Effect of feeding microwave irradiated sorghum grain on nutrient utilization, rumen fermentation and serum metabolites in sheep

Two series of in vitro and in vivo experiments have been conducted in order to investigate microwave irradiation (900 W, 2450 MHz frequency) on sorghum grain. Also, quantitative color analysis of untreated and microwaved irradiated sorghum grain, L⁎, a⁎ and b⁎ color parameters (CIE) and total color differences (ΔE⁎) were investigated. The color analysis revealed an increase (linear effect, P<0.001) in total color differences which is dominated by L⁎, a⁎ and b⁎ variations. In the first experiment, in vitro gas production kinetic and crude protein digestibility of triplicate untreated and microwave irradiated sorghum grain for 3, 5 and 7 min have been studied through using a completely random design. In the second experiment, to investigate effects of microwave irradiation on apparent nutrient digestibility and serum metabolites, three treatments including untreated and microwave irradiated sorghum grain (3 and 5 min) have been supplemented with alfalfa hay (in ratio of 60:40) and fed to twelve adult Ghezel×Arkhar-merino crossbred male sheep (35.9±6.38 kg body weight) on the basis of a completely random design with four replicates for 21 days. Results indicate that microwave processing increased linearly cumulative gas production up to 24 h post incubation (P<0.01) and decreased the lag time significantly (P<0.001). in vitro digestibility of crude protein was significantly decreased (P<0.001) compared with untreated sorghum as microwave irradiation time increased up to 7 min. Results of in vivo experiment revealed that there were no effects of microwave irradiation, neither on apparent digestibility of crude protein, nor on neutral detergent fiber, nor on acid detergent fiber, whereas its dry matter, organic matter and starch apparent digestibility were increased linearly (P<0.01) by irradiation for 5 min. Compared with diet including untreated sorghum grain, significantly higher (P<0.05) concentration of total volatile fatty acids (mM) in rumen fluid were observed by diets containing microwave treated sorghum grain for 3 and 5 min with no difference between these treatments. Moreover, ammonia nitrogen was decreased linearly (P<0.01) as microwave irradiation time increased up to 5 min. Serum metabolites were not affected by feeding microwave irradiated sorghum grain while they were within the normal physiological range in all treatments. Microwave irradiation of sorghum grain for 5 min could improve ruminal escape of protein, in vitro kinetics gas, NH4-N concentration and apparent starch digestibility which are important for animal production and also food production.