Non-Antibiotic Alternatives for Bovine Mastitis Therapy

Non-Antibiotic Alternatives for Bovine Mastitis Therapy

Summary

This project aims to develop intra-mammary, non-antibiotic alternatives to treating mastitis in organically and conventionally raised dairy cows.  We determined the minimum inhibitory concentrations of Manuka honey for E. coli and Streptococcus isolated from cows with clinical mastitis.  The MICs obtained with Manuka honey are likely too high to be able to achieve needed concentrations of honey in the quarters of cows with clinical mastitis.  Hence, we redirected our efforts to involve essential oils from plants that have been shown to have very good antibacterial properties.

Objectives/Performance Targets

The objectives of this project are to:

1. To determine the minimum inhibitory concentration (MIC) of Manuka honey and guava leaf extract to bacteria commonly associated with bovine mastitis. 
2. To establish in-animal safety of candidate formulations and in-milk inhibition metabolites residue depletion
3. To determine cure rate of mild to moderate clinical mastitis in dairy cows using candidate formulations

Work towards completing Objective 1 was performed during 2013.  The first objective of this NCR-SARE project was to assess the in-vitro effect of Manuka Honey and Guava Extract to inhibit the growth of common mastitis pathogens isolated from dairy cows with clinical mastitis.  To accomplish that goal, we proposed to determine the minimum inhibitory concentrations (MIC) of Manuka Honey and Guava Extract for bacteria causing clinical mastitis in dairy cows.  We were not able to identify a source of Guava extract that was consistent in quality and quantity.  

The MICs obtained for Manuka honey ~6-8% (weight/volume) are likely so high that we would not be able to obtain high enough concentrations of the honey in the udder of dairy cows to reach the MIC  needed.

To compensate for the loss of Guava extract and Manuka honey as viable options for treatment of mastitis, we initiated a search for other viable options.  We identified several essential oils that appeared to have much lower MICs than Manuka honey.  These oils include: oregano oil, two constituents of oregano oil; carvacrol and thymol, and trans-cinnamaldehyde.

Manuka honey may still be pursued as a potential emollient for intra-mammary solutions containing mainly essential oils.  In future work we will focus on these essential oils as targets for non-antibiotic treatments of mastitis.

Accomplishments/Milestones

We determined the MICs for Manuka honey to 18 E. coli and 15 Streptococcus isolates, respectively.  We also determined the MICs of these isolates to the antimicrobial drug cephalothin and mock honey (a solution of different sugars). 

For E. coli isolates, the MIC was 6%, 8% and 12% for 11, 6 and 1 isolates, respectively.  The MIC was 6% for all Streptococcus isolates.  Two isolates with a Manuka MIC of 6 or 8% were resistant to the antibiotic Cephalothin.

The project did not progress entirely as expected, because we realized that we would very likely not be able to achieve high enough concentrations of Manuka honey in the udder of a lactating cow in order to treat an infected quarter(s).  Likewise, we were not able to find a high quality Guava product.  However, we identified viable alternatives in the form of essential oils (liquid containing volatile aroma compounds from plants). 

In 2014 we will determine the minimum inhibitory concentrations of close to 100 mastitis pathogens to oregano oil, thymol and carvacrol, and trans-Cinnamaldehyde.

In the upcoming reporting period we will assess the minimum inhibitory concentrations of close to 100 mastitis isolates, and we will initiate the safety trials for intra-mammary application of the essential oils.

Impacts and Contributions/Outcomes

Mastitis is the most common health condition requiring management on both conventional and organic dairy farms.  The cost of each case of mastitis on a dairy averages $155.08 per each episode and is estimated to cost the entire US Dairy industry $1.7 – 2 billion each year.  Vaccinations to reduce the occurrence and/or severity of mastitis, adequate hygiene throughout milking procedures and sanitation in cow housing are effective control methods common to both organic and conventional dairy farms.  Conventional dairies commonly rely on antibiotics to prevent new cases of mastitis during the cow’s non-lactating (dry) period and to treat clinical cases of mastitis during lactation, however antibiotics are not allowed for use in organic dairies under the US National Organic Program.  Both organic and conventional dairy producers would benefit from the development of new non-antimicrobial alternatives to bacterial infections in livestock.  These reasons are based on the intense scrutiny of antimicrobial drug use in animal agriculture because of antimicrobial resistance issues, a decrease in market incentives for developing new antimicrobial drugs, and the growing antibiotic-free segment of the dairy industry.  Hence, developing the described non-antibiotic alternatives to mastitis treatment in dairy cows may increase the sustainability of the dairy industry.  During this year we did not participate in outreach activities.

In 2014 Bo Norby gave a presentation on this work at the NCR-SARE Farmers Forum, held in conjunction with the Ohio Ecological Food and Farm Association (OEFFA) Conference. A video recording of this is available through NCR-SARE’s YouTube channel at: https://youtu.be/Ovz4d5xBwQY?list=PLQLK9r1ZBhhGr9RLwfvRvJLEtHJOLdXZz

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