The extensive application of antibiotics in poultry production has resulted in the emergence of resistant bacteria, which pose a great threat to the health of birds and humans. In this review, the literature is searched using databases such as PubMed, Scopus, Web of Science, and Google Scholar. Studies concerning antimicrobial resistance in poultry, the One Health approach, and alternative strategies to antibiotics are included, while studies not in English, opinion-based papers, and studies not related to poultry or AMR are excluded. This review explores the increasing challenges of antibiotic resistance in poultry, emphasizing the One Health framework related to animal, human, and environmental health. The risks of zoonotic transmission from poultry, the mode of development of resistance, and alternative antibiotics (comprising probiotics, prebiotics, enzymes, and essential oils) are the key topics discussed. This review further touches on critical barriers in fighting antibiotic resistance, which include economic constraints, a lack of awareness, and coordination challenges. This study highlights regulatory and consumer-driven changes in antibiotic use. The poultry industry can reduce the use of antibiotics by adopting the One Health approach and implementing evidence-based alternatives that support productivity. However, sustainable solutions require further research, policy reforms, and collaboration across sectors.

The cardinal Physiology of Gut Health in monogastric animals such as swine and poultry is vital. It is critical for digestive efficiency, immune status, and production levels. This system is related not only to the digestion and absorption of nutrients from feed ingredients contributing to growth and feed utilization efficiency but also to having a strategic microbiota that supports immunity and pathogen resistance, as well as metabolic support. Gut disease, for example, bacterial, viral, or parasitic infection, diet, or stress, can reduce nutrient digestion and absorption. They can also suppress the immune system and render patients more prone to disease. These are efficiency degradations and increase veterinary and husbandry costs. In addition, nutrient absorption because of deteriorated gut health can affect the environment in different ways: removal of nutrients through leaching and the release of gases (including CH₄ and NH₄). These pressures have led to a focus on the gut in animal research to improve the welfare of animals and ensure sustainable practices in animal production. Recent studies have included the use of probiotics, prebiotics, and other feed additives to enhance the positive effects of the gut microbiota. These are also intervention points to increase nutrient absorption and animal well-being, in turn sustainability. Such approaches are expected to promote a stable microbial community with less dependence on the use of antibiotics, less waste generation, and less environmental impact from animal farming. This review provides a critical evaluation of the current literature on gut health in monogastric livestock, with pigs and poultry as the principal focus. We also considered the impact of gut health on production efficiency and Environmental sustainability. Current progress in nutritional modulation of gut health for increased productivity, enhanced animal welfare, and better profitability are presented. Gut-related biological mechanisms are linked to practical nutritional strategies, and subsequently to animal welfare, production efficiency, and environmental effects, offering a coherent concept for moving from mechanism to system-level sustainability.

Resources are needed for growth, reproduction and survival, and organisms must trade off limited resources among competing processes. Nutritional availability in organisms is sensed and monitored by nutrient-sensing pathways that can trigger physiological changes or alter gene expression. Previous studies have proposed that one such signalling pathway, the mechanistic target of rapamycin (mTOR), underpins a form of adaptive plasticity when individuals encounter constraints in their energy budget. Despite the fundamental importance of this process in evolutionary biology, how nutritional limitation is regulated through the expression of genes governing this pathway and its consequential effects on fitness remain understudied, particularly in birds. We used dietary restriction to simulate resource depletion and examined its effects on body mass, reproduction and gene expression in Japanese quails (Coturnix japonica). Quails were subjected to feeding at 20%, 30% and 40% restriction levels or ad libitum for 2 weeks. All restricted groups exhibited reduced body mass, whereas reductions in the number and mass of eggs were observed only under more severe restrictions. Additionally, dietary restriction led to decreased expression of mTOR and insulin-like growth factor 1 (IGF1), whereas the ribosomal protein S6 kinase 1 (RPS6K1) and autophagy-related genes (ATG9A and ATG5) were upregulated. The pattern in which mTOR responded to restriction was similar to that for body mass. Regardless of the treatment, proportionally higher reproductive investment was associated with individual variation in mTOR expression. These findings reveal the connection between dietary intake and the expression of mTOR and related genes in this pathway.

Methionine (Met) is an essential and first limiting amino acid in the poultry diet that plays a significant role in chicken embryonic development and growth. The present study examined the effect of in ovo injection of DL-Met and L-Met sources and genotypes on chicken embryonic-intestinal development and health. Fertilized eggs of the two genotypes, TETRA-SL layer hybrid (TSL) - commercial layer hybrid and Hungarian Partridge colored hen breed (HPC) - a native genotype, were randomly distributed into four treatments for each genotype. The treatment groups include the following: 1) control non-injected eggs (NoIn); 2) saline-injected (SaIn); 3) DL-Met injected (DLM); and 4) L-Met injected (LM). The in ovo injection was carried out on 17.5 d of embryonic development; after hatching, eight chicks per group were sacrificed, and the jejunum was extracted for analysis. The results showed that both DLM and LM groups had enhanced intestinal development as evidenced by increased villus width, villus height, and villus area (P < 0.05) compared to the control. The DLM group had significantly reduced crypt depth, glutathione content (GSH), glutathione S-transferase 3 alpha (GST3), occludin (OCLN) gene expression and increased villus height to crypt depth ratio in the TSL genotype than the LM group (P < 0.05). The HPC genotype has overexpressed insulin-like growth factor 1 (IGF1) gene, tricellulin (MD2), occludin (OCLN), superoxide dismutase 1 (SOD1), and GST3 genes than the TSL genotype (P < 0.05). In conclusion, these findings showed that in ovo injection of Met enhanced intestinal development, and function, with genotypes responding differently under normal conditions. Genotypes also influenced the expression of intestinal antioxidants, tight junction, and growth-related genes.

The study was carried out to determine whether sources or levels of methionine (Met) affect the health status of Tetra-SL (TSL) chicks by examining growth performance, feather growth, and hematological parameters. A total of ninety-six (96) day-old (44.2 ± 0.18 g lw) TSL chicks were randomly allotted to six treatment groups (three levels for each DL and L-Met source) with four replicates of four chicks each. Chicks were fed ad libitum diets supplemented with 90, 100, and 110% of methionine requirements for four weeks after hatch. The parameters examined are bodyweight (BW), average daily gain (ADG), feather length (FL), and hematological parameters, including: red blood cell (RBC) count, hemoglobin (Hb) concentration in the blood, hematocrit (Ht; %), number of white blood cells (WBC), platelet count, mean corpuscular volume of red blood cells (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), lymphocyte (LYM), mid-range (MID), and granulocyte (GRAN). There was no significant effect of Met sources and levels on BW, ADG, and FL of TSL chicks for the first four weeks of rearing. The RBC, Hb, Ht, WBC, LYM, MID, and GRAN values of TSL chicks were statistically influenced by dietary Met sources and Met levels (p < 0.05). Among the treatment groups, the number of white blood cells (WBC) on 90% DL–Met was the lowest. WBC, RBC, Hb, and Ht were higher from chicks that received 100% DL-Met than all other levels, regardless of the Met sources. The MCV, MCH, and MCHC values were not affected by either Met source or levels or their interactions. Met source and level interactively affected the Ht, WBC, LYM %, and GRAN values of TSL chicks (p < 0.05). The platelet number was affected by Met source only (p < 0.05) with chicks receiving L-Met source having more than twofold higher platelet values than DL-Met source. In conclusion, varying Met levels by ±10% of the requirement does not adversely affect the growth performance, feather growth, and hematological parameters of TSL chicks reared for up to four weeks of age. DL-Met increased the body weight and improved the white blood cells, red blood cells, and hematocrit at 28 days after hatch. DL-Met showed similar biological efficacy as L-Met for body weight and feather growth but not for the hematological parameters.

Selenium (Se) is an essential trace element required for various physiological functions in agriculture. Nanotechnology is applied to produce selenium nanoparticles (SeNPs) that offer new advantages, enhancing their bioavailability and reducing toxicity. To further improve the stability of Se nanoelements in the poultry industry, the grey form of Se was recently offered as a potential alternative. However, its impact on bioaccessibility, metabolism, and overall animal efficiency remains undetermined. This study investigates the impact of red and grey SeNPs on Se content in the liver, blood cellular fraction (BCF), kidney, testis, and eyes, as well as the feed intake (FI) and growth performance, of adult Japanese quails. Adult quails were randomly assigned to five groups: a control (C0) and four groups receiving either red or grey Se nanoparticles (SeNPs) at 0.05 or 0.5 mg/kg, in addition to the basal diet which already contained 0.042 mg/kg Se from the premix, resulting in total Se contents of approximately 0.092 and 0.542 mg/kg in the treatment groups (T1–T4), with four replicates per group. The growth performance of quails fed with nano-Se-supplemented diets showed significant variation across groups (p < 0.05), with body weight differing by up to 20% between the highest performing group (T2) and the lowest (T1). FI showed no significant differences across groups. The results indicated that Se accumulation differed significantly between treatments. The selenium levels in the liver increased in a dose-dependent manner, with the highest accumulation observed in T4 (0.5 mg/kg grey SeNPs), at 42% above control levels. This pattern suggests that the liver is a primary organ for selenium storage and metabolism. The greatest Se content in BCFs was recorded in the groups that received grey selenium (T3 and T4) and red selenium at high concentrations (T2), while the group given red selenium at low concentrations (T1) and the control (C0) had the lowest Se accumulation. In the kidney tissues and testis, the Se content exhibited no significant differences between the treated groups and the control. The observed variations in the eye and breast muscle Se content among treatment groups reflect the differences in selenium bioavailability, metabolism, and tissue-specific regulatory mechanisms. These findings demonstrate that grey SeNPs can significantly elevate Se bioavailability in quails, particularly in target organs, and enhance the growth performance without notable changes in feed intake. This highlights the potential of SeNPs in enhancing quail nutrition, although further research is needed to establish optimal dosing strategies for safe, effective use.