cows in the Christchurch supply herds, the producer companies had asked Lincoln College to carry out tests on milk with a view to eradication. Both companies had offered £lO a head compensation for animals which had to be slaughtered, while the farmer received in addition the value of the meat from the freezing works. Results achieved by ring and whey testing of milk having been found consistent with blood serum testing, it had been considered unnecessary to go to the expense and trouble of taking blood samples of cows in the Christchurch scheme. Instead only ring tests of composite milk and agglutination tests of individual cow’s milk were attempted, except where difficulty arose in cleaning up a herd when blood samples were taken from individual cows and submitted to Wallaceville. The first tests had been carried out in December, 1959. At the beginning of the work in the laboratory 92 of 283 Christchurch herds showed a negative ring test. In October, 1962, 19 herds were still affected and while at time of writing this year all herds were free from brucellosis there was still an occasional breakdown. Actual breakdowns had occurred in 23 herds over the last three years, said Dr. Hopkirk. The majority had been cleared up quickly with the slaughter of one or two cows. Five herds had been cleared with some difficulty but were

now dear. To recognise breakdowns composite ring tests were carried out each month, and if a positive result was obtained whey testing was carried out to recognise the affected animal. Should an affected cow be left in the herd the disease began to spread and within a few months many susceptible animals were infected necessitating a considerable amount of slaughter. This had been seen on three occasions.

The cost to the companies and producers had been fairly high. Some 1404 cows had been slaughtered since 1959 but Christchurch had the satisfaction of knowing that herds supplying the city were now free from brucellosis. Affected cows had to go to the slaughterhouse and not to stock saleyards for resale.

Discussing an eradication scheme for this disease, Dr. Hopkirk made four points.

He said: (1) Calves should be vaccinated with Strain 19 vaccine between four and eight months of age. Vaccination later in life interfered with testing and adult vaccination would give a positive result in tests for at least nine months. Vaccination protected the uterus of the adult cow from disease and reduced sterility in a herd, but it apparently did not protect the udder from teat to teat invasion via the milking machine.

(2) Farmers had to comply with instructions as to taking of samples and getting rid of postive reactors. The risk of holding them was too great. (3) Replacements were a difficulty. The purchase of yearlings where vaccination was practised should be a safe procedure. The purchase of cows in the saleyards was always fraught with danger. Such animals should rightly be blood tested before purchase. If this was not done

then such animals should be kept separate and milked last until milk samples had been tested for 14 days after calving and only then, if negative, should the purchased animal be added to the herd. Where replacements were bred on the farm no difficulties should be experienced. (4) Once testing had been started it had to go forward with continuous monthly testing in case of breakdowns. If compulsory area eradication came into effect under Government control, then after a time one would expect the disease to die out, but with control within an infected area safety lay only in monthly testing. As Christchurch city had been successful in its eradication policy, it was expected that other South Island towns would follow suit. Most of them had had a ring test performed and a number had gone further and had whey agglutination tests carried out. Funds obtained from South Island towns had been very useful in keeping the Lincoln laboratory open and it was hoped that towns would shortly see their way to complete