I always get the question: “What is the best substrate ?”
Well, that can be a hard question to answer. There is honestly no single ‘best’ substrate that will work with all rats, as all rats (and humans) are different and can have different allergies and sensitivities, it’s more so what works for you and them the best in terms of absorption, sensitivities, financial sense, and accessibility.
There are the do's and don't's, those that we absolutely should not use and those that are great options for majority of rats: Here is a breakdown of all of this.
Substrate vs Bedding vs Litter: A Quick Breakdown
Substrate: Sits in the base of the cage, meant for absorption as rats scent mark, meant to last a week to even a few months (or permanently with a proper bioactive set up) without being replaced.
Bedding: Soft, not designed for absorption, great for sleeping and nesting. Paper beddings, shredded newspaper, tissues, and toilet paper can make for great ‘bedding’ / nesting materials. Should be replaced frequently.
Litter: Meant to be changed daily or every other day, absorbing but doesn’t need to be the best since it is changed so often. Paper is a good choice for this, many use paper based pelleted cat litter so the rats understand the difference between the floor and bathroom area.
Unsuitable Substrate options:
Cedar:
Cedar should be avoided. Not only is this highly aromatic (risking their sensitive respiratory systems, and covering the smell of urine), but this contains dangerous phenols.This will adversely affect your rats, and is extremely toxic.
Sawdust:
This is not only often a random combination of untreated woods, but this is basically wood dust. This is a poor choice for any animal, especially animals with sensitive respiratory systems like rats. Please avoid this.
Fleece:
Fleece is a poor choice for healthy active rats, and needs changed nearly daily to be suitable. Fleece can be great for rats that have had surgery, or rats with allergies, however loose substrate is much better, for absorption as well as enrichment! Providing it and scatter feeding their food in the substrate is most enriching, stimulating, and simulates their natural environment in the wild.
Clumping Clay Cat Litter:
This is absolutely unsuitable for rats, in both the litter box or the base, as it is extremely dusty. Rats have very sensitive respiratory systems, do not use this in your cage, I see it done far too often. Cats and rats do not have the same sensitivities.
Pelleted Litter:
Pelleted cat litter and such is not good as a base substrate, they can be used in the litterbox (so long as they are 100% paper based recycled pellets, that do not contain baking soda) but they are not comfortable to walk on and they are not enriching. This is heavy, the rats cannot burrow or forage as they would in a loose substrate.
Hay:
As a main substrate, hay is not a good choice. It is not absorbent, gets very messy, and can be quite dusty in large amounts. It can be great for nesting, and holding up tunnels, but it is not a good choice for the entire base.
There are concerns about hay, and rats can technically eat hay without issue, contrary to popular belief. They will not die from it, they simply lack the stomach enzyme that breaks it down to provide nutrients, therefore it passes through their GI tract unchanged and provides them with nothing. It can actually be good for constipation and diarrhea, as it solidifies stools and types of hay can promote bowel movements. There is also concern about it poking their eyes, this is rare but if you notice any irritation, most certainly remove it and stop using it.
Wood Cat/Small Animal Litter:
This is not the best option, even as a litter. When wet, this breaks down. When it becomes dry, it becomes a powder, in which brings forth the same issues as saw dust. This is best to be avoided.
Corn Cob:
Though this is not suitable as a substrate, however you can use this for litter as we spot clean letterboxes nearly daily anyway. As substrate, the concern is not the rats eating it, it is the fact that eventually it will mold.
Traditionally, we deeply clean about once a week. You will be cleaning endlessly with corn cob bedding. You also run the risk of making their environment too damp, which can cause a condition known as ringtail.
Suitable Substrate Options:
Aspen:
Aspen is an absorbent and safe option, it is also quite affordable within the US and Canada (it gets pricy in the Uk... Don't worry, your suggestions are coming!) and can be bought for great prices in bulk. Being a hardwood, there are no harmful phenols, your rats will be safe. Full Cheeks is a great brand for bedding, previously known as All Living Things.
Kiln-Dried Pine:
This is a controversy. There is a strong divide between those for and against kiln dried pine as substrate, and both sides are heavily opinionated. Personally, I sit in the middle. I hear it recommended, it works for others, but with varying information, I avoid it. There is concern that it is heavily aromatic, and that it contains phenols despite the drying process. I simply say to educate yourself and come to your own conclusion.
Hemp:
One of the most affordable UK options, this absorbent and very pleasantly looking substrate is great as a main base. Though, it does easily get kicked out as it is light, it is highly enriching, generally low dust, and keeps smell down. I have heard good things about the Aubiose brand, in both the UK and US/Canada.
Paper:
Paper is quite messy, and alone is not the best substrate option. It is quite expensive, but works very well for litter boxes and hospital cages. This is a comfortable choice, and I suggest mixing it with an aspen or hemp, or even just offering it as nesting materials. Kaytee clean and cozy all natural brown paper, and Eco bedding are both good dust free options.
*Avoid coloured paper, as this has even less absorption due to having to absorb the colour. Avoid scented bedding, this can and will cause respiratory issues.
Bioactive Setup/Coco Coir:
This is a great option for those who can do this. Bioactive set ups involve a CUC (Clean up crew, aka bugs like isopods) and a deep base of at least nine inches in depth, the substrate most commonly used for this is coco coir, which is a natural pet safe soil, and when damp it supports a CUC and is safe for the rats. These usually do not need to be cleaned out at all, other than spot cleaning, assuming the rats are litter trained. 'Naturalistic and Bioactive Rat Setups' is a great source of information and place for advice when looking to build a cage set up like this.