To explore whether or not the gossypol varied in cottonseed by-products affect rumen degradability and fermentation efficiency, an in vitro cumulative gas production experiment was applied with mixed rumen microorganism to compare rumen fermentation characteristics of whole cottonseed (WCS, n = 3 samples), cottonseed meal (CSM, n = 3 samples), and cottonseed hull (CSH, n = 2 samples). The five-replicate fermentation per sample per incubation time continuously lasted for 0.5, 1.5, 3, 6, 12, 24, 36, and 48 h with an automated gas production recording system. Regardless of distinct nutrient differences, the free gossypol level in these cottonseed by-products ranked: WCS > CSH > CSM. After 48 h of incubation, the in vitro dry matter degradability and ammonia N concentration ranked as: CSM > WCS > CSH. The cumulative gas production and total volatile fatty acid (VFA) levels in the culture fluids ranked: CSM > CSH > WCS, in which the average production rate ranked: CSM > WCS > CSH. Regarding the molar VFA pattern, WCS in comparison with CSH and CSM presented the lowest production of non-glucogenic acids (e.g., acetate) and exhibited the highest fermentation efficiency of energy from carbohydrates to VFAs. There was a significant negative correlation between the gossypol content and cumulative gas and total VFA production, suggesting that the greater gossypol in cottonseed by-products, the more detrimental effect occurred for rumen fermentation. In a brief, WCS exhibited mediocre rumen degradability and less microbial fermentation efficiency than CSH and CSM, depending on their gossypol levels.

Cysteamine (CS) is an essential nutritional regulator that improves the productive performance of animals by regulating somatotropic hormone secretion. To investigate the fattening potential and effects of CS on rumen microbial fermentation, 48 feedlot lambs were randomly assigned to four groups and fed diets supplemented with different CS concentrations (0, 20, 40, and 60 mg/kg BW). An increase in dietary CS concentrations linearly increased the average daily gain (ADG) and dry matter intake (p < 0.05) but decreased the feed-to-gain ratio (p < 0.01). For the serum hormone, increasing the dietary CS concentration linearly decreased somatostatin and leptin concentration (p < 0.01) but linearly increased the concentration of growth hormone and insulin-like growth factor 1 (p < 0.01). Regarding rumen fermentation, ruminal pH, ammonia-N, and butyrate content did not differ among the four treatments, although dietary CS supplementation linearly increased microbial protein and propionate and decreased the amount of acetate (p < 0.05). Furthermore, an increase in dietary CS concentrations quadratically decreased the estimated methane production and methane production per kg ADG (p < 0.05). High-throughput sequencing revealed that increased dietary CS concentrations quadratically increased Prevotella (p < 0.05), and Prevotella and norank_f__norank_o__Clostridia_UCG-014 were positively correlated with growth performance and rumen fermentation in a Spearman correlation analysis (r > 0.55, p < 0.05). Overall, a CS concentration higher than 20 mg/kg BW produced growth-promoting effects by inhibiting somatostatin concentrations and shifting the rumen toward glucogenic propionate fermentation by enriching Prevotella. In addition, Prevotella and norank_f__norank_o__Clostridia_UCG-014 were positively correlated with growth performance in lambs.

Deoxynivalenol (DON) is a type B trichothecene mycotoxin produced by Fusarium fungi. To investigate its ruminal degradability and its effect on rumen fermentation, a 2 × 5 factorial experiment was conducted in vitro with two feed substrates with different forage levels (high forage (HF), forage-to-concentrate = 4:1; low forage (LF), forage-to-concentrate = 1:4) and five DON additions per substrate (0, 5, 10, 15, and 20 mg/kg of dry matter). After 48 h incubation, the DON degradability in the HF group was higher than in the LF group (p < 0.01), and it decreased along with the increase in DON concentrations (p < 0.01), which varied from 57.18% to 29.01% at 48 h. In addition, the gas production rate, total VFA production and microbial crude protein decreased linearly against the increase in DON additions (p < 0.05). Meanwhile, the proportion of CH4 in the fermentation gas end-products increased linearly, especially in the HF group (p < 0.01). In brief, rumen microorganisms presented 29–57% of the DON degradation ability and were particularly significant under a high-forage substrate. Along with the increasing DON addition, the toxin degradability decreased, showing a dose-dependent response. However, DON inhibited rumen fermentation and increased methane production when it exceeded 5 mg/kg of dry matter.

Corn silage is an important source of forage, but whether or not bacterial inoculants should be applied is somewhat controversial in ruminant feeding practice. In the present study, chopped whole corn plants treated with a single inoculant of Lactobacillus buchneri (LB), Lactobacillus plantarum (LP), Pediococcus pentosaceus (PP) served as either homofermentation (e.g., lactate only) or heterofermentation (e.g., lactate and acetate) controls and compared with those treated with either a mixture of the lactic acid bacteria (QA: 60% LP, 10%PP, 30% LB) or a mixture of the lactic acid bacteria (QB: 60% LP, 15% PP, 25% LB), to investigate their effects on the fermentation quality, ester-linked phenolic acids, and in vitro digestibility. After 60 day ensiling, the addition of QA exhibited the lowest pH (3.51) with greater lactic acid (LA) production. The ester-linked ferulic acid (FAest) and p-coumaric acid (pCAest) concentrations were significantly decreased during 60 days ensiling. And among all these groups, the LB and QA treated group showed a lower concentration of FAest and pCAest than other groups. After 60 days ensiling, Lactobacillus was the dominant genus in all LAB treated groups. Meanwhile, negative correlations of Bacillus, Bacteroides, Bifidobacterium, Blautia, Prevotella, Ruminococcus, and Roseburia with FAest content after 60 days ensiling occurred in the present study. Komagataeibacter was mainly found in LB and PP addition silages, and presented a significant negative effect with the level of acid detergent fiber (ADF). To explore whether the addition of LABs can improve digestibility of whole corn silage, an in vitro rumen fermentation was conducted using the 60 day ensiled whole corn silages as substrates. The QA addition group exhibited a greater 48 h and 96 h in vitro dry matter and ADF disappearance, greater 48 h gas production and less methane emissions. Even though there were the same neutral NDF levels in corn silages treated with LB and QA after 60 days ensiling, the QA treated silages with lower FAest and pCAest presented higher IVDMD after 96 h and 48 h in vitro fermentation. In brief, the addition of mixed inoculants of 60% LB,10% PP, 30% LB compared with the addition of whichever single HoLAB or HeLAB inoculants, facilitated the release of ester-linked phenolic acids (e.g., ferulic and p-coumaric acids) and remarkably, improved silage quality in terms of sharp pH decline and greater lactate production. Taken together with the improvement in rumen microbial fermentation, the results obtained in the present study provided concrete evidence for the role of mixed LAB application in corn silage preparation for ruminant feeding practices.

Gamma-aminobutyric acid (GABA), known as the most abundant inhibitory neurotransmitter in the mammalian brain, can permeate ruminal epithelia by passive diffusion and enrich in the rumen environment. To explore whether the addition of GABA can regulate rumen fermentation characteristics as well as methane production, a 2 × 6 factorial in vitro rumen batch culture was conducted to determine the supplemental effect of GABA at inclusion levels of 0 (Control), 10, 20, 30, 40 and 50 mg in culture fluids on rumen fermentation of two total mixed rations (HF—a high-fiber ration consisted of 70% corn silage and 30% concentrate; and LF—a low-fiber ration consisted of 30% corn silage and 70% concentrate). After 72 h in vitro incubation of two rations with mixed rumen microoganisms obtained from five rumen-cannulated lactating Holstein dairy cows, increasing GABA addition linearly increased cumulative gas production in the LF group, though in vitro dry matter digestibility was not affected in either the LF or HF group. Kinetic gas production analysis noted that increasing GABA addition mostly decreased the gas production rate (i.e., RmaxG), as well as the ration digestion rate (RmaxS) to reach maximum fermentation. The GABA addition did not affect pH or microbial growth (i.e., MCP). However, total volatile fatty acid production in both LF and HF groups all linearly increased with the increase in GABA addition. Along with the increase in GABA addition in both LF and HF groups, the ratio of non-glucogenic to glucogenic volatile fatty acids both increased, while the molar proportions of propionate and valerate were significantly decreased, and the acetate and butyrate proportions were increased after 72 h in vitro rumen fermentation. The time-course change of fermentation end-products generally showed that carbon dioxide declined from approximately 89% to 74%, and methane increased from approximately 11% to 26%. After 72 h in vitro fermentation, molar methane proportion was greater in the LF than in the HF group, and increasing GABA addition quadratically increased methane production in the LF group while a slight increase occurred in the HF group.

In plant cell wall, ferulic acid (FA) and p-coumaric acid (pCA) are commonly linked with arabinoxylans and lignin through ester and ether bonds. These linkages were deemed to hinder the access of rumen microbes to cell wall polysaccharides. The attachment of rumen microbes to plant cell wall was believed to have profound effects on the rate and the extent of forage digestion in rumen. The objective of this study was to evaluate the effect of bound phenolic acid content and their composition in corn silages on the nutrient degradability, and the composition of the attached bacteria. Following an in situ rumen degradation method, eight representative corn silages with different FA and pCA contents were placed into nylon bags and incubated in the rumens of three matured lactating Holstein cows for 0, 6, 12, 24, 36, 48, and 72 h, respectively. Corn silage digestibility was assessed by in situ degradation methods. As a result, the effective degradability of dry matter, neutral detergent fibre, and acid detergent fibre were negatively related to the ether-linked FA and pCA, and their ratio in corn silages, suggesting that not only the content and but also the composition of phenolic acids significantly affected the degradation characteristics of corn silages. After 24 h rumen fermentation, Firmicutes, Actinobacteria, and Bacteroidota were observed as the dominant phyla in the bacterial communities attached to the corn silages. After 72 h rumen fermentation, the rumen degradation of ester-linked FA was much greater than that of ester-linked pCA. The correlation analysis noted that Erysipelotrichaceae_UCG-002, Olsenella, Ruminococcus_gauvreauii_group, Acetitomaculum, and Bifidobacterium were negatively related to the initial ether-linked FA content while Prevotella was positively related to the ether-linked FA content and the ratio of pCA to FA. In summary, the present results suggested that the content of ether-linked phenolic acids in plant cell walls exhibited a more profound effect on the pattern of microbial colonization than the fibre content.

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The aim of this study was to investigate whether guanidine acetic acid (GAA) yields a response in rapid-growing lambs depending on forage type. In this study, seventy-two small-tailed Han lambs (initial body weights = 12 ± 1.6 kg) were used in a 120-d feeding experiment after a 7-d adaptation period. A 2 × 3 factorial experimental feeding design was applied to the lambs, which were fed a total mixed ration with two forage types (OH: oaten hay; OHWS: oaten hay plus wheat silage) and three forms of additional GAA (GAA: 0 g/kg; UGAA: Uncoated GAA, 1 g/kg; CGAA: Coated GAA, 1 g/kg). The OH diet had a greater dry matter intake, average daily gain, and hot carcass weight than the OHWS diet. The GAA supplementation increased the final body weight, hot carcass weight, dressing percentage, and ribeye area in the longissimus lumborum. Meanwhile, it decreased backfat thickness and serum triglycerides. Dietary GAA decreased the acidity of the meat and elevated the water-holding capacity in mutton. In addition, the crude protein content in mutton increased with GAA addition. Dietary GAA (UGAA or CGAA) might be an effective additive in lamb fed by different forage types, as it has potential to improve growth performance and meat quality.