Compost Bedded Pack Dairy Barns in Ohio

Dr. Lingying Zhao, Extension Dairy Veterinarian, Ms. Amanda Douridas, and Ms. Mary Wicks, Department of Food, Agricultural, and Biological Engineering, The Ohio State University

Most Ohio dairy operations use liquid manure systems, which require careful management to minimize manure runoff and can have high costs associated with transport of manure that is up to 90% water.  For dairy farms to remain economically viable, production systems that improve the health of the cow, minimize manure-handling costs, and reduce potential environmental impacts are needed. If you are a dairy farmer who is investigating alternative manure management systems, a compost bedded pack dairy barn may be an option for you. The compost bedded pack dairy barn is an alternative system with solid manure handling options (Figure 1). Its potential for positive impacts on milk production and cow health, as well as the ability to handle manure as a dry material, have resulted in increased interest.

Figure 1. Compost bedded-pack dairy barns in Ohio.

The compost bedded pack dairy barns had been evaluated by the University of Minnesota (UMN) over the last several years. The Ohio State University (OSU) and the University of Kentucky have conducted preliminary research to analyze the design and management recommendations; document current practices; and evaluate milk production, animal health, indoor air quality, and manure handling of the bedded pack dairy system.

Four Ohio dairy farms using a compost bedded pack system were studied by OSU researchers to assess the barn design and collect data from the farmer on pack and manure handling practices and cow health. Farm visits were made in four seasons during 2008-2009 to monitor air quality, collect bedded pack samples, and record management practices and cow health. 

Barn Layout and Management Practices        

The four study farms generally used the layout and management recommendations developed at the University of Minnesota for compost bedded pack dairy systems. The barns were designed to provide adequate space for all cows to lie down with space available to get up as needed, to enable composting of the manure and pack, and to provide ventilation that compensates for the heat generated from the pack. All barns had a separate feed alley and resting area and a good design for natural ventilation. The sidewalls were high with plenty of openings for good air movement. Some had fans for summer cooling. All farms stirred the pack twice daily and reported adding sawdust every 10 to 14 days when the pack became moist enough to stick to the cow.  For two farms, cows were on pasture during the summer, so the pack was stirred less frequently.  All farms experienced difficulty in obtaining sawdust during the winter months due to availability and cost.  Recommended practices for feed alley scraping and complete barn clean out were generally followed.

Indoor Thermal Environment and Air Quality

In the four barns, average indoor temperature ranged from 28 to 78 oF over a year; average relative humidity ranged from 35 to 90%; and average air velocity from 0.2 to 1.8 m/s. Barn temperature varied with outdoor weather changes and was out of the cow’s comfort zone in summer. Barn relative humidity was within the cow’s comfort zone for most barns, and at most times, except for two barns, the barns had high relative humidity in the spring and fall. Air velocity in barns varied significantly with the season and between barns. Higher air velocity in warmer seasons can enhance cow cooling and water evaporation from the bedded pack.  Air velocity is an indicator of good natural ventilation and management.

Carbon dioxide (CO2) concentrations in the barns ranged from 400 to 700 ppm throughout the whole year, with higher CO2 concentrations in winter due to reduced side-wall openings. Ammonia concentrations (NH3) fluctuated significantly in seasons from 0 to 1.6 ppm in the barns. Hydrogen sulfide concentrations ranged from 1 to 12 ppb with lower concentrations in warm seasons because of wide opening of the side walls, and for the two farms using pasture, the lower concentrations resulted from reduced time inside. In reference of the Occupational Safety and Health Administration (OSHA) indoor air quality standards and the National Institute for Occupational Safety and Health (NIOSH) indoor air quality recommendations, all the gas concentrations were well below the suggested indoor air quality thresholds (25 ppm ammonia and 10 ppm hydrogen sulfide).  This indicates that there is no air quality concern in the compost bedded pack dairy barns.

Composting of Bedded Pack

The average bedding temperatures of approximately 90 to120°F indicates composting (microbial activity) was occurring.  Higher temperatures of 140 to160°F observed in many commercial composting systems were not achieved, probably because of the shallow bedded pack depths (typical compost piles are 6 to 8 feet or more). Oxygen concentrations were at 7 to 9%, well below ambient levels (21%) and another indicator of composting.  These concentrations have been found to be adequate to allow aerobic composting with little offensive odors. The pH values of the bedded pack ranged from 7.9 to 9.6, which indicates that the composting was aerobic in nature since anaerobic activity would produce an acidic compost.  

The NPK values of the bedded pack manure at clean out were analyzed.  The nutrient concentrations on a dry basis of 1.8 to 3.3 for N, ~1 for P2O5, and 2 to 3% for K2O would be considered average to above average compared to most compost. Assuming a 2.5:1:2 fertilizer analysis and approximately 65% moisture for the pack material at clean out, each ton of compost would supply 17.5, 7, and 14 lb of N, P2O5, and K2O per wet ton, respectively. 

Cow Performance, Health, and Comfort

The farmers reported improved feet health, better milk quality, and improved milk production. The cows were consistently much cleaner in the composted bedded pack barns than cows in the traditional bedded pack barns of the past. All farmers reported satisfaction with the new system from a management perspective, as well as cow health and comfort.   

A Multi-State Workshop on the Bedded Pack Dairy Systems

A multi-state workshop educational program was held on Dec. 5th in Ohio, Dec. 12th in Tennessee, and Dec. 13th in Kentucky.  Presentations and video recordings were uploaded to http://airquality.osu.edu/workshops/index.htm. These are an excellent resource for those unable to attend the workshop but interested in more information.

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