Antibiotic Alternatives to Manage BRD

Project Title

Enhancing Respiratory Health of Beef Cattle Through Modulation of Innate Immunity, Analysis of the Resistome, and Identification of Culturable Bacteria

Researchers

Trevor Alexander (Agriculture and Agri-Food Canada Lethbridge) trevor.alexander@canada.ca

Tim McAllister, Wade Abbott, Nilusha Malmuthuge, Emma Stephens (AAFC Lethbridge) Michael Surette (McMaster University) Frank van der Meer (University of Calgary)

Status Project Code
In progress. Results expected in March, 2024 ANH.19.20

Background

Bovine respiratory disease (BRD) is one of the leading causes of illness and death in newly-received feeder cattle, and BRD prevention and treatment is the main reason that antibiotics are given to newly-received feeder cattle.  This team is trying to develop alternatives to antibiotic mass-treatment of feeder cattle for BRD.

Bovine respiratory disease happens when disease-causing microbes get the upper hand on the harmless or beneficial microbes that are normally found in the respiratory tract. Probiotics,  prebiotics, and postbiotics aim to support and maintain a healthy microbial population. Diamond V has developed a yeast-based product that has been demonstrated to improve immune function and help combat BRSV (bovine respiratory syncitial virus, one of several viruses that predisposes cattle to BRD) infections in newborn calves. This team wants to see if (and understand how) feeding this product helps protect feedlot cattle from BRD. This implies that gut microbes interact with microbes in the respiratory tract to help combat BRD; this communication is known as the gut-lung axis.

Objectives

  • Evaluate an in-feed immunomodulator to enhance resistance to BRD pathogenesis,
  • Characterize microbial sources of resistance genes in the respiratory tracts of cattle, and
  • Identify and bank pathogen/commensal bacterial strains isolated from the upper and lower respiratory tract of cattle, to characterize strains implicated in health and disease.

What they will do

First, they will study how the gut talks to the lung – how feeding this extract to the gut benefits respiratory health when cattle from a disease-free herd are challenged with BRD. This will be followed by a 2,400 head feedlot trial with cattle on control, yeast extract, and traditional antibiotic metaphylaxis treatments. Calves will be sampled on arrival and at 40 days for antimicrobial resistance (AMR) genes in the respiratory tract. Pulled animals will be nasal and fecal sampled before antibiotic treatment, and from lungs any cattle that die will be sampled. Differences in the microbiomes and differences in antibiotic resistance between healthy, sick, treated, and dead cattle will be compared. Animal performance, carcass traits, and rates of sickness and mortality will be compared. These samples will also be used to establish novel cultures of different respiratory bacteria to identify potential new BRD pathogens, bacteria in the healthy respiratory tract that may help protect against BRD pathogens, and characterize strain differences in virulence and antibiotic resistance among BRD pathogens. The cost-effectiveness of the yeast product will be compared to traditional antibiotic metaphylaxis.

Implications

Finding ways to cost-effectively prevent BRD while using fewer antimicrobials will help slow the rate of antimicrobial resistance, maintain the effectiveness of antibiotics, and demonstrate the beef industry’s commitment to sustainability.