FIRST CENTURY OF DAIRYING IN NEW SOUTH WALES. 



At what age do cows contract tuberculosis, may be asked, and ex- 

 perience goes to show mostly during their growth. Young cows 

 have least power of resistance to the disease, and are, therefore, mos; 

 easily infected, but as the animal becomes older and has more oppor- 

 tunities o-f infection, in the same proportion does the disease develop. 

 Hence it arises that in post-mortem examinations one often finds 

 full-grown cows more tuberculous than young calves. Cows, after a 

 long season's milking, especially after dropping the second or third 

 calf, are particularly liable to tubercle. First and foremost, 

 cows, then bulls, then bullocks are more frequently affected. 

 In the case of cows, of course, a multitude of circum- 

 stances are at work reducing their power of resistance to the disease, 

 as for instance unnatural feeding, too highly forced milk production, 

 want of exercise in the fresh air, &c. If the bulls are put among 

 the cows of a tubercular herd they as a rule contract tuberculosis. 



As regards breed, it is frequently stated that this or that breed is 

 more susceptible than another. But this all depends on the degree 

 of production and the care and attention to which any breed of cattle 

 are subjected. The reason why good animals are so prone to the 

 mnlady is not to be sought in any greater susceptibility to tuber- 

 culosis than any particular breed possesses so much as their surround- 

 in--;, being more crowded together, while under a very severe strain 

 of milk production. 



Hereditary tuberculosis has in ordinary parlance two meanings, i.e., 

 inherited infection and inherited susceptibility. It is important to 

 separate each from the other. Infection directly inherited is 'some- 

 what rare, according to Professor Bang ; inherited susceptibility, on 

 the other hand, is more common. " It is certain," says Bang, "that 

 an animal born with tuberculosis is somewhat of a rarity ; but still 

 cases do actually occur, and perhaps more -frequently than is believed." 



That tuberculosis in mankind is hereditary has been a deeply-rooted 

 conviction which still to a great extent obtains. It has been 

 analogously assumed that tuberculosis in cattle was hereditary. Both 

 sire and dam are considered capable of conveying the disease to 

 the young one, but the influence of the dam is, of course, incomparably 

 ;?rt?i<er. There are instances on record of bulls suffering from tuber- 

 culosis in the testicles producing healthy calves. Then comes the 

 question of hereditary susceptibility to the disease. All high-c ass 

 dairy cattle by nature are susceptible to tuberculosis, for once their 

 systems are out of order, which is most difficult to avoid in the pro- 

 cess of a few years of high butter yielding, and an adequate sup- 

 ply of tubercle bacilli being available, they always get the 

 disease. Of course, there are varying degrees of susceptibility. Hence 

 some cows resist the disease for a greater length of time than others, 

 while some resist it till they are past the milking stage, whereas there 

 are cows that offer an excellent field for tuberculosis and are struck 

 down on their second or third calf from an attack of but a few 

 months' duration ; others offer a stubborn resistance to it, and are 

 able not infrequently to confine it to a single lymph gland, which re- 

 quired an observant eye to detect. 



Apart from the, so to speak, innate disposition to tuberculosis pre- 

 sent in all good dairy cattle, one may also speak of acquired MI 

 ceptibility to disease ; and the reasons for this might be looked for 

 in the defective feeding ot calves on >ep;irated milk some years :ig>. 

 and prior to the general adoption of the home separator, and even 

 in the defective feeding of calves under the present systems, where 

 tin- milk is sent off the farm tor treatment, and where cheese is manu- 

 factured. 



The aim of any rational dairy farmer in calf raising is -to make the 

 animals as good milkers as possible. In this very often very little 

 judgment and consideration is shown, and the result is partially- 



266. 



