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Investigation of the effectiveness of pre-milking teat cleaning regimes

Project Code: B12003

30/11/2004

School of Applied Sciences, University of Wolverhampton
Gibson, H ; Protheroe, R;
Department of Animal Production and Science, Harper Adams University College
Sinclair, L; Brizuela, C;
School of Applied Sciences, University of Wolverhampton
Worton, H

A Introduction

The study comprised three phases to determine the effectiveness of premilking treatment on reducing the microbial load on teats prior to milking and the consequent effect on milk microbial quality. In phase 1 a questionnaire was issued to determine the range of techniques currently used by farmers and whether these had a relationship with milk bulk tank rolling total bacterial and somatic cell counts. In phase 2, thirty-seven of these farms were selected to assess the effect of their cleaning regime on reducing microbial levels from teats. In phase 3 a range of pre-milking teat cleaning regimes were evaluated to compare the reduction in teat bacterial numbers in herringbone and rotary parlours during the winter and the summer.

B Questionnaire

B.i Farm Characteristics

The questionnaire was mailed to 1000 dairy farmers in England and Wales. A total of 281 responses were received. Of these 75% of farms had herringbone parlours, 17% had abreast parlours, 2% rotary and <1% robotic. The average Bactoscan value across all farms was 29,000/ml and the average somatic cell count (SCC) was 166,000/ml. Cubicle housing was predominant (85% of the respondents), with the majority of these bedded on straw (78%). The average herd size in the responses was 132 cows. Pre-milking teat cleaning regimes were claimed to be practiced on 96% of the farms surveyed, with 43% dry wiping, 20% used either a pre-milking dip or spray, 19% using medi-wipes, 11% cloth and bucket, and 3% used another regime. Post- milking dip/spray was practiced on 100% of herds.

B.ii Correlation Between Milking Routine and Hygienic Quality

Pre-milking routine influenced bulk tank Bactoscan and SCC with farms using a dry wipe as a pre-milking teat cleaning regime tending to have higher bulk tank Bactoscan levels than farms where other cleaning techniques were in place. Additionally, herds with a greater proportion of cows in their 1st lactation had lower bulk tank Bactoscan levels than those with a greater proportion of animals in their 3rd lactation or above.

C Microbial Survey

From the questionnaire respondents, 37 dairy farms with a range of parlour type and pre milking cleaning routines were visited and teat swabs taken before and after the cleaning was applied.

C.i Microbial Load

Microbial levels of all groups measured (total viable count (TVC), staphylococci, coliforms, streptococci, aerobic and anaerobic spores) were significantly reduced by cleaning with reductions in TVC and staphylococci being particularly evident. Listeriae levels, which were low, were not significantly affected by cleaning. Staphylococci and aerobic spores were present in the highest numbers.

C.ii Correlation Between Teat Cleanliness Score and Microbial Levels Before Cleaning

No significant correlation between teat cleanliness score and TVC, staphylococci, coliforms, aerobic or anaerobic levels before cleaning were observed. There was, however, a correlation between visibly dirty teats and the presence of streptococci.

D Controlled Studies of Pre-Milking Cleaning Regimes on Teat and Milk Microbial Load

D.i The Winter Trial

Four pre-milking teat preparation regimes were applied on 8 commercial dairy farms having either herringbone (n=4) or rotary parlours (n=4). The regimes were: dry wipe, alcohol based medicated teat wipe, iodine dip+dry wipe and a hypochlorite and glycerine wash+dry wipe. Teat swabs and milk samples were collected on four occasions over a 12-week period from all farms.

Teat TVC

In both parlour types all four trial cleaning regimes reduced the microbial load on teats (Table 5.2), with the wash+dry, dip+dry and medi-wipe regime being significantly more effective (P<0.05) than the dry wipe. Within the rotary parlour type, application of a cleaning regime achieved a greater reduction in TVC levels than the herringbone parlours for most of the regimes, although interpretation of the results is confounded by the higher initial microbial levels and differences in the length of application of the treatment between the two parlour types.

The results support the hypothesis that by applying a cleaning regime the microbial level, and consequently potential food borne and mastitis causing pathogens, available to pass into raw milk can be reduced. The results also suggest that dry wiping was the least effective regime.

TVC levels were found to be closely correlated with bioluminescence readings. This indicates that bioluminescence is potentially a reliable method for assessing teat hygiene.

The wash+dry regime was the longest to perform and the dry wipe the shortest, with the order remaining the same between the parlours. However, in rotary parlours the effectiveness of a cleaning procedure must be compatible with the continual rotation of the parlour.

Milk TVC

The study did not find a relationship between milk TVC levels and teat TVC levels before or after cleaning. Nor did it find any relationship between the reduction in teat TVC due to pre-milking teat cleaning regimes and milk TVC. This is likely to be a consequence of many *background noise* factors that masked the beneficial effects of the teat cleaning regimes, including contamination from other potential sources such as teat liners, pipe work etc.

D.ii The Summer Trial

Four pre-milking teat preparation regimes were applied within 4 commercial herringbone dairy farms. The regimes were: Dry wipe, chlorine based dip+dry, water wash+dry, chlorine based wash+dry. Four pre-milking teat preparation regimes were also applied within 4 commercial rotary dairy farms. The regimes were: Dry wipe, quaternary ammonium chloride (QAC) based mediwipe, chlorhexidine based medi-wipe, foam dip+dry. Teat swabs and milk samples were collected on four occasions over a 12-week period from all farms.

Teat TVC

i) Herringbone parlours: The study found the chlorine wash+dry regime to be significantly more effective than the other three cleaning regimes (P<0.05) at reducing microbial load (Table 5.10). The results suggest that effectiveness is influenced by the application method and that there is improved cleaning with the presence of a disinfectant in the wash.
ii) Rotary parlours: Chlorhexidine based medi-wipes were found to be significantly better at reducing the microbial load than the other three regimes (P<0.05) tested in the study.

Within herringbone parlours, the dry wipe took approximately half the time of the dip / wash +dry regimes. There was very little difference in length of time required to apply the wash and dip regimes. Within the rotary parlours the medicated wipe and dry wipe took the same amount of time to apply whilst the foam dip+dry took more than twice as long.

Milk Enterobacteriaceae and E.coli

There was a significant relationship (P<0.01) across both parlour types, between Enterobacteriaceae and E.coli levels and the teat TVC levels before cleaning. The higher the initial microbial loading on the teat, the higher the Enterobacteriaceae and E.coli levels in the milk. However, no relationship was found between milk Enterobacteriaceae or E.coli levels and the cleaning regimes surveyed. Factors such as dirty clusters / sampling points, may have masked any inter-regime differences.

**E Mycobacterium paratuberculosis Analysis**

The bulk tank milk from forty-three farms was analysed for the presence of Mycobacterium paratuberculosis. The method used for analysis was PCR. When an appropriate sampling strategy had been developed, Mycobacterium paratuberculosis was not detected in milk from any of the farms tested.

F Interpretations

Microbial load on cows’ teats is variable and independent of the visual cleanliness. The whole herd should be cleaned pre-milking, not just cows with visibly soiled teats
Pre-milking teat cleaning can reduce the microbial load entering the milk as long as it is applied correctly
The consistently least effective pre-milking teat cleaning regime tested was the dry wipe
The study found washing+drying with chlorine to be more effective than dipping+drying with chlorine or washing+drying alone. The study found chlorhexidine based medi-wipes were superior to the quaternary ammonium chloride based medi-wipe and foam dip tested.
Any cleaning regime that is not stringently applied can result in an increase in spread of bacteria between cows and potentially increase bacterial levels in milk.

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