اثرات عملآوری با پرتو الکترون، پراکسید هیدروژن و اسید هیدروبرومیک بر ارزش تغذیهای بقایای ماش

Abstract

Introduction Recently, considering the fact that access to high quality feed stuffs is limited, using agricultural by-products in animal nutrition has taken to consideration. Effective use of these products as alternative energy source for ruminant feeding is important for economical and environmental reasons. Major limitation for using agricultural by-products as ruminant feed stuffs is their low digestibility because of cellulose crystallinity and close physical association between structural carbohydrates and lignin. Physical (soaking, milling and steaming), chemical (alkaline, acidic and oxidative agents), and biological (enzymes, white rot fungi and mushroom) processing methods have been used extensively to break down lignocellulose structure of crop residues. Irradiation is another physical processing because of its effectiveness without any side effects on environment. The concept of feedstuff irradiation refers to using ionizing radiations of gamma ray (GR) or electron beam (EB). The purpose of the present study was to determine the effects of EB, hydrobromic acid (HBr) and hydrogen peroxide (H2O2) on the chemical composition and ruminal degradability of vetch wastes. Materials and method Vetch wastes were prepared from Fars province farms. For the EB processing, samples were subjected to 10 MeV EB of Rhodotron accelerator to doses of 150 and 200 kGy. Irradiated and unirradiated samples were sprayed with HBr and H2O2. 60 ml HBr diluted in 250 ml distilled water /kg of dry matter (DM). In order to processing with H2O2, first the samples pretreated with sodium hydroxide (NaOH, 80 g/kg DM) to attain and maintain a pH of 11.5, then 132 ml H2O2 (purity: 35%) were added. Treated samples were then placed into plastic bags, tied up and stored under anaerobic conditions for 18 days. Then the bags were opened and samples dried by exposure to air. Chemical composition of the samples was determined using the standard methods. Ruminal degradability trial was carried out by the nylon bag technique. Crystallinity degree of the samples was investigated through X-ray diffraction (XRD) technique. The resulting data of the study were analyzed by the SAS software. Results and Discussion Processing was effective on the chemical composition of the vetch wastes (P<0.05). All treatments increased the ash, but decreased the organic matter (OM). Crude protein (CP) was increased by HBr, EB (150 and 200 kGy) and HBr+EB (150 kGy). Treatments reduced the crude fiber (CF) content. The most decrease was observed in EB (150 kGy) treatment. Decrease of CF in agricultural residues by irradiation treatment could be a result of degradation of cellulose and hemicellulose into soluble materials. It is found that under irradiation, cell wall constituents undergo degradation, which is due to the breaking off the glucosidal bond and modification in their structures. Modification may be due to several factors that finally lead to the opening of the anhydroglucose ring. Processing led to an increase of effective rumen degradability (ERD) of DM at outflow rates of 0.02, 0.05 and 0.08 h-1 (P< 0.05). EB (150 and 200 kGy) and the combination of EB with the chemical compounds had the greatest effect on increasing this trait. By examining XRD pattern, it was revealed that all the treatments led to a reduction in crystallinity degree of vetch wastes samples. It is demonstrated that the use of alkaline H2O2, which leads to degradation and solubilisation of lignin, greatly improved cellulose digestibility of agricultural residues. Furthermore the increases reported for CF degradability by HBr could be attributed to a decrease in cell-wall constituents or in lignocellulosic materials, which was probably matched by an increase in the more soluble and easily-digestible forms of carbohydrates. The improvement in the effective degradability of the CF with irradiation is likely to be due to a combination of the decreased particle size increasing the surface area exposed for microbial attachment, the alteration in the chemical composition (especially the reduction in the CF content), depolymerization and the composition of the cellulose and hemicelluloses, and serious weakening of the cellulosic fiber. A reduction in crystallinity of the cellulose is another reason for the increasing degradability of the processed samples Conclusion Totally, the results of this research showed that processing was effective on the improvement of vetch wastes nutritional value. Treatments EB, HBr and their combination had a greater effect on chemical composition and degradability parameters of DM.