Metabolism in most organisms can show variations between the day and night. These variations may also affect the composition of products derived from livestock. The aim of the present study was to investigate the difference in composition between the day milk and night milk of dairy cows. Ten multiparous Holstein cows (milk yield = 25.2 ± 5.00 kg/d) were randomly selected during mid lactation. Milk samples were collected at 0500 h ("night milk") and 1500 h ("day milk") and analyzed to determine their composition. Mid-infrared spectroscopy was used to analyze macronutrient content of milk. Metabolomics and lipidomics were used to detect and analyze small molecules and fatty acids, respectively. An automatic biochemical analyzer and ELISA kits were used to determine biochemical indicators, as well as antioxidant and immune parameters in the milk. Though milk fat, protein, lactose, and total milk solids were not different between day milk and night milk, small molecules, metabolites and lipids, and hormones and cytokines differed between day milk and night milk. Regarding biochemical and immune-related indicators, the concentrations of malondialdehyde, HSP70, and HSP90 in night milk were lower than that in day milk. However, interferon-γ levels were higher in night milk. Additionally, night milk was naturally rich in melatonin. Lipidomics analyses showed that the levels of some lipids in night milk were higher than those in day milk. Metabolomics analyses identified 36 different metabolites between day milk and night milk. Higher concentrations of N-acetyl-d-glucosamine, cis-aconitate, and d-sorbitol were observed in day milk. However, the other 33 metabolites analyzed, including carbohydrates, lipids, AA, and aromatic compounds, showed lower concentrations in day milk than in night milk. The present findings show that the composition of night milk differs considerably from that of day milk. Notable changes in the circadian rhythm also altered milk composition. These results provide evidence to support the strategic use and classification of day milk and night milk.

The aim of this study was to improve the utilization of peanut vines as forage material for ruminants by investigating the degradation pattern of peanut vines in the dairy cow rumen. Samples of peanut vine incubated in cow rumens were collected at various time points. Bacterial diversity was investigated by scanning electron microscopy (SEM) and 16S rRNA gene sequencing. Carbohydrate-active enzymes (CAZymes) were analyzed by metagenomics. The peanut vines degraded rapidly from 2 to 24 h, before slowing from 24 to 72 h. SEM images confirmed dynamic peanut vine colonization. Firmicutes and Bacteroidetes were the two most dominant bacterial phyla throughout. Principal coordinates analysis indicated significant microbial composition changes at 6 and 24 h. This may be because, in the early stage, soluble carbohydrates that are easily degradable were degraded, while in the later stage, fibrous substances that are difficult to degrade were mainly degraded. Glycoside hydrolases (GHs) were the most abundant CAZymes, with peak relative abundance at 6 h (56.7 trans per million, TPM), and reducing at 24 (55.9 TPM) and 72 h (55.3 TPM). Spearman correlation analysis showed that Alistipes_sp._CAG:435, Alistipes_sp._CAG:514, Bacteroides_sp._CAG:1060, Bacteroides_sp._CAG:545, Bacteroides_sp._CAG:709, Bacteroides_sp._CAG:770, bacterium_F082, bacterium_F083, GH29, GH78, and GH92 were important for plant fiber degradation. These findings provide fundamental knowledge about forage degradation in the cow rumen, and will be important for the targeted improvement of ruminant plant biomass utilization efficiency.

Dietary crude protein concentration oscillation can improve the nitrogen utilization efficiency of ruminants. However, little is known about the dynamic changes in microbiota and fermentation in the rumen of calves during the oscillation period. In this study, six calves were fed an oscillating diet at 2-day intervals, including a high-protein diet (HP) and a low-protein diet (LP). The rumen fermentation parameters, plasma urea-N concentration, and rumen bacterial diversity were characterized throughout the oscillation period. The concentrations of volatile fatty acids, NH₃-N, and plasma urea-N in rumen changed significantly with an oscillating diet. The abundance of Prevotella_1, Selenomonadales, Succiniclasticum, Clostridiales, Ruminococcaceae, Lachnospiraceae, and Rikenellaceae_RC9_gut_group showed significant changes with diet. Prevotella_1 was positively correlated, and Lachnospiraceae_AC2044_group and Saccharofermentans were negatively correlated with NH₃-N. The abundance of Amino Acid Metabolism, Metabolism of Other Amino Acids, and Glycan Biosynthesis and Metabolism pathways, annotated by bacterial functional genes, decreased when the diet changed from HP to LP. The abundance of the Carbohydrate Metabolism pathway increased after the two dietary changes. In conclusion, the plasma urea-N concentration was not as sensitive and quick to adapt to diet changes as the rumen fermentation parameters. Rumen bacteria were responsible for increasing the nitrogen utilization efficiency of calves fed an oscillating diet.

Defensins, one of the members of the antimicrobial peptide family, play a vital role in resisting microbial invasion and immune regulation. Porcine β-defensin 2 possesses excellent stability, making it an ideal antibiotic alternative for feed additives. In this study, a total of 15 piglets were used to investigate the effects of supplementing diets with 2.5 mg/kg (LP group) and 5 mg/kg (HP group) of pBD2 to weaned piglets. The results revealed that pBD2 significantly increased the total weight gain and average daily weight gain (p < 0.05), the contents of T-AOC, SOD, IgM, and IL-10 in serum (p < 0.05), the villus-to-crypt ratios, and the expression of tight-junction proteins ZO-1 and claudin-1 (p < 0.05) in the small intestine. Furthermore, pBD2 increased the abundance of beneficial bacteria related to nutrient and energy metabolism while decreasing the abundance of harmful bacteria associated with intestinal inflammation and diarrhea. Alterations in the gut microbiota were closely associated with the levels of T-AOC, SOD, IgM, and IL-10 in serum. pBD2 primarily enhanced the health of weaned piglets by influencing antioxidant capacity, intestinal barrier function, and the intestinal microbiota. Our research provides a novel perspective for addressing the issue of antibiotic residues in feed.