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After many hours of searching the web, I have not found a definitive answer to the pine and cedar shavings debate.  I have come to the conclusion that it is best not to use pine or cedar.  One of the reasons being that it masks the smell of urine.  I personally don't want the smell masked, as they the ammonia build-up in the cage is high, which can harm your rats.  If you can smell urine, it is time to change the bedding.

Many animal/rodent studies show that while using pine and cedar shavings as bedding (or liter), the animals' liver enzymes are high.   What does this mean? Well, in layman's terms, the liver is working extra hard to clean the blood....and is having difficulties because of some toxicity in the body.   This can actually lead to liver problems in your rat....generally undetectable until it is too late.

A comprehensive article on beddings and their hazards:  http://www.bio.davidson.edu/Courses/anphys/1999/Cook/Text.htm

Compare Bedding/Liter Choices

	DUST	ABSORPTION	HEALTH HAZARDS	DISPOSAL
Paper Pulp	Low	Good	None observed	Can be flushed, bagged or composted
Dry Grass Pellets	Low	Good	None observed	Can be flushed, bagged or composted
Generic Clay	High	Good	Irritating to eyes and respiratory tract	Heavy. Unsuitable for garden compost
Dustless Clay	Low	Good	Irritating to GI tract if swallowed	Heavy. Unsuitable for garden compost
Shredded Paper	Low	Fair	Excessive ingestion may cause blockage	Can be bagged for disposal service
Corn Cob	Medium	Fair	Fungal spores may cause mold, can cause fatal blockages if ingested	Can be composted for garden
Straw	High	Poor	None (unless allowed to mold)	Bulky but light. Can be composted
Pine Shavings	High	Good	Phenols may cause liver damage	Can be composted
Cedar Chips	Medium	Fair	Phenols may cause liver damage	Use as mulch around trees & shrubs
Chemical Sand	Medium	Good	Causes deadly blockages in GI tract when ingested.	Can be flushed
Peat Moss	Medium	Fair	High in nitrogen (swallowing unlikely)	Can be added directly to garden soil
Compressed sawdust pellets	Low	Good to Excellent	None observed.	Can be bagged or composted.
Silica-gel litters	Medium	Good	Toxic if eaten; must be placed where rabbits can't eat.	Must be bagged for disposal service.
Pectin-based litters	low	Good	will cause GI problems or obesity if eaten to excess. Will not hold down bacterial growth.	Can be bagged or composted.

The dust content, dust generation, ammonia production, and absorption properties of three different rodent bedding types.

Potgieter FJ, Wilke PI.

Animal Unit G 20, Faculty of Medicine, University of the Orange Free State, Bloemfontein, Republic of South Africa.

Vermiculite, pine shavings and unbleached eucalyptus pulp contact bedding were compared for dust content, dust production (as a result of animal activity), moisture absorption properties and ammonia production. The percentage of dust particles <300 microm found in pine shavings and vermiculite was 18 and 8 times greater respectively than was found in eucalyptus pulp. The lowest ammonia levels (<1-1 ppm), measured on day 7, were obtained using eucalyptus pulp. Although the ammonia levels obtained for vermiculite compared very well with those of pulp, high levels of dust, up to 5 times more than pulp, were experienced with vermiculite. Pine shavings were associated with the highest ammonia concentration (1-3 ppm), but produced approximately 50% less dust than vermiculite. The water absorption properties obtained for pulp were between 35% and 76% higher than those obtained for vermiculite and pine shavings respectively.

Enzyme-inducing and cytotoxic effects of wood-based materials used as bedding for laboratory animals. Comparison by a cell culture study.

Torronen R, Pelkonen K, Karenlampi S.

Department of Physiology, University of Kuopio, Finland.

Enzyme-inducing and cytotoxic effects of wood-based materials used as bedding for laboratory animals were studied in a cell culture system. Mouse hepatoma cell line, Hepa-1, was exposed to acetone extracts of hardwoods (alder and aspen), softwoods (pine and a mixture of pine and spruce) and cellulose materials. Cytotoxicity and induction of cytochrome P450IA1 (aryl hydrocarbon hydroxylase) and aldehyde dehydrogenase were measured. Both softwood and hardwood extracts were shown to contain inducers of these enzymes. Pine appeared to be the most potent inducer and softwoods more potent than hardwoods. The softwoods and alder were clearly more cytotoxic than aspen. The two bleached cellulose materials were found to contain inducers of aryl hydrocarbon hydroxylase. Unlike the wood beddings, the extracts of the cellulose materials were not found to be toxic to the cells. Hepa-1 cell culture system was found to be a rapid and sensitive method for screening and comparative purposes.

Testing for possible effects of cedar wood shavings and diet on occurrence of mammary gland tumors and hepatomas in C3H-A-vy and C3H-Avy-fB mice.

Heston WE.

C3H-A-vy and C3H-A-VY-FB mice transferred from our colony to the laboratory of Dr. J. R. Sabine in Australia had a markedly reduced incidence of both hepatomas and mammary tumors. Sabine and co-workers (J Natl Cancer Inst 50: 1237-1242, 1973) attributed the low incidence of tumors in their laboratory compared to the high incidence in this laboratory to the fact that we routinely use red cedar shavings in the bedding, whereas they use sawdust, predominantly Doublas fir. Results of tests in this laboratory showed that the difference in occurrence of tumors could not be attributed directly to either a difference in diet or bedding. There was no evidence that the cedar shavings were carcinogenic. The animals in Australia on bedding without cedar shavings were not as healthy as our animals, in that they did not grow as well and were infested with ectoparasites; apparently these factors caused the reduced occurrence of tumors.

Bacterial counts associated with recycled newspaper bedding.

Hogan JS, Smith KL, Todhunter DA, Schoenberger PS.

Department of Dairy Science, Ohio State University, Wooster 44691.

Bacterial counts associated with recycled newspaper, wood shavings, and pelleted corn cobs used as bedding for lactating dairy cows were compared. Chopped newspaper and pelleted corn cobs had similar gram-negative bacterial, coliform, and streptococcal bedding counts. Staphylococcal counts in pelleted corn cobs were greater than in chopped newspaper. Conversely, gram-negative bacterial, coliform, and staphylococcal counts in chopped newspaper were greater than in wood shavings. Coliform and streptococcal counts did not differ between chopped newspaper and wood shavings bedding materials. Teat swab counts from cows bedded on pelleted corn cobs were greater than those from cows bedded on chopped newspaper for gram-negative bacterial, coliform, Klebsiella species, and staphylococci. Streptococcal teat swab counts did not differ between cows bedded on chopped newspaper and pelleted corn cobs. Cows bedded on chopped newspaper and wood shavings had similar gram-negative bacterial, coliform, and Klebsiella species teat swab counts. Streptococcal and staphylococcal teat swab counts were greater from cows bedded on chopped newspaper than those from cows bedded on wood shavings. Teat swab and bedding counts were correlated. In general, bacterial counts in bedding suggest no advantage in using chopped newspaper over pelleted corn cobs or wood shavings in reducing exposure of teats to environmental mastitis pathogens.

Incidence of pup mortality in the rat with particular reference to nesting material, maternal age and parity.

Norris ML, Adams CE.

Mortality and hence the proportion of young weaned was markedly affected by the type of nesting material but not by maternal age or parity. With paper tissues for nesting purposes 476/791 (60%) young were lost compared with 216/1182 (18%) with woodwool. Similar results were obtained in 2 additional series. The proportion of young weaned was also affected by litter size; in general, pup mortality was heavier and took place earlier in the large litters (more than 9 young).

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For more information on Rattie Express or any of our animals, please email me (Tara) at rattie.express@comcast.net.