These Useful Articles:
To Look For in Hay:
If the hay has been treated with sodium ascorbate, acetic acid, or proprionic acid as a preservative in damp or improperly cured hay, increased urination of the animals will become a problem if water intake is not increased. [note: apparently these act as diuretics in the animal if hay is too moist]. As far as we know these preservatives are not toxic to chinchillas. They are FDA and USDA approved preservatives in the USA.
Hay that is below 14% moisture has other problems, too little moisture, Hay can be as low as 11% moisture and still be palatable to most animals. Much below that is expensive straw and it really doesn't matter if it is grass hay or legume hay. Molds and dust can still be a problem even if the hay is too dry, don't be fooled by dryness.
To test for moisture content, do what the livestock people do. Take a handful of hay and twist it into a rope [try to spin it into thread].If the twist falls apart immediately or breaks into many pieces, it is too dry and is valueless. If it stays tightly twisted and doesn't expand, then it is too wet and should be stored in a container that is open and has good air circulation. It should be used rapidly, or it will mold. Check it frequently for signs of mold, and smell it before using for freshness. Some molds will change the smell of the hay.
If the twist lightly opens but still holds its shape, then the hay has the correct moisture content, more or less. This hay can be used over a period of time. For horses it is recommended that hay be used within a 90 day period or less.
Grass hays [such as Timothy Hay and Sudan Grass] are good as long as they are free of insects, rodents, molds and weeds. The general storage period for them is 60-90 days. Grain hays [such as barley or oats] must be stored in a rodent and insect free area. If the heads shatter, the value of the hay is nothing. The pest and contamination problem [ergot molds etc.] and shattered heads are a major factor in the value of grain hays. Grain hays should be used within a month or you need to have lots of hungry cats around to keep the rodent population down. Remember, the grain head is the only part of value in a grain hay.
hays [such as Lucerne/alfalfa] can be stored for as long as 6-9 months.
Prebloom and bloom stages are the best quality. Moisture content is
important to the quality. As all of the plant is edible, you do get more
for your money. With some of the legume hays, the estrogen content
be important. If you are having breeding problems, consult with the extension
service or local Agricultural Ministry, or school. Remember, some legume
hays like alfalfa [lucerne], the calcium oxilate can decrease calcium
absorption in some animals. If you use alfalfa on a regular basis,
might want to consider supplementing the diet with a calcium rich food,
such as calf manna.
If you are having problems with your feed, or your chinchilla is throwing most away, and it smells stale to you or you cannot detect a fresh smell [or don't know what a fresh smell is]; go talk to a local horse owner, large animal vet, local rabbitry, 4-H leader, FFA teacher [Future Farmers of America club -- in most midwestern towns] or hay grower. They all deal in hay on a regular basis. Remember, healthy food is a healthy animal.