Association of the M blood group system with bovine mastitis.

Associations of the 11 bovine blood group systems with mastitis were examined in Red Danish dairy cattle. The mastitis status was followed during three lactational periods. A significant effect of the M blood group system on mastitis incidence was observed in the first and second lactation periods and a lower frequency of mastitis is found among animals lacking the M' factor as compared to those having the M' blood group factor. The significance of these results are discussed in view of the close relation between the M blood group system and the bovine lymphocyte antigens (BoLA), and the expected effect of eliminating the M' gene from the breed is estimated. Among the remaining 10 blood group systems, the T' system was the only system showing an overall effect on mastitis, and only in first and third lactation. However, the T' system was inconsistent with regard to the effect of the T' gene on the various mastitis diagnoses.

Herd incidence of bovine mastitis in four danish dairy districts. III. Relation between frequency of mastitis and cell counts on bulk molk samples.

The correlations between monthly bulk milk cell counts and the actual frequency of mastitis was investigated in 399 Danish dairy farms with a total of about 7000 cows. The correlation coefficients varied from 0.3 to 0.5. Correlations were improved by using more than one cell count, but not further improved by using more than two cell counts. The correlations were higher for large than for small herds. It was not possible by combining cell counts in different ways, as indicated in (Table IV, to point out every heavily mastitis-affected herd without also pointing out some not so heavily affected ones. Table IV shows what infection levels can be expected when different criteria based on bulk milk cell counts are applied. The figures cannot be transferred directly from Danish conditions to conditions in other countries, but similar tendencies can probably be found anywhere.

Herd incidence of bovine mastitis in four Danish dairy. districts II. Evaluation of the effect of the mastitis control scheme.

Bacteriological and cytological examinations have been carried out on samples from 6,808 cows belonging to 339 herds in four Danish dairy districts. After a discussion of differences between the districts as regards intensivity of mastitis control, public health surveillance, etc., definitions are given of certain terms, such as presence of bacteria, infection, pathogenic versus non-pathogenic (less pathogenic) organisms. The rate of infection with pathogenic organisms varies between districts from 23% to32% on a cow basis, and from 8% to 12% on a quarter basis. A comparison, on a cow basis, of the occurrence of pathogens as recorded in 1955/58 in three Danish surveys comprising 11 dairy districts, with the occurrence as recorded in four districts in 1972, showed a decline in incidence of between 7 and 9 percentage units. Together with the decline in incidence a definite change in the composition of the udder flora has taken place during that period. In particular, there was a pronounced fall in the occurrence of Group B, C, G, and L streptococci, and a relative increase in the occurrence of Staphylococcus aureus. A comparison, on a quarter basis, with the occurrence of pathogens in 30 English herds subjected through three years to intensive mastitis control, including systematic treatment of dry cows, teat dipping, and weekly inspection, showed that by such a programme a slightly lower level of infection was reached than in the 399 Danish herds which had been subjected to collective control for 10-15 years. The annual financial loss per cow suffering from mastitis being estimated at D.kr. 600.-, the reduction noted in the occurrence of bacteria in cows' udders implies an annual national saving of D.kr. 42 million on account of the Danish mastitis control. The total annual expenditure on Danish mastitis control is estimated at D.kr. 9million expenses would rise to some 70 million D.kr. if all registered cows were to be treated on drying-off, and if general teat dipping was to be carried out.