Nutrient Digestibility and Gas Production of Some Tropical Feeds Used in Ruminant Diets Estimated by the in vivo and in vitro Gas Production Techniques

Some feedstuffs which used in ruminants diet (corn grain, soybean meal, wheat bran and alfalfa) were analyzed for chemical composition, apparent in vivo nutrient digestibility, in vitro fermentation gas production and metabolizable energy. Chemical composition of test feeds differed in nutrient contents. Initially apparent in vivo digestibility of alfalfa nutrients were obtained then digestibility of nutrients for the other test feeds were determined by difference method, using 16 Ghezel mature rams (mean weight of 43.9±4 kg). In vivo DM, CP, NDF and OM apparent digestibility were different among the test feeds (p<0.05). Regarding to the results, corn grain had a high DM and OM digestibility between test feeds and soybean meal had a high CP and NDF digestibility between test feeds (p<0.05). Cumulative gas production was recorded at 2, 4, 8, 12, 16, 24, 36, 48, 72 and 96 h of incubation and the equation of p = A (1-e-ct) was used to describe the kinetics of gas production. Potential gas production (A) and rates of gas production (c) differed (p<0.01) among feeds. Corn grain showed higher potential gas production (A) (326.5 mL g^-1 DM) and wheat bran had higher rate of gas production (c) (0.097 h^-1) than the other feeds, inverses alfalfa (257.6 mL g^-1 DM) and corn grain (0.048 h^-1) had lower potential gas production and rate of gas production than the other test feeds, respectively. The metabolizable energy (MJ kg^-1 DM) content of feeds was calculated using in vivo organic matter digestibility and gas production data. According to in vivo organic matter digestibility data, the ME values ranged from 9.2 in alfalfa to 13.3 MJ kg^-1 DM in corn grain. It was concluded that regarding to different chemical composition of test feeds, the in vivo digestibility, in vitro gas production and ME of feeds showed different values.