Recommendation: Minimises labour and material costs, suitable in some situations. See Horse Bedding for a comparison to other options.
There are three main approaches to mucking out:
The deep bedding approach is most commonly used with straw. One approach is simply to put a thin layer of fresh bedding on top of the soiled bedding, then remove all the bedding periodically (e.g. once per month) and start again. The other approach is to remove the feces, then add a small amount of fresh straw. The former approach is typically used with cattle and the latter approach (which is rather cleaner) is typically used with horses.
If one puts a moderate amount of straw in the stable, it becomes soaked with urine and must be removed to prevent the horses from lying in their own urine. The deep bedding system avoids this, by having a thick layer of bedding which allows the urine to run through to the bottom, while leaving a thick layer of dry straw on top. Consequently, horses can urinate in their stalls for weeks on end and yet the straw they lie on remains dry.
With this method, if one removes the feces, one need add a little straw each day (or even just a couple of times a week) for the horse to have a dry and clean bed to lay on. Consequently, the bedding consumption is very low and the labour involved in mucking out the stalls is very low. Of course, one must periodically remove all the straw and this is a substantial job when it is done. However, averaging the labour and bedding over the long term, it is a very economical approach.
When replacing the straw, rather than add a large amount of straw to begin with, one should add only a moderate amount at first and allow the horse to trample it down before adding more. If one adds too much straw at first, the bedding is unstable (allowing the feet to twist or turn) and tends to lead to strained or stressed ankle or knees.
One issue with deep bedding is that the urine builds up at the bottom of the bedding. Although the top is dry and comfortable to lie on, the urine underneath can lead to ammonia buildup (a potential heath hazard) and odours. To avoid this, one should only use deep bedding in well ventilated stalls. Some stable owners leave the stable doors open during the day to allow the stalls to air but then lock the horses in and close the doors at night, allowing the ammonia to build up to unacceptable levels. Therefore, one should ensure that there is sufficient ventilation even when the horses are locked in and the doors are shut.
Another issue is that the warm and wet conditions at the bottom of the bedding can result in fungus growth and the release of spores. Although this is undesireable for all horses, it should specifically be avoided with horses that have allergies to fungus.