Having a Hay Day

By educating owners of small herbivores about the importance of grass hay in their pets’ diets, retailers can help ensure the health of these popular pets.


Having grown up in the country, I am very familiar with the difference between hay and straw, so I easily spotted an error in a movie I was watching recently. Straw is stiff and brittle, and usually yellow or tan in color, whereas hay is supposed to be green, soft and pliable. Hay is specifically grown as food that can be dried and stored for herbivores, such as cows and horses, as well as small rabbits, guinea pigs and chinchillas kept as pets. Straw, on the other hand, is composed of the stems remaining from grain after the plants are harvested, and the grain seeds removed, and contains very little nutrition. So, when I watched the movie Big Top Peewee and saw Peewee mixing straw instead of hay into his specially concocted food mixture for his farm animals, I was both appalled and amused—but not necessarily shocked. 

Not all pet owners—or movie-screen farmers—know the best way to feed their animals, especially those who own herbivores, and it is up to retailers to educate their customers as to the best food for each type of pet. Most people who own rabbits, guinea pigs and chinchillas know they are herbivores and only eat plants. But there is much more to their specialized digestive systems than most people realize. The most important fact is that these animals’ systems are designed to eat a lot of fiber, so it is imperative that they do eat a lot of fiber. It is necessary to keep the digestive system working normally.

The first evidence of this is in their molars, which grow constantly. If they didn’t, the tough fiber in their diets in the wild would quickly wear away their teeth. This constant growth also means that if these animals don’t eat enough fiber, their molars may overgrow. Overgrown molars can damage the inside of the mouth, causing pain, difficulty eating, slobbering or drooling, and weight loss.

After the food is chewed and swallowed, it passes through the stomach and small intestines. Then it reaches the next specialization: the cecum. A large sack attached where the small and large intestines meet, the cecum is the equivalent to our appendix. But unlike our tiny appendix, the cecum is so large it takes up most of the space in the abdomen. This is where much of the actual digestion occurs. The cecum contains special bacteria and microorganisms that help digest fiber that mammals cannot digest themselves. Because of this, these herbivores are called “hindgut fermenters.” 

Lots of fiber is required to keep the food moving through the digestive tract. A lack of fiber can cause sluggish digestion, resulting in bloat, gastric stasis and cecal impaction leading to enteritis, a potentially fatal bacterial infection of the intestines. In rabbits, a lack of fiber in the diet can also result in the formation of hairballs from the fur they ingest while grooming, which can cause blockages. Lots of fiber is also necessary to keep the proper balance of bacteria in the cecum and large intestines. If the diet contains too many starches or sugars, such as found in grains or fruit, this can upset the balance of these bacteria and result in enteritis.

Grass is Good
Rabbits and guinea pigs also have a unique way of metabolizing calcium that is different than other animals (including chinchillas). These animals absorb all the calcium in their food and then excrete excess amounts in their urine. It is this excreted calcium that makes the urine of rabbits and guinea pigs appear cloudy. Other animals only absorb the amount of calcium from their food that is needed, so they do not excrete high levels of calcium in their urine, and therefore their urine appears clear. The kidneys of rabbits and guinea pigs have to work extra hard to filter out excess calcium, so it’s important that they do not get too much calcium in their diet. Excess amounts of protein in the diet also require their kidneys to work harder. A diet too high in calcium and protein can result in kidney failure and death. 

Fortunately, there is a very simple way to make sure the digestive tracts of these herbivores function properly to keep them healthy: feed them free-choice grass hay. Grass hay has the proper amount of fiber to keep their digestion healthy, and it is also low in calcium and protein. In comparison, alfalfa hay, which is a legume (a plant in the bean family), not grass, is high in both calcium and protein, and therefore it should be fed to adult guinea pigs and rabbits in small amounts as a treat only. Growing rabbits and guinea pigs can have more alfalfa hay in their diets.

The importance of giving grass hay free-choice to all rodent herbivores cannot be emphasized enough. It is almost impossible for these herbivores to have too much fiber in their diet. Retailers need to pass this knowledge on to their customers who own rabbits, guinea pigs, chinchillas and other small herbivores. Grass hay should be the main diet of these animals, and pellets should be used as a supplement. This one rule of husbandry will help to prevent these serious health problems and go a long way toward keeping these pets healthy.

Debbie Ducommun has a B.A. in animal behavior and has worked in the animal field since 1982. She is the author of the book Rats!, the booklet Rat Health Care and, her most recent book, The Complete Guide to Rat Training: Tricks and Games for Rat Fun and Fitness.

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