the effect of monensin or protexin on gas production parameters of alfalfa and barley in the ruminal fungi culture

introduction since the legislation of european :union: has prohibited the use of growth-promoting antibiotics such as: monensin, there is an interest in alternatives to manipulate the rumen fermentation. the use of growth-promoting antibiotics in animal feeds is banned in europe due to having potential risks such as the spread of antibiotic resistance genes or the contamination of milk or meat with antibiotic residues. recently, probiotics have been increasingly evaluated to replace or facilitate reductions in the use of antibiotics. thus, the aim of this study was investigating the comparison of antibiotic (sodium monensin) and probiotic (protexin) on the gas production parameters and organic matter digestibility of feedstuffs (alfalfa hay, barley grain, and alfalfa+ barley mixture) materials and methods experimental treatments were included control (basal feeds without additive), basal feeds supplemented with sodium monensin or protexin probiotic at levels of 500 or 1000 mg per kg of dm in a rumen fungi culture. ruminal fluid was collected from two fistulated sheep (49.5±2.5 kg) and all samples were withdrawn 2 h after the morning ration had been consumed. collected ruminal contents were strained through four layers of cheesecloth and brought immediately to the laboratory. to have a pure ruminal fungi culture, whole ruminal fluid was centrifuged at 1000 g for 10 min and added 0.100 mg/ml antibacterial agent (streptomycin sulfate, penicillin g, and chloramphenicol (14, 35). gas production technique was used to detect the fermentation parameters of the treatments (16).three parallel syringes of each treatment were prepared in this experiment. to measure the total gas production (a) and the rate of gas production (c), cumulative gas production, organic digestibility and metabolizable energy of treatments until 120 h. gas production was measured directly from the volume of the syringes at 0, 3, 6, 16, 24, 48, 72, 96, and 120 h. statistical analysis of data were statistically analyzed in a completely randomized design was performed by sas (9.1 version) and the least square of means. results and discussion results showed the higher level of sodium monensin (1000 mg/kg) decreased fermentable fraction (b), organic digestibility and metabolizable energy of both alfalfa hay and barley grain compared with other treatments significantly. the total gas production (a) and the rate of gas production (c) of gas production, cumulative gas production, organic digestibility and metabolizable energy of alfalfa were highest for control treatment (alfalfa without additives). but the level of 1000 mg/kg of protexin supplemented with barley increased fermentable fraction (b), cumulative gas production, organic digestibility and metabolizable energy than other treatments by ruminal fungi (p<0.05). but treatment contained 1000 mg/kg of protexin supplemented to barley grain decreased (p<0.05) rate (c) of gas production. also, rate (c) of gas production was increased (p<0.05) in treatment contained 500 mg/kg of sodium monensin. also, when the 1000 mg/kg of protexin supplemented to the alfalfa+barley mixture, estimated total gas production (a) and fermentable fraction (b) of gas production were increased (p<0.05) in treatments containing alfalfa+barley mixture. these results are in agreement with the reports of researchers who observed 14 and 8% reduction of gas production when the grass silage or grass silage+concentrate were supplemented with monensin, respectively (32). other researchers indicated that the administration of the 125 or 313 mg monensin per 1 kg of feed with hay and wheat bran increased total gas production, but the levels more than 313 mg monensin/kg feed reduced total gas production. in our study, the protexine supplementation had improved the gas production of the barley fermented in the ruminal fungi culture in compare to the monensin (p<0.05). it may be concluded, the variety of the types of nutrients, (especially the kind of carbohydrate) and the variability of the microorganisms in the different commercial probiotic may increase the gas production and digestibility of the barley grain in the ruminal fungi culture, regardless of any improvement were seen in gas production of other feeds supplemented with protexin. conclusion the results of this experiment showed that the ionophore antibiotics such as monensin can led to the decline of the ruminal fungi fermentation. the probiotics such as protexin may have the beneficial effects on the fungi fermentation of some feeds. due to the environmental and human safety hazardous of using antibiotic in animal nutrition, it would be suggested more studies about the replacement of probiotics with ionophore antibiotics to manipulation and improvement of the ruminal ecosystem and fermentation function are needed.