TUBERCULOSIS AND THE CALF

Press, Volume L, Issue 14889, 31 January 1914, Page 14

TUBERCULOSIS AND THE CALF

SOilE BRITISH EXPERIMENTS.

HKALTHY CALVES FROM AFFECTED COWS.

The British Royal Agricultural Society has been for threo years carrying out a series of tests to demonstrate that by isolation it is possible to rear healthy stock from tuberculous parents. Tho report of the result of these experiments has just become available. Th© place selected for the tests was a farm near Woburn, which was placed at the disposal of the committee in the i autumn of 1910. The buildings intended for tho reception of the young calves were provided with a new impervious concrete floor, with surface drainage, the object being to render cleansing and disinfection easy. Tho floor space was divided up by wooden sparred partitions into pens of a sizo suitable for calves. Two buildings of this description were made available, these being separated by a smaller shed, which oontained a large open copper for heating tho milk, and providing tho boiling water for washing and scalding the milk vessels and | feeding pails. Arrangements were mado with several owners to allow'their cows to be submitted to tho tuberculin test, and to place at the uisposal of the committee any selected as being suitable until after they had calved. As soon as possible after tho tost had been carried out tho selected reacting cows were sent to the society's experimental farm at Woburn, and kept there until they had calved and cleansed, after which they were returned to their owners. In arranging a plan for the experiments, the committee had to toko account of tlie circumstances which might prevent the success of any attempt to rear to maturity and tree from tuberculosis the progeny ot a tuberculous parent. And it may hero be said that although thc plural word was used in the resolution passed by the eouuetl. it was understood by the committee thnt whnt they were desired to demonstrate was tho possibility of rearing in d state of health calves of.which one parent—viz., the female, was tuberculous. A more prolonged and expensive set of experiments would have been required to prove this possibility with regard to the calves ot which* both parents were tuberculous, although there is no reason to suppose that tbe difficulty in breeding and rearing healthy calves from tuberculous cows would be increased in any degree .by the fact of the male parents being also diseased. \ ± Since iUis generally admitted that tuberculosis is a purely contafflous, disease, resulting from the multiplication of tho tubercle bacillus m- the bodies of infected animals, what the committee had really to do was to demonstrate (1) that the bacillus aaia rule not present at the time of birth in the caives of tuberculous cows, and (2) that calves born healthy may bo roared in circumstances that prevent infection with tubercle bacilli It was from the outset clear that the experiment might fail to demonstrate either of these things. In the first place, it admits of no denial that tuberculous cows sometimes nroduce tuberculous calves, but this does not occur once in v hundred times among cows that appear to bo healthy. IS *? .™J> the risk of the experiments failing through some of the calves being born tuberculous was very slight, providing the cows selected for the experiment wero not suffering from what may be called advanced tulwrculosis. Tho only real difficulty m the demonstration, therefore, arose from the 'risk that the calves might become infected after birth, and the problem was to prevent tho access of tubercle bacilli to them. In nature these bacilli come from one source, viz., animals or human beings affected with tuberculosis, and. as regards the bacilli which cause th» disease in cattle, the human source may for all practical purposes bo left out of account. The arrangements had, therefore, to aim at making it imnossible for tubercle bacilli to reach'the calves either directly or indirectly from tuberculous animals, and especially from animals 'of their own species. The most immediate risk obviously was that the calf might become infected from its mother. To .guard against this, each cow at the time ol calving was tied up, and as soon as tho cnlf was born, it was carried into a building that had not previously been used for cattle, where it was rubbed dry. As soon as possible thereafter, it was removed by cart to the calf-rear-ing premises, a milo distant. Further, tlie "man in charge of the calves was kept entirely for this work, and had no contact with other cattle. As the calf houses here had been to a large extent reconstructed, provided with a new floor, cleansed, disinfected, and whitewashed, it was permissible to assume that there was little or no risk that the calves could become infected by bncilli remaining over from the nrevious tenancy. The milk on which the calves were fed was obtained from a farm in the. neighbourhood, and before use it was-raised to a temperaCure of not loss than 100 deg. Fahr. by immersing the vessels containing it in water which was kept boiling in the copper. Assurance was thus obtained that any bacilli which might have been brought' from the cows at the neighbouring farm had been killed. When milk diet was stopped, tho calves were kept on two fields _ which were reserved exclusively for their use, and they were never allowed to come into contact with other animals with the exception of the bull, which was put "with them in September, 1912. This bull had passed the tuberculin test before ho was brought to tho place, and, after arrival, ho was again tested, with the same result. Inasmuch as no evidence of tuberculosis was found in any of the animals after they were slaughtered, these experiments may be held to havo demonstrated "that by means of isolation it is possible to rear healthy stock from tuberculous parents." It is true that thi.s involves the assumption thnt a distinct reaction to tuberculin may in practice be accepted as proof that 'the reacting animals aro tuberculous, for tho cows which gavo birth to the calves were not submitted to post-mortem examination. To furnish absolute proof* that the cows were tuberculous was not considered necessary, and to have done so would have added greatly to the cost of the demonstration. It may bo pointed out, however, that if thero are any breeders who consider the tuberculin test unreliable, the experiments, nevertheless, have considerable value for them, since they prove that by means of isolation it is possible to rear non-reacting calves from reacting cows. Although the experiments assumecj. and were not intended to provo, the reliability of the tubeieulin test when properly carried out, they do -add further testimony to its value. For, on the assumption that the test is quite untrustworthy, there does not appear to bo any reasonable explanation of tho fact ' that, with one exception, none of the calves reacted, while among 116 apparently healthy cows 32 <or 27 per cent.) reacted distinctly. The caso of the calf referred to illustrates one of the sources of error in testing animals with tuberculin. The facts set forth in this animal's record indicate that it suffered from some temporary illness, of which the causo was not determined, and that this illness was responsible for the rise of temperature after the injection of tuberculin.