عنوان مقاله [English]
Introduction: Cereals are the major part of a poultry diet and primary sources of feed energy Because of the worldwide high cost of corn, the use of barley and wheat grain in broiler diets has become more appealing. However, the use of barley in poultry diets because of its high content of non-starch polysaccharides (NSP) is limited. NSP increased intestinal viscosity, reduced litter quality and poor productive performance. Most of the adverse effects of barley in poultry feed have been attributed to the content of β-glucans. The NSP fraction of the cereal protects lipids, starch, and protein, thereby compromising the access of digestive enzymes to dietary components. Therefore, the processing of barley grain to remove anti-nutritional factors and improve its nutrient bioavailability before including it in the diets of one-stomach animals is beneficial. However, information concerning the effect of electron beam radiation on nutritional and anti-nutritional components of barley grain are scarce. Therefore, this study was carried out to evaluate the effects of electron beam radiation on the chemical composition and metabolizable energy of barley grain.
Materials and Methods: The barley samples (cultivar Fajr) were packed in nylon bags and exposed to electron beam irradiation (Rhodotron TT200 accelerator, IBA Co., Belgium) at the Yazd Radiation Processing Center (AEOI, Yazd Center, Iran) at doses of 10, 20, 30, and 40 kGy at room temperature. Chemical composition of the raw and electron beam irradiated barley grain was determined. In order to estimate AMEn Chicks were fed a standard broiler diet for a 15-d pre-experimental period and, after four h of feed deprivation, were randomly distributed into experimental groups (16 treatments, 4replicates and 5 birds in each) in such a way that all groups had a similar average weight. All diets were given in mash form with birds having free access to water and feed throughout the experiment. The basal diet used during the experimental period was based on corn and soybean meal as major ingredients. The raw and electron beam irradiated barley grain (as test ingredient) was included in the basal diet at levels of 7, 14, and 21% to form test diets. The 16 experimental diets, evaluated in a balance trial to determine the AMEn content which contained 0.3% chromium oxide as an indigestible marker. The precision-fed cockerel assay of Sibbald was used for determining the TMEn of the raw and electron beam irradiated barley grain. The birds were housed in individual metabolism cages, following a period of 24 h without feed, 30 g of the different ground barley samples were fed by intubation to 20 (4 per treatment) adult cockerels (Rhode island reds). At the same time, another 4 cockerels were deprived of feed to estimate the endogenous energy losses. Total excreta over the following 48-h period were dried and ground for subsequent analyses, Roosters were assigned to treatments at random.
Results and Discussion: The results showed that percentage of dry matter, crude protein, ether extract, ash, β-glucan, ADF, and starch of barley grain were not affected by radiation. However, electron beam irradiation in all doses significantly decreased (P<0.05) the NDF of samples compared to raw barley grain. The AMEn of barley was calculated by extrapolation of the linear regression equation to a 100% of barley inclusion. These equations indicated that with increasing dose of irradiation, AMEn of barley increased. The AMEn value of raw and irradiated barley at doses of 10, 20, 30 and 40 kGy were 2593.80, 2628.30, 2663.10, 2730.70 and 2795 kcal/kg, respectively. The electron beam irradiation numerically increased (P>0.05) AME, AMEn, TME and TMEn of barley grain in cockerels at doses above 20 kGy. Previous studies using gamma or electron irradiation show a reduction in anti-nutrient content of canola meal, barley, and cottonseed meal and an improvement in their utilization increase in broilers. Gamma and electron radiation can denature proteins, decrease starch crystallinity and increase digestibility of barley and canola meal. Therefore, increased AMEn and TMEn of barley grain were expected in this experiment.
Conclusion: The present study showed that electron beam irradiation reduced NDF and increased AMEn and TMEn of barley grain. It seems that radiation is an effective processing method for improving the nutritive value of barley, but more experiment is needed to evaluate radiation.