اثر جاذب‌هاي آلي و معدني آفلاتوكسين B1 بر قابليت هضم و متغيرهاي تخميري شكمبه در شرايط برون‌تني

The Effect of Organic and Inorganic Aflatoxin B1 Absorbents on in Vitro Digestibility and Rumen Fermentation Characteristics

مایكوتوكسین‌ها، متابولیت‌های تولید شده توسط قارچ‌ها هستند كه باعث بروز مسمومیت در حیوانات و انسان می‌شوند. از مهم‌ترین مایكوتوكسین‌ها، آفلاتوكسین‌ها هستند كه یكی از روش‌های مؤثر برای مقابله با مسمومیت ناشی از آنها، استفاده از جاذب‌های سموم قارچی می‌باشد. هدف از این مطالعه، مقایسه توانایی جاذب‌های مختلف بنتونیت تجاری، بنتونیت فعال، كربن فعال، مخمر و فرم‌های تركیبی بنتونیت+كربن فعال+مخمر به میزان (1 درصد جیره)، در جذب آفلاتوكسینB1 در سطح 5/0 پی پی ام در شرایط برون‌تنی و تأثیر آنها بر قابلیت هضم و فرآسنجه‌های تخمیری شكمبه بود. افزودن جاذب‌های فوق به محیط كشت حاوی آفلاتوكسین B1 پس از گذشت 72 ساعت انكوباسیون، به طور معنی‌داری سبب افزایش قابلیت هضم ماده خشك نسبت به تیمار شاهد شد. فرآسنجه‌های تخمیری شكمبه از جمله نرخ و مقدار تولید گاز ، میزان pH مایع شكمبه و همچنین پارامترهای تخمینی از تولید گاز نیز در تیمارهای حاوی جاذب به طور معنی‌داری بهبود یافت. در رابطه با افزایش داده‌های حاصل از قابلیت هضم، فرآسنجه های تولید گاز، افزایش pH و پارامترهای برآورد شده از تولید گاز استفاده از بنتونیت نسبت به سایر جاذب ها مؤثرتر واقع شد. در خصوص تغییرات نیتروژن آمونیاكی افزودن جاذب‌های مختلف اثر كاهنده‌ای نسبت به تیمار شاهد داشت. به طور كلی می‌توان نتیجه گرفت كه در مقایسه بین جاذب‌های مختلف، بنتونیت بیشترین تأثیر را در بهبود قابلیت هضم و متغیر‌های تخمیری شكمبه در شرایط برون‌تنی داشت.

Introduction Aflatoxins (AF) as secondary metabolites are produced by Aspergillus flavus and Aspergillus parasiticus. The most abundant aflatoxin B1 (AFB1) is toxic and carcinogenic to humans and animals. Utilization of mycotoxin adsorbents are noted as the most practical methods for protection of feed ingredients. The purpose of this study was to investigate the effect of organic and inorganic adsorbents for the adsorption of AFB1 and its effects on dry matter digestibility and rumen fermentation characteristics. Materials and Methods The experimental diet was a mixture of alfalfa silage and concentrate. Procedure of in vitro batch culture was performed according to the Menke and Steingass procedure. In an anaerobic condition, 30 ml of buffered rumen fluid was dispensed with pipetor pump into a 120-ml serum bottle containing 0.5 g DM of the experimental diet. The content of each bottle was contaminated with 0.5 ppm AFB1. Experimental treatments were: the control diet, commercial bentonite, activated bentonite, activated charcoal, the cell wall of Saccharomyces serevisia with 75% purity, bentonite + activated charcoal + yeast, (0.5 + 0.4 + 0.1 percent), bentonite + activated charcoal + yeast, (0.4 + 0.45 + 0.15 percent) and , bentonite + activated charcoal + yeast(0.3 + 0.5 + 0.2 percent) The amount of absorbents for all treatments was 1% of the experimental diets. All bottles were purged with anaerobic CO2, sealed with rubber stoppers and placed in a shaking water bath for 72 h at 38.6 degree centigrade. The amount of produced gas was recorded at 2, 4, 6, 8, 12, 16, 24, 48 and 72 h of the incubation. At the end of incubation, all the bottles were transferred to refrigerator to stop fermentation, and then opened. After pH measurements 2-ml sample of each filtrate bottle was taken and frozen at 20 degree centigrade after acidification with 2-ml of 0.2 N HCl. The biomass residues were centrifuged at 1000×g for 10 min at 4 degree centigrade. The supernatant in each bottle was decanted and the pellet was dried at 65 degree centigrade to a constant weight for the determination of the residues. Results and Discussion Absorbents addition increased the amount of produced gas in all treatments in comparison with the control treatment significantly (P <0.0001). The similar trend was obtained for organic matter digestibility, ME and SCFA (P <0.0001). Within the treatments bentonite was more effective (P <0.0001) in case of the noted parameters. Jiang et al, reported the similar results following fermentation without aflatoxin absorbent probably because the adverse effects of aflatoxin B1 on microbial fermentation in the media. In another report utilization of activated carbon and bentonite increased the rate of gas production after 72 h of incubation significantly. Dry matter digestibility was affected significantly (P <0.0001) by the type of adsorbent. It was concluded that the use of bentonite was more effective in increasing dry matter digestibility compared with other adsorbents. Similar results were reported in an experiment with bentonite added to the alfalfa silage. The aflatoxin adsorbents addition reduced ammonia nitrogen concentration significantly (P <0.0001). Williams and Withers demonstrated that, addition sodium bentonite to the media led to reduction in ammonia nitrogen concentration in the rumen. In another study the activated carbon was able to absorb high levels of ammonia nitrogen first and then it was released to the rumen gradually. The pH of rumen fluid culture was affected by the types of adsorbent significantly (P <0.0001) reported. It was showed that bentonite addition in diets containing aflatoxin B1 significant increase pH levels than the control treatments. Conclusion The results showed that aflatoxin B1 reduced in vitro rumen fermentation characteristics including dry matter digestibility, ammonia-N concentration, pH and produced gas significantly. For overcoming these problems, absorbents addition mainly the activated bentonite is highly recommended.