A study was conducted to develop correlations of the average gas production rate with working volume of digester in batch anaerobic digestion of cattle and poultry manures. A bench-scale digester with gas collection system was constructed. Measurements of chemical oxygen demand, total volatile solids, and pH were taken for the feed and for the withdrawn samples. The gas production parameters and correlations between the gas production rate and the working volume of the digester were developed for both manures. The gas production estimates from the correlations for both manures were in excellent agreement with experimental results at low working volume of digester.