The plasticity of the digestive tract in the first days of life offers a unique window to early orientate digestive functions. Different feeding strategies can be considered to early modulate and improve chicken health and welfare while ensuring feed efficiency. In this trial, the effects of five additives, targeting specific biological functions namely vitamin E, butyrate, capsaicin, carvacrol, and xylo-oligosaccharides on digestive homeostasis were studied in diets based on maize and soybean meal (MS) or on wheat, distillery by-products and horse bean (WB). A total of 432 one-day-old chickens were distributed across 72 pens and reared until 10 days. Data were analysed using ANOVA to assess the effects of additives, diet, and their interaction on growth performance, intestinal enzymatic activities, redox balance indicators, gut morphology and gene expression in both the gut and plasma. Chickens fed the MS-based diet showed a lower feed conversion ratio (FCR) (-4.8%; P < 0.001) over the entire period compared to those fed the WB-based diet, independently of the feed additive supplementation. However, the effect of the additives in the digestive tract were partly dependent of the diet. Vitamin E and carvacrol reduced the activity of the jejunal alkaline phosphatase, only in animals fed the WB-based diet (-50.3% and − 58.6%, respectively; P = 0.001). In the jejunum, the expression of key oxidative stress and inflammation associated genes (NOS2, MYD88, and SOCS1) was significantly increased in chickens subjected to the MS diet compared to those receiving the WB diet (respectively: +90.3%, + 78.3%, + 323.5%, all P < 0.001). Independently of the diet, vitamin E significantly decreased jejunal lipid peroxidation (-39.8%, P < 0.001) confirming its antioxidant properties. Capsaicin supplementation decreased plasma haptoglobin activity (-19.5%, P = 0.004). Only in the WB diet, vitamin E enhanced plasma total antioxidant status (+ 40.3%; P = 0.014). These findings demonstrate that digestive functionalities in young broilers chicks can be modulated early in life through specific feed additives, with effects partly influenced by the diet composition. These early effects on digestive functionality suggest the potential to modulate phenotypic trajectories from the earliest stages, with long-term consequences for performance, health, and welfare.

This study investigated how hatching environment and early-life exposure to an adult hen influence gut microbiota development, immune function, and redox status in broiler chicks. Male chicks were hatched either on-farm (OFH) or in a conventional hatchery (CH), with or without the presence of an adult hen for the first 15 days post-hatching (CH+H, OFH+H). An additional group received antibiotic treatment during this period (CH+AB). At 27 days post-hatching, the chicks faced suboptimal conditions (transport, temperature fluctuations, and increased density) and were vaccinated against Gumboro disease to test their resilience. Cecal bacterial gene communities and immune gene expression in the bursa of Fabricius and cecal tonsils were assessed at 20 and 56 days of age. Plasma immune, metabolic, and redox status were evaluated at 27, 40, and 56 days. At 20 days, hen contact promoted the development of the cecal microbiota, characterized by increased relative abundances of Bacteroides, Prevotellaceae UCG-001, Parabacteroides, Mucispirillum, Desulfovibrio, Succinatimonas, Olsenella, and Sutterella. In OFH chicks, hen contact reduced cecal IgA concentrations. Conversely, in CH+AB chickens, the bacterial diversity diminished, favoring Escherichia-Shigella dominance, and TNF gene expression was increased in the cecal tonsils. While the hatching system alone had no effect on microbiota, it acted synergistically with hen contact and further enhanced microbiota maturity. At 56 days, most early observed differences in microbiota composition had disappeared. However, in CH+H chickens, IgA gene expression decreased in the bursa of Fabricius and CD40 mRNA expression increased in the cecal tonsils. In OFH+H chickens, the lipid oxidative status was reduced in favor of a better redox status compared to OFH chickens. In conclusion, the contact of chicks with a hen during the start-up period had a transient but significant effect on gut microbiota development during the initial colonization window. Although most effects diminished over time, lasting changes in immune function and redox status warrant further investigation to uncover the long-term health benefits of neonatal environmental enrichment in poultry.

1. In chicken production, a delay occurs between hatching and placement in the rearing building. This work analysed the effects of this experience on growth, metabolism, and caecal microbiota and tested whether a nutritional supplement (SUP) could mitigate these effects.2. Chicks were placed directly in a rearing room (Control: C) or were exposed to a 24 h period without feed and water before being placed (Delayed: D). During the 24 h period, half of each group was provided with a SUP.3. The D effect reduced body weight until d 27 in females (p = 0.017) and d 34 in males (p = 0.015). On d 1, the D group had reduced plasma triglycerides (TG) and increased uric acid (UA), total antioxidant status (TAS) and liver thiobarbituric acid reactive species in both sexes (p < 0.050). On d 34, the D group had increased UA and TAS only in females. It increased the α-diversity of microbiota in males (d 12 p = 0.036; d 34 p = 0.038) and the α-diversity in females on d 34 (p = 0.008). Changes in microbiota composition in both males and females were observed until d 34 at the genus level.4. On d 1, the SUP increased glucose concentration in D and C group males (p = 0.001) and females (p = 0.002). The decrease in TG and increase in UA concentrations and TAS in chicks from the D group were mitigated by the SUP in females. On d 34, SUP reduced the haptoglobin-like activity in D and C group males (p = 0.041) and increased the TG concentration in C group males (p = 0.016). The SUP had little effect on the caecal microbiota.5. Delayed placement induced long-lasting effects on growth, metabolism, and caecal microbiota composition. The effects of a nutritional supplement were variable and sex-dependent.

Chicken meat production in organic systems involves free-range access where animals can express foraging and locomotor behaviours. These behaviours may promote outdoor feed intake, but at the same time energy expenditure when exploring the outdoor area. More generally, the relationship of range use with metabolism, welfare including health, growth performance and meat quality needs to be better understood. We studied four strains of intermediate (JA757) to slow-growing (S757N, White Bresse and a dual-purpose strain) meat-type chickens with outdoor access. We selected 25 males high- (HR) and low-rangers (LR) per strain. Only in JA757, HR exhibited lower body weight before range access, which may have predisposed them to use the range more. Carcass weight and/or carcass yield were significantly lower in HR compared to LR, showing a negative trade-off between range use and growth performance in all strains. Breast meat yellowness was higher in HR compared to LR in JA757 and the dual-purpose strain, probably due to carotenoids intake from the grass. No relationship between range use and welfare indicators at slaughter was reported whatever the strain. Chicken metabolism differed by range use as HR and LR diverged for blood biomarkers of oxidative and metabolic status, immune and inflammatory system response.

The evolution of parameters known to be relevant indicators of energy status, oxidative stress, and antioxidant defense in chickens was followed. These parameters were measured weekly from 1 to 42 days in plasma and/or muscles and liver of two strains differing in growth rate. At 1-day old, in plasma, slow-growing (SG) chicks were characterized by a high total antioxidant status (TAS), probably related to higher superoxide dismutase (SOD) activity and uric acid levels compared to fast-growing (FG) chicks whereas the lipid peroxidation levels were higher in the liver and muscles of SG day-old chicks. Irrespective of the genotype, the plasma glutathione reductase (GR) and peroxidase (GPx) activities and levels of hydroperoxides and α- and γ-tocopherols decreased rapidly post-hatch. In the muscles, lipid peroxidation also decreased rapidly after hatching as well as catalase, GR, and GPx activities, while the SOD activity increased. In the liver, the TAS was relatively stable the first week after hatching while the value of thio-barbituric acid reactive substances (TBARS) and GR activity increased and GPx and catalase activities decreased. Our study revealed the strain specificities regarding the antioxidant systems used to maintain their redox balance over the life course. Nevertheless, the age had a much higher impact than strain on the antioxidant ability of the chickens.

The pHu+ and pHu− lines, which were selected based on the ultimate pH (pHu) of the breast muscle, represent a unique model to study the genetic and physiological controls of muscle energy store in relation with meat quality in chicken. Indeed, pHu+ and pHu− chicks show differences in protein and energy metabolism soon after hatching, associated with a different ability to use energy sources in the muscle. The present study aimed to assess the extent to which the nutritional environment of the embryo might contribute to the metabolic differences observed between the two lines at hatching. Just before incubation (E0), the egg yolk of pHu+ exhibited a higher lipid percentage compared to the pHu− line (32.9% vs. 27.7%). Although 1 H-NMR spectroscopy showed clear changes in egg yolk composition between E0 and E10, there was no line effect. In contrast, 1 H-NMR analysis performed on amniotic fluid at embryonic day 10 (E10) clearly discriminated the two lines. The amniotic fluid of pHu+ was richer in leucine, isoleucine, 2-oxoisocaproate, citrate and glucose, while choline and inosine were more abundant in the pHu− line. Our results highlight quantitative and qualitative differences in metabolites and nutrients potentially available to developing embryos, which could contribute to metabolic and developmental differences observed after hatching between the pHu+ and pHu− lines.

This study was designed to improve the hatching performance, chick robustness and poultry health in the event of long-term egg storage and suboptimal age of the reproductive flock. A total of 9,600 eggs from one young breeder flock (28 weeks of age, batch B) and 9,600 eggs from an older breeder flock (59 weeks of age, batch E) were used (ROSS 308). Each batch was separated into three sub-groups and stored for 14 days. The first sub-group of eggs (Cool, group C) was stored at 11.6°C. The second sub-group of eggs (Warm, group W) was stored at 18.3°C with two pre-incubation on days 6 and 10 of the storage period. The final sub-group of eggs (Control, group Ct) was stored at 18.3°C throughout the storage period. Eggs were similarly incubated and hatched birds were raised on the same experimental farm. In both batches, embryonic development was significantly more advanced in W eggs than in C and Ct eggs ( p < 0.01). In both batches, C and W treatments decreased early embryonic mortality by more than 10% compared with Ct, decreased the proportion of late-hatched chicks and improved the percentage of first grade chicks: in batch E, 42% of Ct eggs were first grade chicks vs. 57% in group W and 59% in group C. Benefits were even higher in batch B, where only 60% of Ct eggs gave first grade chicks vs. 83% in others groups. The hatching rate was thus higher in groups C and W regardless of flock age: for batch B eggs, 85% hatched in W and 84% in C vs. 62% in Ct, while for batch E eggs, 59% hatched in W and 61% in C vs. 45% in Ct. Day-old Ct chicks from batch E were heavier than W and C ones, and heavier than W chicks from batch B ( p < 0.05). Long-term parameters on farm were not significantly different between groups. Thermal treatments during the storage of eggs from both young and old breeder flocks counterbalance the negative effects of prolonged egg storage on hatching rate, without altering chicken performance during rearing.