Improving animal comfort in the cold of winter and heat of summer is primary for beef producers in the upper Midwest. That's why mono-slope barns are becoming more popular. Because mono-slope barns are so new to the region, a group of researchers studied environmental quality aspects of these systems at four mono-slope finishing operations in northeast South Dakota and northwest Iowa.
"We spent eight months studying each facility," South Dakota State University environmental quality engineer, Erin Cortus, told participants at a beef facilities conference in Sioux Falls, S.D., recently. According to Cortus, they were researching primarily air quality comparisons between mono-slope structures utilizing the bedding pack manure handling system and a scrape system.
For the purposes of the study, in the pack system, bunk aprons and edges surrounding the pack were scraped weekly and bedding was added to the pack until the cattle were marketed. In the scrape system, all bedding material and manure was removed weekly.
Temperature and air flow were factors Cortus said impacted air quality in the barns. The studies measured five gases including ammonia, hydrogen sulfide, methane, carbon dioxide and nitrous oxide during month-long periods in each barn during fall, winter, spring and summer over a two-year period. Particulate matter or dust was also measured.
"There was greater variability on gas emissions in the pack system compared to the scrape system," Cortus said. "Under the pack system, there was more particulate matter during the bedding event, but bedding events are short-lived."
Overall, within the barns, both scrape and pack systems seemed to operate well within standardized air quality guidelines. "And the barns were lower in particulate matter than open lots," she said.
The study found that gas concentrations within the barns were greatest during animal activity, peaking between 7 a.m. and 9 a.m. and 8 p.m. and 9 p.m., because of the disruption by the animals of the manure or pack surface.
As would be expected, as airflow increased through the barns, gas concentration decreased, said Mindy Spiehs, USDA Agricultural Research Service animal scientist at U.S. Meat Animal Research Center.
Most mono-slope buildings are oriented east and west, taking the best advantage of seasonal winds to provide natural ventilation inside the barns. Normally, mono-slope barns are operated with the curtain open during the summer months, and closed at least partially during the winter to improve animal comfort. Higher air flow and increased curtain opening lessens gas concentration within the barn, but increased airflow increases the emission of gases like ammonia, hydrogen sulfide and methane to the outside, she explained.
"The biggest impact on emissions is by the position of the curtain," said Spiehs. "But, keep in mind that air quality in the barns is only a tiny piece of production decisions."
She said that in future studies they would like to look at the reasons certain barns operate the way they do, how to predict gas emissions from the barns and how producers can positively change air quality in and around the barns. They would also like to look at the differences in air quality attributed to different bedding materials.
You can learn more about the air quality studies by contacting Cortus at 605-688-5144 or Spiehs at 402-762-4271.