PREDICTION OF EXCRETION OF MANURE AND NITROGEN BY HOLSTEIN DAIRY CATTLE

Authors: Wilkerson, Victor; MERTENS, D - 3655-30-00; CASPER, DAVID - 1265-50-00

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Increased size and production of dairy herds has increased the need for managing manure resources and improving whole farm nutrient balances. Current manure production standards for domestic livestock are based on the 1993 publication by the American Society of Agricultural Engineers (ASAE). Research was conducted to define the excretion of manure and nitrogen from Holstein dairy cattle that differed in age and milk production. A data set was developed from past experiments at Beltsville and divided into four groups: high producing cows with daily milk production greater than 44 pounds, low producing cows, nonlactating cows, and growing heifers and steers. Compared to the ASAE standards, high producing cows excreted similar amounts of manure however it contained more nitrogen. Low producing cows and nonlactating cows produced substantially less excreta than indicated by the standards. Growing Holstein cattle produced less excreta than the standards for lactating cows, but excreted more manure and nitrogen than the standards for growing beef. We found that estimates of manure production and nitrogen excretion can be improved using equations that include variables for milk production, dietary protein and fiber concentrations, body weight, day of lactation, and day of pregnancy. We concluded that current average standards are inadequate to estimate excretions of manure and nitrogen by many dairy herds. The equations we developed can be used to design manure handling and management systems that improve the recycling and balance of nutrients on dairy farms and reduce the chances of environmental pollution.

Technical Abstract: Nitrogen balance data, measured in calorimetry chambers, were compiled to define average excretion of manure and N and to developing empirical equations for estimating excretions from Holstein dairy herds varying in milk production. The data set was partitioned into four groups: 590 high producing cows, 404 low producing cows, 521 nonlactating cows, and 286 growing heifers and steers. Average excretion of manure (wet feces plus urine) for high producing cows agrees with ASAE 1993 Standards (89.0 vs. 86 kg per 1000 kg of BW/d, respectively); N excretion was higher (.542 vs. .45 kg per 1000 kg of BW/d, respectively). Excretion of manure and N for low producing and nonlactating cows were substantially lower than ASAE values, 65.9 and .399; 34.8 and .237 kg per 1000 kg of BW/d, respectively. Growing dairy animals excreted more manure (67.5 kg per 1000 kg of BW/d), and N (.447 kg per 1000 kg of BW/d) than values reported by ASAE for beef steers (58 and .34 kg per 1000 kg of BW/d, respectively), which may be related to the high- protein, forage-based diets that were fed to animals in our data set. Accuracy of estimating excretion of manure and N can be improved by using regression equations that include variables for milk production, dietary CP and NDF concentrations, body weight, day of lactation, and day of pregnancy. Accurate estimates of excreta output can impact the planning of storage and handling systems for manure and the calculation of nutrient balances on dairy farms.