Managing the Sand Bedding
Cows drag sand contaminated with feces and other waste material out of the stalls on a daily basis. Therefore, it is required to refill the stall with fresh sand every 12-14 days with additional sand between these days to keep the curb from protruding (Schoonmaker, 1999). The total sand required in a US dairy is 20 to 25kg per stall per day which is equivalent to 7.3 to 9.1 tons per stall every year.
The depth of the bedding and the concavity of the middle portion of the sand influences the cow’s overall productivity and wellness. Fresh or recycled sand placed in the stalls is not compact until a cow steps and lays on it. Sand will compact the most within the first day of placing fresh or recycled sand due to the amount of air within the sand. Drissler (2010) found that daily lying times were 1.15 hours shorter in stalls with the lowest amount of bedding and for every 1-centimeter decrease in bedding, cows spent 11 minutes less time lying down. An increase in concavity for an extended period will cause lameness and hock lesions in cows. Sand must be raked to reduce the concavity. Araneda et al. (1970) obtained a correlation that for every 2.5 centimeters that the sand gets depressed, the possibility of a severe hock injury increases by 1.08 times. If a farmer is using a skid steer in the freestall barn, then a small cultivator could be placed on the side of it to loosen the layers of packed sand. Breaking the layers apart can help to reduce the amount of new or recycled sand required and help to reduce sand dampness. It has been shown that on average cows will lay down 4 more hours every day when provided with a dry lying surface (Jose et al., 2008).
Sand laden dairy manure is a mixture of two different materials, manure and sand. Since sand has lower absorbability than organic bedding, the manure management needs careful consideration. The alley floor is best cleaned with a rubber scraper blade mounted to a skid steer or small farm tractor when bedding with sand as the rubber scraper is durable and can withstand the abrasive nature of sand. Other methods currently utilized include flush cleaning with a wave of water. However, the volume of water needed to ensure proper removal of manure from the alley floors is something to consider. Length of the alley, width of the alley, slope of the alleys, and size of the sand grains determine the required volume of water in this process. Complete removal of the manure component is essential to clean the shelter, but residual sand left in the alley is acceptable as it enhances traction. Flushing is normally done when the cows are at milking parlor when the stalls are free. A slope of 2.5 to 4% (3% optimal slope) is advisable to obtain optimal flushing when sand bedding is used.
Two methods of sand separation are currently being used in the US. In the non-mechanical separators, known as the sedimentation process which is used to separate sand from manure. A sand trap is a good example of this method. These traps slow down the velocity of the flush less than one foot per second for a retention time of approximately one minute which leads to most sand and some manure to settle. These sand traps should be emptied regularly, and the sand from these traps contain some organic matter which requires further cleaning before reuse. In general, separation and recovery units are suggested to be 12 feet wide and 300 feet long with a minimum lane curb of 12 inches and a lane floor slope of 0.2%.
References: Available upon request.
Editor’s note: Part I appears in the Aug. 19 edition of DairyBusiness Digital. Both articles appear in the July issue of the newsletter published by the Texas Association of Dairymen.