تولید گاز و قابلیت هضم آزمایشگاهی انواع کربوهیدرات های غیر الیافی و پروتئین قابل تجزیه شکمبه‌ای

این آزمایش به منظور بررسی تاثیر منابع مختلف کربوهیدرات‌های غیرالیافی (نشاسته، ساکارز، پکتین و دکستروز) و پروتئین با قابلیت تجزیه‌پذیری متفاوت بر تولید گاز و فراسنجه‌های تخمیری در شرایط آزمایشگاهی انجام شد. کنجاله سویای عمل‌آوری شده با دمای 160 درجه سانتی‌گراد به مدت 60 دقیقه و کنجاله سویای بدون عمل‌آوری به ترتیب به عنوان سطوح پایین و بالا پروتئین تجزیه‌پذیر شکمبه‌ای انتخاب شدند. دو آزمایش تولید گاز و کشت بسته در قالب طرح فاکتوریل (4×2) با چهار نوع کربوهیدرات غیرالیافی (نشاسته، ساکارز، پکتین و دکستروز) و دو سطح پروتئین تجزیه‌پذیر انجام شد. نتایج نشان داد که در سطح پروتئین تجزیه‌پذیر پایین، ساکارز بالاترین مقادیر پتانسیل تولید گاز، نرخ تولید گاز، انرژی قابل متابولیسم، انرژی خالص و غلظت اسیدهای چرب کوتاه زنجیر را در مقایسه با سایر منابع قندی داشت. بالاترین و پایین‌ترین غلظت نیتروژن آمونیاکی در بین تیمارهای آزمایشی به ترتیب مربوط به تیمارهای نشاسته همراه با پروتئین تجزیه‌پذیر بالا و پروتئین تجزیه‌پذیر پایین بود. در بین تیمارهای دارای منبع پروتئینی با قابلیت تجزیه‌پذیری پایین، تیمار پکتین بالاترین مقدار تولید توده میکروبی و در بین تیمارهای دارای منبع پروتئینی با قابلیت تجزیه‌پذیری بالا، تیمار نشاسته بالاترین مقدار تولید توده میکروبی و عامل تفکیک را داشت. نتایج این مطالعه نشان داد هنگامی که سطح پروتئین تجزیه‌پذیر خوراک پایین است ساکارز عملکرد بهتری از نظر پارامترهای تخمیری دارد، در حالیکه هنگام استفاده از پروتئین تجزیه‌پذیر بالا تفاوت معنی‌داری بین کربوهیدرات‌های مختلف مشاهده نشد. به نظر می‌رسد این اثرات متقابل باید در تنظیم جیره‌ها مورد توجه قرار گیرد.

Gas Production and In vitro Digestibility of Various Sources of Nonfiber Carbohydrates and Rumen Degradable Protein

Introduction :Carbohydrates are generally classified as either nonstructural or structural carbohydrates. Structural carbohydrates include cellulose, hemicellulose and lignin, and nonfiber carbohydrates (NFC) are present inside the plant cells and are usually more digestible than carbohydrates found in plant cell walls. Dietary nonfiber carbohydrates are the main source of energy for highproducing dairy cows, which provide 30 to 45 percent of the dry matter intake. They are a very diverse group of nonfiber carbohydrates, which include starch, sugars, fructans, and pectin substances. Although the total amount of nonfiber carbohydrates is referred to as a single value, different types of NFC have different effects on digestibility and production properties. The dietary profile of NFC has the potential to alter the supply of metabolizable nutrients to the animal because NFC differ in digestion and fermentation characteristics. Sucrose is rapidly fermented in the rumen compared with corn starch. In vitro fermentation of sucrose, starch, and pectin resulted in different organic acid profiles, digestion characteristics, and maximal microbial protein yields. In addition, these effects may be affected by other feed components, such as the amount of rumen degradable protein. Some researchers have been showed that the impact of starch and sugars on low quality forage utilization may interact with the amount of supplemental rumen degradable protein.;This experiment was conducted to investigate the effect of various sources of nonfiber carbohydrates (starch, sucrose, pectin, dextrose) in combination with different levels of rumen degradable protein on gas production and digestibility of fermentation parameters in in vitro condition.;Materials and Methods: Soybean meal treated with heating at 160°C60 min and untreated soybean meal were selected as low rumen degradable protein (RDP) and high RDP sources, respectively. Four types of nonfiber carbohydrates (dextrose, sucrose, starch and pectin) supplemented with two levels of rumen degradable protein (RDP) in a 2×4 factorial arrangement by gas production and batch culture. A basal diet including: alfalfa (30%), corn silage (10%), barley grain (25%), wheat barn (9%), salt (0.5%), mineralvitamin supplement (0.5%), soybean meal (15%) and non fiber carbohydrate source (10%) was prepared. This study was conducted in two experiments. In the first experiment, the gas production parameters for two levels of high and low rumen degradable protein and four types of nonfiber carbohydrates (starch, sucrose, pectin and glucose) using the gas production technique. In the second experiment, the digestibility of the first experimental treatments were measured in an in vitro batch culture method. In the first experiment, the gas pressure was recorded with the pressure gauge at 0, 2, 4, 6, 8, 12, 24, 36, 48, 72, 96 h after incubation. In the second experiment treatments were incubated in batch culture conditions for 24 hours and the degradability parameters were determined using equations.;Results and Discussion: the obtained results showed that sucrose had highest gas production potential, organic matter digestibility (OMD), metabolizable energy (ME) and short chain fatty acids; (SCFAs) than other NFC type in low RDP level. There was a significant difference in digestibility of organic matter and dry matter between treatments (P <0.05). The highest and lowest ammonia nitrogen concentrations were obtained from treatments with starch in combination with high and low RDP, respectively. Treatments had a significant effect on partitioning factor and production of microbial mass (P <0.05). Among the lowdegradability proteinbased treatments, pectin treatment had the highest amount of microbial production and among the treatments with high degradability protein content, starch treatment had the highest production of microbial mass and partitioning factor. Overall, the results showed that when the RDP level is low, sucrose has a better performance in terms of fermentation parameters, whereas when using the high RDP, there was no significant difference between different types of carbohydrates. It seems that these interactions should be considered in regulating diets.;Conclusion: The results of this experiment showed that different types of nonfiber carbohydrates and levels of rumen degradable protein had a different responses to fermentation parameters. When using low protein levels, it seems that there is a greater difference between different sources of nonfiber carbohydrates, while at high levels of protein degradation there is no significant difference between the different sources of nonfiber carbohydrates in terms of digestibility. Based on these results, it can be concluded that the nonfiber carbohydrate sources, along with the degradable protein supplement, has the ability to change the characteristics of ruminal fermentation, the source of food and the production.; ;