The development and effectiveness of the standard milking time hygiene practices and dry cow therapy were established in the 1960's. Because of the effectiveness of these practices, mastitis has evolved on many farms to primarily environmental rather than contagious pathogens. The purpose of this article is to perform a literature review (especially trying to find studies published after the year 2000) as to the effectiveness of the various mastitis control practices in today's progressive dairy farm.

Pre-dipping milk preparation

Pre-dipping with a germicide is used to kill bacteria on the teat surface and teat orifice and improves milk quality by helping to ensure that the teats a clean at the time of milking. Most studies indicate that pre-dipping with an effective germicide that is left on for the required amount of time is effective in controlling new environmental cases of mastitis. Oliver and others conducted a predipping efficacy study using 0.25% iodine and found that new mastitis infections by gram-negative bacteria were significantly lower in quarters with teats predipped and postdipped versus quarters receiving only postdip (Oliver et al., 1993). There were 48.6% fewer new infections due to major pathogens in the predipped quarters. In a more recent study of the efficacy of a phenolic-containing predip compared to a negative control, predipping was significantly more effective in preventing new intramammary infections (IMI) than was postmilking teat dipping alone (Oliver et al., 2001). Predipping is not thought to be very effective against preventing new IMI due to contagious mastitis pathogens. However pre-dipping is preferred over the use of water for udder preparation.

Single service paper or cloth towels are highly recommended to decrease the chance of transferring pathogens from one cow to another. This procedure is most important in controlling contagious pathogens and because most farms still have contagious pathogens, this control measure is still important. Fox (1997) investigated different methods to sanitize cloth towels and had the following results:
     1. The use of udder cloth towels and laundering towels between milkings is very economical as compared to use of paper towels.
     2. Laundering practices should include at least one of the following three practices: hot water wash; use of bleach; and hot air drying (all 3 or even 2 are not necessary).
     3. Washing towels in cold water only, without hot air drying and/or bleach, could result in the transmission of contagious mastitis pathogens.

Only one study could be found that investigated the ability of a medicated udder wipe product to reduce bacterial numbers on the teat surface premilking (Gibson et al., 2008). Although there was no significant difference between the 4 teat cleaning regimens (dry wipe with paper towel, alcohol-based medicated wipe, iodine-based dip and dry with paper towel and hypochlorite wash and dry with paper towel), numerically the dry wipe alone was the least effective.

Gloves

The use of gloves during milking has been strongly advocated by many in the dairy industry. Unfortunately, this strong advocacy is without strong research to back it up. In fact, until recently, there have been no published studies on the efficacy of glove use during milking. In theory, the use of gloves is thought to decrease the transfer of pathogens especially contagious pathogens via the milker's hands. A couple of studies have found that always wearing gloves while milking increased the risk of clinical mastitis (Peeler et al., 2000; O'Reilly et al., 2006). Wearing gloves for one year was not associated with a lower incidence of mastitis, and the authors are unaware of any evidence that wearing gloves reduces the incidence (O'Reilly et al., 2006). A more recent study stated that milker's wearing gloves during milking was a best-practice frontier because it was a cost-efficient measure despite it having a minimal effect on clinical mastitis (Huijps et al., 2010). The authors of this study could only find 3 articles that described the effects of wearing milkers' gloves (two are mentioned above, the third was not referenced...so it's not really clear why wearing gloves constitutes a "best-practice frontier").

Milking first lactation cows first

I could not find any recent studies that evaluated the effect of milking first lactation cows first. In fact, I could only find one study that evaluated this. Grommers and van de Geer (1979) reported that milking primiparous animals first failed to result in a significant decrease of the level of udder infection during the first half of lactation. Although not significant, they state that there was a rise in infection level among the older animals of the experimental group and a decline in the controls at the same time. This procedure was developed to help control contagious mastitis pathogens and may actually be a good practice in herds that have a high percentage of cows infected with contagious pathogens. In herds with good control of contagious pathogens, this procedure may not be appropriate because ~4% of heifers freshen with Staphylococcus aureus mastitis.

Complete milk-out (machine or hand stripping)

No studies could be found regarding this relatively old recommendation to help prevent mastitis.