Author
 |
Powell, Joseph |
|
Submitted to: Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 5/7/2014 Publication Date: 5/7/2014 Citation: Powell, J.M. 2014. What dairy cows are fed impacts manure chemistry and the environment. In: Proceedings of the Advanced Topics in Feed Mangement Meeting, May 8, 2014, Pennsylvania State University Extension, Lancaster, Pennsylvania. p. 1-45. Interpretive Summary: Technical Abstract: Over the past 20 years or so there has been increasing evidence and concern that nutrients contained in animal manures can adversely impact water and air quality. Research has demonstrated that the diets fed to dairy cows can be modified to reduce nutrient excretions in manure and environmental impacts. In Wisconsin, we found that the mineral phosphorus (e.g., mono-sodium phosphate, di-calcium phosphate) added to dairy cow rations had no impact on animal performance but increased the concentrations of total phosphorus (P) and soluble P in manure, which increased P in runoff from fields after manure land application. Increases in manure P excretions due to mineral P supplements also increased the cropland area dairy farmers needed to spread manure. Manure P increases due to excessive ration P also elevated the P to nitrogen (N) ratio (P:N) of manure. When manure land applications are based on crop N requirements, this elevated P:N ratio leads to excessive manure P applications, which increases soil test P levels. The simple practice of adopting National Research Council’s recommendations related to concentrations of P in rations would reduce the land area in positive P balance on Wisconsin dairy farms by approximately two-thirds, which would greatly facilitate P-based Comprehensive Nutrient Management Plans (CNMP). The type and amount of crude protein (CP) and forage fed to dairy cows also impact manure chemistry and manure N cycling in soil, including plant N uptake. Ammonia emissions from soil after manure application can be related back to the urea N excreted by dairy cows in urine, which is linked to the concentrations of CP in cow rations and the type of forage fed. Our recent dairy nutrition research revealed that adding small amounts of a tannin extract [a mixture from red quebracho (Schinopsis lorentzii) and chestnut (Castanea sativa) trees] to a typical TMR did not significantly impact animal performance but increased feed N use efficiency (amount of feed N secreted as milk N) and decreased urea N excretion. Using the excreta produced by cows on this nutrition trial, recent lab-scale trials revealed that reduction in urea N excretion and urease activity in feces due to tannin extract feeding leads to dramatic decreases in NH3 emissions from dairy barns and soils after slurry application. Overall research results demonstrated that profitable rations could be fed to satisfy the nutritional demands of healthy, high producing dairy cows, reduce manure excretion and therefore facilitate environmental compliance by the dairy industry. |
