Project Number: 1902-13000-009-02
Project Type: Reimbursable

Start Date: Dec 01, 2002
End Date: Nov 30, 2005

Objective:
The overall objective of this project is to develop feeding programs for lactating dairy cows using common ration formulations that can result in a minimum amount of manure P. We expect a 30-35% reduction in manure P excretion compared to current feeding practices. Previous work of some of the principal investigators of this project demonstrated that a reduction of manure P excretion is possible. The proposed project will expand this research to include the influence of several common feeding practices on manure P excretion. It will also address the mechanism of fecal P excretion through which a reduction in manure P can be obtained by manipulating feeding practices. The developed feeding programs will be evaluated based on animal performance, manure P excretion, soil P loss when applied to cropland, and overall farm performance and economics. This project will engage multidisciplinary expertise in a collaborative effort to develop dairy feeding strategies that help dairy producers minimize the environmental consequences of their operation while sustaining their animal husbandry and farm profitability. The specific objectives are: 1. Determine the effect of alternative dairy feeding practices on the amount and chemical form of P excreted in manure; 2. Assess the potential P loss in runoff for the different manures applied to soil; 3. Develop a routine manure testing method for environmental risk assessment based upon the chemical form of P; 4. Assess the long-term effects of these feeding and manure management practices on dairy farm production, economic viability, and nutrient losses using a whole-farm simulation model (DAFOSYM).

Approach:
Controlled feeding studies will be conducted at Penn State's Dairy Cattle Research and Education Center. Runoff studies will use field plots and simulated rainfall. Dietary treatments will include: low P-low forage, low P-high forage, high P-low forage, and high P-high forage. The dietary P levels will be 0.38 and 0.48% and the forage levels will be 48 and 58% of the diet on a dry-matter basis. The sources of forage in all treatments will be alfalfa silage, alfalfa hay, and corn silage. Corn will be the major concentrate source of the diets and will be steam-flaked to enhance rumen fermentability. Thirty-two early to mid lactation cows will be individually fed for 15 weeks. Feed intake and milk yield will be recorded daily. Fecal and urinary samples will be and analyzed for P content. Chromic oxide will be used as an external marker to quantify fecal P excretion. Manure from each of the feeding trials will be used in the manure P composition and surface runoff studies. Manure samples will be collected and analyzed at monthly intervals during the feeding trial to determine the effect of change in diet on manure P composition. Surface runoff trials will be conducted using field plots established in our research watershed, FD-36 (a sub-watershed of the Mahantango Creek) and a portable rainfall simulator, using national protocols already standardized for this equipment. Extensive runoff and watershed studies are ongoing in this watershed, which will provide supporting information on transport potential and watershed impacts relevant to this project. We will develop a simple manure P test based on water extractable P concentration of the manure, by assessing the effect of various methodological components on manure water extractable P estimation in collaboration with Penn State's Ag. Analytical Services Laboratory. Results of this study will yield a recommended environmental P manure test for use by agricultural analytical laboratories, which will have wide applicability in current national efforts to rank site vulnerability to P loss and target field for manure management that will minimize P loss in runoff. Information obtained from the animal feeding and nutrient loss experiments will be used to further develop and calibrate a whole-farm model (DAFOSYM). This model simulates crop production, feed use, and the return of manure nutrients back to the land over many years of weather. The model will be used to evaluate whole farm impacts (performance and economics) of feeding changes. Simulations will include farms with enough cropland to utilize available manure nutrients and supply the majority of the feed needed for the herd, as well as farms with limited crop acreage and a dependence on imported forage and grain feeds. Farms will be evaluated for a location in Central Pennsylvania. Soils common to this area will be used where the predominant soil on the farm will vary from soils high in clay content to those with a more coarse texture.

Project Team

Sharpley, Andrew Rotz, Clarence - Al

Project Annual Reports

FY 2003

Related National Programs

Water Quality & Management (201)   Manure and Byproduct Utilization (206)