اثر افزودني باكتريايي و مواد جاذب رطوبت بر قابليت تخمير و تركيب مواد مغذي سيلاژ تفاله چغندرقند با استفاده از سيلوهاي آزمايشگاهي

Effects of Bacterial Inoculants and Absorbents on Fermentation Properties and Chemical Composition of Fresh Sugar Beet Pulp Silage Using Laboratory silos

هدف از این مطالعه بررسی نقش افزودنی میكروبی تولید كننده اسید لاكتیك و همچنین جاذب¬های مختلف در كاهش پس¬آب و بهبود ویژگی¬های شیمیایی و تخمیری سیلاژ تفاله چغندرقند تازه بود. در آزمایش اول تفاله چغندر بصورت خالص یا به صورت مخلوط شده با 5 درصد كاه یا 5 درصد پیت بمدت 90 روز سیلو شد. در آزمایش دوم تفاله چغندر با افزودنی میكروبی، پیت و یا مخلوط آنها سیلو شد. غلظت ماده خشك و دیواره سلولی در سیلاژهایی كه كاه یا پیت دریافت كرده بودند بیشتر از تیمار شاهد بوده و پس¬آب تولیدی كاهش پیدا كرد (01/0P <). افزودن جاذب¬ها موجب كاهش غلظت اسید لاكتیك (01/0P <) و افزایش pH (05/0P <) و نیتروژن آمونیاكی (01/0P <) در سیلاژ تفاله چغندرقند تازه گردید. اضافه كردن كاه و افزودنی میكروبی باعث افزایش غلظت اسید استیك و اسید بوتیریك و كاهش لاكتات (01/0P <) و نسبت لاكتات به اسید¬های چرب فرار شد. در مقابل، افزودن پیت باعث كاهش غلظت اسید استیك، اسید پروپیونیك و لاكتات (01/0P <) و افزایش نسبت لاكتات به اسید¬های چرب فرار (01/0P <) گردید. افزودنی میكروبی موجب كاهش pH و افزایش غلظت نیتروژن آمونیاكی و نسبت نیتروژن آمونیاكی از كل نیتروژن سیلاژ شد (01/0P <). بدلیل تخمیر با تولید بیشتر لاكتات، غلظت پائین تر نیتروژن آمونیاكی و تاثیر منفی كمتر بر قابلیت هضم سیلاژ در تیمار پیت نسبت به كاه و افزودنی میكروبی، توصیه می¬شود كه تفاله چغندرقند تازه با 5 درصد پیت سیلو گردد.

Introduction Ensiling is one of the common preserving methods for forage or other organic materials. In this method, organic matters were preserved by proving an aerobic condition and then by reducing the pH with increasing acids production (mainly lactic acid). Some circumstances like enough soluble carbohydrates, low buffering capacity and appropriate dry matter concentration are needed in ensilages for an ideal silage production. Seepage production during ensiling is one of the most problems especially when high moisture materials (like fresh beet sugar pulp) are ensiled. Silage seepage can pollute the environment and make loses in nutrients like soluble carbohydrates, protein, organic acids and etc. Moreover, lactic acid bacteria inoculants (Mainly consist of Lactobacillus plantarum) have been widely used for improving fermentation pattern in ensilages. These external provided bacteria usually enhance lactic acid production in silage and then accelerate the falling of pH values in silages. Rapid decrease in pH can inhibit non-beneficial bacteria from activity which finally preserves nutrients from un-necessary fermentation or oxidation. The aim of this study was to investigate the interactive effects of lactic acid bacteria inoculants and some absorbents (straw and pith) on chemical properties and fermentation profile of wet sugar beet pulp silage. Materials and Methods In the first experiment, fresh wet sugar beet pulp was treated with 5% straw or 5% pith in order to investigate the effects of these absorbents on chemical composition, fermentation characteristics and effluent production during ensiling period. In the second experiment, fresh wet sugar beet pulp was treated with a commercial lactic acid bacteria inoculants (Ecosyle) and/or 5% pith in order to investing the main and interaction effects of the bacterial bacteria inoculants and the best absorbents from the experiment 1. In both experiments, triplicate samples were prepared for each treatment after mixing the fresh sugar beet pulp with absorbents or inoculants. Ensilages were filled in laboratory silos and packed and then were kept for 90 d in room temperature at dark. After opening the concentration of volatile and non-volatile fatty acids, crude protein, fibers, total and ammonia-N and the values of pH were measured in final produced silages. Results and Discussion In the experiment 1, concentration of dry matter (DM), neutral detergent insoluble fibers (NDF) and acid detergent insoluble fibers were higher in absorbents treated silage (P >0.01) when compared with untreated one. Application of absorbents resulted in silages with lower seepages (P >0.01) production compared to the control. However, application of the absorbents to the beet pulp produced silages with lower in vitro DM digestibility (P >0.05). Straw treated silage had the highest NDF concentration and the lowest apparent and true in vitro DM digestibility. Application of absorbents produced silages with lower lactic acid (P >0.01) and higher pH (P > 0.05) and ammonia-N (P >0.01) concentration. Adding straw to sugar beet pulp produced silages with higher acetate concentration, total volatile fatty acids concentrations (VFA) (P > 0.01), the ratio of ammonia-N from total N (P >0.01) but lower ratios of lactate to acetate (P >0.01), lactate to acetate + propionate (P >0.01) and lactate to VFA (P >0.05) when compared with control group. In contrast, adding pith to sugar beet pulp produced silages with lower acetate concentration (P >0.01), propionate concentration (P >0.01), total VFA (P > 0.01) but higher ratios of lactate to acetate (P > 0.01), lactate to acetate + propionate (P > 0.01) and lactate to VFA (P >0.05) when compared with control group. The Fleig point was not affected by the different treatments. Application of bacterial inoculant resulted in silages with higher DM concentration (P >0.01), water soluble carbohydrates concentration (P > 0.01) and in vitro DM digestibility (P >0.05) but lower crude protein concentration (P >0.05). Moreover, Application of bacterial inoculant resulted in silages with higher butyric acid concentration (P >0.01), VFA concentration (P >0.01), ammonia-N concentration (P >0.01) and Fleig point (P >0.01) but lower pH values (P >0.01). Simultaneous application of bacterial inoculant and straw to sugar beet pulp silage resulted in silages with lower concentrations of lactic acid, acetic acid, propionic acid, total VFA but higher Fleig point. Conclusion Finally, according to homolactic fermentation, lower ammonia-N and less negative effect on digestibility in pith in comparison with straw and bacterial inoculant, it is suggest that to use 5% pith for treating sugar beet pulp prior to ensiling.