Constant light in early life induces fear-related behavior in chickens with suppressed melatonin secretion and disrupted hippocampal expression of clock- and BDNF-associated genes

Effects of different photoperiods on melatonin level, cecal microbiota and breast muscle morphology of broiler chickens

Long photoperiods are often characterized by enhanced oxidative stress-induced damage to skeletal muscle, reduced melatonin (MT) levels and intestinal microbiota dysfunction in broilers. In this study, we aimed to investigate the association of breast muscle morphology with melatonin levels and the cecal microbiota of broilers under different photoperiods. A total of 216 healthy 5-day-old Arbor Acres (AA) male broilers were randomly assigned to 12 L:12D, 18 L:6D and 24 L:0D photoperiods for 4 weeks (L = hours of light, D = hours of darkness). The concentration of inflammatory factors and MT concentrations was measured using ELISA kits, whereas breast muscle morphology was examined through the hematoxylin (H) and eosin (E) staining, and microbiota composition was identified through 16 s rRNA analysis. Extended light exposure significantly improved the growth rate of broilers, but significantly decreased feed efficiency (FE). Furthermore, it upregulated the concentration of IL-1β, IL-6 and TNF-α and induced an abnormal breast muscle morphology. Extended light exposure significantly decreased MT levels in the hypothalamus, cecum and breast muscle, while triggering the cecal microbiota composition disorder. Specifically, there was significant alteration to the dominant bacterial phylum, following exposure to long photoperiods, with the abundance of Firmicutes decreasing and the abundance of Bacteroidota increasing. Notably, the relative abundance of Lactobacillus showed a positive correlation with MT levels and a negative correlation with inflammatory cytokines. In conclusion, the present findings indicated that extended light exposure reduced the MT levels, which were related to disturbed cecal microbiota, damaging breast muscle morphology and inducing breast muscle inflammation in broilers.

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.

Photostimulation decreases fearfulness, but improves growth performance and egg quality of breeder Pekin ducks

Lighting is a critical environmental factor that influences production performance and welfare of poultry, however Pekin ducks can typically be housed under 24 h (24 h) of light. 460 hatchlings were randomly allocated to 4 rooms with two pens in each room. The rooms were allocated to 24 h light or PS. PS was achieved by gradually increasing photoperiod by half an hour per week from days 112 to 238 and held at 18 h light for the rest of life. Prior to the onset of lay, pens were organized with 30 hens and 7 drakes/pen (4 pens/treatment). We measured bodyweight at weeks 0, 1, 2, 5, 10, 19, and 29, feed intake at weeks 1 to 7 and feed conversion ratio (FCR) was calculated for weeks 1, 2, and 5. Eggs laid were recorded daily from weeks 20 to 31. Novel object test (NOT) was done at weeks 1, 5, 10, 19, and 29, transect welfare scoring at week 30, egg quality assessment at weeks 28 and 29, and fertility was determined at weeks 28 and 29. Statistical analyses were done using 2-way ANOVA, T-test, or Friedman Test with a Tukey-Kramer test as post-hoc. A p ≤ 0.05 was considered significant. Drakes bodyweight was higher in the PS compared to 24h treatment at weeks 5 (p < 0.01) and 10 (p < 0.001). No difference was observed in FCR, fertility, or transect data. NOT showed lower fear response (p < 0.05) at weeks 5 and 10 in the PS compared to 24 h treatment. The 24 h treatment increased the percent eggs laid at weeks 23 (p < 0.05), 24 (p < 0.01) and 25 (p < 0.05) compared to the PS. However, there was a higher egg weight (p < 0.001), yolk weight (p < 0.05), Haugh unit (p < 0.05), and shell weight (p = 0.05) in the PS compared to 24 h treatment. Our findings support that PS may help decrease fearfulness, improve growth performance and egg quality of breeder ducks.

Characterisation of runs of homozygosity and inbreeding coefficients in the red-brown Korean native chickens

OBJECTIVE

The analysis of runs of homozygosity (ROH) has been applied to assess the level of inbreeding and identify selection signatures in various livestock species. The objectives of this study were to characterize the ROH pattern, estimate the rate of inbreeding, and identify signatures of selection in the red-brown Korean native chickens.

METHODS

The Illumina 60K single nucleotide polymorphism chip data of 651 chickens was used in the analysis. Runs of homozygosity were analysed using the PLINK v1.9 software. Inbreeding coefficients were estimated using the GCTA software and their correlations were examined. Genomic regions with high levels of ROH were explored to identify selection signatures.

RESULTS

A total of 32,176 ROH segments were detected in this study. The majority of the ROH segments were shorter than 4 Mb. The average ROH inbreeding coefficients (FROH) varied with the length of ROH segments. The means of inbreeding coefficients calculated from different methods were also variable. The correlations between different inbreeding coefficients were positive and highly variable (r = 0.18-1). Five ROH islands harbouring important quantitative trait loci were identified.

CONCLUSION

This study assessed the level of inbreeding and patterns of homozygosity in Red-brown native Korean chickens. The results of this study suggest that the level of recent inbreeding is low which indicates substantial progress in the conservation of red-brown Korean native chickens. Additionally, Candidate genomic regions associated with important production traits were detected in homozygous regions.

Effect of Short Photoperiod on Behavior and Brain Plasticity in Mice Differing in Predisposition to Catalepsy: The Role of BDNF and Serotonin System

Seasonal affective disorder is characterized by depression during fall/winter as a result of shorter daylight. Catalepsy is a syndrome of some grave mental diseases. Both the neurotransmitter serotonin (5-HT) and brain-derived neurotrophic factor (BDNF) are involved in the pathophysiological mechanisms underlying catalepsy and depressive disorders. The aim was to compare the response of behavior and brain plasticity to photoperiod alterations in catalepsy-resistant C57BL/6J and catalepsy-prone CBA/Lac male mice. Mice of both strains were exposed for six weeks to standard-day (14 h light/10 h darkness) or short-day (4 h light/20 h darkness) conditions. Short photoperiod increased depressive-like behavior in both strains. Only treated CBA/Lac mice demonstrated increased cataleptic immobility, decreased brain 5-HT level, and the expression of Tph2 gene encoding the key enzyme for 5-HT biosynthesis. Mice of both strains maintained under short-day conditions, compared to those under standard-day conditions, showed a region-specific decrease in the brain transcription of the Htr1a, Htr4, and Htr7 genes. After a short photoperiod exposure, the mRNA levels of the BDNF-related genes were reduced in CBA/Lac mice and were increased in the C57BL/6J mice. Thus, the predisposition to catalepsy considerably influences the photoperiodic changes in neuroplasticity, wherein both C57BL/6J and CBA/Lac mice can serve as a powerful tool for investigating the link between seasons and mood.

Effects of different light-emitting diode light on hatch performance, embryo development, eye structure, and plasma melatonin in layer incubation

Light intensity, wavelength, and photoperiod have a combined effect on chicken incubation. This study was conducted to evaluate the effect of 12-h light, 12-h dark (12L:12D) photoperiod of white light (380-780 nm, WL), blue light (455/447.5-462.5 nm, BL), and green light (525/515-535 nm, GL) in chicken perceived light intensity during layer incubation on hatching performance, embryo development, eye structure, and melatonin concentration. Three batches of eggs from Jinghong No. 1 layer breeder were used in this experiment. Light stimulation had no effect on hatchability, and no consistent effect on embryo weight and newly hatched chick weight. However, the average hatching time of white light group and green light group was 7.3 h and 5.5 h later than that of the control group. Therefore, the holding period of chicks was significantly shortened (P = 0.001) in these 2 light groups. Light stimulation had a significant effect on the thickness of retinal layers (P < 0.05), retinal layers of white light group was thicker than that of the other 3 groups. Melatonin levels of chicks hatched in the green light and blue light were significantly higher than that of chicks hatched in the white light and darkness (P < 0.05). It indicated that the monochrome green and blue light promoted the expression of melatonin in chicken embryos. No significant diurnal rhythms were found at the level of plasma melatonin in 4 groups on d 21 using cosine analysis. It was concluded that green light has a positive effect on embryo development and melatonin secretion, while white light probably has positive effect on eye development. Furthermore, both green and white light stimulation resulted in late hatch for layer egg incubation. The obtained results are important in determining the light protocol for chicken incubation.

Measuring Chronic Stress in Broiler Chickens: Effects of Environmental Complexity and Stocking Density on Immunoglobulin-A Levels

Commercial housing conditions may contribute to chronic negative stress in broiler chickens, reducing their animal welfare. The objective of this study was to determine how secretory (fecal) and plasma immunoglobulin-A (IgA) levels in fast-growing broilers respond to positive and negative housing conditions. In three replicated experiments, male Ross 708 broilers (n = 1650/experiment) were housed in a 2 × 2 factorial study of high or low environmental complexity and high or low stocking density. In experiments 1 and 3 but not in experiment 2, high complexity tended to positively impact day 48 plasma IgA concentrations. When three experiments were combined, high complexity positively impacted day 48 plasma IgA concentrations. Stocking density and the complexity × density interaction did not impact day 48 plasma IgA concentrations. Environmental complexity and the complexity × density interaction did not impact day 48 secretory IgA concentrations. A high stocking density negatively impacted day 48 secretory IgA concentrations overall but not in individual experiments. These results suggest that environmental complexity decreased chronic stress, while a high stocking density increased chronic stress. Thus, plasma IgA levels increased under high-complexity housing conditions (at day 48), and secretory IgA levels (at day 48) decreased under high-density conditions, suggesting that chronic stress differed among treatments. Therefore, these measures may be useful for quantifying chronic stress but only if the statistical power is high. Future research should replicate these findings under similar and different housing conditions to confirm the suitability of IgA as a measure of chronic stress in broiler chickens.

LED Light Applied to the Feeder: Impact on Growth Performances of Chickens under Productive Conditions

This study assessed the use of feeders equipped with light-emitting diodes and their effects on the productivity of broiler chickens under productive conditions. A total of 87,200 ROSS 308 chickens, 1-day old, were housed in two poultry houses (CONTROL, F-LED). In CONTROL, 20,000 females (mean body weight 41.12 ± 3 g) and 25,000 males (mean body weight 41.56 ± 3 g) were housed, while 19,200 females and 23,000 males of the same genetic make-up and mean body weight were housed in F-LED under the same environmental conditions. In F-LED, to encourage chickens to feed and to redistribute more feed down the feeding line, a feeder equipped with a LED light has been installed at the end of each line. In CONTROL, no light was located on the feeders. At the end of the cycle, the average body weight never showed significant differences both for females (1345 g in CONTROL; 1359 g in F-LED) and for males (2771 g in CONTROL; 2793 g in F-LED). Uniformity improved in F-LED, at 75.2% in females and 54.1% in males, compared to CONTROL, at 65.7% and 48.5%, respectively, for females and males. The feed conversion ratio followed the same trend, being more favorable in chickens reared in F-LED (1.567) compared to those raised in CONTROL (1.608). The application of a single F-LED at the end of each feeding line demonstrated its utility in improving size uniformity and feed conversion.

Constant light exposure in early life induces m 6A-mediated inhibition of IGF gene family in the chicken

Insulin-like growth factor (IGF) family plays important roles in regulating the development of various organ systems through stimulating cell proliferation and differentiation. Photoperiod is an important factor affecting growth and development in the chicken, yet the effect of constant light exposure in early life on IGF1 and IGF2 expression in the chicken remains unclear. In this study, one-day-old chickens were kept in either constant light (24L:0D, LL) or natural photoperiod (12L:12D, LD) for the first week of life and then maintained in constant light from 8 d to 21 d of age. Constant light exposure in early life reduced mRNA expression of IGF gene family, including mRNA expression of IGF1, IGF2 and IGF2 binding proteins (IGF2BPs), in the hippocampus, hypothalamus and liver of chickens at both 7 d and 21 d of age. Moreover, constant light exposure increased mRNA expression of genes involved in RNA methylation N6-methyladenosine (m 6A) in a tissue-specific manner. Interestingly, higher m 6A on 3'UTR of IGF2 mRNA coincides with lower IGF2 mRNA, indicating a possible role of m 6A in the post-transcriptional regulation of IGF2 expression in the hippocampus, hypothalamus, and liver of chickens. These findings suggest a m 6A-mediated gene regulation of IGF gene family in different organs of chicken and expand our knowledge on mechanism of gene regulation in response to early life experience.

Myeloperoxidase expression in diencephalon is potentially associated with fear‐related behavior in chicks of laying hen

Preventing feather pecking (FP) in adult laying hens is important for the welfare of intensively poultry farming. Fear-related behavior in growing female layer chicks may predict FP in adult hens. In this study, in two representative laying breeds (White Leghorn [WL] and Rhode Island Red [RIR]) that have different FP frequencies, we identified a candidate gene associated with fear-related behavior in chicks and FP in adult hens. In the tonic immobility test and open-field test, the behavioral activity was lower in WL chicks than in RIR chicks (P < 0.01), suggesting that WL chicks were more fearful than RIR chicks. Based on previous studies, 51 genes that have been found to be differentially expressed in the brain between high- and low-FP populations were chosen, and their expression levels were screened in the chick diencephalon. This analysis revealed that myeloperoxidase (MPO) gene expression level was higher in WL chicks than that in RIR chicks (P < 0.05). Furthermore, STRING analysis predicted the gene network including MPO and MPO-related genes and revealed the association of these genes with fear-related behavior. These results suggest that MPO is potentially associated with fear-related behavior in growing female layer chicks and FP in adult hens.