The choice of bedding is steeped in as much tradition as saddlery. Every horseperson has his preference. Some like the smell of sweet cedar shavings, some the traditional look of a deep straw bed, while others prefer the softness and absorbency of peat moss. But which bedding is really best for your horses?
In a study conducted at the Equine Research Centre in Guelph, Ontario, Canada, five different beddings were put to the test. The main criterion was absorbency. Theoretically, the more absorbent a bedding is, the lower the levels of moisture (promoting mold growth) and ammonia (a noxious gas that irritates the airways) there should be in the barn. This should improve the respiratory health of the horses. Absorbent beddings also tend to be less dusty and easier to muck out because the soiled bedding clumps together, aiding removal and perhaps allowing less bedding to be used overall.
Researcher Susan Raymond compared straw, shavings, peat moss, hemp fibers and shredded paper in her absorbency test. When water was added to 10 grams of each bedding material, shredded paper came out the clear winner, absorbing 100 milliliters, as compared to hemp (45 ml), shavings (30 ml), and peat moss (30 ml). The most traditional bedding, straw, was the least absorbent of the samples, soaking up only 25 ml of water.
Bedding and Respiratory Health
Paper, being the most absorbent substance, might protect the horse from ammonia. To do so, it must "hide" and "trap" ammonia. It will take further testing to confirm this feature of paper.
Molds, on the other hand, thrive in moisture so paper bedding should reduce molds if it is removed promptly. Herein lies one of the problems of a highly absorbent substance for bedding. Because it is so absorbent, the moisture accumulates in spots, exposing the horse to clumps of moist bedding, unless it is meticulously managed.
Maximum Absorbency Brings Added Weight
Of course, with maximum absorbency comes a downside: added weight. Anyone who has mucked out a truly soaked stall can attest that it can become backbreaking labor. In this regard, shredded paper might be a liability because Raymond's study showed that at maximum water absorption it could increase its weight by a staggering 900 percent. By comparison, hemp - at its maximum absorption level - increases by 400 percent, peat moss by 300 percent, shavings by 250 percent and straw by 225 percent.
Also, you can make your straw or shavings just as absorbent as paper, by adding three times as much, which is typically done. The use of more straw adds other benefits of course, such as greater floor padding, less direct contact of the horse to the moisture, and a "thermal barrier" from the ground.
Molds in Bedding
Other studies performed by the ERC's respiratory health research team have indicated that when it comes to mold, straw comes out the loser, harboring hundreds of times more mold spores than other beddings even when it appears clean and bright.
Mold is incorporated into straw at baling time, originating from the natural environment and the grass itself. Moisture present at baling time increases mold growth. Straw that was bailed very dry will harbor much less mold than straw that was baled damp. You can't smell or even see the mold in many cases, as the spores (dormant stage of the mold) are microscopic. The significance of mold of course is that it can be breathed in, causing inflammation in the airways, leading to cough, exercise intolerance, and worse, heaves.
Bedding Mares and Foals
Straw is still the bedding of choice, however, for foaling mares. Most farms find that straw is far less irritating to the mare and newborn foal and the stall much easier to clean afterward. The foals like to sleep in the straw and get some thermal protection from the cold ground when it is thickly bedded. Straw allows the moisture to seep through, so there is less direct skin contact with urine on straw. Within a week of foaling, many farms switch the bedding to wood shavings or another clean, absorbent bedding.
Horses That Eat Bedding
Straw is a favorite snack of some horses, and because it is so dry, the horse needs to drink more water. If a horse really goes for the straw, it may promote digestive problems (e.g. impactions) if they're not used to it. It may also substitute for more nutritious feeds.
Disposal of Beddings
In terms of compost, straw breaks down faster than other types of bedding, with the possible exception of hemp. Shavings and shredded paper, in particular, may not significantly change their composition on your manure pile for months or years.
All of these factors may have a bearing on which bedding you choose. But you also will have to take into account local availability, cost, your storage facilities and the type of horses you're housing.