The extra fiber in hay is important, as a matter of fact many exotic pet vets will put your chin on strictly water and hay when they are sick.
But ... the pellets are just fine also ...
IF they are high quality and contain
all that a chin needs ... many/most do not. Mazuri or Oxbow are two great ones for providing a chin what they need in their pellets. Make sure there are no added treats mixed in with the pellets. If your chin's pellets contain anything other than pellets, it is usually because the pellets are not as good a quality as they should be. Treats are treats and should be treated as such. If your chin gets treats mixed in with his pellets ... he is just like a little kid ... they like to eat the treats and leave the stuff that is good for them. The "treats" I am referring to are usually a different color and shape than the original green pellets. Never buy the pellets that are in an open container at the pet store ... these are exposed to anything and everything you can imagine. Do not buy chinchilla food that is in a package that exposes the pellets to the light constantly.
What brand chinchilla food are you using?
Now, let us get back to the hay. When you say "fresh" hay, do you mean fresh out of the field (still containing it's natural moisture) or fresh as in recently purchased dried hay? Also keep in mind there are many different types of hay. The main hays provided for chinchillas are Timothy, Alfalfa and meadow hay. Which ever one you can get on a regular basis and that is the freshest is the best. Timothy hay is a normal staple for chins. Meadow hay is one that is good also, but is usually used when Timothy or Alfalfa is not readily available. Alfalfa hay is the richest and is usually used for the females when they are in breeding, while pregnant and while nursing. As a personal preference, I use Alfalfa also during the first 6 months of a chin's life ... this is when he/she grows and develops the most. I have grown hay in containers in the house and given my chins an occasional treat of freshly grown hay, but they need the dried hay also.
Bad hay ... hay that has mold or mildew is worse than no hay at all. Always smell of the hay before you give it to your chin. If it has a musty or sour smell to it ... get rid of it and thoroughly clean the container and anything (cages, toys, etc) that may have been exposed to it. If you are not sure ... when in doubt throw it out!
My chins have access to their pellets at all times. I try to keep fresh hay available at all times also. If you give your chins hay, make sure it is in a container and not left on a shelf or the floor of the cage. I use empty toilet paper rolls to stuff hay in ... or a small empty cereal box or a separate bowl other than where their pellets are or a piece of PVC pipe or a wire holder. Always make sure to clean out and dispose of any hay that is left over from the day or night before. The reason for this is that the chins urinate and poop almost everywhere ... it can fall down between the wires or shelves and land on the hay ... this is one of the first steps to cause a good hay to go bad. The moisture can cause mildew and can set up the perfect growing place for germs that can sicken and even kill your chinchilla.
Keeping a chin's teeth worn down to the proper size is very important. They do this by chewing their food, their hay, wooden toys and the use of a pumas
lava stone. They should have access to all of these on a constant basis. When we think of tooth problems, we think of going to the dentist ... a matter of discomfort to humans ... but, if a chin's teeth grow to long, or grow into the jaw or brain a tooth problem can be extremely painful and even kill a chin ... in a very slow and painful way. If you notice any drooling or notice he is eating only on one side of his mouth, he probably has a serious problem and needs to see a qualified vet a.s.a.p. Not a week from now, but as soon as you see the problem. It could be a bone spur, a cracked tooth, a chip off of a tooth or something as simple as a piece of hay stuck between two teeth, but if he is not seen to find out and fix the problem, the situation can get very bad very quickly.
Sorry about being so long-winded, but I hope this helps and has answered some of you questions.
Jo Ann