Managing manure in a composting bedded pack
Dairymen have several options for dairy cattle housing: tie-stalls, free-stalls, pasture, composting bedded pack or a combination of methods. No matter what the system, manure management is always a factor in keeping cows clean and healthy.
During the North American Manure Expo, OMAFRA Livestock Specialist Christoph Wand presented information on composting bedded packs for dairy cows. Wand said that while the system isn’t for everyone, it’s an attainable alternative to tie-stalls.
“Managing the pack is like managing another animal,” said Wand. “You need to recognize the signs of what’s going on. Anybody can compost in summer – the challenge will be winter.”
When describing the system, Wand emphasized the term “composting” to clarify that the pack isn’t just a bed of compost – it’s alive and contributing to the barn environment.
Wand reviewed composting basics. “The composting process is the function of microbial action in the pack,” he said. “It’s based on carbon (sawdust) as the energy source balanced with nitrogen which comes from manure. One of the most important things to manage is the carbon-to-nitrogen ratio.” The goal of proper composting in a bedded pack is to produce heat, which helps rid the pack of water.
Wand added that heat also helps control pathogens that influence udder health.
He explained that the surface temperature of the pack is not related to the temperature at depth and recommended measuring the pack temperature at one foot. He suggested using a probe to measure the temperature in several places throughout the pack.
A properly managed composting bedded pack should result in relatively clean cows. Assessing animals for cleanliness involves selecting several animals and examining them for wet spots, staining and the condition of teat ends. Udders and flanks should be clean.
Barn design affects the performance of composting bedded packs. Two options for design are continuous access, which allows cows to move from the pack to the feed alley from any point. Gates separate cows from the pack for cultivation or cleanout. Limited access design includes gated openings for cows to access the pack area. With limited access, cow traffic can result in wet access points and may require extra bedding.
Wand explained that given urine output and the wet nature of cow manure, the barn design should allow 120 square feet per cow. “We need to blow off half a liter of water per square foot of pack per day,” he said. “This moisture has to leave either through chimneys or vents, via the scraper alley or the barn has to have the ability to accumulate [moisture] in the bedding, which is not really feasible.”
The pack can easily be checked for moisture content. Wand suggested picking up a wad of compost material from the pack, compressing it into a ball and tossing it down. If the moisture level is reasonable, the ball should shatter completely. Wand said some dairy farmers do a complete pack clean in winter, but added that this can be avoided with proper management.
The expo included a virtual tour of Canadian dairy farmer Dale Martin’s Margrove Holsteins during which Dale and his son Ian discussed what they’ve learned about managing a composting bedded pack over the past five years.
Before deciding to construct a composting bedded pack barn, they toured several compost barns. “The sick cow pens in those barns were empty,” said Dale. “We’ve been very happy with herd health and have lost very few cows to injuries. It replicates cows on pasture as close as it can.”
The barn at Margrove Holsteins is 85 feet wide by 460 feet long, and there’s a reason it’s long. “We took a long, narrow approach for easier ventilation to get as much air moving over the pack as possible,” said Ian. “We built for the future – we’re able to milk 165 cows; currently we’re milking 110.”
The Martins work the pack twice a day, first lengthwise then in a circular motion to get as many passes over the pack as possible. This action moves oxygen to the bottom of the pack and helps moisture move out of the pack to evaporate. The result is less additional bedding and sufficient heating for good composting action.
In winter, the Martins add fresh bedding to the pack once a week, with bedding amounts based on the weather. “We work the pack harder in winter,” said Ian. “We take more passes over the pack to keep the evaporation going in the cold, wet winter months. Another important thing to do in a pack barn is to ventilate – you have to be aggressive with ventilation to get humidity out of the barn and get good air exchange.”
The scrape alley on one side of the barn is 12 feet wide and 412 feet long. The Martins run the scraper every two hours to help reduce wear on the scraper and improve hoof health. They’ve noticed fewer cases of mastitis because cows’ feet are cleaner.
Ian explained that the pack is 50 feet wide, and between the scrape alley and the pack is a curb that allows manure to spill over into the scrape. He noted that while the pack builds up over winter, it shrinks in summer due to better composting action.
“The shrinking naturally pulls the material up … as we cultivate the pack,” said Ian. “We don’t need to add any bedding because the pack shrinks and we pull the dry bedding from the bottom.”
Dairy farms with composting bedded packs have several options for working the pack. The Martins use a cultivator with 24-inch shanks to work the pack to 12 inches deep. Their goal is always to move wetter material to the top and allow moisture to evaporate, which keeps the pack “working” and saves bedding.
A liquid manure tank holds scraped liquid manure and wastewater from the milk house. In spring, manure is spread on corn ground and on alfalfa. The Martins use a solid manure spreader to spread new sawdust on the pack.
by Sally Colby
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