In a series of short-term experiments cows were subjected to exaggerated bacterial challenge and accentuated milking machine conditions known to predispose to new mammary infection. The incidence of new intramammary infection was significantly greater in quarters with peak flow rates > 1*6 kg/min whether they were exposed to impacts (P < 0-05) or milking without pulsation (P < 0-001). The infection rates were much lower (P < 0 -001) in quarters milked with 'pulsation and shields' to protect against these two machine factors. Despite this, quarters with peak flow > 1-6 kg/min still showed a 12-fold increase in mastitis incidence compared with quarters with peak flow < 0-8 kg/min. Rates of milk flow have increased dramatically in the last 40 years through selection and breeding: whole udder peak flow rates in heifers have doubled from 1-9 to 3 -8 kg/min. Increased emphasis, therefore, should be placed on hygiene, husbandry and milking techniques to minimize bacterial numbers at teat ends to control mastitis as the drive for higher flow rate and yield make cows increasingly more susceptible to infection. These results suggest that the benefits of reduced infection rate from mastitis control are significantly underestimated since animals are now considerably more susceptible than 40 years ago.

With two groups of 12 cows, a procedure involving foremilking, teat washing and drying before milking was compared with no premilking preparation for its effects on mastitis and teat contamination. Half the cows in each group were deliberately infected in a single udder quarter with Staphylococcus aureus and milked alternately with uninfected cows for 9 weeks. To minimize transfer during milking all cows were milked with the use of a multi-valved claw.Five new staphylococcal infections developed in the 12 animals in the teat preparation group compared to one in the control group. A significantly higher incidence of teat orifice colonization developed in the prepared cows compared to the control cows (17 v. 7). Foremilking and teat preparation led to transfer of staphylococci between quarters (within cow) but this was effectively prevented by the multi-valve claw in the absence of teat preparation.Staphylococcus aureus is a common cause of intramammary infection and the sources of the pathogen are mainly infected udder quarters and infected skin lesions. These are spread over the skin of the teats and udder and from cow to cow during the preparation for milking (Bramley, 1981;

The multivalve or ball claw was developed to prevent the detrimental effects on udder disease from both 'impacts' and 'cross contamination' during machine milking. Air-bleeds were fitted to the short milk tubes to achieve a milking action similar to conventional machines and in contemporary comparisons with conventional clusters the multivalve claw reduced total new infections by 14 per cent and clinical mastitis by 25 per cent. Subsequent research revealed that exclusion of air from the multivalve claw (hydraulic milking) produced the expected flooding of the liners and a milking action that was gentler to the teats and gave advantages in terms of milking performance, reduced lipolysis and milk sensing. Although the pulsation rates and vacuum levels developed for conventional milking appear to be suitable for hydraulic milking, recent research demonstrates that there are many possibilities for modifying and controlling the operating conditions so as to improve the milking performance and the control over the forces applied to the teats. The electronic monitoring of milk components during milking and the metering of milk yield may also be made simpler.