It depends on overall composition, but you can estimate it pretty closely if you know (a) the ash content (% on a dry basis) and (b) the moisture content (% on a wet basis). Feedlot manure that has been stripped of all its ash and thoroughly dried has a "higher heating value," or maximum fuel value, of about 8,500 BTU per pound. Ash and moisture reduce that value proportionately. In general, the simplest formula for estimating the fuel value of feedlot manure on an "as-is" basis is:

HHV(BTU/lb) = 0.85 x (100 - ash%) x (100 - moisture%)

Thus, a manure sample with 20% moisture (wet basis) and 35% ash (dry basis) would have a higher heating value of approximately HHV = 0.85 x 65 x 80 = 4,420 BTU/lb.