Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 16, 1999
Publication Date: September 29, 1999
Citation: Rotz, C.A., Satter, L.D., Mertens, D.R., Muck, R.E. 1999. Feeding strategy, nitrogen cycling, and profitability of dairy farms. Journal of Dairy Science. 82:2841-2855. Interpretive Summary: Dairy farming in the U.S. is facing economic and environmental challenges to remain a viable industry. Profit in dairy production has decreased encouraging the growth of larger and more efficient farms. Efficiency has improved with the use of commercial fertilizer and the import of supplemental feeds. With this import of nutrients though, there is greater ropportunity for nutrient buildup in the soil and the loss of excess nutrients to ground and surface waters. Dairy producers must adopt new strategies to reduce the loss of nitrogen from their farms while reducing their costs and improving profit. More efficient use of feed protein reduces the excretion of excess nitrogen in manure and the subsequent loss to the environment. A dairy farm simulation model provides a tool for evaluating and comparing feeding alternatives to determine systems that reduce nitrogen losses while maintaining or improving farm profit. Simulations illustrate that using more expensive protein supplements that better meet the nutrient needs of animals can substantially reduce nitrogen loss to the environment and improve farm profit. These results will encourage dairy producers and dairy nutritionists to use these more expensive supplements in feeding programs. The reduction in nitrogen loss obtained will reduce the contamination of water supplies and the volatile loss of nitrogen to the atmosphere.
Technical Abstract: On a typical dairy farm today, large amounts of N are imported as feed supplements and fertilizer. If this N is not recycled through crop growth, it can lead to large losses to the atmosphere and ground water. More efficient use of protein feed supplements can potentially reduce the import of feeds and reduce losses to the environment. A simulation study using a dairy farm model (DAFOSYM) illustrated that more efficient feeding and use of protein supplements increased farm profit and reduced N loss from the farm. Compared to soybean meal as the sole protein supplement, use of soybean meal along with a less rumen degradable protein mix reduced volatile N loss by 13 to 32 kg/ha of cropland with a small reduction in N leaching loss. Using the more expensive but less degradable protein supplement along with soybean meal improved farm net return by $40 to $64/cow per year. Environmental and economic benefits from more efficient supplementation of protein were generally greater with more animals per unit of land, at higher milk production levels, on more sandy soils, or when a daily manure hauling strategy was used. Relatively less benefit was obtained when either alfalfa or corn silage was the sole forage on the farm or when relatively high amounts of forage were used in animal rations.