August 21, 2018

 

Antibiotics degrade faster in composted manure, says study

 

 

Research conducted by the Agriculture Canada's Lethbridge Research Centre has found that composting manure reduces the concentration of the compounds formed from the antibiotics taken by livestock.

 

About 1.6 million kilogrammes of antimicrobials are used every year in Canadian livestock, and 30% to 90% of the products may be excreted as original compounds or byproducts called metabolites.

 

The Lethbridge Research Centre tested raw manure, stockpiled manure and compost to see which antibiotics were present, how quickly they degraded and if potential antimicrobial-resistant genes appeared in environmental bacteria after these products were spread on cropland, The Western Producer reports.

 

The study concluded that composted manure reduced the concentration of the compounds in the antibiotic products, as well as lessened any potential environmental impact.

 

Broad spectrum antibiotics

 

Cattle in feedlots were fed the broad-spectrum antibiotics chlortetracycline, tylosin and sulfamethazine at the recommended rates.

 

These products can be broken down in the animal's digestive system and can end up in manure.

 

Studies found chlortetracycline had a half-life of 15 to 20 days in the compost; this means 50% of the concentration decreased in 15 to 20 days.

 

Tylosin had a half-life of about 30 days, and sulfamethazine 32 days.

 

If these were applied directly to the land, the compounds could last 121 days, said Srinivas Sura, an analytical chemist and toxicologist who was part of the project.

 

The study concluded that dissipation of antimicrobial-resistant genes was higher in composted than stockpiled manure.