ANIMAL HUSBANDRY

Hauraki Plains Gazette, Volume XXXX, Issue 5485, 9 October 1929, Page 4

ANIMAL HUSBANDRY

DISEASES IN DAIRY CATTLE. CONTAGIOUS ABORTION. (By the Department of Agriculture.) Among the diseases of stock there are several which are met with commonly in almost every country where intensive operations are pursued. It appears to be the usual sequence of intensive farming practice that diseases of stock are more numerous and perhaps more acute than in countries where animals are allowed more freedom, and where fanning might .be described as extensive. Such a condition is more or less expected when one considers that dairy cows under intensive dairying systems are subject to the strain of regular annual breeding and regular and increasing production of milk annually. By selective breeding the modern high yielding dairy cow has been aptly described as a veritable milking machine. Therefore if both the breeding properties are to be maintained in our dairy herds increasing demands will continue in order to prevent either a break in the continuity of breeding or a derangement of the milking apparatus, the mammary gland. So elaborate and so highly developed has the modern cow become that diseases of the mammary gland and those associated with breeding are assuming far greater enconomic. importance. Mammitis was referred to some time ago in these notes, and farmers were advised through the department’s Journal of Agriculture and through the Press as regards the prevention of this trouble. This advice is now available in a bulletin which can be obtained free by all owners on application to any officer of the department. Contagious abortion in dairy cows in the Dominion, resulting as it does in the loss of calves, and loss of milk supply, is such that the disease requires the most careful attention and care by all owners of cattle. It is only by studying the nature of the disease that proper and effective measures can be taken to control and prevent the spread throughout a herd. There is also the serious factor of sterility and loss of breeding as a sequel to the disease which requires careful consideration. Probably contagious abortion is a more common factor than any other in causing permanent sterility in cows, as distinct from the conditions of temporary sterility in cows, which so frequently occurs here.

The disease is a very insidious one and may be present in a herd for some weeks or months before an actual abortion takes place, which act is the only outward sign the farmer has that something is amiss. The disease is due to a specific organism, Bang’s bacillus, which invades the womb of the pregnant animal, setting up a chronic inflammation between the membranes and the wall of the womb. Later the blood supply of the developing foetus is cut off by this inflammation, the foetus acts as a foreign body, and the stimulus is given for the act of abortion and the calf is born prematurely. All pregnant bovines are liable to infection, but probably first-calving heifers are more susceptible as they have not previously had an opportunity of developing any immunity to the organism. Once an animal has aborted, a certain degree of immunity is developed, which may not, however, be sufficient to enable the animal to remain pregnant throughout the full period of a second pregnancy. Invariably, however, the infected animal will carry her third calf the full period. At each and all of these births the cow is a possible source of contamination of pasture through the discharges which come away at parturition. At the time of abortion there is generally a profuse discharge of a yellowish-chocolate coloured nature, which is most dangerous from an infective viewpoint. As infection occurs in the majority of cases through ingestion of food or water contaminated from a previous case of the disease the necessity of detecting a recently aborted cow, isolating such an animal in a paddock by herself, effectively dealing with all the discharges by burning, burying, or spreading them ovei’ with freshly-burnt lime, keeping the animal isolated from the herd until all discharge has ceased, washing the vaginal passage and the womb itself (when possible) at regular intervals while the discharge lasts, washing the external genitals and tail with weak antiseptic solutions at regular intervals, and taking all other known precautions to prevent contamination of the remainder of the herd, at once becomes apparent. It is true that occasionally abortion of a sporadic nature, and not due to the above organism, does occur. Such cases result as a rule from an injury, a fall on rough country, excessive dogging and trucking, dietetic causes such ak frosted roots and fermenting foodstuffs likely to cause severe indigestion and “bloating.” It is much safer in dealing with this disease to treat every case as contagious and adopt preventative measures until the cause is proved otherwise. In the detection of this disease the farmer himself, or a reliable deputy, should carefully examine his herd twice daily at each milking time. In this way any animal suspected of early or premature calving, as shown by the appearance of the external genitals, can be isolated from the herd. A small isolation paddock close to the homestead is absolutely essential for this purpose, such a paddock can be used for calves if not otherwise required. When abortion has taken place there is a tendency for retention of the foetal membranes. Such retention is likely to cause a chronic inflammation of the womb through the invasion of secondary organisms, which is undoubtedly a common cause of sterility afterwards. This being so, certain measures such as the careful removal by hand with frequent flooding and washing out of the womb with weak antiseptics at regular intervals, are recommended.

As curative measures are not satisfactory, and as vaccination against the disease is unsatisfactory in bringing about immunity .against an attack, owners are advised to use all their powers of observation in the early detection of the disease and to take every possible precaution to prevent its entry and spread in a herd.

The method of control of the disease which in the present state of world knowledge offers more hope of success than any other is the building up of an abortion-free herd in the case of an already badly infected herd, and in the case of a slightly infected herd the elimination of all reactors. In regard to this disease more than any other the farmer should provide his own young stock by rearing his own heifers, and thus prevent the introduction of the disease from outside sources. When getting rid of animals which have aborted the works should be availed of, as if these animals pass through the saleyards an unsuspecting buyer may thus introduce the disease to his herd.

There is probably no disease in which careful management and regular attention by the owner is better repaid. The bull may transmit the disease from an infected animal to a clean animal through actual physical contact or through service. The bull may even harbour the organism in his genital organs. By far the commonest method of infection in cows is, however, by ingestion of contaminated food or water.

In the diagnosis of the extent of the disease in any herd a physical examination of the herd is not of much assistance. A laboratory test known as the agglutination test is quite dependable, and to enable this to be carried out samples of blood taken under conditions which prevent contamination are necessary. The Veterinary Laboratory at Wallaceville tests hundreds of samples of blood for owners annually and gives them the true percentage of the disease in their herds.

After abortion has taken place it frequently happens that such animals appear in season very soon afterwards. On no account should these animals be allowed to the bull until at least six weeks or two months after all discharge has ceased. To effect this it is Absolutely essential that the bull should be kept under- control and not allowed to mix with the herd. The following control measures are absolutely essential in combating the ravages of contagious abortion :—

1. Do not allow the bull to mix with the herd ; take the cows to the bull for service when considered clean. 2. Wash out the sheath of the bull after service of a suspected unclean cow.

3. Isolate a cow immediately abortion has taken place, or preferably before the act has taken place, if possible.

4. Destroy the foetus and all discharges afterwards by burning or by lime.

5. Keep the cow in isolation until all discharge has ceased, and do not allow service until at least six weeks after all discharge' has ceased. 6. Frequent and regular douching and washing of the womb and external genitals immediately after abortion and while the discharge is coming away.

7. The Solutions for douching recommended are weak solutions of Condy’s crystals in water, or normal saline solution (one ounce of salt to a gallon of water). 8. By rearing his own heifer calves the farmer is independent of outside buying ; hence less risk of introducing the disease into a clean herd.

9. When disposing of aborting animals send them to the works. The risk of contaminating saleyards and other clean cattle at sales is a serioufe consideration.

10. When buying animals to introduce into a clean herd, buy subject to passing the agglutination test. 11. Bulls should not be allowed to wander at large ; the scrub bull is always a menace in this respect.