Case Study: Effect of alley floor scraping frequency on environmental mastitis-causing pathogen counts

Abstract Text:

The objective of this case study, conducted at the University of Kentucky Coldstream Dairy from August 21, 2013 to September 29, 2013, was to determine if increased alley scraping frequency decreased teat end and milk environmental mastitis-causing pathogen counts (EMC). Sixteen Holstein cows were monitored during 2, 3-week treatments; removing manure from the alley floors once (1X) or twice daily (2X).  Milk and teat end swab samples were collected twice weekly to observe changes in EMC and somatic cell score (SCS).  The GLM procedure of SAS (SAS Institute, Inc., Cary, NC) was used to evaluate fixed effects of treatment, parity group (1 or ≥ 2), and DIM group (≤ 150 or > 150) and their interactions on  teat end and milk Escherichia coli, total coliform, Klebsiella spp., and streptococci counts, with cow as subject.  Stepwise backward elimination was used to remove non-significant interactions (P ≥ 0.05) and all main effects were kept in each model regardless of significance level.  The CORR procedure of SAS was used to evaluate the correlations between all study variables.  LSMeans (± SE) indicated increased scraping frequency decreased milk sample total coliform count from 0.30 to 0.05 ± 0.09 log₁₀ cfu/g (P < 0.05).  Likewise, teat end total coliform, E. coli, and streptococci counts decreased between 1X and 2X; 2.11 to 1.56 ± 0.14 log₁₀ cfu/g, 1.86 to 1.30 ± 0.14 log₁₀ cfu/g, and 5.06 to 4.10 ± 0.19 log₁₀ cfu/g, respectively (P < 0.01).  Increased scraping frequency did not significantly affect SCS, milk E. coli, streptococci, and Klebsiella spp. counts, or teat end Klebsiella spp. counts (P > 0.05).  Teat end total coliform and streptococci counts were moderately correlated with the same bacteria counts within the milk (r = 0.53, P < 0.01 for both species).  Milk streptococci counts were moderately correlated with SCS (r = 0.40, P< 0.05).  Because increased scraping frequency decreased EMC, which could reduce intramammary infection risk, this practice could reduce mastitis caused by environmental mastitis-causing pathogens.

Keywords: scraping frequency, pathogen counts, environmental mastitis