ARS | Publication request: PREDICTING NUTRIENT EXCRETION BY DAIRY CATTLE

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: August 3, 1999
Publication Date: N/A

Technical Abstract: Increasing milk production and herd sizes has increased difficulties in planning whole farm nutrient and manure management systems. Current manure production and nitrogen (N) excretion standards for livestock are based on estimates provided by the American Society of Agricultural Engineers (ASAE). The ASAE standards are estimates of average manure productions and compositions for dairy cows that are often used for planning new or expanding existing facilities and designing manure management programs for farms. Type of dairy cow, stage of production, and quality of diet influence manure production, but these factors are not considered in current standards. We compiled data collected during net energy experiments in the Energy Metabolism Unit of the USDA-Agricultural Research Service at Beltsville, MD to: (1) define the average manure production and N excretion of Holstein cattle, (2) develop equations for estimating manure excretion that use easily-obtainable animal and diet characteristics, and (3) estimate the annual manure production and N excretion for Holstein dairy herds with various levels of milk production. Our data indicates that using ASAE standards for dairy and beef cows may lead to inaccurate estimates of manure storage requirements for modern dairy herds that are producing more than 16,000 lb/yr. More accurate estimates are obtained by using equations that adjust manure production and N excretion for differences in herd production and ration characteristics. Our new equations indicate that lactating cows in a herd producing 21,000 lb/yr would excrete 14% more manure than current standard estimate. Providing more accurate estimates of manure output would improve our ability to design storage facilities and manage manure use on modern dairy farms.