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Ruminant Nutrition and Forage Utilization
Asian-Australasian Journal of Animal Sciences 2009;22(4): 534-541.
DOI: https://doi.org/10.5713/ajas.2009.80567    Published online March 4, 2009.
Effects of Gamma Irradiation on Chemical Composition, Antinutritional Factors, Ruminal Degradation and In vitro Protein Digestibility of Full-fat Soybean
M. Taghinejad*, A. Nikkhah, A. A. Sadeghi, G. Raisali, M. Chamani
Correspondence:  M. Taghinejad,
Abstract
The aim of this study was to evaluate the effects of gamma irradiation (??irradiation) at doses of 15, 30 and 45 kGy on chemical composition, anti-nutritional factors, ruminal dry matter (DM) and crude protein (CP) degradibility, in vitro CP digestibility and to monitor the fate of true proteins of full-fat soybean (SB) in the rumen. Nylon bags of untreated or ??irradiated SB were suspended in the rumens of three ruminally-fistulated bulls for up to 48 h and resulting data were 詮걎ted to a nonlinear degradation model to calculate degradation parameters of DM and CP. Proteins of untreated and treated SB bag residues were fractionated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Digestibility of rumen undegraded CP was estimated using the three-step in vitro procedure. The chemical composition of raw and irradiated soybeans was similar. Results showed that phytic acid in ??irradiated SB at dose of 30 kGy was eliminated completely. The trypsin inhibitor activity of 15, 30 and 45 kGy ??irradiated SB was decreased (p<0.01) by 18.4, 55.5 and 63.5%, respectively. From in sacco results, ??irradiation decreased (p<0.05) the washout fractions of DM and CP at doses of 30 and 45 kGy, but increased (p<0.05) the potentially degradable fractions. Gamma irradiation at doses of 15, 30 and 45 kGy decreased (p<0.05) effective degradability of CP at a rumen out詮굊w rate of 0.05 h-1 by 4.4, 14.4 and 26.5%, respectively. On the contrary, digestibility of ruminally undegraded CP of irradiated SB at doses of 30 and 45 kGy was improved (p<0.05) by 12 and 28%, respectively. Electrophoretic analysis of untreated soybean proteins incubated in the rumen revealed that ??conglycinin subunits had disappeared at 2 h of incubation time, whereas the subunits of glycinin were more resistant to degradation until 16 h of incubation. From the SDS-PAGE patterns, acidic subunits of 15, 30 and 45 kGy ??irradiated SB disappeared after 8, 8 and 16 h of incubation, respectively, while the basic subunits of glycinin were not degraded completely until 24, 48 and 48 h of incubation, respectively. It was concluded that 款-irradiated soybean proteins at doses higher than 15 kGy could be effectively protected from ruminal degradation.
Keywords: Full-fat Soybean; Gamma Irradiation; Protein Degradibility; SDS-PAGE


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