This study investigated the impact of dietary supplementation with hydrolyzed yeast (Kluyveromyces marxianus) on growth performance, humoral immunity, jejunal morphology, cecal microbiota and metabolic pathways in broilers raised at 45 kg/m². A total of 1,176 mixed sex 1-day-old Ross 308 broilers were distributed into 42 pens and randomly assigned to either the control group, the control + 250 g hydrolyzed yeast (HY)/ton, 250HY group, or the control + 500 g HY/ton, 500HY group for 42 d. HY did not affect growth performance. However, HY reduced (P < 0.05) mortality at 25 to 35 d. Dietary HY lowered the heterophil/lymphocyte ratio and enhanced the villus height/crypt depth ratio and Newcastle disease titer (P < 0.05). Compared with HY250 and the control, HY500 upregulated (P < 0.05) IL-10. HY enhanced the α diversity, inferring the richness and evenness of the ceca microbiota. HY500 had greater β diversity than the control (P < 0.05). Six bacterial phyla, namely, Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Verrucomicrobia, and Cyanobacteria, were found. The relative abundance of Firmicutes was greater in the HY500 treatment group than in the HY250 and control groups. HY decreased the abundance of Actinobacteria. HY supplementation altered (P < 0.05) the abundance of 8 higher-level taxa consisting of 2 classes (Bacilli and Clostridia), 1 order (Lactobacillales), 1 family (Streptococcaceae), and five genera (Streptococcus, Lachnospiraceae_uc, Akkermansiaceae, PACO01270_g, and LLKB_g). HY500 improved (P < 0.05) the abundance of Bacilli, Clostridia, Lactobacillales, Streptococcaceae, Streptococcus, PACO01270_g, and Lachnospiraceae_uc, while HY250 enhanced (P < 0.05) the abundance of Akkermansiaceae and LLKB_g. HY improved the abundance of Lactobacillus and Akkermansia spp. Minimal set of pathway analyses revealed that compared with the control, both HY250 and HY500 regulated 20 metabolic pathways. These findings suggest that dietary K. marxianus hydrolysate, especially HY500, improved humoral immunity and jejunal morphology and beneficially altered the composition and metabolic pathways of the cecal microbiota in broilers raised at 45 kg/m².

High stocking density (HSD) and heat stress (HS) challenge broiler production. While antibiotics can mitigate the adverse effects of HS and HSD, their restricted use underscores the need to explore phytochemicals, particularly their combined effects under such conditions. This study investigated the influence of flavonoids, isoquinoline alkaloids, and their combinations as alternatives to bacitracin on growth performance, inflammatory status, gut morphology, and ceca microbiome in broilers raised under HSD and HS. A total of 2100 one-day-old male Ross 308 broiler chicks were distributed into 70 replicates, randomly assigned to one of seven dietary treatments and raised during the summer for 37 days. The treatments included normal stocking density (NSD, 10 birds/m²); HSD (15 birds/m²); HSD + 50 ppm of bacitracin (BCT); HSD + 300 ppm of flavonoids (FVNs); HSD + 80 ppm of isoquinoline alkaloids (IQAs); HSD + FVNs (1–10 days) and IQAs (11–37 days) (FVN-IQA); and HSD + IQAs (1–10 days) and FVNs (11–37 days) (IQA-FVN). The HS index reached or exceeded 160 during most of the experimental period. From 11 to 24 days of age, the HSD and BCT birds had lower body weight gain. The FVNs, IQAs, and their combinations decreased the corticosterone, IL-6, malondialdehyde, and heterophil–lymphocytes ratio compared to the HSD. Jejunal, ileal, and duodenal villi height/crypt depth ratio was lower in HSD than in other treatments except BCT. The α- and β-diversity, microbiota composition, and metabolic pathways were affected by treatment groups. Overall, FVNs, IQAs, and their combinations improved the growth performance, anti-inflammatory response, and gut health in broilers under HSD and HS, with the combinations exerting synergistic effects.

This study investigated the effect of isoquinoline alkaloids as an alternative to bacitracin on growth performance, oxidative stress, inflammatory status, and ceca microbiome of broilers raised under high stocking density (HSD). A total of 1,500 one-day-old male Ross 308 chicks were randomly assigned to five treatment groups, with 10 replicate pens per group and 30 birds per pen, for 37 days. The treatments included normal stocking density (NSD, 10 birds/m²), HSD (15 birds/m²), HSD with 50 ppm Bacitracin (BCT50), HSD with 80 ppm isoquinoline alkaloids (IQA80), and HSD with 100 ppm isoquinoline alkaloids (IQA100). From days 11 to 24, HSD birds had lower feed efficiency (P < 0.05) compared to those in other treatments. The heterophil-to-lymphocyte ratio and malondialdehyde levels were lower in NSD and IQA80 birds compared to HSD and BCT50 birds (P < 0.05). HSD birds had higher IL-6 and a lower villus height and villus height-to-crypt depth ratio compared to birds in other groups (P < 0.05). Serum TNF-α was lower in NSD and IQA80 birds compared to those in the HSD group. Alpha diversity was not affected by the treatments; however, beta diversity was lower in HSD birds compared to other treatments. HSD birds showed reduced microbial diversity, with a higher prevalence of Enterococcaceae and Peptostreptococcaceae. NSD enhanced the abundance of Lactobacillaceae, Clostridiaceae, and Rikenellaceae. BCT50 increased and decreased the abundance of Enterococcaceae and Rikenellaceae respectively. IQA80 and IQA100 increased the abundance of Lachnospiraceae, Leuconostocaceae, and Coriobacteriaceae. HSD altered metabolic pathways related to carbohydrate and lipid metabolism, and amino acid biosynthesis. BCT50 modulated microbial functions, particularly those related to cell wall synthesis, while isoquinoline alkaloids upregulated pathways involved in energy production, secondary metabolite biosynthesis, and antioxidant production. Both Bacitracin and isoquinoline alkaloids were effective in mitigating the negative effects of HSD on immunity, gut health and microbiota in broilers. Given the concerns about antimicrobial resistance, isoquinoline alkaloids are a potent alternative to bacitracin, with IQA80 being particularly recommended.

This study evaluated the effects of phytochemicals on growth performance, immune response, gut morphology, and cecal microbiome of broilers fed an aflatoxin-contaminated diet under high stocking density and heat stress. A total of 2,800 one-day-old male Ross 308 broiler chicks were raised at 18 birds/m² during the summer. The birds were assigned to seven dietary treatments: (1) corn-soybean meal basal diet (CON), (2) CON + 50 ppb aflatoxin (AFT), (3) AFT + 50 ppm bacitracin (BCT), (4) AFT + 300 ppm flavanone (FVN), (5) AFT + 80 ppm isoquinoline alkaloids (IQA), (6) AFT + FVN (1–10 days) and IQA (11–37 days) (FVN-IQA), and (7) AFT + IQA (1–10 days) and FVN (11–37 days) (IQA-FVN) for 37 days. The heat stress index exceeded 160 for most of the experimental period. Feed efficiency was significantly lower in the AFT group than in the CON, FVN, IQA, and combination groups, while the BCT group showed no significant difference from others. The heterophil-to-lymphocyte ratio was higher in the AFT group than in the CON, IQA, FVN-IQA, and IQA-FVN groups. The AFT group exhibited higher interleukin-6 levels than other groups. Serum malondialdehyde was lower in the CON, FVN, and IQA-FVN groups than in the AFT group. Duodenal and jejunal villi height and villi height-to-crypt depth ratio were reduced in the AFT group. The AFT group showed reduced α-diversity, evaluated by Chao1 and Shannon indices. Treatment groups significantly affected β-diversity and microbiota composition at the phylum, family, and species levels. Compared to the CON group, AFT altered 125 metabolic pathways, while BCT, FVN, IQA, FVN-IQA, and IQA-FVN altered 347, 91, 38, 153, and 396 metabolic pathways, respectively, relative to the AFT group. Exposure to 50 ppb aflatoxin under high stocking density and heat stress impaired feed efficiency, immune status, and gut health in broilers. Supplementation with FVN, IQA, or their combinations mitigated these effects, with the combinations showing the greatest efficacy.

This study evaluated the effects of dietary supplementation of an olive pomace extract (OPE), with or without salinomycin, on growth performance, gut health, immune indices, carcass and meat quality in broiler chickens raised under tropical conditions. A total of 1,500 one-day-old male Ross 308 chicks were randomly assigned to six treatments with 10 replicates of 25 birds per replicate in a 3 × 2 factorial design with three levels of OPE (0, 600, or 1,200 ppm) and two levels of salinomycin (SAL; 0 or 66 ppm). Birds were raised during the hot summer season in Thailand for 40 days across three feeding phases. Results revealed that OPE supplementation improved body weight gain (BWG) in a dose-dependent manner, with OPE₁₂₀₀ reducing feed conversion ratio (FCR) at the grower, finisher and overall phases (P < 0.05). Salinomycin supplementation increased BWG while reducing feed intake, FCR, and mortality. SAL and OPE independently enhanced lymphocyte counts (L), and lowered heterophil counts (H) and H/L ratio (P < 0.05). SAL reduced serum fluorescein isothiocyanate-dextran, IL-8, and incidence of foot pad dermatitis (P < 0.05). Neither additive affected gut health indices or carcass traits. OPE₁₂₀₀ reduced drip loss and lipid oxidation and enhanced total, monounsaturated, saturated and polyunsaturated fatty acids in breast meat. No significant interactions between OPE and SAL were observed, indicating independent effects. Overall, OPE and SAL independently enhanced growth performance and immune status, with OPE additionally improving meat quality traits in broiler chickens under tropical conditions.

Journal of Animal Science and Technology (JAST) is a peer-reviewed, open access journal publishing original research, review articles and notes in all fields of animal science. Topics covered by the journal include: genetics and breeding, physiology, nutrition of monogastric animals, nutrition of ruminants, animal products (milk, meat, eggs and their by-products) and their processing, grasslands and roughages, livestock environment, animal biotechnology, animal behavior and welfare.