Early Dry Period Research Articles

627. Udder infections in the ‘dry period’: V. The effect of teat disinfection at drying-off on the incidence of infections in the early dry period

1. The effect of disinfecting the skin of the teats at drying-off on the incidence of new infection in the early dry period has been studied. After the last milking of lactation the udders of alternate cows to go dry were washed with sodium hypochlorite solution (800 p.p.m.), dried, and each teat immersed in a 5% iodine tincture for 20 sec., and then again immersed 24 hr. later.2. There was significantly (P <0·05) less new infection in cows that had teats disinfected than in control cows. This difference in infection was highly significant (P <0·01) for cows that were not infected on drying-off.3. The treatment effect was due to a highly significant (P <0·01) reduction in the incidence of infection by Staph. aureus. New infection caused by Str. uberis was not affected.

625. Udder infections in the ‘dry period’: III. The method of drying-off cows at the end of lactation

1. An experimental study was made of the effect of drying-off by ‘stop’ or intermittent milking on the incidence of new infection in the early dry period of dairy cows. Ninety-one and ninety-seven dry periods were examined following the treatments, and the results were analysed on a cow and quarter basis.2. The incidence of new infection was similar for groups of cows dried off by ‘stop’ or intermittent milking.3. The quarters of cows that were not infected on drying-off showed a significantly higher incidence (P <0·05) of new infection following ‘stop’ than following intermittent milking.4. Of the cows that were not infected at the time of drying off, those which had a previous history of infection showed a significantly higher (P <0·01) incidence of new dry-period infection than cows that had not been infected before.5. There was a much higher incidence of new infection in cows that were already infected on drying-off compared with cows free from infection at that time.6. About half of all the new dry-period infections persisted until the next lactation, and about one-third of these resulted in mastitis in the affected quarter.7. The method of drying-off had no effect on infections that were already established in quarters going dry.8. The types of pathogen causing infection were similar for both methods of drying-off.9. The method of ending lactation did not affect milk yield in the lactation following the dry period studied.