Authors
1
Agricultural Sciences and Natural Resources University of Khuzestan
2
Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, P.O. Box 61357-43169, Khuzestan, Iran. 2Biotechnology and Biological Science Research Center, Shahid Chamran University of Ahvaz, P.O. Box 61357-43169, Khuzestan, Iran.
3
Department of Animal Sciences, Sari Agricultural Sciences and Natural Resources University
Abstract
Background and Objectives: Lignocellulosic material is important in ruminant rations and because of its cost-effectiveness and effect on optimum rumen performance and its health included in ruminant rations. Although these compounds can be fermentable by many rumen microbes, the presence of proteins, fibers and other edible source nutrients in the feces shows that the rumen ecosystem does not have high efficacy for digestion. Thats way, it seems necessary, the manipulation of the rumen to increase of this performance. Therefore, this study was carried out with the aim of the Investigation of optimization growth of cellulolytic bacteria isolated from gastrointestinal tract of Arabian horse and the effect of transferring to the rumen fluid on the in vitro parameters of gas production and digestibility of wheat straw.
Materials and Methods: This research was conducted in vitro based on a completely randomized design. The cellulolytic bacteria isolated from the gastrointestinal tract include Paenibacillus polymyxa L11, Paenibacillus polymyxa L12, Enterobacter cloacae L2, and Escherichia coli Z2. At first, optimization of temperature and pH for growth and production of the enzymes of these bacteria was carried out at two temperatures of 25 and 39 ° C and three pHs of 2.5, 7.5 and 6.2. In the next step, these bacteria were transferred to the rumen fluid and gas production parameters and in vitro digestibility of wheat straw were investigated using gas production techniques and two step digestion, respectively. For this purpose, rumen fluid was taken from four sheep. In both methods, rumen fluid was inoculated with bacteria and incubated with wheat straw.
Results: The results showed that Paenibacillus polymyxa L12 had the best growth at 39 ° C and pH 5.2 and had the highest enzyme activity at 39 ° C, pH 5.7 and 24 hours. The optimum temperature and pH for growth of Paenibacillus polymyxa L11 and Enterobacter cloacae L2 were 39 ° C and 6.2. These two bacteria exhibited the highest enzymatic activity at 39° C and pH 6.2, at 24 and 48 hours, respectively. Escherichia coli Z2 showed the highest growth at 39 ° C and pH 6.2, but the most enzymatic activity of this bacterium was 39 ° C, pH 5.2 and 48 hours. The isolates reduced the gas production of wheat straw, increased truly degraded organic matter, microbial biomass and microbial biomass efficiency (p < 0.05). The highest and lowest potential of gas production was allocated to control and Z2 treatments, respectively. The lowest and highest amount of truly degraded organic matter was related to the control and L11 treatment, respectively. There was no significant difference between partitioning factor, microbial biomass and microbial biomass efficiency of bacterial treatments (P> 0.05), but they were metergent fiber. The control had the least digestibility of dry matter, organic matter and neutral detergent fiber. There was no significant difference for digestibility of acid detergent fiber among L12, L2 and Z2 treatments and control (P> 0.05).
Conclusion: Generally, temperature and pH had an effect on the growth and production of enzymes of isolates. All isolates grew at a temperature of 39 ° C, which is the optimal temperature of the rumen, better than 25 ° C and had more enzymatic activity at 39 ° C. These bacteria were able to improve rumen fermentation and in vitro digestibility of wheat straw. In the bacterial treatments, the fermentation pathway went towards producing less gas and more microbial protein, and the digestibility of nutrients in these treatments increased.
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