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J Appl Microbiol. 2019 Apr 22. doi: 10.1111/jam.14288. [Epub ahead of print]

Fate of Mycobacterium avium subsp. paratuberculosis and changes in bacterial diversity populations in dairy slurry after chemical treatments.

Author information

1
Instituto de Medicina Preventiva Veterinaria.
2
Escuela de Graduados, Facultad de Ciencias Veterinarias.
3
Instituto de Investigaciones Agropecuarias (INIA), Centro Regional de Investigación Remehue, Osorno, Chile.
4
OMICS, Valdivia, Chile.
5
Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
6
Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin, Madison, USA.

Abstract

AIMS:

A major drawback of using dairy slurry as fertilizer is that it may contains pathogens such as Mycobacterium avium subsp. paratuberculosis (MAP), and it could represent a risk to animal and public health. Thus, the aim of this study was to evaluate the fate of MAP and bacterial communities in dairy slurry after chemical treatments.

METHODS AND RESULTS:

Cattle slurry, naturally contaminated with MAP, was collected from a dairy herd and divided into 32 glass bottles which were assigned to eight different treatments (control, 3.0% CaO, 0.5% NaOH; 0.087%, 0.11% and 0.14% H2 SO4 ; and 1.0% and 2.5% KMnO4 ). Treated dairy slurry samples were evaluated at 0, 1, 3, 7, 15, 30- and 60-days following treatments application for viable MAP and dairy slurry pH, and in addition temperature in this material was monitored continuously. Bacterial counts were estimated at each sampling time. A Bayesian zero-inflated Poisson mixed model was fitted to assess the effect of each treatment on the count of MAP cells. Model results indicated that only the 3.0% CaO treatment had a statistically important negative effect on MAP counts during the study period. For most treatments, MAP was undetectable immediately after chemical treatment but re-appeared over time, in some replicates at low concentrations. However, in those cases MAP counts were not statistically different than the control treatment. Regarding the fate of the other bacterial populations, the Firmicutes phylum was the dominant population in the un-treated slurry while Clostridia class members were among the most prevalent bacteria after the application of most chemical treatments.

CONCLUSION:

Only 3% CaO treatment had a statistically important negative effect on MAP viability in cattle slurry.

SIGNIFICANCE AND IMPACT OF THE STUDY:

This study provides evidence of MAP partial control in dairy slurry. This information should be considered as a best management practice to reduce MAP and other pathogens for slurry management on dairy farms. This article is protected by copyright. All rights reserved.

KEYWORDS:

Dairy cattle; Mycobacterium avium subspecies paratuberculosis; chemical treatment; dairy slurry, Firmicutes; pathogens

PMID:
31009147
DOI:
10.1111/jam.14288

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