The present study was undertaken to analyze the primary limiting factors of pig manure for biogas production. Eight numbers of fresh pig manure samples were collected for primary compositions and the data were analyzed and reasons for poor biogas production probability were ascertained after comparing pig manure with cattle dung composition. The moisture, total solid and volatile solid percentage of fresh pig manure was 79.27%, 19.73% and 82.04% respectively. The ash, crude fiber and ether extract percentage were 17.96, 13.96 and 4.45 respectively. The C:N ratio in pig manure was 14:1. The ammonical nitrogen was 2.58% in fresh pig manure and it was 25 % of total nitrogen estimated on total dry mater basis, which was quite higher side for biogas production. The pH of fresh pig manure was slight acidic (6.73) which is in the range of desirable range pH for optimum biogas production, i.e. 6.5 to 7.5. The microbial consortia in fresh manure were detectable in terms of TBC and E. coli, where as no salmonella and salmonella like organism was found in fresh pig manure. Comparing the compositional values between cow dung and pig manure major shortfall was found in terms of C: N ratio, ammonical nitrogen and pH in pig manure for efficient biogas production, which are the major primary limiting factors in pig manure, which needs to be conditioned with suitable techniques of carbonization, dilution and acidification respectively for efficient biogas production.