This post is part of the Science Tuesday feature series on the USDA blog. Check back each week as we showcase stories and news from the USDA’s rich science and research portfolio.
News by USDA’s Agricultural Research Service (ARS) indicates that moving dairy cows out of climate-controlled barns and onto the land may help to lessen the ecological impact of dairy farming without any corresponding loss of production.
A team of ARS scientists in University Park, Pa., conducted a modeling study that evaluated how different management systems on a typical 250-acre Pennsylvania dairy farm would affect the environment. The scientists collected a range of field data and input it into their model to evaluate the environmental dynamics of four different dairy farms in all types of weather over 25 years.
All four systems were set to produce the same amount of milk, adjusting for fat and protein, on the same land. The model generated estimates for ammonia emissions from manure, impact on the soil including erosion and leaching of nitrates, and phosphorus losses from field runoff.
Total emissions for the greenhouse gases methane, nitrous oxide, and carbon dioxide were 8 percent lower in year-round outdoor production than with cows tucked away in the barn. Keeping dairy cows outdoors all year reduced the dairy operation’s ammonia emissions by about 30 percent.
While barn-bound cows were estimated to each produce 22,000 pounds of milk per year, compared to only 13,000 pounds per foraging cow, the total amount of milk protein and fat produced was essentially the same. That’s because the foraging cows produced milk that contained more fat and protein.