Polyphenol-rich grape pomace (GP) represents a valuable processing by-product with considerable potential as sustainable livestock feed. This study aimed to investigate the effects of different levels of GP on the growth performance and nitrogen utilization efficiency, antioxidant activity, and rumen and rectum microbiota of Angus bulls. Thirty Angus bulls were allocated three dietary treatments according to a completely randomized design: 0% (G0), 10% (G10), and 20% (G20) corn silage dry matter replaced with dried GP dry matter. The results showed that the average daily gain (ADG) of the G0 group and G10 group was higher than that of the G20 group (p < 0.05); urinary nitrogen levels decreased linearly with the addition of GP (linear, p < 0.05). In terms of antioxidants, the levels of catalase (CAT) in the G10 group were higher than in the G0 and G20 groups (p < 0.05), and the total antioxidative capacity (T-AOC) was significantly higher than that in the G20 group (p < 0.05). In addition, in the analysis of a microbial network diagram, the G10 group had better microbial community complexity and stability. Overall, these findings offer valuable insights into the potential benefits of incorporating GP into the diet of ruminants.

This study aimed to investigate the effects of rumen-protected guanidinoacetic acid (RP-GAA) on growth performance, gut microbiota, and serum metabolism in beef cattle under chronic heat stress. A randomized block design was employed to allocate 14 F1 Simmental crossbred cattle (Simmental ♂ × Bos indicus ♀) with an average body weight of 312.5 ± 55.0 kg into two groups (n = 7): a control group was fed a basal diet without RP-GAA and a treatment group was fed the same basal diet supplemented with 10.0 g/day of RP-GAA. During feeding experiments, at 2 p.m., the average temperature increased to 31.5°C, with a relative humidity of 69.5% and a THI of 83.2. All animals are under chronic heat stress. The results indicated that RP-GAA supplementation significantly increased dry matter intake and feed conversion ratio in beef cattle under chronic heat stress (p < 0.05). RP-GAA supplementation tended to reduce respiratory rate or rectal temperature (p < 0.1). Compared to the control group, the treatment group exhibited significantly higher glucose, blood urea nitrogen, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol levels (p < 0.05). 16S rRNA gene sequencing revealed that RP-GAA supplementation significantly altered the ruminal microbiota composition, increasing the abundance of Firmicutes and Bacteroidota (p < 0.05), while reducing Proteobacteria (p < 0.01). Principal coordinate analysis (PCoA) and Adonis test (R² = 0.190, p = 0.003) jointly revealed a distinct difference in fecal microbiota structures between the two groups. Metabolomic analysis identified significant changes in pathways related to creatine synthesis, energy metabolism, and nitrogen utilization, supported by the orthogonal partial least squares discriminant analysis model (R²Y = 0.983, Q² = 0.836, p < 0.05). These findings suggest that RP-GAAenhances energy homeostasis, supports gut health, and mitigates the adverse effects of heat stress, providing a promising strategy to improve production efficiency and animal welfare in heat-stressed cattle.

Buffalo meat is gaining popularity for its nutritional properties, such as its low fat and cholesterol content. However, it is often unsatisfactory to consumers due to its dark color and low tenderness. There is currently limited research on the regulatory mechanisms of buffalo meat quality. Xinglong buffalo are raised in the tropical Hainan region and are undergoing genetic improvement from draught to meat production. For the first time, we evaluated the meat quality traits of Xinglong buffalo using the longissimus dorsi muscle and compared them to Hainan cattle. Furthermore, we utilized a multi-omics approach combining transcriptomics and metabolomics to explore the underlying molecular mechanism regulating meat quality traits. We found that the Xinglong buffalo had significantly higher meat color redness but lower amino acid content and higher shear force compared to Hainan cattle. Differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) were identified, with them being significantly enriched in nicotinic acid and nicotinamide metabolic and glycine, serine, and threonine metabolic pathways. The correlation analysis revealed that those genes and metabolites (such as: GAMT, GCSH, PNP, L-aspartic acid, NADP+, and glutathione) are significantly associated with meat color, tenderness, and amino acid content, indicating their potential as candidate genes and biological indicators associated with meat quality. This study contributes to the breed genetic improvement and enhancement of buffalo meat quality.

The objective of this study was to evaluate the effects of potato vine and leaf mixed silage (PVS) on rumen fermentation and the microbe in ruminants and to improve the utilization of PVS resources in ruminants through in vitro gas production and feeding trials. The experiment was divided into three groups: PVS1 (50% corn + 50% potato vine and leaf silage), PVS2 (75% potato vine and leaf + 15% rice straw + 10% cornmeal silage) and whole-plant corn silage (CS). The in vitro gas production results showed that there was a significant reduction in PVS groups in the indexes of total gas (p < 0.05) and CH₄ production (p < 0.05). The digestibility of dry matter (p < 0.05), neutral detergent fiber (NDF) (p < 0.05), and acid detergent fiber (ADF) (p < 0.05) at 48 h were decreased in the PVS group. For the rumen fermentation indexes, the pH (p < 0.05), microbial crude protein (MCP) (p < 0.05), and acetate to propionate (p < 0.05) showed an increase in the PVS group, but a decrease in the total volatile fatty acid concentration (p < 0.05). In the feeding trial, different silages in diets had no significant effect on the rumen fermentation indexes (p > 0.05). In the rumen microbe composition, the PVS diet significantly reduced the abundance of Prevotella (p < 0.05) compared with the CS diet group. The PVS2 diet significantly increased the abundance of the Lachnospiraceae_XPB1014_group (p < 0.05) and Bacteroidales_bacterium_Bact_22 (p < 0.05) compared with the CS diet group. In conclusion, PVS had no negative effect on rumen fermentation characteristics and rumen microbial flora and could significantly reduce rumen gas production compared to CS, positively mitigating animal husbandry CH₄ emissions and environmental protection.

Raw potato fries are a type of potato by-product (PBP), and they have great potential as a partial replacement of grain in animal feeds to improve the environmental sustainability of food production. This study aimed to investigate the effects of replacing corn with different levels of PBP (0%, 12.84%, 25.65%, and 38.44%) in the total mixed ration (TMR) of Angus bull. Sixty 16-month-old Angus bulls (548.5 ± 15.0 kg, mean ± SD) were randomly assigned to four treatments. The results indicated that with the increase in the substitution amount of PBP, the body weight decreased significantly. The dry matter apparent digestibility and starch apparent digestibility linearly decreased as PBP replacement increased. The feed ingredient composition in the TMR varied, leading to a corresponding change in the rumen microbiota, especially in cellulolytic bacteria and amylolytic bacteria. The abundance of Succiniclasticum in the 12.84% PBP and 38.44% PBP diets was significantly higher than that in the 0% PBP and 25.65% PBP diets. The abundance of Ruminococcus linearly increased. In conclusion, using PBP to replace corn for beef cattle had no negative impact on rumen fermentation, and the decrease in apparent digestibility explained the change in growth performance. Its application in practical production is highly cost-effective and a strategy to reduce food waste.

This study aims to explore the different growth performances of the Angus bull on potato vine and leaf mixed silage in the early fattening period and to provide a reference animal production trial. Thirty-six 13-month-old Angus bulls were divided into three groups with 403.22 ± 38.97 kg initial body weight and fed with three different silage diets: (1) control: whole-plant corn silage as control (CS); (2) treatment 1: 50% whole-plant corn +50% potato vine and leaf silage (PVS1); and (3) treatment 2: 75% potato vine and leaf +15% rice straw +10% cornmeal silage (PVS2). After the 14 days pre-feeding, the formal experiment was carried out for 89 days. The result showed that the ash content of the potato vine and leaf mixed silage (PVS) in the treatment groups was higher than that in control group, and the ash content of PVS1 and PVS2 even reached 10.42% and 18.48% (DM%), respectively, which was much higher than that of the CS group at 4.94%. The crude protein content in silage also increased with the additional amount of potato vine and leaf. The apparent crude protein digestibility of the PVS groups was also significantly higher than that of the CS group (p < 0.05). In terms of serum biochemical indexes, blood urea nitrogen (BUN) in the experimental groups was significantly higher than in the control group (p < 0.05). Compared with PVS2, cholesterol (CHO) was significantly lower in the CS and PVS1 groups (p < 0.05). Moreover, the high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) of PVS2 were significantly higher than those of the CS and PVS1 group (p < 0.05), and daily gain (ADG) as a key production index had a significantly negative correlation with the CHO (r = −0.38, p < 0.05) and HDL-C (r = −0.40, p < 0.05) of cattle. In conclusion, PVS had higher crude protein content and ash but less starch than whole-corn silage. The PVS could replace whole-plant corn silage at the same dry matter status and did not affect the weight gain in this trial.