This study compared serum immunological parameters, cytokines, intestinal permeability, fecal microbiota, and short-chain fatty acids (SCFAs) between healthy and diarrheic suckling calves. Serum and facecal samples were analyzed using ELISA kits, 16S rDNA sequencing, and targeted metabolomics. Compared with healthy calves, the serum levels of aspartate aminotransferase, interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), endotoxin (ET), and diamine oxidase (DAO) were significantly higher (p < 0.05), whereas the serum levels of immunoglobulin A (IgA), immunoglobulin G (IgG), and interleukin-10 (IL-10) were significantly lower in diarrheic calves (p < 0.05). The contents of propionic acid, butyric acid, and valeric acid significantly decreased in the fecal of diarrheic calves (p < 0.05). Moreover, the Chao1 and observed_features index of fecal microbiota significantly decreased in diarrheic calves (p < 0.05). The relative abundance of Escherichia-Shigella, Clostridium_sensu_stricto_1, and Streptococcus was significantly higher (p < 0.05), whereas Phascolarctobacterium, Ruminococcus torques group, and Faecalibacterium were significantly lower in diarrheic calves (p < 0.05). Escherichia-Shigella abundance was positively correlated with ET, DAO, IL-1β, and TNF-α levels (p < 0.05). Faecalibacterium abundance was significantly positively correlated with IgG, IgA, IL-10, and butyric acid but negatively correlated with ET and DAO levels (p < 0.05). In summary, diarrheic suckling calves exhibited reduced immune function, inflammatory response, and increased intestinal permeability. The relative abundance of fecal microbiota of Escherichia-Shigella and Clostridium_sensu_stricto_1 increased, while propionic acid, butyric acid, and valeric acid concentration were decreased in calves with diarrhea. This underscores the critical interplay between microbiota balance and gut health in diarrhea.

This experiment investigated the effects of rumen-protected leucine (RP-Leu) supplementation on growth performance, rumen fermentation parameters, and rumen microbiota of fattening sheep. Forty fattening sheep (19.03 ± 0.38 kg) were randomly divided into four groups. The four groups were fed the basal diet supplemented with RP-Leu at 0 (L-0), 0.5 (L-0.5), 1.0 (L-1.0), or 1.5 (L-1.5) g/d. The experimental period lasted 67 d. The results demonstrated that compared with the L-0 group, the L-1.0 and L-1.5 groups significantly increased the average daily gain (ADG) by 22.2% and 18.0%, respectively (p < 0.05), and reduced the feed-to-gain ratio (F:G ratio) by 20.0% and 13.4% (p < 0.05); the L-1.5 group significantly increased the concentrations of propionate and isovalerate (p < 0.05) and significantly decreased the acetate to propionate ratio (A:P) by 25.7% (p < 0.05); and the L-1.0 group significantly decreased the concentrations of free branched-chain amino acids (BCAAs) in rumen (p < 0.05). A microbiota analysis showed that RP-Leu enriched the abundance of fiber-degrading bacteria. A correlation analysis showed that acetic acid and A:P were positively correlated with norank_f_F082 and norank_f_UCG-011 (p < 0.05). Phenylalanine, isoleucine, valine, and leucine were negatively correlated with norank_o_Bacteroidales (p < 0.05). In conclusion, RP-Leu improved the growth performance of fattening sheep by changing the rumen fermentation parameters and patterns; the optimal supplementation level is 1.0 g/d.

This study investigated the effects of dietary supplementation with varying doses of Clostridium butyricum (C. butyricum) on growth performance, diarrhea incidence, serum biochemical parameters, fecal short-chain fatty acids (SCFAs), and fecal microbiota in preweaning Holstein calves. Forty healthy newborn Holstein heifer calves with comparable birth weights were randomly assigned to four groups (control, 1 g/d supplementation, 3 g/d supplementation, and 5 g/d supplementation) for a 60-day trial. Growth parameters, diarrhea incidence, serum immunoglobulins (IgA, IgG, IgM), cytokines (IL-1β, TNF-α), antioxidant indicators (T-AOC, MDA), fecal short-chain fatty acids (SCFAs), and microbial composition were measured to evaluate the effects of C. butyricum. The results indicated that calves in the 5 g/d group exhibited a significantly higher average daily gain (ADG) compared with the control group (804.67 vs. 701.67 g/d, p < 0.05), with no significant differences in feed intake observed among groups (p > 0.05). During Days 22–42, the diarrhea incidence in the 5 g/d group was 7.74% lower than that in the control group (p < 0.05). This group exhibited significantly elevated serum IgM levels (Day 42, p < 0.05) and reduced IL-1β concentrations (Day 42, p < 0.05). Additionally, total antioxidant capacity (T-AOC) was significantly enhanced (Days 42 and 60, p < 0.05), while malondialdehyde (MDA) content was significantly decreased (Days 21 and 42, p < 0.05). At Day 42, fecal propionate and butyrate concentrations were significantly elevated in the 5 g/d group (p < 0.05), while the relative abundances of Bacteroides, Acidaminococcus, Bifidobacterium, Olsenella, Faecalitalea, and Ruminococcus were significantly increased (p < 0.05). The increase in these short-chain fatty acids and beneficial bacteria contributes to improved intestinal health and thus helps alleviate diarrhea. These findings indicate that supplementing preweaning calves’ milk with 5 g/d of C. butyricum significantly enhances growth performance and intestinal health. This provides evidence for the use of C. butyricum as a natural alternative to antibiotics in calf rearing.

The optimal timing for initiating starter feeding in lambs remains controversial, warranting a systematic evaluation of its effects across multiple indicators. This study investigated the effects of initiating starter feeding at 7, 14, or 21 days of age on growth performance, rumen fermentation, serum immunity, gastrointestinal development, and microbiota in Hu lambs. Forty-five newborn lambs were randomly assigned to three groups (n = 15 per group) and fed starter until slaughter at weaning (60 days). The 14-day group exhibited significantly higher body weight (BW) at 49 and 60 days compared with the 7-day group (p < 0.05), and greater average daily gain (ADG) during 28–35 days than the 21-day group. Rumen ammonia nitrogen (NH₃-N), acetate, propionate, valerate, and total volatile fatty acids (VFAs) were higher in the 7-day and 14-day groups than in the 21-day group (p < 0.05). The 14-day group showed lower pro-inflammatory cytokines (IL-1β, TNF-α) and higher immunoglobulins (IgA, IgG, IgM) and anti-inflammatory cytokines (IL-2, IL-4) (p < 0.05). This group also displayed improved rumen papilla width, jejunal villus dimensions, and reduced crypt depth. Beneficial microbes such as Christensenellaceae_R-7_group and Butyrivibrio were enriched in the 14-day and 21-day groups. In conclusion, initiating starter feeding at 14 days of age optimizes growth, rumen function, immune response, and colonization of beneficial microbiota in Hu lambs.