Control programmes for contagious mastitis pathogens, primarily Streptococcus agalactiae and Staphylococcus aureus, consisting of milking hygiene, treatment or isolation of infected cows and post-milking teat disinfection are relatively effective (McDonald, 1970; Natzke, 1977; Fox & Gay, 1993). Similar control programmes are often ineffective in the prevention of intramammary infections caused by environmental bacteria (Eberhart, 1977; Smith et al. 1985; Erskine et al. 1991; Smith & Hogan, 1993). This disparity of success relates to the fact that the principal source of environmental mastitis pathogens is the cow's environment, rather than another cow with an intramammary infection (Eberhart, 1977; Smith et al. 1985). Infections of environmental origin are particularly noteworthy because they may remain common in well managed herds, and these infections often cause severe clinical signs and high case fatality rates (Eberhart, 1977; Smith et al. 1985; Erskine et al. 1991; Smith & Hogan, 1993).

Control programmes for environmental mastitis usually include premilking teat disinfection, decreased use of water in udder preparation, increased concentrations of dietary vitamin E and selenium, improved sanitation of the environment and modification of cow behaviour in the post-milking period (Eberhart, 1977; Smith et al. 1984, 1985; Weiss et al. 1990; Erskine et al. 1991; Smith & Hogan, 1993). Environmental infections are thought to result when bacteria lacking specific virulence factors penetrate the teat sphincter (Eberhart et al. 1979; Smith et al. 1985). The bulk of these exposures are thought to occur between milkings. Control of these infections is problematic because the cow's teat sphincter remains open after mechanical milking (McDonald, 1975a). Presumably, cows are predisposed to intramammary infections when the open teat sphincter is exposed when cows lie down. Hence, dairy managers are advised to offer fresh feed to cows immediately after milking to increase the likelihood that the teat sphincter will close at least partly before cows become recumbent.

The purpose of this study was to determine the effect of feed availability on post-milking behaviour in dairy cows. Specifically, the measured dependent variable was the length of time that cows remained standing after leaving the milking parlour.