Investigating the main mastitis causing pathogens plaguing Western sheep flocks

University of Wyoming, Department of Animal Science

Project Report

Performance Narrative: To date, we have accomplished all sample collection on this project and

are approximately 50% complete with sample laboratory and statistical analysis. Graduate

student, Ryan Knuth, has completed quantifying the prevalence of subclinical mastitis in this

research program set of ewes. He has also completed antimicrobial susceptibility testing of milk derived

bacterial isolates and quantified the cure rate of the weaning treatments in the study

design. Microbial DNA isolation is nearly complete on all samples and we are preparing those

samples for metagenomic sequencing. These samples will provide a robust picture of the

common pathogens causing mastitis in Western sheep flocks as well as address impacts on the

milk microbiome, antimicrobial susceptibility, and insight into potential managements strategies

to mitigate mastitis.

Activities Performed

# Accomplishment/Activity Relevance to Objective

1 - Continuation of laboratory work: microbial DNA extraction completed on bedding samples, DNA of milk and bedding samples prepared for library pooling and sequencing.

Samples are being prepared for sequencing and microbial species identification.

2 - Subjected select bacterial isolates to antimicrobial susceptibility testing. Identified levels and types of antimicrobial resistance in additional milk-derived bacteria isolates following preliminary results.

3 - Published and presented on a conference proceedings paper at the Western Section of the American Society of Animal Science annual meeting in October 2021.  Presented results pertaining to prevalence of subclinical mastitis and antimicrobial resistance to a scientific-minded population.


# Challenge or Development Corrective Action or Project Change

1 - SARS-CoV-2 Pandemic supply chain disruptions

The global pandemic and associated repercussions have caused disruptions to production and distribution of laboratory supplies, resulting in delays in laboratory work. Also, inflation is impacting  the scientific communities and the cost of supplies has increased.

  # Outcome/Indicator Quantifiable Results

1 - Quantify prevalence of subclinical mastitis Quantified prevalence of subclinical mastitis from milk bacterial culture data using 212 milk samples accumulated over each sampling time point

2 - Quantify bacterial resistance against commonly used antimicrobial agents Preliminary data from bacterial isolates indicate antimicrobial resistant bacterial isolates are derived from ewe milk

3 - Quantify the cure rate of subclinical mastitis following treatment at weaning.  Preliminary data from bacterial isolates of ewe milk show subclinical mastitis prevalence does decrease following treatment with penicillin at weaning and/or reducing the plane of nutrition for 2 days prior to and 3 days post-weaning.

# Activities Anticipated


1 - Finish antimicrobial susceptibility testing on streptococci (waiting on lab supplies expected to ship in late December).

January 2022

2 - Laboratory analyses: extract and sequence microbial DNA from lamb and ewe rumen fluid samples.

January 2022

3 - Bioinformatic analyses on sequenced samples May 2022