Profile of clinical and subclinical mastitis pathogens isolated from cows housed on compost bedding

Abstract Text: Compost bedding has been increasingly used worldwide. The organic nature of the bedding calls for investigations regarding the role and diversity of pathogens causing intramammary infections in cows housed in this system. The objective of this longitudinal study was to describe the distribution of mastitis pathogens isolated from cows housed on compost bedding. Three farms were visited monthly between May 2013 and January 2014. Farms A, B and C had 33, 53 and 145 lactating cows and used peanut shell, sawdust and wood shavings as bedding, respectively. Bedding was cultivated twice a day with new material added to the barn twice a month. Quarter milk samples were collected monthly from a sample of high SCC cows (> 200,000 cells/mL) in each heard and from all cases of clinical mastitis. Pathogens were grouped as environmental streptococci (Streptococcus uberis, Streptococcus dysgalactiae and Enterococcus spp), CNS (coagulase-negative staphylococci), coliforms (Escherichia coli, Klebsiella spp and Enterobacter spp) and others (Serratia spp, Pseudomonas spp and Bacillus spp). The average monthly prevalence of subclinical mastitis (based on SCC) per farm was 39.6, 44.0 and 43.5% for farms A, B and C, respectively. The distribution of culture results for subclinical mastitis (N = 469 quarters) was: negative: 39.4%; Corynebacterium bovis: 19.0%; CNS: 10.2%; environmental streptococci: 9.4%; Staphylococcus aureus: 6.2%, Streptococcus agalactiae: 6.0%; contaminated: 4.9%; coliforms: 3.2%; other: 1.3%, yeast: 0.2%, and Prototheca spp: 0.2%. Culture results for clinical mastitis (N = 128 quarters) were: negative: 34.3%; coliforms: 16.4%; C. bovis: 9.4%; Strep. agalactiae: 9.4%; contaminated: 8.6%; CNS: 7.8%; environmental streptococci: 7.0%; other: 3.9%, and Staph. aureus: 3.1%. The most prevalent coliforms causing clinical and subclinical mastitis were E. coli (67% of 21) and Klebsiella spp (74% of 15 cases), respectively. Preliminary results suggest that the distribution of pathogens was similar to those previously reported in Brazil for farms that used other bedding materials such as sand or pasture. Prototheca spp was isolated from one cow on Farm C. Nocardia spp infections were not found and the prevalence of other pathogens of concern such as Serratia spp and Pseudomonas spp was low.            

Keywords: milk quality, mastitis, compost bedding