Texas Tech University

Researcher Awarded USDA-NIFA Grant to Develop Targeted Antimicrobial Use in Cows

George Watson

October 11, 2019

dairy cattle

Vinicius Machado will examine the underlying factors associated with metritis, a bacterial infection that affects dairy cattle leading to reduced milk production and infertility.

The use of antimicrobial drugs in food-producing animals continues to be crucial to animal health and financial sustainability. Yet antimicrobial resistance (AMR) continues to be a health concern for both humans and animals.

Being able to maintain health animals and a sustainable agricultural product while also keeping antimicrobial use at a minimum is the goal for the agriculture industry, health officials and the general public.

Vinicius Machado, an assistant professor in the Department of Veterinary Sciences in the College of Agricultural Sciences & Natural Resources at Texas Tech University, is hoping to improve the judicious use of antimicrobial drugs by predicting spontaneous cure and treatment failure of metritis in dairy cattle, one of the more common diseases for which the drugs are used.

Vinicius Machado

By identifying the novel predictors that indicate treatment outcomes, Machado hopes to develop selective treatment-management strategies that will keep antimicrobial drug use to a minimum in dairy cattle. His effort is being supported by a $464,338 grant over three years from the United States Department of Agriculture-National Institute of Food and Agriculture's Cooperative State Research Education & Extension Service.

"Within the dairy industry, treatment of metritis is one of the major drivers of antimicrobial drug usage in lactating cows," Machado said. "However, antimicrobial therapy changes the outcomes of clinical cure in only 20 percent of metritis cases. Our objective is to identify cow-related factors that can be used to predict which metritis cases likely will benefit from antimicrobial therapy."

Machado is joined on the project by Michael Ballou, chairman of the Department of Veterinary Sciences and an expert in ruminant nutrition and immunology, as well as researchers Klibs Galvao from the University of Florida, Fabio Lima from the University of Illinois and Noelle Noyes from the University of Minnesota.

Metritis is a painful, postpartum uterine bacterial infection in dairy cows associated with decreased levels of milk production and fertility. It is one of the major drivers of antimicrobial drug use in lactating cows, most often the drug ceftiofur, a third-generation cephalosporin.

The World Health Organization considers ceftiofur as a drug of highest priority to public health, and its use needs to be reduced when at all possible. Plus, studies have shown that more than half of all metritis cases are cured on their own with no need for antimicrobial drugs, and cows show no sign of the disease two weeks after initial diagnosis. Ceftiofur treatment, however, has a failure rate of up to 26 percent, resulting in an approximately 20 percent difference in cure rate between treated and untreated cows.

Therefore, finding the cow-related factors that can be used to predict metritis cases that will benefit from antimicrobial drug use is crucial to determining which cows should receive antimicrobial therapy.

Machado feels he will be able to identify the metabolic, inflammatory and immunological markers associated with metritis cases that will likely be cured with antimicrobial treatment and where treatment failure happens.

Machado said recent studies have shown that metritic cows treated with ceftiofur have better fertility than cows left untreated, but there was no difference in milk production between the two. So, the feasibility of any targeted treatment strategies developed from this study will depend on economics and drawbacks of AMR development associated with metritis therapy. Data on AMR associated with metritis treatment with ceftiofur is scarce.

"Upon completion of this project, robust evidence on the potential economic benefits and antimicrobial resistance drawbacks due to ceftiofur treatment of metritis will be readily available to stakeholders and lawmakers," Machado said. "That will be instrumental to evidence-based decisions towards metritis treatment protocols and policies."