When evaluating manure keep in mind the many pitfalls.  Fresh manure is very valuable, but if you obtain some that has been has been heaped up and permitted to heat up, much of its nitrogen may already have dissipated as ammonia while the valuable digestive enzymes will have been destroyed by the high temperatures at the heap’s core.  A similar degradation happens to digestive enzymes when manure is dried and sacked.  Usually, dried manure comes from feedlots where it has also first been stacked wet and gone through a violent heating process.  So if I were going to use sacked dried manure to lower the C/N of a compost pile, I’d evaluate it strictly on its cost per pound of actual nitrogen.  In some cases, seed meals might be cheaper and better able to drop the heap’s carbon-to-nitrogen ratio even more than manure.

There are many kinds of manure and various samples of the same type of manure may not be equal.  This demonstrates the principle of what goes in comes out.  Plants concentrate proteins and mineral nutrients in their seed so animals fed on seed (like chickens) excrete manure nearly as high in minerals and with a C/N like seed meals (around 8:1).  Alfalfa hay is a legume with a C/N around 12:1.  Rabbits fed almost exclusively on alfalfa pellets make a rich manure with a similar C/N.  Spring grass and high quality hay and other leafy greens have a C/N nearly as good as alfalfa.  Livestock fed the best hay supplemented with grain and silage make fairly rich manure.  Pity the unfortunate livestock trying to survive as “strawburners” eating overly mature grass hay from depleted fields.  Their manure will be as poor as the food and soil they are trying to live on.

When evaluating manure, also consider the nature and quantity of bedding mixed into it.  Our local boarding stables keep their lazy horses on fir sawdust.  The idle “riding” horses are usually fed very strawy local grass hay with just enough supplemental alfalfa and grain to maintain a minimal healthy condition.  The “horse manure” I’ve hauled from these stables seems more sawdust than manure.  It must have a C/N of 50 or 60:1 because by itself it will barely heat up.

Manure mixed with straw is usually richer stuff.  Often this type comes from dairies.  Modern breeds of milk cows must be fed seed meals and other concentrates to temporarily sustain them against depletion from unnaturally high milk production.

After rabbit and chicken, horse manure from well-fed animals like race horses or true, working animals may come next.  Certainly it is right up there with the best cow manure.  Before the era of chemical fertilizer, market gardeners on the outskirts of large cities took wagon loads of produce to market and returned with an equivalent weight of “street sweepings.”  What they most prized was called “short manure,” or horse manure without any bedding.  Manure and bedding mixtures were referred to as “long manure” and weren’t considered nearly as valuable.