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22 Biological quality of drinking water for dairy cows - A risk oriented evaluation of influencing factors


 Despite its importance, legal regulations and official guidelines regarding the quality of livestock drinking water are rather unspecific. The study aimed to investigate biological livestock drinking water quality considering influences of risk factors and relations to biofilm development and hygiene status of dairy troughs. On 24 dairy operations in Western Germany, 105 troughs were sampled. Water and biofilm were analyzed for aerobic total viable count (TVC), coliform count (CC), Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamases building bacteria (ESBL). 33 possible influences on biological water quality for each trough were either recorded or inquired. The troughs surface was examined with protein- and adenosine triphosphate (ATP)-rapid tests for hygiene. A mixed model and Spearman rank correlations (SAS 9.4) were used for estimating the probability of quality impairment in relation to recorded influences. Average TVC in water samples was 4.4 log10 cfu/ml. Coliforms were detectable in 94.3% of all troughs and E. coli in 48.6%. CC seems to be a more sensitive and suitable indicator to check fecal contamination because 16 water samples were positive for CC (>2.0 log10 cfu/ml) but negative for E. coli. MRSA were found in livestock drinking water of a single, and ESBL on three farms, suggesting that troughs might contribute to an exchange of antibiotic resistant bacteria in some dairy farms. Risk factors (P < 0.05) for at least one quality criteria (TVC, CC or E. coli) were water origin, trough type, degree of trough soiling, visible biofilm, ambient temperature and distance to the milking parlor. Water CC (r = 0.46; P < 0.001) and E. coli (r = 0.31; P < 0.01) correlated with their equivalent in biofilm and with hygiene tests on trough surfaces (0.31 >r >0.19; P < 0.05). Biological livestock drinking water quality can be improved by addressing the risk factors and be monitored with hygiene tests.