Scanning electron microscope analysis of untreated and electron beam irradiated wheat straw pre- and post-incubation in the rumen of sheep
Hosein Zadegi-Mirzaei
1
(
SRB-IAU
)
Parvin Shawrang
2
(
AEOI
)
Farahnaz Motamedi-Sedeh
3
(
AEOI
)
Mohammad Chamani
4
(
IAUSRB
)
Mehdi Aminafshar
5
(
SRB
)
Keywords: Radiation, electron beam, fibrolytic bacteria, digestibility, cell wall,
Abstract :
Aim: Increasing the fiber digestibility in the rumen and the total digestive tract of ruminants is very important to improve the feed conversion ratio. One of the methods used for feed processing is electron beam irradiation. Increased fiber digestibility occurred in irradiated feeds, the cause of which is unknown, therefore it is necessary to evaluate the structural condition of fibrous materials pre- and post-processing and also during incubation in the rumen with an electron microscope. The present study was aimed to evaluate the effect of electron beam irradiation on the microscopic structure of wheat straw fibers, the relative abundance of fibrolytic bacteria and the fiber digestibility in the total digestive tract of sheep. Materials and methods: Wheat straw sample was subjected to electron beam irradiation with electron beam power of 10 mega electron volts and electron beam current of 6 mA at doses of 250 and 500 kGy. The straw sample was transferred to bags and then inserted in the rumen for 12 hours, and the structure of the cell wall pre- and post-irradiation, as well as pre- and post-incubation in the rumen, was imaged and analyzed with a scanning electron microscope. The relative abundance of fibrolytic bacteria was evaluated by polymerase chain reaction and horizontal electrophoresis. Results: The relative abundance of Ruminococcus flavofaciens and Fibrobacter succinogenes in the rumen content showed a significant increase (P0.05) on the relative abundance of Ruminococcus albus. Electron beam irradiation increased (P<0.05) the dry matter digestibility of wheat straw. Dry matter digestibility increased (P<0.05) as irradiation dose increased, and the dose of 500 kg had the greatest effect on dry matter digestibility of wheat straw. Scanning electron microscope showed a huge increase in the destruction of the cell wall structures in 500 kGy irradiated wheat straw, which resulted in an increase of the permeability of fibrolytic bacteria to the internal parts of the cell wall structure. Increasing the permeability of fibrolytic bacteria ultimately led to increased access to the substrate and an increase in the relative abundance of bacteria and higher digestibility of fibers. Conclusion: Electron beam radiation at dose of 250 kGy can change the structure of the cell wall and improve the digestibility of fibrous materials. Increasing the dose to 500 kGy causes more disruption of the cell wall structure, increasing the relative abundance of fibrolytic bacteria and increasing the digestibility of fibrous materials.
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