Using ruminally, abomasally and ileally cannulated wethers, an in vivo experiment was conducted to compare supplementing ensiled, deepstacked and composted broiler litter as N sources with soybean meal. Sheep were fed isonitrogenous (10.3% CP) and isocaloric (56% TDN) corn cob-based diets. Apparent digestibility of CP was somewhat depressed by feeding deepstacked and composted litters; however, N retention was affected by N sources. Nitrogen source did not alter flow and partial digestion of DM, OM and ADF through the digestive tract of sheep, with the exception of higher OM digestion in the large intestine of sheep fed deepstacked and composted litters than ensiled litter. Diets containing soybean meal, and ensiled, deepstacked and composted litter had 12.2, 25.2, 29.1, and 25.5% protein undegradability, respectively. Feeding litter increased dietary undegraded N flow and decreased microbial N flOw, compared to feeding soybean meal. Efficiency of microbial protein synthesis was not affected by N source. Available N (g/d) in the small intestine was similar among all diets. An in situ bag experiment showed that CP of ensiled, deepstacked and composted litter consisted of 80 to 89% of soluble A fraction, 8 to 13% of degradable B fraction, and 3 to 6% of undegradable C fraction. The ruminal degradability of CP was approximately 89 to 94% for processed litters, and 75% for soybean meal. Nitrogen solubilities of ensiled, deepstacked and composted broiler litter, determined in autoclaved ruminal fluid, were 62, 59, and 41%, respectively, when that of soybean meal was 12%. Another in situ experiment was conducted to determine ruminal DM and CP characteristics of broiler litter from surface and charred areas in the deepstacks. The low DM content in charred litter reflected more susceptibility of the locally high moisture litter for charring. Surface litter contained less CP than normal litter. Charred litter had higher undegradable protein fractions and lower CP degradability than normal litter. These studies illustrated that broiler litter processed by ensiling, deepstacking and composting could be efficiently utilized as a protein source for ruminants. / Ph. D.