The cedar shavings debate still rages, thanks to a couple articles by a university student and a breeder of rats.
These two articles allege respiratory problems in rodents due to untreated cedar, however the articles also mention pine by virtue of its quality as a softwood.
If you like, you can read the articles yourself. We’ll give
you links to both articles below, plus explain our viewpoint.
Untreated cedar litter smells very strongly, and breeders simply choose to be safe rather than sorry. Heat-treated cedar, however, is safe, according to the science (see our Pine Shavings page).
In the opinion of Raising-Rabbits.com, the low cost
and ready availability of heat-treated and kiln-dried pine shavings
(completely safe - see the science at our Pine
Shavings page) eliminates any attraction to
untreated cedar shavings, even if they could be readily obtained.
The articles recommend avoiding all softwood shavings. This is an overreaction, in my opinion, though you might be cautious with how you use untreated cedar shavings.
Doctoral student of Epidemiology Jeff Johnston wrote the article, "Respiratory toxicity of cedar and pine wood: A review of the biomedical literature from 1986 through 1995."
According to the studies:
The full title lists pine, but the preponderance of the human research was done on cedar. (I have no qualms using untreated pine, however heat-treated pine is readily available.)
Mr. Johnston describes a hyperactivity of the immune system resulting in asthma. It is very clear that humans whose immune systems cannot properly handle an exposure to the irritant in cedar dust (plicatic acid) need to not be working in a cedar sawmill.
Mr. Johnston’s paper was published on the "Rat Fan Club" site, along with an article by Debbie "The Rat Lady" Ducommun. Ms. Ducommun’s article, "The Toxicity of Pine and Cedar Shavings," is based on Mr. Johnston’s presumptions, but also includes her opinions about the studies relating to liver enzymes and drug detoxification times (go to Rabbit Litter for our discussion on liver enzymes and rabbit litter, and to Pine Shavings for the science).
In her article, Ms. Ducommun makes a citation that I would find concerning if I were a rat breeder, and I quote:
56% mortality in pups is not good. If I were a rat breeder using untreated cedar shavings, I might have already noticed problems if the study data were accurate.
As an aside, Ms. Ducommun mentions at the end of her article that CareFRESH "makes some rats sneeze." If you’ve already visited our Rabbit Litter page, you will have seen that CareFRESH does not control ammonia levels.
High ammonia is a sure recipe for respiratory problems, at least in rabbits, and apparently also in rats.
In the case of Mr. Johnston’s review of research done on sawmill workers, it is not scientifically possible to assume that rats, or rabbits, will react to the phenols in cedar as the humans do. This is because the rabbits are not sucking in many board-feet of plicatic-acid-laden dust every day, while they guide logs through shredders while enveloped in clouds of sawdust.
First, where’s the clinical evidence in rabbits? Where are the thousands of rabbits getting sick due to cedar? I know of a LOT of rabbits with snuffles or coccidiosis, but these illnesses were not contracted from acute cedar-osis.
Today, almost no one uses untreated cedar for their rabbits, however 20 or 30 years ago, cedar was a common bedding. Rabbits were not dropping like flies at the time.
Second, in a scientific research paper, you cannot make leaps into conjecture as does Mr. Johnston. He states, "The effect on small mammals is likely to be even more pronounced, especially if they are in close, continual contact with wood chips." Significantly, there are no animal studies cited by Mr. Johnston.
The reason you can’t make this leap is because of
differences, both in biology and in nutrition, between species.
Ms. Ducommon cited a rat study; still, there are enough differences between rats and rabbits in size, metabolism, and species that I'd truly like to see the results of an actual rabbit study which could corroborate or falsify Johnston's assumptions.
Third, it is not possible to extrapolate results from carnivore/omnivore species to an herbivore species, since digestive systems, nutritional needs, lungs, and metabolism are entirely different. (See Herbivore for more detail.)
Rabbits are herbivores. They chew on tree bark in the wild - including cedar bark - with no adverse reactions. This is why you cannot extrapolate from a study of sick humans and assume that smaller herbivore animals will sicken in a similar manner or worse.
Very few animal owners use untreated cedar these days. There are many other very good bedding options available such as heat-treated pine shavings which are cheap, plentiful, and effective.
While caution should be applied to using untreated cedar shavings, don't be afraid to utilize heat-treated pine shavings, which are completely safe.