Application of Fermentation Technology in Animal Nutrition

Fermentation technology has been utilized in animal nutrition worldwide for an extended period, with particular focus on animal feed. The principal objective of such methods is to preserve feedstuffs over an extended period. Harvested forages, putrefactive agro-industrial or food processing by-products, and total mixed rations are frequently ensilaged to ensure that the stability, palatability, and safety standards of animal feed are maintained over time [1]. Enhancing the nutritive value or safety of underutilized feed resources through fermentation technology to eliminate the risk of toxicity or low digestibility is also of considerable interest. To achieve those objectives, a range of microbiological, chemical and physical techniques have been developed. This Special Issue on “Application of Fermentation Technology in Animal Nutrition” comprises 11 original research articles and 1 communication. Collectively, these contributions illustrate the promising future of fermentation technology in animal nutrition research, one that is committed to both tradition and innovation, with the objective of advancing the frontiers of fermentation science.

In light of the growing popularity of Greek yogurt, significant quantities of acid whey are being generated on a global scale. However, the utilization of yogurt acid whey in animal nutrition remains constrained. Palamidi et al. [2] investigated the impact of incorporating yogurt acid whey powder (YAWP) into forage maize prior to ensilage on the microbial, nutritional, and fermentation quality of the resulting maize silage and found that adding 5 and 10% YAWP during silage preparation improved the fermentative and nutritional quality.

Improper disposal of vegetable waste can cause significant environmental contamination. However, due to their high moisture and organic matter content, these materials are not suitable for disposal via landfill or incineration. However, vegetable waste contains a substantial quantity of nutrients and, when combined with rice straw, exhibits certain complementary effects in terms of its moisture levels, nutrients, and physical structure. Lu et al. [3] assessed the safety profile of the mixed silage by quantifying the mycotoxin, vitamin, heavy metal, and pesticide residue content, as well as conducting a feeding trial with Hu sheep. The feed safety index content of the mixed silage complied with the Chinese feed safety and hygiene standards and had no adverse effect on the growth of the Hu sheep. Furthermore, the silage enhanced the digestive tract and immune performance of the sheep, facilitating their healthy development.

Dhakal et al. [4] examined the influence of in vitro rumen fermentation on the microbial community compositions and structure of rumen fluid, comparing samples taken before and after fermentation assays. The in vitro procedure did not impact the bacterial community structure in comparison to the original rumen fluid inoculum. It is important to note that evaluating the microbiome at a single endpoint (i.e., 48 h) was insufficient, as it did not provide a comprehensive understanding of the microbiome profile dynamics. Nevertheless, this study established a basis for future microbiome-based in vitro fermentation experiments and confirmed that this technique permits a high degree of species diversity that approximates the function of the rumen in vivo.

Sugarcane (Saccharum officinarum) bagasse (SCB) is one of the most extensively produced lignocellulosic biomasses and has significant potential for sustainable food production if recycled as ruminant animal feed. Nevertheless, due to the presence of severe lignification, namely lignin–(hemi)–cellulose complexes, ruminants are only able to utilize a small portion of the polysaccharides in such recalcitrant lignocellulosic biomasses. Khan et al. [5] systematically evaluated the improvement in nutritive value, the in vitro dry matter digestibility, and the extent and rate of in vitro total gas and methane production during the 72-hour in vitro ruminal fermentation of SCB, in which it underwent bioprocessing with Pleurotus djamor, Agaricus bisporus, Pleurotus ostreatus and Calocybe indica under solid-state fermentation for 0, 21 and 56 days. Treating SCB with lignin-degrading white-rot fungi enhanced its nutritive value and digestibility. In particular, C. indica shows excellent potential for selective, extensive and rapid degradation of lignin, as well as for enhancing SCB’s nutritive value and digestibility for ruminant nutrition.

Silage is a fundamental element of a ruminant diet, and it plays a pivotal role in ruminant production in terms of both productivity and animal health. Nevertheless, there is a paucity of data concerning the impact of mixed silage as an unconventional roughage on the fecal microbiota and metabolites in Hu sheep. Li et al. [6] examined the impact of mixed silage comprising rice straw and Chinese cabbage waste (mixed silage) on the fecal microbiota and metabolites in Hu sheep, employing metabolomic and Illumina sequencing analysis, and concluded that adding mixed silage to the diet of Hu sheep could change the microbial community structure of hindgut and regulate the metabolism of nucleotides and amino acids, which influences the animal performance.

Pineapple residue (PR), which contains substantial amounts of water-soluble carbohydrates, protein, and fiber, is another potential food source for ruminants. However, its high moisture levels make storage challenging. Corn straw (CS) is a common roughage source for ruminants and is frequently utilized for ensilage; thus, co-ensiling of CS and PR might prove an effective solution to the storage issue. Li et al. [7] evaluated the fermentation quality, chemical and microbial compositions of CS silage mixed with PR; said mixture exhibited a reduced pH value and elevated acetic and lactic acid concentrations. Furthermore, the addition of PR enhanced the relative abundance of Lactobacillus in the mixed silage. It was concluded that PR can enhance the quality of CS ensilage. The optimal proportion of PR was determined to be 15% based on fresh weight.

Lactobacillus delbrueckii has attracted considerable interest due to its contributions to diarrheal treatment and prevention, gut microecological balance, growth promotion, immune modulation, and meat quality enhancement in livestock. Nevertheless, there is a paucity of documented evidence concerning its effect on the liver metabolism and gut microbiota in weaned piglets. Wang et al. [8] studied the impact of Lactobacillus delbrueckii on liver metabolism changes in weaned piglets, investigated the mechanisms by which it influences their productive performance and supplied key theoretical support and reference data for applying Lactobacillus delbrueckii formulations in antibiotic-free diets and actual production for weaned piglets. In comparison to the control, Lactobacillus delbrueckii augmented liver glycogen content, mitigated weaning stress-induced liver damage and metabolic disorders, and reinforced liver antioxidant function by optimizing the metabolism of carbohydrates and lipids, improving liver function.

Essential oils have been found to effectively control fungal growth in silage. Nevertheless, the efficacy of essential oils may be contingent upon the chemical constituents and concentration of each oil. Utilizing essential oil combinations could result in additive, antagonistic, or synergistic effects. Aniceto et al. [9] assessed the influence of those essential oils and their combinations on the fermentation characteristics, microbial numbers, losses by effluents and gases, aerobic stability, and nutritive value of sorghum silage. The researchers concluded that the essential oils and their blends had disparate impacts on sorghum silage. Among the essential oils, rosemary (Ros) and blends containing Ros demonstrated superior efficacy. The addition of rosemary (Ros) was found to enhance the aerobic stability and nutritive value of sorghum silage.

To supplement existing feed resources, Li et al. [10] studied the influences of additives, moisture level, and their interactions on the fermentative profile, aerobic stability, and in vitro digestibility of mixed silage composed of cornmeal and amaranth. The optimal fermentation quality, aerobic stability and in vitro digestibility of cellulase+ Lactobacillus plantarum-treated cornmeal and amaranth mixed silage were achieved at a moisture level of 60%. This study corroborates the potential of amaranth as a silage feedstock and its potential application for enhancing feed quality and animal performance. These findings could provide farmers with a greater range of feed options and opportunities for resource utilization, thereby promoting the sustainable development of the animal husbandry.

Plant extracts are a promising alternative to synthetic drugs due to the secondary compounds they contain, including tannins, saponins, essential oils, and flavonoids, which exhibit a range of biological activities. Freitas et al. [11] assessed the impact of hydroalcoholic (HE) and ethanolic (EE) extracts of Urochloa brizantha at varying concentrations on rumen fermentation through an in vitro gas production technique. Both the HE and EE extracts of U. brizantha influenced rumen fermentation kinetics, with the HE extract demonstrating a greater level of protodioscin. More research is required to optimize extraction methodologies, comprehensively profile secondary compounds and evaluate the efficacy of different doses to determine the viability of U. brizantha extract as an additive.

Co-ensiling has been extensively applied to improve fermentation quality. Nevertheless, there is still a lack of clarity regarding the potential for producing quality silages by co-ensiling Napier grass (NG) with sugarcane tops (STs). Xie et al. [12] assessed the fermentative profile and the chemical and microbial compositions of silage produced from mixtures of ST and NG in different proportions. This study suggests that quality silage could be produced with NG:ST ratios of 40:60 to 20:80, and that these silages could optimize the nutrient supply for ruminants.

The soybean (Glycine max (L.) Merr.) is a significant oilseed crop which is renowned for its abundant nutritive value and quality protein. To enlarge the feed protein resources and enhance the utilization of soybeans as a raw material, Meng et al. [13] studied the feasibility of employing whole-plant soybean as silage and identified the optimal fermentation duration. WPS silage is a potential feed source; however, under natural fermentation conditions, it is susceptible to undesirable fermentation.

Together, this Special Issue presents several original studies in the field of animal nutrition, including research on co-ensiling technology, silage additives, rumen fermentation, and related topics. These findings could help to improve feed resources, optimize silage quality and improve animal performance. As this Special Issue draws to a close, it is obvious that the field of silage research is not merely evolving but undergoing a revolution. The challenges that lie ahead are considerable, but so are the opportunities. By addressing these challenges and pursuing the research directions outlined above, it is possible to ensure that fermentation technology will remain a critical aspect of animal nutrition, meeting the evolving needs of animal husbandry.