Application technique

The aim of the application is to deliver disinfectant to the whole surface of all four teats. To achieve this, two main techniques have been developed - dipping and spraying (KINGWILL et al. 1977). Similar efficacy has been observed, so long as good coverage is achieved when spraying (PANKEY and WATTS 1983).

For the dipping technique, a hand-held dip cup is filled with the disinfectant. All four teats are immersed into the disinfectant immediately after each milking.

The spraying technique was developed as an alternative to teat dipping. Spray devices include hand-held reservoirs with a pressure plunger or larger reservoirs with electric pumps and drop hoses located in the milking parlour.

The advantages of the teat spray devices include speed, reduced spillage of the sanitiser and less risk of contamination with organic matter. Reservoir units with an electric pump provide the optimal spray pressure and easy access to the spray nozzles (PEARSON et al. 1975; MILNE 1977b).

In most countries, teats are dipped. New Zealand is an exception with 77 per cent of farms having adopted the spraying technique to maximise cow throughput in the dairy (IDF 1990). The recommendations are that the sanitiser be delivered at a pressure of approximately 20 psi, sprayed directly from below the teats from a distance of ten to 15 cm, and using five to seven ml of sanitising mixture for each cow (MILNE 1977c).

The effectiveness of both techniques has been tested (PANKEY and WATTS 1983).

Teat spraying and dipping were equally effective against a Sc. agalactiae experimental challenge in direct comparison, using a 0.5 per cent quaternary ammonium sanitiser. It was concluded that post milking teat sanitiser can be applied effectively as spray (HAYWARD and WEBSTER 1977), but spraying was only as good as its application. For good effectiveness, it must be applied to the teat from directly below, to cover all sides, until a drop of sanitiser collects on the distal end of the teat (PANKEY and WATTS 1983). Other authors observed the same effects, comparing a hand-held teat sprayer with teat dipping. The effectiveness of an iodine solution on the reduction of staphylococci and coliforms on teats was the same (BUSHNELL et al. 1978). The incidence of teat orifice infections was reduced by spraying and dipping with an iodophor teat disinfectant to the same degree (MEANEY 1974).

Automated teat sanitising systems have been developed. For example, a system installed in a round barn in the floor of the milking parlour, working under the udder of each cow (BUSHNELL et al. 1978). A fine spray of teat dip is forced onto the teats of each cow, just five seconds after the milking unit has been removed.

This system was compared to teat dipping with the same germicide during an eight-month period. Ninety-six per cent of teats were adequately sprayed at the tip, with varying results for the sides. The spray system was recognised as equally effective for maintaining the same health status as the dipping method (BUSHNELL et al.

1978).

2.4.2.1 Time of application

Teat sanitisers are usually applied subsequent to milking; to reduce the chance of bacteria invading the teat canal directly after milking, the degree of bacterial contamination of the teat during the inter-milking period and thereby decrease the risk of IMI occurring. The effectiveness of this procedure has been demonstrated (SCHULTZE and SMITH 1972; BUSHNELL et al. 1978; PANKEY et al. 1984;

DRECHSLER et al. 1990).

For improved udder hygiene, teat dips or sprays can be applied before milking. Pre-dipping reduces the amount of bacteria entering the bulk tank and reduces the exposure of teat skin to these pathogens during milking (NICKERSON 1998). Yet, this procedure is not allowed in Europe.

Teats were sprayed before and after milking with an iodine solution of different iodine concentrations and the efficacy was determined for the reduction in staphylococci and coliform numbers on the teat skin (BUSHNELL et al. 1978). They observed a similar effect for pre-milking sanitising on bacterial reduction as for post milking. Low concentrations of iodine (i.e. 25, 30 and 80 ppm) were not effective against staphylococci, but reduced the total number of bacteria by 30 to 80 per cent.

Concentrations of 200 ppm were equally effective as a pre-milking or post milking application against staphylococci, coliforms and total number of bacteria (BUSHNELL et al. 1978).

Some post milking teat dips are used as pre-milking teat disinfectants. Three different germicides (one per cent titratable iodine, 5.25 per cent sodium hypochlorite and 1.94 per cent DDBSA containing 12 per cent glycerine) were tested for their effects on bacterial counts in milk when used as a pre-milking teat disinfectant. All three products reduced bacterial populations in milk, but DDBSA was the least effective for coliform counts (GALTON et al. 1986).

The efficacy of pre-milking teat disinfection was tested (PANKEY et al. 1987). The teat dips contained different concentrations of iodine. Pre-dipping reduced the rate of new IMI with major pathogens by 54 per cent. Aesculin-positive streptococci and coliform infections were inhibited by more than 51 per cent but infections with coagulase-negative staphylococci were not controlled (PANKEY et al. 1987). These results were seen as evidence that the environmental pathogens, aesculin-positive streptococci and coliforms, caused new infections during milking. With an effective teat dip, the number of these pathogens can be reduced prior to milking, possibly decreasing the new infection rate (PANKEY et al. 1987).

2.4.3 Effects of sanitiser on teat skin condition, contamination and new