تأثير افزودن اوره، ملاس و سود بر تركيب شيميايي، تجزيه‌پذيري و خصوصيات توليد گاز گياه كامل ني(Pragmates austrialis)

Chemical composition, rumen degradability and fermentation characteristics of fresh pragmates australis ensiled with different additives

در این مطالعه تركیب شیمیایی، مقدار تولید گاز و تجزیه‌پذیری شكمبه‌ای گیاه كامل نی (Pragmates australis) عمل‌آوری شده با افزودنی‌های مختلف بررسی شد. تیمارهای آزمایشی شامل: 1) گیاه كامل نی تازه سیلو شده بدون افزودنی (شاهد)، 2) عمل‌آوری شده با 4% سود، 3) عمل‌آوری شده با 4% اوره، 4) عمل‌آوری شده با 10% ملاس، 5) عمل‌آوری شده با 4% اوره + 10% ملاس و 6) عمل‌آوری شده با 4% اوره + 10% ملاس + 4% سود بود. در كلیه تیمارها گیاه كامل نی خرد شده با مواد مختلف مخلوط سپس در ظروف آنتی باكتریال (با نام تجاری TETRA LOCK) به مدت 60 روز سیلو شد. درصد NDF و ADF در تیمار حاوی اوره بالاترین و در تیمار عمل‌آوری شده با سود كمترین مقدار بود (01/0 >P). میزان پروتئین خام و خاكستر به ترتیب در تیمار عمل‌آوری شده با اوره و در تیمار عمل‌آوری شده با سود بیشترین مقدار داشت. میزان نیتروژن آمونیاكی در سیلاژ حاوی اوره بالاترین و سیلاژ دارای مكمل ملاس پایین‌ترین pH را نشان داد. نرخ تولید گاز در نی عمل‌آوری شده با اوره كمتر از سایر تیمارها بود. پتانسیل تجزیه‌پذیری شكمبه‌ای در نمونه‌های عمل‌آوری شده با سود و ملاس به‌صورت معنی‌داری (05/0 >P) بالاتر از تیمارهای شاهد و عمل‌آوری شده با اوره بود. این مطالعه نشان داد كه برداشت، عمل‌آوری و ذخیره‌ سازی گیاه كامل نی به‌ صورت سیلو می‏تواند به عنوان یك منبع غذایی مناسب به ویژه در مناطقی كه با كمبود خوراك دام روبرو است، مد نظر قرار گیرد.

Introduction: Pragmates australis (Pa) (common reed) is a riverside perennial grass found in wetlands throughout temperate and tropical regions of the world. Pa grows in many wetlands around rivers in Iran. Animal feed restriction is the main problem of Iranian animal production systems and this feed resource can be fed to native livestock especially in rural areas. Ensiling Pa could improve its feeding value. The aim of this study, therefore, was to measure the chemical composition, gas production and rumen degradability characteristics of the fresh and ensiled Pa with different additives. Materials and Methods: Plant samples were harvested during growth season from the city of Bojnoord,in Iran. The Pa samples were chopped and ensiled into airtight plastic bags as follow; 1)the fresh whole plant of Pa as control (Pa), 2) pa + 4% NaOH, 3) Pa+4% urea, 4) Pa+10% molasses, 5) Pa+4% urea +10% molasses and 6) pa+4% urea + 10% molasses +4% NaOH (on DM basis). Duration of the ensiling process lasted 60 days. Chemical composition of the samples was measured through the ordinary lab methods. The in vitro gas production was determined at 2, 4, 6, 8, 12, 24, 36, 48, 72 and 96 hrs intervals after incubation. The in situ rumen degradability was also determined at 0, 2, 4, 8, 12, 24, 36, 48, 72, 96 hrs after incubation. The experiment data were analyzed in a completely randomized design. Results and Discussion: NDF and ADF contents of the ensiled samples with urea were the highest whereas they were the lowest in the NaOH treated samples. CP content of the urea treated Pa was higher than other samples. Ash content of the NaOH treated forage was significantly (P <0.05) higher than other treatments. Ammonia nitrogen level of urea-treated silage was highest whereas it was lowest for the Pa treated with the molasses. The urea-treated Pa samples had lowest rate of gas production. Potential of degradability (PD) level of molasses and NaOH treated silages were higher (P <0.05) than the control and urea-treated silages. The results of rumen dry matter degradability demonstrated that the quickly degradable fraction of Pa treated with urea and molasses was significantly (p <0.5) highest among the silages whereas the value b fraction (slowly degradable) for urea-treated silage and urea and molasses treated silage were higher than other treatments. Quickly degradable fraction of molasses treated samples was lowest among all treatment samples probably because of higher fermentation process in the silages. The c fraction (rate of degradation) of NaOH treated forage was significantly (p <0.5) higher than that for other treatments whereas lowest level of c was observed in urea and molasses treated samples. According to the results urea-treatment led to higher crude protein content and NaOH-treating was perfect for destruction of crude fiber of the Pa samples. Effective degradability (ED) of NDF was significantly (P <0.05) highest in NaOH treated silage while PD of NDF was highest in Pa treated with urea and molasses. Gas production rate in all silages with different additives was higher (P <0.05) than the control samples. Conclusion: It was concluded that the fresh Pa can be harvested and treated with the appropriate supplements (e.g. molasses and NaOH) and ensiled for subsequent better utilization in ruminant feeding specially in the areas with low rainfall and feed scarcity problem. Quality of Pa silage is directly affected by harvesting time and its lignification. Therefore by harvesting at the appropriate time the Pa could be a perfect forage or silage for ruminant animals. Key words: Chemical composition, Degradability, Gas production, Pragmates australis, Silage.