Timothy Hay is the most-recommended hay for rabbits. It looks like a dried blade of grass, fairly wide and its color is a soft green to grey/brown green. Timothy hay also has "solid cattails" which distinguishes it from Orchard grass which has "broken cattails." Much of the Timothy is imported from Northern states (Oregon or Washington). Timothy hay is included in all of our mixed boxed hay.
Orchard Grass is very similar in appearance to Timothy but the "cattails" have small segments missing from them every 1/32 of an inch. Also the cattails tend to be pale brown, whereas Timothy cattails are green to light yellow. Orchard Grass makes a large part of the hay boxes we pack for the community.
Oat Hay consists of large hollow cylindrical stalks and flat blades that are golden yellow to light green with oats on the end. The coloration and the presence of oats distinguishes this hay from others. Oat hay can vary widely in appearance and oat count, depending on the harvest season. New harvests are generally oat laden, whereas later harvest such as Dec-Feb can be very light, with minimal oats. Many people confuse Oat hay with Straw. The similarity is in the coloration. Straw is not a food source, but is typically used for bedding, mostly in the horse and farming communities. Oat hay is an excellent source of fiber. Bunnies tend to enjoy mostly the oats, but will sporadically munch on the hay stalks.If bun's diet is high in oat hay, the pellets she produces will be larger, lighter in color, and will look like sawdust if crushed. Many bunnies would benefit from eating more oat hay, an excellent preventative for GI Stasis. HRS boxed hay may contain oat hay or other fiber rich types to provide variety.
Bermuda Grass is a good all around food source with a moderate amount of calories. Bermuda grass contains the same nutritional content as Timothy or Orchard grass, so these can be fed interchangeably. The thing about Bermuda grass is that rabbits don't care for it very much. They don't find it as appealing as Orchard or Timothy hays.
Alfalfa is distinguished by stalks, usually brittle and flat green to brown leaves. Very high in calcium, can cause "sludge" in bunny's urine. High calories. Watch for gummy droppings, weight gain, sludge, and cecal pellets not being eaten. These are usually problems of the older (2+ yr. bunny). Hay can vary from dark lime green to yellow/green/brown depending on the season. There is almost always some alfalfa in HRS boxed hay. Alfalfa is easy to come by in San Diego County. Many horse people feed alfalfa, but a strict alfalfa diet for bunnies can lead to some of the problems listed above. HRS recommends a mixture of hay varieties and "not" a diet high in alfalfa hay.