Dust, or what regulators call particulate matter, is a significant issue for feedyards and dairies, with implications for animal health and community relations. During last week’s Academy of Veterinary Consultants conference in Colorado Springs, Brent Auverman, PhD, a professor of biological and agricultural engineering with Texas A&M AgriLife, presented results of research into air-quality options for livestock operations.
Auverman notes that feedyards typically experience an “evening dust peak,” which is the primary target for overall dust reduction. Several factors contribute to peak levels of airborne dust in the evening. Cooler temperatures encourage cattle activity – walking and playing – that stirs up dust, and pen surfaces typically are at their driest level of the day at this time. Also, a temporary atmospheric temperature inversion often occurs in the evening, holding much of the airborne dust close to the ground. Dust emissions during this time can reach eight to 15 times the average levels for the day.
The evening peak does not typically occur in dairies, largely because milking schedules tend to distribute animal activity throughout the day.
Dust emissions are a function of pen-surface dustiness and animal activity, so managers can reduce emissions by managing one or both of those factors. Sprinkler systems are an effective tool for managing pen surfaces, but they are expensive to install and water availability can be a limiting factor.
Auverman and his team designed a research trial to evaluate stocking density as a means of reducing dust in feedyard pens. Concentrating animals in a pen can help shade the pen surface, reduce activity and concentrate urine and manure to keep the pen surface moist.
The researchers used a pen-surface assessment system to score the potential for pens to create dust emissions, using a scale of A through F, with A representing a well-packed pen surface and F representing a surface covered with an inch or more of fine, non-compacted manure. An additional designation of W designates a wet surface with virtually no potential for dust emissions.
They set up the trial with control pens stocked at a normal density of 150 square feet per animal, and treatment pens double-stocked at 75 square feet per animal. They then modified an ATV, using an optical device for measuring airborne dust and a GPS recording system. Researchers drove the ATV down an alley bordering the downwind side of the single-stocked and double-stocked pens at a consistent speed several times each day.
In this trial, double stocking reduced dust emissions by 60 to 80 percent during peak periods. During the trial, the researchers never recorded a W rating in single-stocked pens, or an F rating in the double –stocked pens.
Auverman believes additional observations probably will result in reductions averaging closer to 50 percent.
Auverman summarized his presentation by outlining three management options for reducing dust emissions.
- Manure harvesting – Timely pen scraping still represents one of the best ways to minimize dust.
- Sprinkler systems – These can reduce dust emissions significantly, but cost and water use are high.
- Stocking density manipulations – Increasing stocking rates during the dusty season can reduce water-use requirements and extend the benefits of rainfall events. Cross-fencing with electric wire can increase stocking density in the pen while preserving bunk space per head.