H.—29.

Experimental work on mastitis may be summed up as follows : — (1) Three cows received drops of acute streptococcic udder secretion directly on to the ends of their teats after milking, for a period of weeks but without deleterious effect. (2) Drops of streptococcic milk instilled into the conjunctival sac of a cow did not harm the eye nor produce mastitis. (3) Vaccine virus (cow-pox) was used on clean heifers to find its possible action in production of mastitis. In one heifer the end of a teat was scarified and vaccine rubbed into the area. The resultant pustule was infected with streptococcus mastitidis and an infection of the quarter occurred with the usual change in secretion. This later subsided and the cow became normal in some weeks time. Quarters of two heifers were injected as far as the milk sinus with vaccine virus in saline, and both developed acute streptococcic mastitis, which later subsided and the quarters became normal. Another cow was given an intravenous injection of vaccine virus, with the result that the four quarters showed a definite increase in cell count, which persisted until the animal dried off. No pustules developed. This cow came in after calving with streptococcic mastitis in one quarter. (4) Two heifers were given injections, the one of washed streptococcus mastitidis, the other of streptococcic mastitis milk into the uterus after calving, without deleterious effect. (5) As an aid to bacteriological work Mr. Gill carried out experiments with boric acid, and found an amount which kept the milk exactly as it was taken from the cow without increase or decrease of flora. This improvement in technique will enable a considerable amount of bacteriological work on milk-samples from a distance to be carried out at a minimum cost. It may be stated that any work now performed on cows requires as a basis that no leucocytes be present at the commencement of the experiment, and that the full udder history of the cow be known to guard against latent streptococcic infection, &c. The view which is now taken of mastitis by New Zealand workers is that there is considerable subacute mastitis present in herds where the organism present (possibly not causative) is a micrococcus. Streptococci are present in the minority of cases, but when streptococci are present the mastitis frequently is persistent and acute. Following these premises it seems fair to base mastitis on a leucocyte count rather than on the presence or absence of streptococci as formerly. The mode of entry of organisms is still undetermined, though the effect of vesicles of cow-pox on teats is a factor which is being given every attention. Temporary Sterility in Dairy Cows. Messrs. Webster and Blake are still busily engaged in field laboratory work on this condition. The results obtained last year in examination of bulls has been confirmed in the present year's experience, particularly by Mr. Blake in the Waikato, where at least one hundred and fifty bulls have been under observation with regard to their spermatozoan morphology and herd efficiency. As a result of large numbers of examinations, experience is being gained with a view to developing a system of diagnosis of soundness for bulls of dairy-farmers. Mr. Webster in his report says : — " Work was continued on similar lines to those of the past two seasons. Cultural work has amply confirmed the view that the causative agent is invariably some strain of alpha streptococcus. Forty-six cultures have been forwarded for typing at Wallaceville. " Semen examinations have confirmed previous work, and there is no doubt that semen examination is a valuable diagnostic aid. Cultures from the semen of bulls in herds suffering from epidemic sterility consistently give a profuse streptococcic growth. Sound bulls do not give this organism on culture. " Treatment was carried out on as extensive a scale as time and opportunity would allow. The method was a development of that given a preliminary trial during the previous season—i.e., injecting a bland antiseptic in paste form into the cervix. Improved technique enabled the material to be placed in the deepest parts of the cervix. Various combinations of chinosol, bismuth subnitrate, boracic, and glycerine were used. From a bacteriological and clinical point of view the treatment appeared most successful and from a practical aspect the breeding results following treatment were most successful, especially when a dilute chinosol mixture was employed. " A new line of attack on the sterility problem in first-calvers has been followed up in taking an extensive series of blood-samples for chemical analysis and correlating the results with clinical records. The evidence is at times somewhat contradictory, but taken as a whole there is a definite tendency for low phosphate to be associated with a normal clinical appearance and vice versa—i.e., when blood phosphorus was normal there was frequently clinical evidence in the shape of cervicitis, slight endometritis, &c., to account for the failure to breed. Further work is required in this direction, however. Speaking generally, I feel hopeful that the sterility problem is largely solved in so far as its causes and effects are concerned, and that a definite line of treatment has been established. However, there is still room for much work regarding the most satisfactory agents to employ in rational treatment." Mr. Blake in his report gives a table of the findings in his microscopical examinations of the semen of a large number of the bulls examined by him, as follows : — 23 good bulls used on an average of 40 cows each have 76 per cent, held to first service. 17 fair bulls used on an average of 29 cows each have 64 per cent, held to first service. 26 poor bulls used on an average of 34 cows each have 39 per cent, held to first service. 38 bad bulls used on an average of 29 cows each have 31 per cent, held to first service. 2 sterile bulls used on an average of 18 cows each have 0 per cent, held to first service. The history of all bulls examined is not yet to hand. The words "good," "fair," "poor," and "bad" refer to the microscopical picture of morphology of sperm heads, and can be reduced to definite percentages of abnormality in sperm heads in a given sample. This is a phase of the work yet to be completed. Mr. Blake also considers from his district observations that on occasions a really good bull used after a poor or bad animal is able to overcome the effects of infection in the cow, and may put many empty ones in calf to first service. The evidence is based on experience, without bacteriological examination of seminal fluid of the bull or cervices of cows. At Wallace ville a small breeding experiment was carried out on maiden heifers to find (1) whether bulls became infected from recently served or returning cows ; (2) whether cows returning to one bull would hold when put to a second bull; (3) how long infection remained present in the bull and in the cow. A bull which had a poor sperm morphology and had been giving considerable trouble in a Taranaki herd was brought to the Laboratory and served a maiden heifer. A young unused 15-months bull was at once placed on the same heifer to become infected. The heifer served by two bulls proved to be in calf. The Taranaki bull subsequently got another maiden heifer and a cow in calf at first service, suggesting that the primary infection had passed

53