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Silage is the most important component of a ruminant diet and has important production and health significance in ruminant production. The aim of the research was to investigate how the mixed silage of Chinese cabbage waste and rice straw (mixed silage) impacts the fecal microorganisms and metabolites in Hu sheep using Illumina sequencing and metabolomic analysis. A total of 16 Hu sheep (8 rams and 8 ewes) weighing about 39 kg and 5.5 months old were used as experimental sheep and divided into two groups (4 rams and 4 ewes, n = 8) using the principle of randomized trials: the control group with peanut sprouts, corn husks, and sorghum husks as roughage and the silage group with the mixed silage as roughage. There were no significant differences in the average daily gain (ADG), dry matter intake (DMI), or feed conversion rate (FCR) between the control group and the mixed silage groups (p > 0.05). Microbiome results showed that 15 microorganisms such as Ruminococcaceae UCG 010, Breznakia, Erysipelothrix, Desulfovibrio, Succiniclasticum, and Shuttleworthia were significantly different between the two groups. In addition, metabolomics showed that the mixed silage modulated the concentrations and metabolic pathways of metabolites in the manure. Significantly different metabolites were mainly enriched in amino acid anabolism (“glycine, serine, and threonine metabolism”, “valine, leucine, and isoleucine biosynthesis”, “arginine biosynthesis”, etc.), nucleic acid metabolism (pyrimidine metabolism). In conclusion, the addition of mixed silage to the diet of Hu sheep can alter the structure of the hindgut microflora and regulate the metabolism of amino acids and nucleotides, which affects health performance.

Improper disposal of vegetable waste can cause serious environmental pollution, but because they contain huge water content and organic matter, they are not suitable for disposal by methods such as incineration and landfill. However, vegetable waste contains a large amount of nutrients and have some complementary effects with rice straw in terms of physical structure, nutrients, and moisture. In this experiment, the plant feed (corn husk, peanut shells and sorghum shells) was used as the control group (CON group), and the mixed silage of Chinese cabbage waste and rice straw (mixed silage) was used as the experiment group (TRE group), and its safety performance was evaluated by testing its toxin content, pesticide residues, vitamin contents and feeding experiment of Hu sheep. In the animal experiment, 16 healthy Hu sheep (5.5 months, 39.11 ± 4.16 kg) were randomly divided into two groups of 8 each. The results of the safety performance evaluation showed that the content of mycotoxins, heavy metals, and nitrites as well as pesticide residues in the crude feeds of both groups were within the range of Chinese feed hygiene standards. In addition, the levels of deoxynivalenol (DON) and aflatoxin (AFT) in the CON group were lower, while the content of ochratoxin (OTA) and zearalenone were higher than those in the TRE group (p < 0.05). The levels of plumbum(Pb), chromium (Cr), cadmium (Cd), and nitrite in the CON group were lower than the mixed silage, while the levels of As were higher than the mixed silage (p < 0.05). It is worth noticing that the content of vitamin B2 (VB2) and vitamin C (VC) in the TRE group was higher than the CON group (p < 0.05). The results of the feeding experiment showed that the mixed silage did not affect the growth performance, nutrient digestibility, organ index, and intestinal index of Hu sheep (p > 0.05). In addition, the mixed silage reduced the weight of omasum, the proportion of omasum to live weight before slaughter, the amount of compound stomach, and the proportion of compound stomach to live weight before slaughter, which were higher than those in the TRE group (p < 0.05). The thickness of the basal layer of the rumen abdominal sac, the red blood cell count, the content of IL-10, and TNF-α in the blood, and TNF-α content in the rumen of the Hu sheep in the TRE group were higher than the CON group (p < 0.05). In conclusion, the feed safety index content of the mixed silage did not exceed the Chinese feed hygiene and safety standards and did not cause adverse effects on the growth performance of the Hu sheep, and it improved the immune performance of the body and digestive tract of the sheep to a certain extent and promoted the healthy development of the sheep.

The study was conducted in vitro to investigate the effects of different ratios of Urtica cannabina and Leymus chinensis on fiber microstructure and digestibility in ruminal fluid. The experiment was divided into five groups based on the U. cannabina/L. chinensis ratios: A (0:100), B (30:70), C (50:50), D (70:30), and E (100:0). The culture medium was collected at 0, 1, 3, 6, 12, and 24 h. The results showed that: (1) in vitro crude protein degradability (IVCPD) was higher in group A, whereas in vitro neutral detergent fiber degradability (IVNDFD) was higher in group C (p < 0.05); (2) protozoa count was increased from 1 h to 3 h and decreased afterwards, with significant differences observed in several genera (p < 0.05); (3) microbial crude protein (MCP) contents at 1, 3, 6, and 24 h were higher in groups A and C (p < 0.05); (4) the basic tissue of U. cannabina was gradually degraded. At 24h, the secondary xylem vessel structure was observed in groups B and C, but not in groups D and E. In summary, there was higher neutral detergent fiber (NDF) digestibility, higher rumen MCP contents, and lower protozoa count, showing the significance of the 50:50 ratio for microbial growth and fiber digestibility.