With the correct management approach, dairy farmers are finding they can successfully bed stalls with manure solids.
Readily available sources of separated manure solids, coupled with new technology, have renewed dairy farmer interest in using this material for freestall bedding. The concept often produced poor results in the past, but farmers are now achieving success with the right management techniques.
Recent anaerobic digester installations on Ontario dairy farms provide them with a continuous source of separated manure solids. Producing separated solids with drum composters is also becoming popular. Like so many aspects of dairy farming, much of the success and failure comes down to management. Let's take a closer look at using manure solids to bed cows.
Anaerobic digesters produce stall bedding as byproduct
Anaerobic digestion breaks down organic material by microbial action in an oxygen-free environment. It produces a mixture of methane and carbon dioxide called biogas, used to generate electricity. Another product is a nutrient-rich slurry called digestate. You can dewater digestate to produce livestock bedding. Ontario dairy farmers with anaerobic digesters have been dewatering digestate by passing it through a screw press or roller press. They produce a bedding product with 65 to 68 per cent moisture.
They spread the separated solids fresh to avoid heating in a storage pile. The bedding works best when spread in a two-inch layer four or five times per week to avoid heating in the stalls. One producer notes the separated solids have very fine particles that will stick to teat ends. It is important to clean udders thoroughly before milking.
Drum composters speed up manure composting process
During composting, a natural biological process, micro-organisms break down plant or animal material in aerobic conditions. A drum composter speeds up the process by drawing oxygen through the material while constantly turning and mixing it. This process can create an alternate bedding material from manure.
First you process liquid manure through a screw press to reduce separated solids moisture content to 68 per cent. Depending on the amount of manure to be processed, the screw press is set on a timer to run a certain percentage of the time.
Dewatered material is then loaded into a rotating drum that draws in air to feed the micro-organisms. The compost in the drum reaches a temperature of 65 to 70 degrees Celsius (150 to 160 Fahrenheit), killing most weed seeds and pathogens. The material usually passes through the rotating drum in two to three days.
Experience has shown the compost is best used as bedding every day or two. If you store it too long, it will start to reheat. You can spread it quite liberally in the stalls to a depth of about two inches.
Use bedding fresh for best results
Regardless of the process you use to source manure solids for bedding, it is important to use the separated solids fresh and not let them sit in a pile too long. If stored for more than two to three days, they will start to re-heat. A few dairy farmers are considering drying solids before using them as bedding.
You can spread separated solids in stalls several times per week in a twoinch- thick layer-a bucket slinger works well. Since moisture causes this material to start reproducing bacteria, removing it from the stall when it gets wet is important.
Whether separated from anaerobic digestate or from manure and then composted in a drum, these solids are working well for the Ontario dairy producers using them. The key is managing them properly.
Recycled manure experiences show some mixed results
Experiences using recycled manure for bedding have been well documented by veterinarians, producers and researchers. Dr. Kenn Buelow, a producer-veterinarian, has described experiences on two separate dairy farms in Wisconsin with a plugflow digester at each. Solids were separated from the manure after it passed through the digester.
The experience was mostly positive with a somatic cell count of 185,000 at one farm and 100,000 at the second.
The outcome on a New York state operation, documented by veterinarian Dr. Peter Ostrum, turned out differently. The farm had been using sand bedding and switched to manure solids for environmental reasons. The solids were separated directly from manure and then left to heat in a pile and used within three weeks of storage.
They observed a dramatic increase in coliform mastitis. Consequently, they discontinued manure solids use and returned to sand bedding.
Dr. Marcia Endres, associate professor of dairy science at the University of Minnesota, recently studied 38 dairy farms in Minnesota, Wisconsin, South Dakota and Iowa. One of the objectives was to describe animal welfare in dairy operations using recycled manure solids for bedding.
The study looked at the welfare assessments for lameness prevalence, hock lesion prevalence and hygiene. Preliminary results indicated the study barns were generally similar to sand-bedded freestall barns and appeared to offer good cow comfort. Lameness prevalence averaged 17.1 per cent across all farms. Barns with deep-bedded recycled solids had 14 per cent compared to 18 per cent for barns with mattresses. The prevalence for barns with mattresses was less than in previous studies. The 60 per cent overall average for hock lesions was between the lower levels of sand-bedded barns at 28 to 32 per cent and the higher levels in mattress barns with other types of bedding at 68 to 75 per cent. Only five per cent of the cows in deep-bedded barns studied had severe lesions, or swollen hocks, slightly lower than sand at seven to nine per cent. Only compost barns, at 0.5 per cent, had a lower incidence.
The SCC information has not been tabulated for all the herds, but appears to average around 300,000 with the lowest herd at 180,000. More study data still has to be summarized and analysed, but preliminary results indicate solids can be a satisfactory freestall bedding option, Endres notes.
References: Buelow, Kenn. How to Make Digested Manure Solids Work in the Midwest. Proceedings of the National Mastitis Council 47th Annual Meeting. January 20-23, 2008. New Orleans, Louisiana; Endres, Marcia. Use of recycled 'fiber' bedding in freestall barns. Published in Dairy Star February 5, 2010; Endres, Marcia. Overview of Trends in Use of Manure Solids and Compost Bedded Packs. Proceedings of the National Mastitis Council 47th Annual Meeting. January 20-23, 2008. New Orleans, Louisiana; Ostrum, Peter. Sand and Recycled Manure: Headaches and Train Wrecks in the Northeast. Proceedings of the National Mastitis Council 47th Annual Meeting. January 20-23, 2008. New Orleans, Louisiana
Harold K. House is OMAFRA's engineer,dairy and beef housing and equipment,based in Clinton, Ontario.
This article first appeared in the February 2012 Milk Producer magazine.
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