Improvement of Ruminal Neutral Detergent Fiber Degradability by Obtaining and Using Exogenous Fibrolytic Enzymes from White-Rot Fungi

Effects of Different Additives and Ratios on Broom Sorghum Straw Silage Characteristics and Bacterial Communities

As a large agricultural country, China produces a large number of agricultural and sideline products while harvesting agricultural products every year. Crop straw is one of them. Broom sorghum is a traditional crop in China, which produces a large amount of straw resources every year. These straw resources are placed in the field and cannot be used efficiently. The purpose of this study was to solve the problem of straw utilization of Broom sorghum, one of the main food crops in arid and semi-arid areas of northern China. Broom sorghum is not only a nutritious food crop, its straw is also rich in crude fiber and mineral elements, which has high utilization value. However, due to the high content of lignocellulose in straw, the texture is hard, which limits its digestion and utilization efficiency as feed. In this study, the broom sorghum straw was used as the research object, and the straw raw materials were treated with Lactobacillus plantarum, cellulase and xylanase, respectively. After silage fermentation for 30 d and 60 d, the bags were opened to determine the nutritional quality, fermentation quality, microbial community structure and other indicators. The best fermentation time and additives for broom sorghum straw silage were comprehensively screened to improve the nutritional value of straw and animal production performance. The results showed that the nutritional quality of silage straw increased with the extension of fermentation time. Compared with silage straw after 30 days of fermentation, the nutritional quality and fermentation quality of straw were significantly improved after 60 days of fermentation. Lactobacillus plantarum, cellulase and xylanase could improve the silage performance of broom sorghum straw by improving the microbial community structure in straw, and the effect of cellulase was the best. When cellulase was used in straw at the standard of 20 U/g FM, the content of water-soluble carbohydrates could be significantly increased to 31.35 g/kg FM, and the concentration of lactic acid was also significantly increased to 23.79 g/kg FM. Therefore, in actual production, it is recommended to use cellulase at a dose of 20 U/g FM in broom sorghum silage and open the bag after 60 days of silage fermentation. The results of this study provided a scientific basis for the efficient utilization of broom sorghum straw as feed.

Microencapsulation technology for delivery of enzymes in ruminant feed

The ruminant digestive system is uniquely designed to make efficient use of high-fibre feed, including forages. Between 40 to 100% of the ruminant diet consists of forages which are high in fibre and up to 70% of this may remain undigested in the ruminant gut, with substantial impact on feed utilisation rate and productivity and the economic and environmental sustainability of livestock production systems. In ruminants, feed costs can make up to 70% of the overall cost of producing an animal product. Increasing feed utilisation efficiency, i.e., more production with less feed lowers feeding costs and improves livestock economic viability. Strategies for improving nutrient utilisation in animal feed has been investigated over the years. Incorporation of fibre digesting enzymes in the feed to facilitate the digestion of the residual fibre in hind gut is one of the proposed strategies. However, delivering such enzymes to the hind gut in active state is challenging due to the unfavourable biochemical environment (pH, microbial proteases) of ruminant's gastrointestinal tract. This review discusses the potential application of microencapsulation for protected and targeted delivery of enzymes into the hind gut of ruminants.

Chemical Composition and In Vitro Ruminal Fermentation Characteristics of Native Grasses from the Floodplain Lowlands Ecosystem in the Colombian Orinoquia

Grasses from lowland ecosystems in flooded savannahs are useful to feed extensive grazing animals; however, scarce information about its agronomic and fermentation characteristics exists. This study aims to determine the chemical composition and fermentation parameters of native grasses from the floodplain lowlands ecosystem in the Colombian Orinoquia. Three native grasses (Leersia hexandra, Acroceras zizanioides and Hymenachne amplexicaulis) and a "control" grass (introduced Urochloa arrecta-Tanner grass) were sown and sampled at 30, 40 and 50 days of age. On each sampling date, biomass production in a 1 m2 frame was estimated, and the chemical composition and fermentation parameters were analyzed using near-infrared spectroscopy and the in vitro gas production technique, respectively. Data were analyzed using a mixed model for repeated measures and the least significant difference (LSD) was used for mean differentiation (p < 0.05). The grasses' nutritional characteristics varied as follows: dry matter (DM, 0.7-2.0 ton/ha), crude protein (CP, 6.1-12.2%), neutral detergent fiber (NDF, 56.6-69.6%), ash (5.8-15.8%) and dry matter digestibility (DMD) between 20.8 and 60.6% from 12 to 48 h of fermentation. Native plants such as L. hexandra and A. zizanioides presented higher biomass production, CP, ash, cellulose, and Ca levels than the control plant. During the experimental period (30 to 50 days), the grasses did not present significant nutrient availability changes. In terms of fermentation characteristics, L. hexandra increased ammonia concentrations and total volatile fatty acids (TVFA) and butyric acid. This latter effect was also observed in A. zizanioides grass. L. hexandra and A. zizanioides grasses constitute a valuable alternative forage resource during the flooding times of the studied ecosystem.

Advances in microbial pretreatment for biorefining of perennial grasses

Perennial grasses are potentially abundant sources of biomass for biorefineries, which can produce high yields with low input requirements, and many added environmental benefits. However, perennial grasses are highly recalcitrant to biodegradation and may require pretreatment before undergoing many biorefining pathways. Microbial pretreatment uses the ability of microorganisms or their enzymes to deconstruct plant biomass and enhance its biodegradability. This process can enhance the enzymatic digestibility of perennial grasses, enabling saccharification with cellulolytic enzymes to produce fermentable sugars and derived fermentation products. Similarly, microbial pretreatment can increase the methanation rate when the grasses are used to produce biogas through anaerobic digestion. Microorganisms can also increase the digestibility of the grasses to improve their quality as animal feed, enhance the properties of grass pellets, and improve biomass thermochemical conversion. Metabolites produced by fungi or bacteria during microbial pretreatment, such as ligninolytic and cellulolytic enzymes, can be further recovered as added-value products. Additionally, the action of the microorganisms can release chemicals with commercialization potential, such as hydroxycinnamic acids and oligosaccharides, from the grasses. This review explores the recent advances and remaining challenges in using microbial pretreatment for perennial grasses with the goal of obtaining added-value products through biorefining. It emphasizes recent trends in microbial pretreatment such as the use of microorganisms as part of microbial consortia or in unsterilized systems, the use and development of microorganisms and consortia capable of performing more than one biorefining step, and the use of cell-free systems based on microbial enzymes. KEY POINTS: • Microorganisms or enzymes can reduce the recalcitrance of grasses for biorefining • Microbial pretreatment effectiveness depends on the grass-microbe interaction • Microbial pretreatment can generate value added co-products to enhance feasibility.