Today most dairy producers planning new facilities will at least consider sand bedding as an option. They will talk to other producers, salesmen and other experts and discover a love/hate relationship toward this particular technology. The one thing all do agree on is that sand is definitely different. It has some clear benefits and a definite downside as well.
One benefit claimed by producers working with sand is a lower incidence of clinical mastitis caused by environmental organisms such as E. coli. and environmental streptococci. While there is no clear research data on this, a lower incidence of clinical mastitis would be logical since no organic bedding is used and there would be less opportunity for bacterial growth. Producers also claim their somatic cell count goes down when they switch to sand, but a recent survey of herds in newer barns in Wisconsin showed no difference in average SCC between herds using sand or mattresses. This outcome probably reflects the fact that coliform infections are frequently clinical and therefore result in milk being withheld from bulk tanks.
Herd bulk milk SCCs may not be the appropriate measure of the impact of sand on environmental mastitis. Sand may only be part of the solution to environmental mastitis. It is not able to overcome poor milking practices, ventilation and barn hygiene. Nonetheless, the survey results are a bit surprising in light of strong producer testimonials.
Clear benefit of sand bedding include the reduction in the number of cows with swollen hocks, hair off hocks, and knee injuries. Field surveys in Ontario showed 9% of cows with swollen hocks on mattresses and many more with hair off, in comparison to none on sand.
Producers also report better footing and fewer problems with slipping in alleyways. They claim this leads to fewer injuries and stronger heat signs. Along with the better traction, there appears to be more uniform hoof wear. While there is no research, field experience suggests less trimming is needed with sand bedding.
Proponents of sand bedding also claim that sand bedded stalls are more comfortable. However, the research does not support this claim. One published study compared 3 inches of sand over clay with a mattress and the cows preferred the mattress. A properly designed sand stall has 8 to 10 inches of sand and there are no studies to indicate if the preference for mattresses would remain with this deeper base of sand. In any event, there is no evidence of stall refusal with sand, so the level of comfort appears to be adequate.
Stall construction is cheaper by $60-80 since the need for a mattress and 30 square feet of concrete are eliminated. Operating costs using sand at $8 to $10 per tonne are also low compared to organic bedding at $40 to $50 per tonne.
Many producers argue straw is free and readily available. While they will have a hard time with $40 per tonne, the real costs of handling and storage may be this high even if the straw is free.
The economics of sand bedding are not all positive. Elaborate manure systems and extra wear and tear on equipment may cost as much or more than the savings described above.
Stall Design and Management
Stall design and management with sand bedding requires careful attention to detail. A 4-row tail to tail layout is not recommended for sand bedded barns, since no sand gets in the alley at the manger and there will be a large difference in traction in this alley. The freestall should include a 6 or 8 inch curb with a rounded top edge, and 45 degree slope to the inside of the stall to ensure there is always sand between the rising cow and the curb. The base of clay, or packed screenings should be at least 6 to 8 inches below the curb. This assures there is always a minimum of 6 inches of sand in the stall. Most producers refill as soon as sand level is 1 to 2 inches below the curb.
Stalls should be standard length and can be a bit narrower than with other bases. Producers report good results with Holsteins in 45-inch wide stalls. Most are not using a brisket board and locate the headrail 48" above the height of the curb. This makes it lower than normal when new sand is added. Since sand is added infrequently, stalls have a lot of slope and low neck rails after sand is added and this gradually changes to a level stall, exposed curb and higher neck rail. The changing configuration at the front of the stall is a frustration for some producers and is the main reason brisket boards are not used.
Typically, cows kick 20 to 25 Kg of sand per day out of each stall when the level of sand is above the curb and 10 to 15 Kg when it is below the curb.
Common management practice is to fill the stall with a skid steer, dumping a full bucket in each stall. To facilitate this, alleys must be wide enough for turning. Mid size machines will need at least 9 feet. Machines with a long bucket are needed to dump in the front half of the stall and avoid the need to move the sand forward. The sand is added once every 3 to 4 weeks and is at least 6 or 7 inches above the curb right after filling. Stalls filled to this level result in a lot of sand being kicked out but decreases the labour of stall cleaning since cows kick the manure out with the sand. Stalls with sand below curb level can become very difficult to keep clean, so regular filling and maintenance is a must. Between fillings the back of the stall should be cleaned daily like any other freestall. Leveling the stall with a rake periodically is also recommended to keep it comfortable. A common practice is to do the leveling under suspended partitions with a small cultivator attached to the side of the skid steer bucket.
Adding sand to the stalls is labour intensive and it is difficult to distribute evenly with the skid steer. Many farms have invested in sand slingers to do this job. The simplest are 1 to 1.5 cubic yard front-end loader buckets, which cost $3000 to $6000. These are scooped full at the pile, and then emptied with a belt in the bottom that throws the sand out the side of the bucket as you drive along the back of the freestalls.
Since one yard only does a few stalls, larger farms often choose trailer slingers with a 3 to 6 yard capacity and a price tag of $20,000 to $25,000. Loaded, these trailers weigh 14 to 20 tonne, so floors, and especially slatted gutters must be constructed to handle this load. One goal of putting sand in the stalls with a slinger is to put in less sand and do it more often to keep the stall just above level full. This should reduce the amount of sand in the manure without sacrificing cow comfort.
Some producers and suppliers are trying to reduce sand use by putting in various types of sand traps. The cheapest and most common is 4 whole and 2 half tires, open to the rear curb, bolted together throughout the row of stalls and placed on the base so the side is just below curb height. The entire row must be bolted or lagged together with heavy lag screws to ensure cows do not dig out individual tires. In Western Ontario, a tire recycling company can supply and install these tires for a small fee. Commercial products to trap sand are also available but there is no data available on how well these work. One company offers a mattress system they install 3 to 4 inches below the curb, which maintains comfort while reducing sand use.
Sand used in stalls should be clean and free of soil particles. Silt and clay will cake up and turn to mud in the stall. Sand must be free of stones, especially small sharp ones that can become embedded in cows hooves. Most producers are happy to pay the extra for screened sand.
Sand will stick to cows udders, especially if it is very fine. To remove this sand at milking, wiping with a damp or spun dry cloth towel, used for a single cow and washed between milkings, is preferred. Just like at the beach, a little sand does get into everything, including filters, bulk tanks, and vacuum pumps, so plan for extra wear especially to the washing machine used for the towels.
Manure handling is the biggest challenge in sand bedded barns. In the barn, tractor scraping is the simplest option. While there is more wear on the floor and scraper than usual, with a rubber scraper this is not a serious concern. Mechanical alley scrapers will wear a track in the center of the floor where the cable or chain runs. When pouring the floor, a thicker layer of concrete will prevent sawing the floor in half with the chain, but even so, be prepared to fill this groove with concrete every 5 or 6 years.
Most producers with sand barns are replacing scraper cables annually. Despite this cost, their experience with chain scrapers is worse, since chains cut a deep groove in the floor and do not last much longer than cables. In long barns using several scraper units that shuttle the manure, and using flat bar instead of chain or cable for sections that do not go around corner wheels, reduces maintenance cost, but leaves piles of manure in the middle of the barn for cows to walk through.
Flush barns with sand require at least 2 to 2.5% slope to keep heavy sand moving in the flush liquid. Holding areas washed with a hose cause sand to separate from the manure so many designs include a collection trench at the bottom of the holding area to catch the liquid and drain it off. The trench is usually cleaned manually to remove sand whenever it is full.
In the barn, tractor scrape systems may dump directly into the storage located across the end of the barn. Alley scrapers (or tractors as well) can dump in a deep trench across the center or end of a barn but unless there is a way to remove settled sand this trench will eventually fill up. A ramp into it will work, but to save the cost of ramping both this pit and the storage, many producers locate the storage near the barn, ramp the storage and design the collection gutter so it is big enough to drive into from the storage. Stable cleaners are also used to move and laden manure across the barn to the storage, but tend to wear out quickly. A better choice are augers specially designed for the sand and gravel industry which never touch the sides of the trench and run below half full, thereby minimizing wear. Transfer systems involving gravity flow pipes have tended to plug and are not recommended. Specially designed ram pumps have been used successfully. So have sloped pipes washed daily with manure liquids.
The design of the manure storage needs to include the ability to clean out separated sand. Removing this with a high hoe is one practical option, but this restricts the width and depth of storage to twice the reach of the largest locally available hoe. As an alternative, the storage can be designed to permit a loader tractor and V box manure spreader to drive into the storage. This means a concrete floor throughout the storage and a ramp with a slope not more than 12 to 15 %. Such a ramp is very costly since it is 50 to 60 feet long. On a round tank, it changes the reinforcing parameters to require a much stronger footing.
When handling the sand manure mixture be aware that added water and agitation cause sand to separate. When handling it as a pumped liquid, do not add extra water and do not over agitate. This material reacts to water and agitation in a manner completely opposite to manure without sand. Most producers just pump with minimal agitation and then scoop out what is left with semi solid equipment.
Systems to separate sand from manure either prior to or in the storage are mostly experimental. The McLanahan sand/manure separator is one device that works well. It consists of an auger system that washes sand out of the mixture in the boot. Clean reusable sand goes up the auger while manure spills out over the side of the boot. In very large herds the $40,000 cost may be recoverable by reusing the sand. Currently, no one in Ontario is using this technology because of the high cost.
One flush barn in southwestern Ontario is successfully washing sand out of manure by trapping the flush in a shallow basin after it leaves the barn. This basin drains slowly so that sand and some manure solids stay behind. Although this has worked well to date, a more severe winter may cause a problem with this system.
A scrape barn with a flushed settling pit to transfer manure to long term storage is on the drawing board, as well as a project involving a raceway style gutter and a special storage designed to encourage separation through agitation and settling. There are also a number of barns with multi stage storages or transfer gutters with walls in them to encourage sand separation but most are too new to provide any answers at this stage.
Sand applied to the land is not thought to be detrimental. Over a lifetime the amount of sand added to fields through manure application will not be enough to change the soil type.
The use of sand bedding in tie stall barns has a lot of extra challenges. Most tie stalls are not well designed for bringing sand in. As well, stable cleaner wear is a big issue. In tie stalls smaller amounts of sand must be added more often, and the height of the manger must be at least as high as the sand in the front of the stall. Sand in box stalls also does not work well because the box stalls are very difficult to keep clean. Most producers with sand barns use box stalls with a sand base and a layer of straw on top.
There have been sand bedded barns in Ontario for more than twenty years, so not all of this technology is new. However, there is definitely a lack of research and a need to find answers to some very clear challenges, especially in manure handling. These circumstances and the current strong interest in this technology make it an important area of work for OMAF dairy housing specialists, such as Harold House and Jack Rodenburg. Both have extensive experience with sand barns and are working with producers and contractors to develop and evaluate new solutions.
By Jack Rodenburg - Dairy Production Systems Program Lead/OMAFRA
Government of Ontario Ministry of Agriculture, Food and Rural Affairs