Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 18, 2001
Publication Date: November 20, 2001
Citation: Soder, K.J., Rotz, C.A. 2001. Economic and environmental implications of four levels of concentrate supplementation in grazing dairy herds. Journal Of Dairy Science. 2001. v.84(11). p. 2560-2572. Interpretive Summary: Economic and environmental concerns are stimulating changes in dairy production. Inflation-adjusted milk prices have remained stable or declined for many years, but the cost of production inputs have continued to increase. As sustainable dairy farms are developed for the future, changes must be made to improve their productivity, profitability, and environmental impact. Low cost pasture-based forage systems are a viable management alternative to more traditional stored forages for dairy producers. Grazing dairy cows typically decreases input costs, but at the same time decreases milk production. Supplementation of these grazing cows decreases forage demand and increases milk production to more acceptable levels. However, maximum profitability may not occur at the highest level of supplementation due to the law of diminishing returns. A systematic whole farm analysis was done to determine how varying the level of concentrate supplementation to grazing dairy cows impacts farm productivity, profitability, and nutrient balance. A grazing dairy farm was simulated with four levels of supplementation, and then was compared with a similarly sized confinement farm that fed stored forages. In general, profitability increased as level of supplementation increased in the grazing herds, but at a decreasing rate with each successive level of supplementation. Increasing level of supplementation had a mixed impact on nutrient balance of the grazing farm. The loss of nitrogen to leaching was decreased on the grazing farms, but soil phosphorus accumulation tended to increase when more supplement was imported on the grazing farm.
Technical Abstract: Low cost pasture-based forage systems are a viable management alternative for dairy producers. A whole farm analysis was conducted to evaluate the potential long-term environmental impact and economic benefit of varying the level of concentrate supplementation on spring-calving grazing dairy farms. Representative dairy farms were simulated with various production strategies over 25 years of historical Pennsylvania weather using the Dair Forage System Model (DAFOSYM). A representative grazing farm was simulated with four levels of concentrate fed to the lactating cows. These farm systems were then compared to a confinement system on the same land base where total mixed rations were fed. The five systems were simulated for three scenarios. In the first scenario, total milk sold/farm was similar across all systems. In the second scenario, cow numbers were held constant across all farms, and total milk sold/farm varied. In the third scenario, stocking rate was adjusted so that forage consumption matched forage production on the farm. Profitability increased as supplementation level increased in the grazing systems, but at a decreasing rate with each successive level of supplementation. At higher levels of supplementation, the grazing dairy farms showed greater profitability than the confinement systems. Economic risk or year-to-year variation also decreased as concentrate supplementation level increased. The grazing systems showed an environmental benefit compared to the confinement systems by decreasing the loss of nitrogen by leaching. Concentrate supplementation of grazing lactating dairy cows provided an increase in profitability and a mixed impact on nutrient balance of the farm.