WASHINGTON – How oxytetracycline (O.T.C.), an antibiotic that is administered to animals, breaks down in cattle manure is being studied by Scott Yates, Agricultural Research Service (A.R.S.) scientist, writes the agency’s Ann Perry.
In the U.S., livestock producers often use antibiotics to control disease in their animals, and confined U.S. livestock and poultry generate about 63.8 million tons of manure every year. The drugs are often only partially absorbed by the digestive tract, and the rest are excreted with their pharmaceutical activity intact.
In controlled laboratory conditions, O.T.C. in cattle manure was degraded more quickly as temperatures increased and as the moisture content in the manure increased, Mr. Yates, who works at the A.R.S. Contaminant Fate and Transport Research Unit in Riverside, Calif., found. But as water saturation levels neared 100%, the O.T.C. breakdown slowed. Mr. Yates concluded this slowdown resulted when oxygen levels were not high enough to fuel the O.T.C. biodegradation.
O.T.C. breaks down more quickly in manure than in soil, Mr. Yates also noted. Compared to soil, manure has higher levels of organic material and moisture, which support the microorganisms that break down this pharmaceutical.
Ms. Perry writes this laboratory research may be useful in designing studies that evaluate the potential effects of lagoons, holding ponds and manure pits on bacteria and antimicrobial resistance.
Livestock producers may also use results from this study to maximize the breakdown of organic materials and potential antibiotics in manure by designing storage environments with optimum temperatures and moisture levels, she concluded.