This study aimed to study compound probiotics’ (Lactobacillus casei, Lactobacillus acidophilus and Bifidobacterium) effects on production performance, lipid metabolism and meat quality in heat-stressed broilers. A total of 400 one-day-old AA broilers were randomly divided into four groups, each containing the same five replicates, with 20 broilers in each replicate. The control (21 °C) and experiment 2 were fed a basic corn–soybean meal diet. Experiment 1 (21 °C) and experiment 3 were fed a basic corn–soybean meal diet with 10 g/kg compound probiotics on days 7 and 28, respectively. The ambient temperature of experiment 2 and experiment 3 was increased to 30–32 °C (9:00–17:00) for 28–42 days, while the temperature for the other time was kept at 21 °C. The results showed that, compared with the control, the production performance and the content of high-density lipoprotein cholesterol in experiment 1 and triglyceride (TG) in experiment 2 increased (p < 0.05). Compared with experiment 2, TG decreased and the production performance increased in experiment 3 (p < 0.05). However, there was no significant change in meat quality indicators. Weighted gene co-expression network analysis (WGCNA) was used to analyze the intramuscular fat, abdominal fat and five blood lipid indicators. We found five related modules. Fatty acid biosynthesis, glycerolipid metabolism, and fat digestion and absorption were the pathways for KEGG enrichment. Additionally, NKX2-1, TAS2R40, PTH, CPB1, SLCO1B3, GNB3 and AQP7 may be the hub genes of compound probiotics regulating lipid metabolism in heat-stressed broilers. In conclusion, this study identified the key genes of compound probiotics regulating lipid metabolism and provided a theoretical basis for the poultry breeding industry to alleviate heat stress.

Abdominal fat (AF) and intramuscular fat (IMF) are key carcass traits in broilers but managing both is challenging due to their contrasting effects. Arginine (Arg) supplementation has potential effect in lipid metabolism, however its tissue specific effect remains poorly understood. The objective of this study was to investigate the tissue specific effect of Arg supplementation on growth performance and fat metabolism in both liver and pectoral muscle in broilers. A total of 480 Arbor Acre chicks were randomly assigned to four groups: Control (0 g/kg), Arg (1.8 g/kg), 5 × Arg (9 g/kg) and 10 × Arg (18 g/kg), with 12 replicates of 10 birds each. Overall, high Arg supplementation (5 ×, 10 ×) significantly impaired growth performance, reducing average daily gain and feed intake, accompanied by elevated serum AST and IFN-γ levels (P < 0.05). Liver transcriptomics analysis revealed that 10 × Arg significantly enriched PPAR signaling pathway, promoting fatty acid oxidation while suppressing lipogenic genes. Conversely, in pectoral muscle, high Arg (10 ×) promoted intramuscular fat deposition which was associated with downregulation of PPAR-α (P < 0.05) and increased expression of key lipogenic genes involved in de novo lipogenesis (SREBP-1c, FAS, ACC and SCD). Moreover, Arg supplementation modulated drug metabolism genes in liver, including EPX and RRM2, suggesting potential impacts on detoxification pathways. These findings underscore the importance of precise Arg dosing to optimize broiler growth, immune function, and carcass quality by targeting its tissue specific metabolic effect.

Background: Low birth weight (LBW) is correlated with gut microbiota dysbiosis and intestinal barrier function disruption, increasing susceptibility to enteric diseases. These alterations underscore the critical need to identify key regulators of gut homeostasis, among which bile acids are increasingly recognized as pivotal for barrier integrity, microbial ecology, and host metabolism. Methods: Eight pairs of LBW (the initial BW was 0.850 ± 0.053 kg) and normal-birth-weight (NBW; 1.488 ± 0.083 kg) piglets were compared to evaluate cecal morphology and bile acid profiles. Subsequently, sixteen LBW piglets and eight NBW piglets were allocated into three groups: NBW (1.563 ± 0.052 kg), LBW control (LBW-CON; 0.950 ± 0.120 kg), and LBW with bile acid supplementation (LBW-bile powder; 0.925 ± 0.116 kg). Piglets in the LBW-bile powder group received 25 mg/kg BW of bile powder (hyodeoxycholic acid-enriched) by daily oral gavage for 14 days. Results: LBW piglets exhibited retarded cecal development and lower abundance of hyocholic acid species (p = 0.006). Importantly, bile powder supplementation significantly improved cecal length (p = 0.009) and mucosal thickness (p = 0.020) compared with LBW-CON piglets. Microbial analysis showed that the microbial dysbiosis index was restored to near-normal levels. Transcriptomic analysis revealed impaired extracellular matrix structure and mucus secretion in LBW piglets. Notably, bile powder supplementation markedly upregulated the protein expression of WNT8B (p < 0.001) and the bile acid receptors (i.e., GPBAR1 and FXR), alongside enhanced tight junctions and the goblet cell marker mucin-2 expression (p < 0.05). Conclusions: These findings suggest that specific bile acid supplementation improves gut barrier function and partially supports cecal development in LBW piglets.

Heat stress represents a key environmental challenge in poultry production, markedly impairing broiler health and productivity. This study investigated the association between compound probiotic supplementation and the gut microbial community structure in heat-challenged broilers, analyzing the cecal contents from both groups using 16S rDNA amplicon sequencing. Compound probiotic supplementation was associated with changes in alpha diversity and richness of the cecal microbiota, with lower Shannon, Chao1, and ACE indices (p < 0.05). At the phylum level, compound probiotic supplementation significantly increased the relative abundance of Bacteroidota (p < 0.001) while decreasing that of Proteobacteria (p < 0.0001) in the cecum of broilers, whereas the relative abundances of Firmicutes and Verrucomicrobiota showed increasing trends. At the genus level, the relative abundance of Bacteroides (p < 0.0001) was significantly increased in the HP group, whereas Lactobacillus and Fusobacterium exhibited decreasing trends compared with the HS group. LEfSe analysis suggested Verrucomicrobia as a potentially enriched taxon in the HP group. Furthermore, KEGG level 3 functional prediction suggested enrichment of predicted pathways related to starch and sucrose metabolism, as well as amino acid and nucleotide metabolism in the HP group. These findings suggest that compound probiotics are associated with changes in gut microbial composition and predicted functions in heat-stressed broilers, providing preliminary, exploratory insights into their potential associations under heat stress.