623. Variations in the incidence of udder infection and mastitis with stage in lactation, age and season of the year

Abstract

1. The detailed udder health records of 530 lactations have been analysed on a monthly and lactation basis, so that separate studies of the first infection rate, re-infection rate, total new infection rate and total infection and mastitis incidence for both cows and quarters could be made. These data have been used to study the relationship of stage of lactation, age and season of the year with udder infection and mastitis.2. With advancing lactation there was a decline in the rate of first infection, reinfection, total new infection and in mastitis in infected cows and quarters.3. In early lactation there was a marked tendency for infected cows and quarters to develop clinical symptoms.4. During the last 4 months of lactation there was no significant rise either in infection or in mastitis.5. There was an increase in infection and mastitis with advancing age, but infected older cows were not more liable to develop clinical symptoms than younger cows.6. There was an indication that the longer a quarter was free from infection the greater were its chances of remaining so.7. No major seasonal trends were found in the incidence of udder infection and mastitis, although the incidence was slightly higher in the summer months.