The effect of early administration of antibiotics or feeding a diet containing a coccidiostat on inflammatory responses and the morphological structure of selected organs of the immune system in young meat-type turkeys

Antibiotics/coccidiostat exposure induces gut-brain axis remodeling for Akt/mTOR activation and BDNF-mediated neuroprotection in APEC-infected turkeys

The poultry industry relies extensively on antibiotics and coccidiostats as essential tools for disease management and productivity enhancement. However, increasing concerns about antimicrobial resistance (AMR) and the toxicological safety of these substances have prompted a deeper examination of their broader impacts on animal and human health. This study investigates the toxicological effects of antibiotics and coccidiostats on the gut-brain axis and microbiota in turkeys, with a particular focus on molecular mechanisms that may influence neurochemical and inflammatory responses. Our findings reveal that enrofloxacin exposure leads to the upregulation of BDNF, suggesting a neuroprotective effect, while monensin treatment significantly increased eEF2 kinase expression, indicative enhanced neuronal activity. In turkeys infected with Avian Pathogenic Escherichia coli (APEC), early administration of doxycycline and monensin significantly upregulated the mTOR/BDNF and Akt/mTOR pathways, along with elevated histamine levels, underscoring their role in inflammatory responses modulation. However, treatments administered at 50 days post-hatch did not significantly alter protein levels, though both enrofloxacin and monensin increased serotonin and dopamine levels, suggesting potential neurotoxicological impacts on mood and cognitive functions. These results highlight the complex interactions between antibiotic use, gut microbiota alterations, and neurochemical pathways, with toxicological implications for environmental pollution and public health. This research provides critical insights into the potential toxic effects of prolonged antibiotic and coccidiostat exposure in poultry production, emphasizing the need for responsible use to mitigate risks to ecosystems and human health.

Nano-emulsified black soldier fly oil concerning performance traits, health, and immunity of broilers

In the antibiotic-free era, traditional antibiotics have been suggested as alternatives to antibiotic-based growth promoters. Among the various methods, self-nano-emulsifying drug delivery systems (SNEDDS) are increasingly utilized to improve the bioavailability of oils containing essential substances. In this study, we evaluated the effects of black soldier fly oil (BSFO) SNEDDS in chicken drinking water on growth performance, small intestine histomorphology, and poultry health status. We divided 225 male Indian River strain broiler chickens into five treatment groups, each consisting of 5 replicates. The chickens were reared from to 0 to 35 d of age in a controlled environmental housing system. The BSFO SNEDDS was administered via drinking water. Treatments included ordinary drinking water (P1), bacitracin (P2), and 10 mL/L (P3), 20 mL/L (P4), and 30 mL/L (P5) BSFO SNEDDS. The observed parameters included growth performance, carcass yield, blood hematology, intestinal histomorphology, digestive microflora, and immunoglobulin (Ig) levels. Data were analyzed using analysis of variance (ANOVA) and Duncan's test. The results indicated that administering BSFO SNEDDS via drinking water improved feed conversion (P < 0.05), enhanced the performance index (P < 0.05), increased carcass percentage (P < 0.001), and increased the weight of the carcass parts. Additionally, it increased villus height (P < 0.01), lowered jejunal pH (P < 0.001), reduced pathogenic bacteria in the jejunum, and decreased the leukocyte count. BSFO SNEDDS in drinking water is expected to be used as a traditional antibiotic with the potential to replace synthetic antibiotic growth promoters in broiler chickens.

The effect of early administration of antibiotics or feeding a diet containing coccidiostats on the level of their accumulation in liver and the redox status of turkeys

Early administration of antibiotics may worsen the functioning of the turkeys' antioxidant system. It was also assumed that the longer the time of administration of an antibiotic, e.g. a coccidiostat, the greater the risk of its accumulation in the liver. The study aimed to determine whether early administration of antibiotics or feeding a diet containing coccidiostats causes accumulation in the liver and whether it affects the deterioration of the antioxidant system, and whether preventive vaccinations can intensify it. A total of 3 080 female turkeys were randomly allocated to eight groups. The experiment had a two-factorial design, with four treatments (C, M, E, D) and two groups of birds (vaccinated +, unvaccinated -). The C group did not receive the coccidiostat or antibiotics. Group M was administered monensin at 90 mg/kg feed for 56 days of life. Group E received enrofloxacin at 10 mg/kg BW, and group D received doxycycline at 50 mg/kg BW, added to drinking water, for the first 5 days of life. One-day-old turkeys from groups C+, M+, E+, and D+ were administered live-attenuated vaccines against turkey rhinotracheitis and Newcastle disease by coarse spray; 28-day-old birds were administered a subcutaneously injected inactivated vaccine against Ornithobacterium rhinotracheale. Turkeys from groups C-, M-, E-, and D- were not vaccinated. It was determined that as a result of administration of enrofloxacin or doxycycline until the 5th day of life, biotransformation of these antibiotics occurred in the liver until the 56th day of life of the turkeys, which was confirmed by their lower level than the Maximum Residue Level. Because the concentration of monensin in the liver of turkeys gradually increased with the extension of the time of its administration in the diet, it is probable that discontinuing its addition a day before the slaughter of birds will result in the presence of this coccidiostat in the liver of turkeys. Despite the accumulation of monensin in the liver of turkeys, this coccidiostat did not increase oxidative reactions in the organism of turkeys. Vaccination of turkeys can reduce oxidative reactions and apoptosis in the body. However, the effect of the redox system reaction is different immediately after vaccination, which is due to the mechanism of action of the immune system. If it is necessary to administer an antibiotic in the early rearing period, the effects of doxycycline on the organism's immunity including antioxidant defence will be less severe than those of enrofloxacin.

Gastrointestinal response to the early administration of antimicrobial agents in growing turkeys infected with Escherichia coli

This study investigated the effects of the early administration of enrofloxacin (E) or doxycycline (D) for the first 5 consecutive days of life, or the continuous administration of the coccidiostat monensin (M) throughout the rearing period on gastrointestinal function in turkeys infected with avian pathogenic Escherichia coli (APEC) in an early or later stage of rearing. Experiment 1 lasted 21 d, and turkeys in groups E, D, and M were infected with APEC on d 15. Experiment 2 lasted 56 d, and it had a factorial arrangement of treatments where birds in groups E, D, and M were infected with APEC on d 15 or d 50. In both experiments, control groups (C) consisted of infected and uninfected birds without antibiotic or coccidiostat administration. On d 21 (Experiment 1) and d 56 (Experiment 2), 8 birds from each subgroup were killed, and the ileal and cecal digesta were sampled to analyze the activity of bacterial enzymes and the concentrations of short-chain fatty acids (SCFA). The experimental treatments did not affect the final body weight or body weight gain of birds. Both experiments demonstrated that APEC contributed to an increase in ammonia levels of the cecal digesta (means from 2 experiments: 0.311 vs. 0.225 mg/g in uninfected birds) and ileal pH (6.79 vs. 6.00) and viscosity (2.43 vs. 1.83 mPa⋅s). Moreover, the E. coli challenge enhanced the extracellular activity of several cecal bacterial enzymes, especially in older turkeys infected with APEC in a later stage of life. The continuous administration of monensin throughout the rearing period resulted in a weaker gastrointestinal response in older birds, compared with the other 2 antibiotics administered for the first 5 d of life. The results of the study are inconclusive as both desirable and undesirable effects of preventive early short-term antibiotic therapy were observed in turkeys, including normalization of ileal viscosity and cecal ammonia concentration (positive effect), and disruption in cecal SCFA production (negative effect).

Antibiotic Cocktail Effects on Intestinal Microbial Community, Barrier Function, and Immune Function in Early Broiler Chickens

This study investigated the effects of an antibiotic cocktail on intestinal microbial composition, mechanical barrier structure, and immune functions in early broilers. One-day-old healthy male broiler chicks were treated with a broad-spectrum antibiotic cocktail (ABX; neomycin, ampicillin, metronidazole, vancomycin, and kanamycin, 0.5 g/L each) or not in drinking water for 7 and 14 days, respectively. Sequencing of 16S rRNA revealed that ABX treatment significantly reduced relative Firmicutes, unclassified Lachnospiraceae, unclassified Oscillospiraceae, Ruminococcus torques, and unclassified Ruminococcaceae abundance in the cecum and relative Firmicutes, Lactobacillus and Baccillus abundance in the ileum, but significantly increased richness (Chao and ACE indices) and relative Enterococcus abundance in the ileum and cecum along with relatively enriched Bacteroidetes, Proteobacteria, Cyanobacteria, and Enterococcus levels in the ileum following ABX treatment for 14 days. ABX treatment for 14 days also significantly decreased intestinal weight and length, along with villus height (VH) and crypt depth (CD) of the small intestine, and remarkably increased serum LPS, TNF-α, IFN-γ, and IgG levels, as well as intestinal mucosa DAO and MPO activity. Moreover, prolonged use of ABX significantly downregulated occludin, ZO-1, and mucin 2 gene expression, along with goblet cell numbers in the ileum. Additionally, chickens given ABX for 14 days had lower acetic acid, butyric acid, and isobutyric acid content in the cecum than the chickens treated with ABX for 7 days and untreated chickens. Spearman correlation analysis found that those decreased potential beneficial bacteria were positively correlated with gut health-related indices, while those increased potential pathogenic strains were positively correlated with gut inflammation and gut injury-related parameters. Taken together, prolonged ABX application increased antibiotic-resistant species abundance, induced gut microbiota dysbiosis, delayed intestinal morphological development, disrupted intestinal barrier function, and perturbed immune response in early chickens. This study provides a reliable lower-bacteria chicken model for further investigation of the function of certain beneficial bacteria in the gut by fecal microbiota transplantation into germ-free or antibiotic-treated chickens.