Effectiveness of automatic cleaning of udder and teats and effects of hygiene management

Teat cleaning is necessary to prevent milk from contamination with manure, dirt and included bacteria. Clean udder and teats before milking is also a requirement according to Council Directive 89/362/EEC. A lot of research has already been done to investigate the effect of teat cleaning on milk quality. In automatic milking (AM) systems the mechanisation of teat cleaning has become part of the procedure. Still missing is the online control of teat cleaning efficiency. The assessment of the teat cleaning efficiency of different types of cleaning devices in AM systems was the subject of this research.
The methods for evaluating teat cleaning efficiency had to be developed for this purpose. Part of these methods was presented in deliverable D13, another part is presented in this deliverable.

Two different approaches were chosen for evaluation of teat cleaning devices: In the first approach teats were artificially contaminated with a tracer substance and carry over of the tracer into milk was determined. The protocol consisted of applying a mixture of poppy seed and manure (20% w/w) on teats of ten cows per farm. Five cows were milked after teat cleaning and five cows were milked without a previous teat cleaning. Milk per cow was filtered through a cotton filter. The filters were dried and the poppy seed was counted.
Two farms per brand of AM system were selected by the producers/suppliers. Six brands including 12 farms and two farms with conventional milking systems were tested. Results showed significant effects of teat cleaning versus no teat cleaning and between different brands. From three brands teat cleaning was effective (more than 85% reduction in poppy seed in milk versus no cleaning) and from three other brands teat cleaning was less effective (50-70% reduction in poppy seed in milk). Conventional teat cleaning gave a reduction of 99%. Teat cleaning in practice might be less effective, because the waiting time after application was less than one hour and the adhesion of poppy seed is probably less strong than of dried manure and/or bacterial spores.

In the second approach a combination of visual evaluation of teats before and after teat cleaning, sediment tests after teat cleaning and the determination of total bacterial counts and ATP in teat swabs taken before and after cleaning was applied. 6 brands with 3 farms per brand were tested. On every farm 50 cows were sampled on two teats each.
Results showed large variation within and between individual farms. An analysis of variance showed that significant differences existed between teat cleaning efficiency of 4 brands versus 2 other brands. The ranking of brands regarding teat cleaning efficiency was similar independent of the method applied and also consistent with the results from part 1 of this study. Only for one brand deviating results were found by the combination of 4 methods. This was probably due to the fact, that no samples could be taken from teats directly after teat cleaning. The cleaning effect determined in this case was at least in part due to teat washing during milking.

The comparison of teat cleaning devices with brushes with those working with cups showed different effectiveness dependent on teat contamination level. Brushes seemed to be less effective with low level contamination, leading to a higher bacterial load on teat surfaces when teat contamination was low. With high contamination levels, brushes were more effective than cups in removing bacteria and organic material.

An analysis of variance was carried out to find out which of the factors brand, farm, position of quarter and initial contamination of teats was most important for teat cleaning efficiency. Although significant differences between brands were found, the most important factors were the individual farm and the initial contamination before teat cleaning. These findings underline the importance of management to ensure an effective teat cleaning. In the last deliverable of this work package different management factors will be evaluated regarding their influence on teat cleanliness.

From some observations during this study it can be concluded that good maintenance of the cleaning device is important for an effective teat cleaning procedure. Based on the findings from our study a pragmatic approach for evaluation of teat cleaning efficiency on farms is suggested. The procedure is based on ATP measurements with HyLite® 2 in teat swabs suspended in 8.0 ml sodium-peptone solution. 50 cows per farm should be sampled after teat cleaning at two teats each. Not more than 25 % of teats should exceed a proposed value of 3.2 Log₁₀ RLU after cleaning. This approach can also be applied on farms with conventional milking systems.

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