Impact of in ovo feeding of grape pomace extract on the growth performance, antioxidant status, and immune response of hatched broilers

Delivering natural antioxidants via in ovo feeding holds promise for enhancing the antioxidant status and performance of chickens. Therefore, The objective of this study was to evaluate the impacts of in ovo feeding during early embryonic development using grape pomace extract as a natural antioxidant on hatchability, productive performance, immune response, and antioxidant status in broilers. A total of 900 fertile broiler eggs from the Arbor Acres strain were utilized. Each egg was individually weighed, with egg weights ranging from 61.88 ± 3 g. On the 17.5th d of incubation (DOI), the fertile eggs were divided into 6 groups. The first treatment group was untreated and designated as the control (C). The second group was the sham group (Sh), receiving a simulated injection. The third group, designated as the vehicle group (V), was injected with 100 µl of dimethyl sulfoxide (DMSO). The fourth group received an injection of 100 µL of grape pomace dissolved in DMSO at a concentration of 2 mg (T2). Similarly, the fifth and sixth groups were injected with 100 µL of grape pomace dissolved in DMSO at concentrations of 4 mg and 6 mg, (T4), (T6) respectively. Subsequently, all groups were raised under uniform conditions in terms of management, environment, and nutrition till 5 wk of age. The grape pomace extract (GPE), obtained is rich in total phenolic content (16.07 mg/g), total flavonoid content (7.42 mg/g), and total anthocyanin (8.37 mg/g). Grape pomace extract has exhibited significant antioxidant properties as evidenced by its effectiveness in DPPH scavenging and reducing power assays. Significant improvements in body weight at hatch were observed with in ovo feeding of grape pomace extract, particularly at the 4 mg level, surpassing the effectiveness of the 2 mg and 6 mg grape pomace levels, and this enhancement in body weight continued until the age of 5 wk. GPE injection also led to a significant reduction in cholesterol levels, with the lowest levels recorded for the T4 group. Plasma total Antioxidant Capacity (TAC) levels were significantly elevated in groups treated with T4, T6, and T2 compared to the control group. Conversely, the control group showed a significant increase (P < 0.01) in plasma malondialdehyde (MDA) levels. The immune response of hatched chicks from grape pomace extract-injected groups, especially the T4 group, exhibited improvement through increased IgM and IgG. These findings demonstrate that in ovo feeding of GPE, particularly at a dosage of 4 mg, enhances growth performance, immune response, and antioxidant status in hatched chicks. Thus, administering natural antioxidants, such as grape pomace extract, to developing broiler embryos via in ovo feeding could serve as a valuable strategy for enhancing the subsequent post-hatch productive performance, as well as bolstering the antioxidant and immunological status of broiler chicks.

In-ovo injection of Bacillus subtilis, raffinose, and their combinations enhances hatchability, gut health, nutrient transport- and intestinal function-related genes, and early development of broiler chicks

An experiment was conducted to assess the response of chicks to in-ovo injection of Bacillus subtilis (probiotic), raffinose (prebiotic), and their combinations. The study used 1,500 embryonated eggs allotted to 10 groups/ 6 replicates (150 eggs/group). The experimental treatments were: 1) un-injected control (NC); 2) sham (sterile distilled water) (PC); 3) probiotic 4 × 105CFU/egg (LBS); 4) probiotic 4 × 106CFU/egg (HBS); 5) prebiotic 2 mg/egg (LR); (6 prebiotic 3 mg/egg (HR); 7) probiotic 4 × 105CFU + prebiotic 2 mg/egg (LBS+LR); 8) probiotic 4 × 105CFU + prebiotic 3 mg/egg (LBS+HR); 9) probiotic 4 × 106CFU + prebiotic 2 mg/egg (HBS+LR); and 10) probiotic 4 × 106CFU + prebiotic 3 mg/egg (HBS+HR). Results showed that in-ovo inclusion of Bacillus subtilis, prebiotic, and their combinations improved hatchability, yolk-free chick weight, and chick weight compared to the control group. Moreover, the in-ovo treatment reduced residual yolk weight on the day of hatch compared to the control group. Different levels of in-ovo B. subtilis alone or combined with raffinose significantly (P ≤ 0.001) reduced total bacterial count and total yeast and mold count compared to the negative control group. Total coliform and E. coli decreased significantly (P ≤ 0.001) in groups treated with probiotics, prebiotics, and synbiotics with different doses during incubation compared to those in the control. Clostridium spp. was not detected in the groups injected with B. subtilis alone or combined with raffinose. In-ovo probiotics and synbiotics (LBS+LR & LBS+HR) significantly (P ≤ 0.001) increased ileal villus length compared to other groups. In-ovo treatment increased mRNA expression of JAM-2 compared to the control group. The fold change significantly increased in group LBS+HR for genes MUC-2, OCLN, VEGF, SGLT-1, and EAAT-3 compared to the negative control. In conclusion, in-ovo injection of a low dose of B. subtilis plus a high or low dose of raffinose can positively affect hatching traits, cecal microbial populations, intestinal histomorphometry, nutrient transport- and intestinal function-related genes, and chick quality of newly hatched broiler chicks.

Integrative Analysis of the Microbiome and Metabolome of Broiler Intestine: Insights into the Mechanisms of Probiotic Action as an Antibiotic Substitute

Antibiotic substitutes have become a research focus due to restrictions on antibiotic usage. Among the antibiotic substitutes on the market, probiotics have been extensively researched and used. However, the mechanism by which probiotics replace antibiotics remains unclear. In this study, we aimed to investigate this mechanism by comparing the effects of probiotics and antibiotics on broiler growth performance and intestinal microbiota composition. Results shown that both probiotics and antibiotics increased daily weight gain and reduced feed conversion rate in broilers. Analysis of ileum and cecum microorganisms via 16S rRNA gene sequencing revealed that both interventions decreased intestinal microbial diversity. Moreover, the abundance of Bacteroides increased in the mature ileum, while that of Erysipelatoclostridium decreased in the cecum in response to both probiotics and antibiotics. The main metabolites of probiotics and antibiotics in the intestine were found to be organic acids, amino acids, and sugars, which might play comparable roles in growth performance. Furthermore, disaccharides and trisaccharides may be essential components in the ileum that enable probiotics to replace antibiotics. These findings provide important insights into the mechanisms underlying the use of probiotics as antibiotic substitutes in broiler breeding.

In ovo probiotic supplementation supports hatchability and improves hatchling quality in broilers

In modern broilers, the period of embryonic development constitutes a greater proportion of a broiler's productive life. Hence, optimum embryonic development can exert a significant influence not only on chick hatchability and hatchling quality but also on overall broiler growth and performance. Further healthy and active hatchlings are correlated with improved posthatch performance. In this regard, probiotics are good candidates to mediate early-life programming. Therefore, we evaluated the effect of In ovo probiotic spray application on broiler hatchability and hatchling quality. The experiment was set out as a completely randomized study with 2 independent trials. In each trial, 540 eggs (Ross 308) were either sprayed with phosphate buffered saline (PBS; control) or probiotics [∼9 log CFU/egg of Lactobacillus rhamnosus NRRL B-442(LR) or Lactobacillus paracasei DUP 13076 (LP)] during incubation. On day 18, eggs were transferred to the hatcher and set up for hatching. Starting on day 19, eggs were observed for hatching to determine the spread of hatch and hatchability. Hatched chicks were then assessed for quality using the Tona and Pasgar score and morphometric measurements including hatchling weight, yolk-free-body-mass and hatchling length were measured. Further, chicks were reared in floor pens for 3 wk to assess posthatch growth. Overall, In ovo probiotic supplementation improved hatchability and hatchling quality. Specifically, the spray application of LP improved hatchability by ∼ 5% without affecting the spread of hatch. Further, both LR and LP significantly improved Pasgar and Tona score, indicating an improvement in hatchling quality. Also, LP and LR significantly improved hatchling weight, yolk-free-body-mass, and posthatch growth in chicks. LR significantly improved hatchling weight and hatchling length (P < 0.05). Moreover, this increase in posthatch growth was positively correlated with hatchling weight in the probiotic groups. Overall, our study demonstrates that In ovo probiotic application exerts a positive effect on hatchability, hatchling quality, and subsequent posthatch growth.

Perspectives on chick embryo models in developmental and reproductive toxicity screening

Teratology, the study of congenital anomalies and their causative factors intersects with developmental and reproductive toxicology, employing innovative methodologies. Evaluating the potential impacts of teratogens on fetal development and assessing human risk is an essential prerequisite in preclinical research. The chicken embryo model has emerged as a powerful tool for understanding human embryonic development due to its remarkable resemblance to humans. This model offers a unique platform for investigating the effects of substances on developing embryos, employing techniques such as ex ovo and in ovo assays, chorioallantoic membrane assays, and embryonic culture techniques. The advantages of chicken embryonic models include their accessibility, cost-effectiveness, and biological relevance to vertebrate development, enabling efficient screening of developmental toxicity. However, these models have limitations, such as the absence of a placenta and maternal metabolism, impacting the study of nutrient exchange and hormone regulation. Despite these limitations, understanding and mitigating the challenges posed by the absence of a placenta and maternal metabolism are critical for maximizing the utility of the chick embryo model in developmental toxicity testing. Indeed, the insights gained from utilizing these assays and their constraints can significantly contribute to our understanding of the developmental impacts of various agents. This review underscores the utilization of chicken embryonic models in developmental toxicity testing, highlighting their advantages and disadvantages by addressing the challenges posed by their physiological differences from mammalian systems.

In ovo feeding of probiotic lactobacilli differentially alters expression of genes involved in the development and immunological maturation of bursa of Fabricius in pre-hatched chicks

Compelling evidence indicates that immunological maturation of the gut-associated lymphoid tissues, including the bursa of Fabricius, is dependent upon antigenic stimulation post-hatch. In view of these data, the present study investigated the impact of exposing the immune system of chick embryos to antigenic stimuli, via in ovo delivery of poultry-specific lactobacilli, on the expression of genes associated with early bursal development and maturation. Broiler line embryonated eggs were inoculated with 106 and 107 colony-forming units (CFUs) of an individual or a mixture of Lactobacillus species, including L. crispatus (C25), L. animalis (P38), L. acidophilus (P42), and L. reuteri (P43), at embryonic day 18 (ED18). The bursa of Fabricius was collected from pre-hatched chicks (ED20) to measure the expression levels of various immune system genes. The results revealed that L. acidophilus and the mixture of Lactobacillus species at the dose of 106 CFU consistently elicited higher expression of genes responsible for B cell development, differentiation, and survival (B cell activating factor (BAFF), BAFF-receptor (BAFF-R)), and antibody production (interleukin (IL)-10) and diversification (TGF-β). Similar expression patterns were also noted in T helper (Th) cell-associated cytokine genes, including Th1-type cytokines (interferon (IFN)-γ and IL-12p40), Th2-type cytokines (IL-4 and IL-13) and Th17 cytokine (IL-17). Overall, these results suggest that the supplementation of poultry-specific lactobacilli to chick embryos might be beneficial for accelerating the development and immunological maturation of the bursa of Fabricius. However, further studies are required to determine if the changes in gene expression are associated with the developmental trajectory and phenotypes of bursal cells.

Selection and evaluation of lactic acid bacteria from chicken feces in Thailand as potential probiotics

Background

Lactic acid bacteria (LAB) are widely used as probiotics in poultry production due to their resilience to low pH and high bile salt concentrations, as well as their beneficial effects on growth performance and antagonistic activity against enteric pathogens. However, the efficacy of probiotics depends on strain selection and their ability to colonize the host's intestine. This study aimed to select, identify, and evaluate LAB strains isolated from chicken feces in Thailand for potential use as probiotics in the chicken industry.

Methods

LAB strains were isolated from 58 pooled fresh fecal samples collected from chicken farms in various regions of Thailand, including commercial and backyard farms. Gram-positive rods or cocci with catalase-negative characteristics from colonies showing a clear zone on MRS agar supplemented with 0.5% CaCO3 were identified using MALDI-TOF mass spectrometry. The LAB isolates were evaluated for acid (pH 2.5 and pH 4.5) and bile salt (0.3% and 0.7%) tolerance. Additionally, their cell surface properties, resistance to phenol, antimicrobial activity, hemolytic activity, and presence of antimicrobial resistance genes were determined.

Results

A total of 91 LAB isolates belonging to the Pediococcus, Ligilactobacillus, Limosilactobacillus, and Lactobacillus genera were obtained from chicken feces samples. Backyard farm feces exhibited a greater LAB diversity compared to commercial chickens. Five strains, including Ligilactobacillus salivarius BF12 and Pediococcus acidilactici BF9, BF14, BYF20, and BYF26, were selected based on their high tolerance to acid, bile salts, and phenol. L. salivarius BF12 and P. acidilactici BF14 demonstrated strong adhesion ability. The five LAB isolates exhibited significant cell-cell interactions (auto-aggregation) and co-aggregation with Salmonella. All five LAB isolates showed varying degrees of antimicrobial activity against Salmonella strains, with P. acidilactici BYF20 displaying the highest activity. None of the LAB isolates exhibited beta-hemolytic activity. Whole genome analysis showed that L. salivarius BF12 contained ermC, tetL, and tetM, whereas P. acidilactici strains BF9 and BF14 carried ermB, lnuA, and tetM.

Conclusion

The selected LAB isolates exhibited basic probiotic characteristics, although some limitations were observed in terms of adhesion ability and the presence of antibiotic resistance genes, requiring further investigation into their genetic location. Future studies will focus on developing a probiotic prototype encapsulation for application in the chicken industry, followed by in vivo evaluations of probiotic efficacy.

Biophysiology of in ovo administered bioactive substances to improve gastrointestinal tract development, mucosal immunity, and microbiota in broiler chicks

Early embryonic exogenous feeding of bioactive substances is a topic of interest in poultry production, potentially improving gastrointestinal tract (GIT) development, stimulating immunization, and maximizing the protection capability of newly hatched chicks. However, the biophysiological actions and effects of in ovo administered bioactive substances are inconsistent or not fully understood. Thus, this paper summarizes the functional effects of bioactive substances and their interaction merits to augment GIT development, the immune system, and microbial homeostasis in newly hatched chicks. Prebiotics, probiotics, and synbiotics are potential bioactive substances that have been administered in embryonic eggs. Their biological effects are enhanced by a variety of mechanisms, including the production of antimicrobial peptides and antibiotic responses, regulation of T lymphocyte numbers and immune-related genes in either up- or downregulation fashion, and enhancement of macrophage phagocytic capacity. These actions occur directly through the interaction with immune cell receptors, stimulation of endocytosis, and phagocytosis. The underlying mechanisms of bioactive substance activity are multifaceted, enhancing GIT development, and improving both the innate and adaptive immune systems. Thus summarizing these modes of action of prebiotics, probiotics and synbiotics can result in more informed decisions and also provides baseline for further research.

Research Note: In ovo and in-feed probiotic supplementation improves layer embryo and pullet growth

Probiotics are widely used as feed supplements in the poultry industry to promote growth and performance in chickens. Specifically, this supplementation starts around the time of lay and continues through the production cycle in laying hens. However, the embryonic period is critical to the growth and development of metabolically active organs thereby influencing subsequent health and productivity in adult birds. Therefore, the present study investigated the potential use of probiotics to promote embryonic growth in layers. Further, a pilot grow-out study was conducted to evaluate the effect of in ovo and in-feed probiotic application on pullet growth. For the study, fertile White Leghorn eggs were sprayed with phosphate buffered saline (control, CON) or probiotic cocktail (in ovo only, IO; Lactobacillus paracasei DUP 13076 and L. rhamnosus NRRL B 442) prior to and during incubation. The embryos were sacrificed on d 7, 10, 14, and 18 of incubation for embryo morphometry. On d 18, remaining eggs were set in the hatcher to assess hatchability and hatchling morphometry. For the pullet trial, hatchlings were raised on feed with or without probiotics until wk 5. Pullets were sacrificed weekly, and morphometric parameters were recorded. Results of our study demonstrate that in ovo probiotic application significantly improved relative embryo weight, crown-rump length, hatchability, and hatchling weight when compared to the control (P < 0.05). Further, this enhanced embryonic development was associated with a concomitant increase in posthatch growth. Specifically, pullets raised from probiotic-sprayed eggs had significantly improved crown-rump length, tibial length, tibial bone weight, and body weight when compared to the control (P < 0.05). Moreover, among the different treatment schemes employed in this study [CON (no probiotics), in-feed only (IF), IO only, and in ovo and in-feed probiotic supplementation (IOIF)], sustained probiotic supplementation (IOIF) was found to be the most effective in promoting growth. Therefore, in ovo and in-feed probiotic supplementation could be employed to promote embryo and pullet growth to support subsequent performance in layers.

Effect of combined in ovo administration of zinc glycine chelate (Zn-Gly) and a multistrain probiotic on the modulation of cellular and humoral immune responses in broiler chickens

The aim of the study was to determine the effect of in ovo administration of zinc glycine chelate (Zn-Gly), and a multistrain probiotic on the hatchability and selected parameters of the cellular and humoral immune response of chickens. The study was conducted on 1,400 fertilized eggs from commercial broiler breeders (Ross x Ross 708). Material for the study consisted of peripheral blood and spleens of chicks taken 12 h and 7 d after hatching. The results showed that both combined and single in ovo administration of the multistrain probiotic and zinc glycine chelate significantly reduced hatchability of chicks. The flow cytometry study showed that the highest percentage of CD4+ T cells, CD4+CD25+, and high expression of KUL01 in the serum were obtained in the group supplemented with probiotic and Zn-Gly both 12 h and 7 d after hatching. In birds supplemented with probiotic and zinc chelate, a high percentage of TCRγδ+ cells was found in serum and spleen 12 h after hatching and in serum after 7 d. The percentage of Bu-1A+ lymphocytes in serum and spleen 12 h and 7 d after hatching was the highest in the group supplemented with probiotic and Zn-Gly. The highest expression of CD79A was observed in the group supplemented only with zinc chelate. There were no significant differences in the percentage of CD4+ cells in the spleens of birds in the groups receiving the multistrain probiotic at 12 h after hatching, and after 7 d, the percentage of CD4+ T cells was lower in the experimental groups than in the control group. The percentage of CD8+ cells in the serum of birds after hatching was lower in the group supplemented with multistrain probiotic and Zn-Gly than in the control group, but reached the highest value on d 7 after hatching. The obtained results confirm the strong effect of the combined administration of a multistrain probiotic and Zn-Gly chelate on lymphocyte proliferation and stimulation of cellular immune mechanisms in birds.

Synergistic influence of probiotic and florfenicol on embryonic viability, performance, and multidrug-resistant Salmonella Enteritidis in broiler chickens

This study was conducted during the period of August 2021 to April 2022 and divided into two parts. The first part involved the isolation and characterization of Salmonella from 200 diseased broiler chickens collected from farms in Dakahlia Governorate, Egypt, with the detection of its antimicrobial susceptibility. The second experimental part involved in ovo inoculation of probiotics and florfenicol to evaluate their effects on hatchability, embryonic viability, growth performance traits and the control of multidrug-resistant Salmonella Enteritidis infections post hatching. The point prevalence of Salmonella in the internal organs of diseased chickens was 13% (26/200), including 6 serotypes: S. Enteritidis, S. Typhimurium, S. Santiago, S. Colindale, S. Takoradi and S. Daula. Multidrug resistance was found in 92% (24/26) of the isolated strains with a multiantibiotic resistance index of 0.33-0.88 and 24 antibiotic resistance patterns. The in ovo inoculation of probiotic with florfenicol showed significant improvement in the growth performance parameters compared with other groups and had the ability to prevent colonization of multidrug resistant S. Enteritidis in the majority of the experimental chicks, and the remaining chicks showed very low colonization, as detected by RT‒PCR. These findings suggested the application of in ovo inoculation techniques with both probiotics and florfenicol as a promising tool to control multidrug-resistant S. Enteritidis in poultry farms.

In ovo probiotic supplementation promotes muscle growth and development in broiler embryos

In chickens, muscle development during embryonic growth is predominantly by myofiber hyperplasia. Following hatch, muscle growth primarily occurs via hypertrophy of the existing myofibers. Since myofiber number is set at hatch, production of more muscle fibers during embryonic growth would provide a greater myofiber number at hatch and potential for posthatch muscle growth by hypertrophy. Therefore, to improve performance in broilers, this study investigated the effect of in ovo spray application of probiotics on overall morphometry and muscle development in broiler embryos. For the study, fertile Ross 308 eggs were sprayed with different probiotics; Lactobacillus paracasei DUP 13076 (LP) and L. rhamnosus NRRL B 442 (LR) prior to and during incubation. The embryos were sacrificed on d 7, 10, 14, and 18 for embryo morphometry and pectoralis major muscle (PMM) sampling. Muscle sections were stained and imaged to quantify muscle fiber density (MFD), myofiber cross-sectional area (CSA), and nuclei density. Additionally, gene expression assays were performed to elucidate the effect of probiotics on myogenic genes. In ovo probiotic supplementation was found to significantly improve embryo weight, breast weight, and leg weight (P < 0.05). Further, histological analysis of PMM revealed a significant increase in MFD and nuclei number in the probiotic-treated embryos when compared to the control (P < 0.05). In 18-day-old broiler embryos, myofibers in the treatment group had a significantly smaller CSA (LP: 95.27 ± 3.28 μm², LR: 178.84 ± 15.1 μm²) when compared to the control (211.41 ± 15.67 μm²). This decrease in CSA was found to be associated with a concomitant increase in MFD (fibers/mm²) in the LP (13,647 ± 482.15) and LR (13,957 ± 463.13) group when compared to the control (7,680 ± 406.78). Additionally, this increase in myofibrillar hyperplasia in the treatment groups was associated with upregulation in the expression of key genes regulating muscle growth including MYF5, MYOD, MYOG, and IGF-1. In summary, in ovo spray application of probiotics promoted overall embryo growth and muscle development in broilers.

Effects of the In ovo Administration of the 6/85 Mycoplasma gallisepticum Vaccine on Layer Chicken Embryo Hatchability and Early Posthatch Performance

In ovo administration as a possible alternative method of 6/85 MG vaccination was assessed. After 18 days of incubation (doi), the eggs were administered a particular dosage of a live attenuated 6/85 MG vaccine in either the air cell (AC) or amnion (AM). The treatments included non-injected eggs and eggs injected into the AC or AM with diluent alone as controls. Treatments also included eggs injected with diluent, which contained 1.73 × 102, or 1.73 × 104 CFU of 6/85 MG. Hatchability of viable injected eggs (HI) and residual embryonic mortality were determined at 22 doi. At hatch and at three weeks posthatch, one hatched chick per treatment replicate was bled and swabbed for the detection of 6/85 MG in the choanal cleft using PCR, serum plate agglutination (SPA), and ELISA methods. The results show that AC in ovo injection of 6/85 MG had no negative impacts on HI or on the live performance of pullets, but that it failed to provide adequate protection (p ≤ 0.0001) in hatchlings or three-week-old pullets. The 1.73 × 104 6/85 MG CFU dosage injected into the AM decreased the hatchability of injected eggs containing viable embryos (HI; p = 0.009) and was associated with a significant increase in late dead mortality (p = 0.001). Hatchling and three-week-old chick mortalities (p = 0.008) were significantly greater in the 1.73 × 104 CFU-AM treatment group in comparison with the other treatment groups. In addition, the 1.73 and 1.73 × 102 6/85 MG-AM treatments had no negative effects on the hatching process or on posthatch growth, and the 1.73 × 102 6/85 MG-AM treatment was more effective in the protection of pullets against MG (p ≤ 0.0001) as compared with the low dosage and non-injected treatment groups. Further research is needed to examine the influence of the 6/85 MG in ovo vaccine on layer immune competence.

Physiological effects of in ovo delivery of bioactive substances in broiler chickens

The poultry industry has improved genetics, nutrition, and management practices, resulting in fast-growing chickens; however, disturbances during embryonic development may affect the entire production cycle and cause irreversible losses to broiler chicken producers. The most crucial time in the chicks' development appears to be the perinatal period, which encompasses the last few days of pre-hatch and the first few days of post-hatch. During this critical period, intestinal development occurs rapidly, and the chicks undergo a metabolic and physiological shift from the utilization of egg nutrients to exogenous feed. However, the nutrient reserve of the egg yolk may not be enough to sustain the late stage of embryonic development and provide energy for the hatching process. In addition, modern hatchery practices cause a delay in access to feed immediately post-hatch, and this can potentially affect the intestinal microbiome, health, development, and growth of the chickens. Development of the in ovo technology allowing for the delivery of bioactive substances into chicken embryos during their development represents a way to accommodate the perinatal period, late embryo development, and post-hatch growth. Many bioactive substances have been delivered through the in ovo technology, including carbohydrates, amino acids, hormones, prebiotics, probiotics and synbiotics, antibodies, immunostimulants, minerals, and microorganisms with a variety of physiological effects. In this review, we focused on the physiological effects of the in ovo delivery of these substances, including their effects on embryo development, gastrointestinal tract function and health, nutrient digestion, immune system development and function, bone development, overall growth performance, muscle development and meat quality, gastrointestinal tract microbiota development, heat stress response, pathogens exclusion, and birds metabolism, as well as transcriptome and proteome. We believe that this method is widely underestimated and underused by the poultry industry.

The effect of Bacillus subtilis and its delivery route on hatch and growth performance, blood biochemistry, immune status, gut morphology, and microbiota of broiler chickens

This study evaluated the effect of probiotics (Bacillus subtilis fermentation extract) and its delivery route (in-feed or in ovo) on hatch and growth performance, blood biochemistry, immune status, gut morphology, and microbiota of broiler chickens. Hatching eggs were incubated for 21 d. On d 12, viable eggs were randomly allotted to 4 groups: the noninjected, in ovo saline (S), in ovo Bacillus subtilis 1 (P1), and in ovo Bacillus subtilis 2 (P2). On d 18, S, P1, and P2 groups received 0.2 mL saline diluent, 10 × 10⁶, and 20 × 10⁶ CFU of the bacterium via the amnion, respectively. At hatch, chicks were re-allotted to 5 new treatment groups: P1, P2, 0.005% in-feed Bacillus subtilis extract (P3), 0.05% in-feed bacitracin methylene disalicylate (BMD,), and corn-wheat-soybean diet negative control (NC) in 9 replicate pens (22 birds/pen) and raised for 35 d. Hatch parameters were assessed on d 0, and growth performance indices measured weekly. On d 25, 1 bird/cage was euthanized, and samples collected for further analysis. Data were analyzed by generalized linear model. Treatments S and P2 recorded higher (P = 0.01) chick BW/ Egg Weight values compared to the non-injected eggs. P3 and P2 reduced (P = 0.02) FI at week 5 compared to the NC treatment. However, no change in average body weight gain (ABG) and feed conversion ratio (FCR) were observed during the same period. At d 35, while BMD treatment showed a tendency (P = 0.09) to increase FI compared to the NC treatment, ABG and FCR were similar for all treatments. Blood sodium and chloride levels were increased (P < 0.05) by the BMD treatment compared to the NC treatment. Compared to other treatments, BMD and P3 treatments increased (P < 0.001) jejunal and ileal villus height to crypt depth ratios, respectively. However, P1 and P2 increased (P < 0.001) villus height to crypt depth ratio in the duodenum compared to NC treatment. Treatments did not affect gut microbial diversity; however, BMD treatment increased (P < 0.05) the proportion of bacteria in the genus Enterococcus in the ileum and reduced (P < 0.05) the proportion of bacteria in the genus Streptococcus in the ceca. All probiotics treatments (irrespective of route and dose) reduced (P < 0.001) the levels of serum IgG compared to the NC treatment. However, P1 and P2 had the lowest numerical decrease in serum IgG concentrations, suggesting that Bacillus subtilis (especially in ovo delivered) might provide broiler chickens with better immunological protection by neutralizing pathogenic organisms that could result in the production of natural antibodies.

Characterizing the chicken gut colonization ability of a diverse group of bacteria

The development of probiotics for chickens is a rapidly expanding field. The main approach to probiotics is to administer the probiotic strain throughout the bird's life, usually through incorporation in the feed. However, probiotics which would utilize bacterial strains capable of permanently colonizing the gut after a single exposure are likely to have a greater impact on the developing gut community as well as on the host, would simplify probiotic use and also reduce costs in an industrial setting. Finally, very limited and conflicting information about the colonization ability of different bacterial strains has been reported. Here we report 2 colonization experiments using 14 different bacterial strains from diverse phylogenetic groups. In both experiments, groups of chicks were orally inoculated on the day of hatch with different bacterial strains that had been previously isolated from adult heavy breeders. In the first experiment, colonization of the bacterial strains in broiler chicks was determined 7 d after treatment. In the second experiment, colonization was followed in layer chicks until d 17. Ten of the bacterial strains, including Lactobacillales and Bacteroidales strains, were able to colonize chicks after a single exposure for the duration of the experiment. For a few of these strains, exposure had little effect compared to non-treated chicks due to natural background colonization. Only 4 strains failed to colonize the chicks. Moreover, it is shown that fecal samples are useful to identify and provide a dynamic view of colonization. We further analyzed the effects of artificial colonization on microbiota composition. Some of the strains used in this research were found to reduce Enterobacteriaceae family abundance, implying that they might be useful in reducing relevant pathogen levels. To conclude, our results show that the development of single exposure based probiotics is possible.

Chicken Incubation Conditions: Role in Embryo Development, Physiology and Adaptation to the Post-Hatch Environment

The chicken hatching egg is a self-contained life-supporting system for the developing embryo. However, the post-hatch performance of birds depends on several factors, including the breeder management and age, egg storage conditions and duration before incubation, and the incubation conditions. Studies have determined the effect of incubation factors on chick post-hatch growth potential. Therefore, chick physical quality at hatch is receiving increasing attention. Indeed, although incubation temperature, humidity, turning and ventilation are widely investigated, the effects of several variables such as exposure of the embryo to high or low levels, time of exposure, the amplitude of variations and stage exposures on embryo development and post-hatch performance remain poorly understood. This review paper focuses on chick quality and post-hatch performance as affected by incubation conditions. Also, chick physical quality parameters are discussed in the context of the parameters for determining chick quality and the factors that may affect it. These include incubation factors such as relative humidity, temperature, turning requirements, ventilation, in ovo feeding and delay in feed access. All these factors affect chick embryo physiology and development trajectory and consequently the quality of the hatched chicks and post-hatch performance. The potential application of adapted incubation conditions for improvement of post-hatch performance up to slaughter age is also discussed. It is concluded that incubation conditions affect embryo parameters and consequently post-hatch growth differentially according to exposure time and stage of exposure. Therefore, classical physical conditions are required to improve hatchability, chick quality and post-hatch growth.

Gastrointestinal Microbiota and Their Manipulation for Improved Growth and Performance in Chickens

The gut of warm-blooded animals is colonized by microbes possibly constituting at least 100 times more genetic material of microbial cells than that of the somatic cells of the host. These microbes have a profound effect on several physiological functions ranging from energy metabolism to the immune response of the host, particularly those associated with the gut immune system. The gut of a newly hatched chick is typically sterile but is rapidly colonized by microbes in the environment, undergoing cycles of development. Several factors such as diet, region of the gastrointestinal tract, housing, environment, and genetics can influence the microbial composition of an individual bird and can confer a distinctive microbiome signature to the individual bird. The microbial composition can be modified by the supplementation of probiotics, prebiotics, or synbiotics. Supplementing these additives can prevent dysbiosis caused by stress factors such as infection, heat stress, and toxins that cause dysbiosis. The mechanism of action and beneficial effects of probiotics vary depending on the strains used. However, it is difficult to establish a relationship between the gut microbiome and host health and productivity due to high variability between flocks due to environmental, nutritional, and host factors. This review compiles information on the gut microbiota, dysbiosis, and additives such as probiotics, postbiotics, prebiotics, and synbiotics, which are capable of modifying gut microbiota and elaborates on the interaction of these additives with chicken gut commensals, immune system, and their consequent effects on health and productivity. Factors to be considered and the unexplored potential of genetic engineering of poultry probiotics in addressing public health concerns and zoonosis associated with the poultry industry are discussed.

The Role of Nutraceuticals and Phytonutrients in Chickens’ Gastrointestinal Diseases

Simple Summary

The use of nutraceuticals and phytonutrients in poultry nutrition has been extensively explored over the past decade. The interest in these substances is linked to the search for natural compounds that can be effectively used to prevent and treat some of the main diseases of the chicken. The serious problem of antibiotic resistance and the consequent legislative constraints on their use required the search for alternatives. The purpose of this review is to describe the current status of the effects of some substances, such as probiotics and prebiotics, organic acids, vitamins and phytogenic feed additives, focusing specifically on studies concerning the prevention and treatment of four main gastrointestinal diseases in chicken: salmonellosis, necrotic enteritis (caused by Clostridium perfringens), campylobacteriosis, and coccidiosis. A brief description of these diseases and the effects of the main bioactive principles of the nutraceutical or phytonutrient groups will be provided. Although there are conflicting results, some works show very promising effects, with a reduction in the bacterial or protozoan load following treatment. Further studies are needed to verify the real effectiveness of these compounds and make them applicable in the field.

Abstract

In poultry, severe gastrointestinal diseases are caused by bacteria and coccidia, with important economic losses in the poultry industry and requirement of treatments which, for years, were based on the use of antibiotics and chemotherapies. Furthermore, Salmonella spp., Clostridium perfringens, and Campylobacter jejuni can cause serious foodborne diseases in people, resulting from consumption of poultry meat, eggs, and derived products. With the spread of antibiotic resistance, which affects both animals and humans, the restriction of antibiotic use in livestock production and the identification of a list of “critically important antimicrobials” became necessary. For this reason, researchers focused on natural compounds and effective alternatives to prevent gastrointestinal disease in poultry. This review summarizes the results of several studies published in the last decade, describing the use of different nutraceutical or phytonutrients in poultry industry. The results of the use of these products are not always encouraging. While some of the alternatives have proven to be very promising, further studies will be needed to verify the efficacy and practical applicability of other compounds.

Long-chain glucomannan supplementation modulates immune responsiveness, as well as intestinal microbiota, and impacts infection of broiler chickens with Salmonella enterica serotype Enteritidis

The zoonotic pathogen Salmonella enterica serotype Enteritidis (SE) causes severe disease in young chickens. Restriction on antibiotic use requires alternative SE control strategies such as nutritional solutions to improve the resistance of chickens. In this study, chickens were fed long-chain glucomannan (GM) or standard diet and challenged with SE at seven days of age. During 21 days post-infection (dpi), we determined numbers and responsiveness of natural killer (NK) and T cells in ileum and spleen, and SE-specific antibody titers in serum. Microbiota compositions in ileum and caeca were determined, as well as correlations of these with numbers and function of immune cells. Some of the samples in the control group had numerically higher CFUs than the GM-treated group. In addition, the relative abundance of SE based on DNA assessment was significantly lower at 21 dpi upon GM supplementation. At 3 dpi, numbers of intraepithelial NK cells were significantly higher, while activation of intraepithelial NK cells (7 dpi), numbers of intraepithelial cytotoxic CD8⁺ T cells (14 dpi) and SE-specific antibodies (14 dpi) were numerically higher. Furthermore, relative abundance of the commensal lactic acid bacteria (LAB) significantly increased with GM supplementation post-infection. Higher relative abundance of streptococci was associated with reduced SE in ileal and caecal contents at 21 dpi. Relative abundance of streptococci negatively correlated with SE counts and positively correlated with NK cell activation and SE-specific antibodies, which suggests involvement of the commensal LAB in NK cell responsiveness. These results indicate that GM supplementation modulates the immune system, intestinal microbiota and impacts SE infection of young chickens.

Effect of Bacillus subtilis on the microarchitectural development of the immune system in Salmonella-challenged broiler chickens

The effect of Bacillus subtilis on the immune responses and morphometry of the immune organs was evaluated in broilers challenged with S. gallinarum. For this purpose, Salmonella-free birds (n = 240) were split into four groups with six replicates of ten birds each. Groups included an NC (negative control, non-infected + non-medicated), a PC-S (positive control, Salmonella-infected + non-medicated), an AT-S (Salmonella-infected + medicated with enrofloxacin), and a BS-S (Salmonella-infected + B. subtilis (2.0 × 1010 cfu/g; 0.1 g/kg) group. On day 21, the thickness of the thymus cortex and medulla, germinal centre area of the spleen, bursal follicular length and bursal follicular area increased (P < 0.05) in the BS-S when compared to the NC and PC-S groups. On day 35, the BS-S group exhibited a higher (P < 0.05) antibody titre against the Newcastle disease virus (NDV), and cortex of the thymus was thicker (P < 0.05) compared to the other groups. A decrease in the thymus medulla thickness, germinal area of the spleen and bursal follicular number were noted in the PC-S group when compared to the other treatment groups. In conclusion, the prophylactic use of B. subtilis type probiotics alleviated the stress resulting from a Salmonella gallinarum infection and improved the immune organs development and function in infected broilers.

Non-Antibiotics Strategies to Control Salmonella Infection in Poultry

Salmonella spp. is a facultative intracellular pathogen causing localized or systemic infections, involving economic and public health significance, and remains the leading pathogen of food safety concern worldwide, with poultry being the primary transmission vector. Antibiotics have been the main strategy for Salmonella control for many years, which has allowed producers to improve the growth and health of food-producing animals. However, the utilization of antibiotics has been reconsidered since bacterial pathogens have established and shared a variety of antibiotic resistance mechanisms that can quickly increase within microbial communities. The use of alternatives to antibiotics has been recommended and successfully applied in many countries, leading to the core aim of this review, focused on (1) describing the importance of Salmonella infection in poultry and the effects associated with the use of antibiotics for disease control; (2) discussing the use of feeding-based (prebiotics, probiotics, bacterial subproducts, phytobiotics) and non-feeding-based (bacteriophages, in ovo injection, vaccines) strategies in poultry production for Salmonella control; and (3) exploring the use of complementary strategies, highlighting those based on -omics tools, to assess the effects of using the available antibiotic-free alternatives and their role in lowering dependency on the existing antimicrobial substances to manage bacterial infections in poultry effectively.

Managing Gut Microbiota through In Ovo Nutrition Influences Early-Life Programming in Broiler Chickens

The chicken gut is the habitat to trillions of microorganisms that affect physiological functions and immune status through metabolic activities and host interaction. Gut microbiota research previously focused on inflammation; however, it is now clear that these microbial communities play an essential role in maintaining normal homeostatic conditions by regulating the immune system. In addition, the microbiota helps reduce and prevent pathogen colonization of the gut via the mechanism of competitive exclusion and the synthesis of bactericidal molecules. Under commercial conditions, newly hatched chicks have access to feed after 36-72 h of hatching due to the hatch window and routine hatchery practices. This delay adversely affects the potential inoculation of the healthy microbiota and impairs the development and maturation of muscle, the immune system, and the gastrointestinal tract (GIT). Modulating the gut microbiota has been proposed as a potential strategy for improving host health and productivity and avoiding undesirable effects on gut health and the immune system. Using early-life programming via in ovo stimulation with probiotics and prebiotics, it may be possible to avoid selected metabolic disorders, poor immunity, and pathogen resistance, which the broiler industry now faces due to commercial hatching and selection pressures imposed by an increasingly demanding market.

In ovo Feeding as a Tool for Improving Performance and Gut Health of Poultry: A Review

Early growth and development of the gastrointestinal tract are of critical importance to enhance nutrients' utilization and optimize the growth of poultry. In the current production system, chicks do not have access to feed for about 48-72 h during transportation between hatchery and production farms. This lag time affects early nutrient intake, natural exposure to the microbiome, and the initiation of beneficial stimulation of the immune system of chicks. In ovo feeding can provide early nutrients and additives to embryos, stimulate gut microflora, and mitigate the adverse effects of starvation during pre-and post-hatch periods. Depending on the interests, the compounds are delivered to the embryo either around day 12 or 17 to 18 of incubation and via air sac or amnion. In ovo applications of bioactive compounds like vaccines, nutrients, antibiotics, prebiotics, probiotics, synbiotics, creatine, follistatin, L-carnitine, CpG oligodeoxynucleotide, growth hormone, polyclonal antimyostatin antibody, peptide YY, and insulin-like growth factor-1 have been studied. These compounds affect hatchability, body weight at hatch, physiological functions, immune responses, gut morphology, gut microbiome, production performance, and overall health of birds. However, the route, dose, method, and time of in ovo injection and host factors can cause variation, and thereby inconsistencies in results. Studies using this method have manifested the benefits of injection of different single bioactive compounds. But for excelling in poultry production, researchers should precisely know the proper route and time of injection, optimum dose, and effective combination of different compounds. This review paper will provide an insight into current practices and available findings related to in ovo feeding on performance and health parameters of poultry, along with challenges and future perspectives of this technique.

Recovery of probiotic bacteria from the intestinal tract of broilers after noninvasive pre-hatch application

This paper reports the success of intestinal colonisation of chickens and foetuses by probiotics after different methods of pre-hatch application. Hatcheries not using in ovo injection of probiotics or wish to avoid the reduced hatchability associated with in ovo injections prefer using alternatives to in ovo technologies. Therefore, we used noninvasive pre-hatch application methods. This included the vertical transmission of probiotics from the mother hen to offspring, application of probiotic late in incubation and transmission of probiotics during hatch. Enterococcus faecium (NCIMB11181) and Lactobacillus animalis (DSM33570) were used as probiotics. Probiotics were applied either through drinking water for the mother hens, by dipping the eggs in a probiotic solution on days 16-18 of incubation or through drops/spray on the eggshell of the fertilised eggs. Similarly, intestinal colonisation of the probiotic in chickens was investigated either before hatch (pre-hatch) or immediately after hatch (post-hatch). Based on the performed experiments, it is concluded that E. faecium was vertically transmitted from the mother hen to the offspring, as E. faecium was recovered in 20 and 33% of the offspring pre- and post-hatch, respectively. When applied on the eggshell, the recovery of E. faecium before hatch depended on the application method and ranged from 0 to 9%. In contrast, L. animalis was not recovered before hatch. Moreover, when sampling post-hatch 100% of the chickens were colonised when E. faecium was used and 54% were colonised when L. animalis was used. Furthermore, spray application with E. faecium was the most successful application method as 9% of the foetuses were colonised pre-hatch and 100% became colonised post-hatch. Therefore, pre-hatch application by, for example, spray of probiotics on the eggshell can be used as an easy-to-use, noninvasive method for early life colonisation of chicken gut.

Effect of in ovo feeding of probiotic, prebiotic and synbiotic to Broiler embryos on growth performance, Mucin-2 gene expression and gut colonization of microbiota

Supplementation of antibiotics in poultry diet was banned in several countries due to development of antibiotic resistance. In ovo feeding of prebiotics, probiotics and synbiotics have gained more attention recently. The present study was carried out in 2018 to investigate the effect of in-ovo feeding of probiotic, prebiotic and symbiotic on growth performance and gut microbiome of broiler chicken. On 18th day of incubation, 600 eggs were randomly divided into five treatments each with four replicates of 30 eggs each and were injected with different bio-active compounds, viz. 0.2 ml of Lactobacillus acidophilus 3×107 cfu, 0.5% Mannan-oligosaccharide (MOS), synbiotic (0.1 ml each of Lactobacillus acidophilus 3×107 cfu and 0.5% MOS) along with injected and non-injected controls. After hatch, 400 chicks were sorted out as per treatment with four replicates of 20 chicks each. Birds were reared under deep litter system and fed with experimental diet ad lib. In ovo feeding of Lactobacillus acidophilus, MOS either separately or in combination significantly improved hatch weight, fifth week body weight and gain. However, hatchability, cumulative feed intake, cumulative FCR and cumulative livability were not affected. Improved colonization of Lactobacillus acidophilus and suppressed colonization of Salmonella, Escherichia coli and Staphylococcus in all intra-amniotic groups was noticed. Ileal Mucin-2 gene was significantly up-regulated in the order of MOS, L. acidophilus and synbiotic injected broilers. The results concluded that the in ovo delivery of Lactobacillus acidophilus and MOS either separately or in combination had beneficial effect on growth and gut health of broiler chicken.

Effects of in ovo feeding of vitamin E or vitamin C on egg hatchability, performance, carcass traits and immunity in broiler chickens

The effect of in ovo feeding of different levels of vitamins C and E on egg hatchability, immune response, growth and carcass traits of broiler chickens were investigated. A total of 672 fertilized eggs were assigned to one of eight experimental groups having three replicates with 28 eggs as follows: (1) negative control (not injected); (2) positive control (injected with 0.2 mL deionized water); (3) vitamin C at 1 mg; (4) vitamin C at 3 mg; (5) vitamin C at 6 mg; (6) vitamin E at 0.5 IU; (7) vitamin E at 0.75 IU; and (8) vitamin E at 1.0 IU. At the end of incubation, the number of chicks hatched, and their individual body weight were recorded. Among hatched birds, a total of 240 mixed chicks were randomly selected (30 subject per group equally shared in three pen floors). Chicks were vaccinated against Avian Influenza, Gumboro, Bronchitis, and Newcastle disease virus. Performance parameters were weekly evaluated until 42 days of age. At days 28 and 42, broiler serum and spleen and Bursa of Fabricius relative weight were assessed as well as on day 42 the carcass traits. From results, in ovo injection with 3 mg of vitamin C or 0.75 IU of vitamin E, increased significantly (p < .05) the embryos hatchability when compared to the negative control. However, body weight at hatch and growth performance parameters showed no differences among treatments. Similarly, in ovo concentrations of vitamins C or E showed no differences on carcass traits, immunity-related organs weight or immune response for anti-Newcastle disease hemagglutination-inhibition and total immunoglobulins against sheep red blood cells (SRBC) when compared to the control groups. Based on findings, it can be concluded that in ovo feeding vitamins E and C supported positively chicken embryos hatchability demonstrating the key-role as antioxidant agents; however, further studies are currently being evaluated.

Eggshell and Feed Microbiota Do Not Represent Major Sources of Gut Anaerobes for Chickens in Commercial Production

In this study, we addressed the origin of chicken gut microbiota in commercial production by a comparison of eggshell and feed microbiota with caecal microbiota of 7-day-old chickens, using microbiota analysis by 16S rRNA sequencing. In addition, we tested at which timepoint during prenatal or neonatal development it is possible to successfully administer probiotics. We found that eggshell microbiota was a combination of environmental and adult hen gut microbiota but was completely different from caecal microbiota of 7-day-old chicks. Similarly, we observed that the composition of feed microbiota was different from caecal microbiota. Neither eggshell nor feed acted as an important source of gut microbiota for the chickens in commercial production. Following the experimental administration of potential probiotics, we found that chickens can be colonised only when already hatched and active. Spraying of eggs with gut anaerobes during egg incubation or hatching itself did not result in effective chicken colonisation. Such conclusions should be considered when selecting and administering probiotics to chickens in hatcheries. Eggshells, feed or drinking water do not act as major sources of gut microbiota. Newly hatched chickens must be colonised from additional sources, such as air dust with spores of Clostridiales. The natural colonisation starts only when chickens are already hatched, as spraying of eggs or even chickens at the very beginning of the hatching process did not result in efficient colonisation.

Assessment of In Ovo Administration of Bifidobacterium bifidum and Bifidobacterium longum on Performance, Ileal Histomorphometry, Blood Hematological, and Biochemical Parameters of Broilers

Bifidobacterium is one of the most promising probiotics which was recently used as an alternative growth promoter in poultry. This trial was considered to evaluate the potential effects of in ovo administration of Bifidobacterium bifidum and Bifidobacterium longum on growth performance and biochemical parameters of broilers. Three hundred broiler breeder eggs were incubated and candled individually at day 17 of embryogenesis; then, eggs that had live embryos were randomly divided into six groups. The first and second groups were of intact (without injection) and vehicle-injected (sterile distilled water) control groups, respectively. Other groups were in ovo injected with 1 × 10⁹ and 1 × 10⁷ CFU B. bifidum, and 1 × 10⁹ and 1 × 10⁷ CFU B. longum, respectively. Hatchability was significantly (P < 0.001) affected by in ovo inoculation of bifidobacteria strains. Body weight gain and feed conversion ratio were significantly improved (P = 0.014 and 0.019, respectively) in all treatment groups. Protein fractions, aspartate aminotransferase, and alanine aminotransferase activities were not significantly altered by bifidobacteria strains in ovo injection. Regarding ileal histomorphometry parameters, a significant elevation in villus height and villus height/crypt depth ratio values were recorded while crypt depth was insignificantly affected by in ovo treatments. It could be concluded that the tested manual method of in-yolk sac injection at day 17 of incubation is more favorable in easier delivering of bifidobacteria strains which improve broiler growth performance and ileal development without any undesirable effects on blood indices and liver and renal functions.

The Effects of In Ovo Injection of Synbiotics on the Early Growth Performance and Intestinal Health of Chicks

In this study, the effects of synbiotic inclusion at the intra-amniotic stage in layer chicks were evaluated with different parameters, such as performance, immunological function, intestinal development, and cecal microflora content. A total of 1,200 eggs with fertile embryos were allocated into four treatment groups. For every treatment, five replicates were used, and 60 eggs were included in each replicate. The following four treatment groups were established: the non-injected group, 0.9% physiological saline injection (saline) group, 1 × 10⁶ CFU/egg Lactobacillus plantarum injection (probiotic) group, and 1 × 10⁶ CFU/egg L. plantarum + 2 mg/egg Astragalus polysaccharide injection (synbiotic) group. In ovo injection was carried out at 18.5 days of incubation. The results showed that in ovo injection of probiotics or synbiotics did not affect the hatching or growth performance of the chicks but significantly increased their feed intake (FI), body weight (BW), and the feed conversion ratio (FCR). Additionally, in ovo injection of synbiotics enhanced the levels of serum interleukin-2 (IL-2), interferon-γ (IFN-γ), and secretory immunoglobulin A (SIgA) in intestinal lavage fluid and the histomorphological development of the small intestine. Our results also indicated that intra-amniotic synbiotic injection significantly increased Lactobacillus and Bifidobacterium colonization while decreasing the relative abundance of Escherichia coli in the chicken cecum (P < 0.05). In summary, in ovo injection of synbiotics had positive impacts on the performance, immunological function, gut development, and microbiota of growing chicks.

In Ovo and Oral Administration of Probiotic Lactobacilli Modulate Cell- and Antibody-Mediated Immune Responses in Newly Hatched Chicks

There is some evidence that lactobacilli can strengthen the immune system of chickens. This study evaluated the effects of in ovo and oral administration of a lactobacilli cocktail on cytokine gene expression, antibody-mediated immune responses, and spleen cellularity in chickens. Lactobacilli were administered either in ovo at embryonic day 18, orally at days 1, 7, 14, 21, and 28 post-hatches, or a combination of both in ovo and post-hatch inoculation. On day 5 and 10 post-hatch, spleen and bursa of Fabricius were collected for gene expression and cell composition analysis. On days 14 and 21 post-hatch, birds were immunized with sheep red blood cells (SRBC) and keyhole limpet hemocyanin (KLH), and sera were collected on days 7, 14, and 21 post-primary immunization. Birds that received lactobacilli (107 CFU) via in ovo followed by weekly oral administration showed a greater immune response by enhancing antibody responses, increasing the percentage of CD4+ and CD4+CD25+ T cells in the spleen and upregulating the expression of interferon (IFN)-α, IFN-β, interleukin (IL)-8, IL-13, and IL-18 in the spleen and expression of IFN-γ, IL-2, IL-6, IL-8, IL-12, and IL-18 in the bursa. These findings suggest that pre-and post-hatch administration of lactobacilli can modulate the immune response in newly hatched chickens.

In ovo administration of Bacillus subtilis serotypes effect hatchability, 21-day performance, and intestinal microflora

Recent research has tried to maximize broiler chick health and performance by utilizing commercial in-feed probiotics to inoculate fertile hatching eggs, and thus expose birds earlier to beneficial bacteria. However, the in ovo inoculation of a specific serotype of Bacillus subtilis was detrimental for broiler hatchability. Therefore, the objective of this study was to determine if other B. subtilis serotypes negatively affect hatchability or if it is associated with a specific serotype. It was also of interest to determine if the B. subtilis serotype influence chick performance and intestinal microflora. On d18 of incubation, 1886 fertile broiler eggs were in ovo inoculated with the following treatments (T): T1 = Marek's vaccine (MV), T2 = MV + B. subtilis (ATCC 6051), T3 = MV + B. subtilis (ATCC 8473), and T4 = MV + B. subtilis (ATCC 9466). It should be noted that in a previous study, T2 was detrimental to hatchability. Inoculated eggs were transferred to 3 hatchers/T. At hatch, chicks were weighed, feather sexed, and hatch residue analysis was conducted. Male chicks were randomly assigned to 40 raised wire cage so that there were 10 birds/cage. On d 0, 7, 14, and 21 of the grow-out, chicks and feed were weighed to calculate performance data. On these days, the ileum and ceca were aseptically collected to enumerate total aerobes and coliforms. No differences were observed for percentage of mid dead embryos, cracked eggs, and cull chicks (P > 0.05). However, hatch of transfer was significantly reduced by T2 compared to T1, T3, and T4 (P < 0.001). T2 had significantly higher percentages of late dead embryos and pips when compared to the other treatments (P = 0.002 and P < 0.001, respectively). Chicks hatched from T2 were not vigorous and, thus, not used for the grow-out trial. No differences were observed for growth performance characteristics for any of the treatments (P > 0.05). For bacterial enumeration, the ileum had equal or fewer bacterial counts for T3 and T4 when compared to T1 on most sampling days, except on d21 where T4 had higher aerobic and coliform counts (P ≤ 0.0001). For the ceca, T3 and T4 had equal or fewer bacterial counts than T1 on every sampling day (P ≤ 0.0001). These data demonstrate that not all B. subtilis evaluated are detrimental to hatchability, but rather, serotype dependent. In addition, different B. subtilis serotypes can modify the intestinal microflora with potential to reduce pathogenic bacteria present in young broiler, without impacting overall performance.

EFFECTS OF IN OVO SYNBIOTIC INJECTION ON GROWTH PERFORMANCE, INTESTINAL BACTERIAL LOAD AND ANTIBODY TITRES IN BROILER CHICKENS VACCINATED AGAINST INFECTIOUS BURSAL DISEASE

The present study investigated the efficacy of a synbiotic (Lactobacillus delbrueckii subsp. bulgar-icus, Streptococcus salivarius subsp. thermophilus, and mannan oligosaccharide) along with an infectious bursal disease (IBD) vaccine in Cobb 500 broilers. A total of 1200 embryonated chicken eggs were randomly allocated in 10 groups with eight replicates. The first group did not receive any treatment. The second group was vaccinated post-hatch (PV), the third group was vaccinated in ovo (IV), the fourth group received dietary synbiotic and in ovo vaccination (DS+IV), the fifth group was treated in ovo with synbiotic (IS), the sixth group received in ovo and dietary synbiotic (IS+DS), the seventh group received in ovo synbiotic plus post-hatch vaccination (IS+PV) and the eighth group  in ovo and dietary synbiotic and post-hatch vaccination (IS+DS+PV). In the ninth group, the synbiotic and the vaccine were administered in ovo (IS+IV) while the tenth group re-ceived in ovo and dietary synbiotic, plus in ovo vaccine (IS+DS+IV). The in ovo treatment with the synbiotic in combination with DS, IV or PV had a positive effect on weekly weight gain. The sixth group provided a better feed conversion ratio at the end of fourth week. The synbiotic appli-cation, individually in sixth group or along with PV or IV treatment in eighth and tenth groups, elevated feed intake in fifth and sixth weeks respectively.The antibody titre of IBD was higher for groups which received IV along with IS. It is concluded that the application of synbiotic along to IBD vaccine improved growth performance and had positive effects on IBD antibody titres.

Effects of in ovo probiotic administration on the incidence of avian pathogenic Escherichia coli in broilers and an evaluation on its virulence and antimicrobial resistance properties

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in poultry, which has been traditionally controlled by the prophylactic in-feed supplementation of antibiotics. However, antibiotics are being removed from poultry diets owing to the emergence of multidrug-resistant (MDR) bacteria. Therefore, alternatives to control APEC are required. This study aimed to evaluate the effects of in ovo inoculation of probiotics on the incidence of APEC in broilers and evaluate the virulence and antimicrobial resistance properties of the APEC isolates. On embryonic day 18, 4 in ovo treatments (T) were applied: T1 (Marek's vaccine [MV]), T2 (MV and Lactobacillus animalis), T3 (MV and Lactobacillus reuteri), and T4 (MV and Lactobacillus rhamnosus). A total of 180 male broilers per treatment were randomly placed in 10 pens. The heart, liver, spleen, and yolk sac were collected on day 0, 14, 28, and 42. Presumptive E. coli isolates were confirmed by real-time PCR. The positive isolates were screened for the APEC-related genes (iroN, ompT, hlyF, iss, and iutA), and E. coli isolates containing one or more of these genes were identified as APEC-like strains. A total of 144 APEC-like isolates were isolated from 548 organ samples. No differences (P > 0.05) among treatments were observed for the incidence of APEC-like strains in all organs when averaged over sampling days. However, when averaged over treatments, the incidence in the heart, liver, and yolk sac was different among sampling days; a significant increase was observed in these organs on day 14 compared with day 0. Twenty-five antimicrobial resistance genes were evaluated for all APEC-like isolates, and 92.4% of the isolates carried at least one antimicrobial resistance gene. Thirty-seven isolates were then selected for antimicrobial susceptibility testing; MDR strains accounted for 37.8% of the isolates. In conclusion, the in ovo inoculation of a single probiotic strain did not confer protection against APEC strains in broilers. The high prevalence of MDR isolates indicates that further research on antibiotic alternatives is required to prevent APEC infections in broilers.

Bacillus subtilis delivery route: effect on growth performance, intestinal morphology, cecal short-chain fatty acid concentration, and cecal microbiota in broiler chickens

As the poultry industry recedes from the use of antibiotic growth promoters, the need to evaluate the efficacy of possible alternatives and the delivery method that maximizes their effectiveness arises. This study aimed at expounding knowledge on the effect of the delivery method of a probiotic product (Bacillus subtilis fermentation extract) on performance and gut parameters in broiler chickens. A total of 450 fertile eggs sourced from Cobb 500 broiler breeders were randomly allotted to 3 groups: in ovo probiotic (n = 66), in ovo saline (n = 66), and noninjection (n = 200) and incubated for 21 d. On day 18.5 of incubation, 200 μL of either probiotic (10 × 10⁶ cfu) or saline was injected into the amnion. At hatch, chicks were reallotted to 6 new treatment groups: in ovo probiotic, in ovo saline, in-feed antibiotics, in-water probiotic, in-feed probiotics, and control (corn-wheat-soybean diet) in 6 replicate cages and raised for 28 d. Of all hatch parameters evaluated, only percentage pipped eggs was found significant (P < 0.05) with the noninjection group having higher percentage pipped eggs than the other groups. Treatments did not affect the incidence of necrotic enteritis on day 28 (P > 0.05). Irrespective of the delivery method, the probiotic treatments had no significant effect on growth performance. The ileum villus width of the in ovo probiotic treatment was 18% higher than the in ovo saline group (P = 0.05) but not statistically higher than other groups. The jejunum villus height was 23% higher (P = 0.000) in the in ovo probiotic group than in the control group. There was no effect of treatment on total cecal short-chain fatty acid concentration and cecal gut microbiota composition and diversity (P > 0.05), although few unique bacteria differential abundance were recorded per treatment. Conclusively, although probiotic treatments (irrespective of the delivery route) did not affect growth performance, in ovo delivery of the probiotic product enhanced intestinal morphology, without compromising hatch performance and gut homeostasis.

In ovo inoculation of an Enterococcus faecium-based product to enhance broiler hatchability, live performance, and intestinal morphology

Previous studies have suggested the use of probiotics, as alternative to antibiotics, to enhance broiler performance. The administration of probiotics in feed has been widely explored; however, few studies have evaluated the in ovo inoculation of probiotics. Therefore, the objective was to evaluate the impact of in ovo inoculation of different concentrations of GalliPro Hatch (GH), an Enterococcus faecium-based probiotic, on hatchability, live performance, and gastrointestinal parameters. Ross x Ross 708 fertile eggs were incubated, and on day 18, injected with the following treatments: 1) 50 μL of Marek's vaccine (MV), 2) MV and 1.4 × 105 cfu GH/50 μL, 3) MV and 1.4 × 106 cfu GH/50 μL, 4) MV and 1.4 × 107 cfu GH/50 μL. On the day of hatch, chicks were weighed, feather sexed, and hatch residue was analyzed. Male birds (640) were randomly assigned to 40 floor pens. On day 0, 7, 14, and 21 of the grow-out phase, performance data were collected. One bird from each pen was used to obtain yolk weight and intestinal segment weight and length. Hatchability was not impacted by any GH treatment (P = 0.58). On day 0, yolk weight was lower for all treatments than for MV alone. On day 0 to 7, feed intake was lower for 105 and 107 GH; the feed conversion ratio (FCR) was lower for all treatments than for MV alone (P = 0.05; P = 0.01, respectively). From day 14 to 21, the 107 GH treatment had higher BW gain (P = 0.05). For day 0 to 21, 107 GH had a lower FCR than MV alone (P = 0.03). On day 0, all GH treatments resulted in heavier tissues and longer jejunum, ileum, and ceca lengths than MV alone (P < 0.05). Spleen weight was higher for 105 and 107 GH than for MV alone. In conclusion, GH does not impact hatchability, and some concentrations improved live performance through the first 21 d of the grow-out phase. These improvements could result from the increased yolk absorption and improved intestinal and spleen morphology seen in this study.

In ovo Administration of Defined Lactic Acid Bacteria Previously Isolated From Adult Hens Induced Variations in the Cecae Microbiota Structure and Enterobacteriaceae Colonization on a Virulent Escherichia coli Horizontal Infection Model in Broiler Chickens

The effects of in ovo administration of a defined lactic acid microbiota (LAM), previously isolated from adult hens, in the cecae microbiota structure and Enterobacteriaceae colonization after exposure to virulent Escherichia coli during the hatching phase of broiler chickens were evaluated. Embryos inoculated with LAM showed a significant (P < 0.05) reduction of Enterobacteriaceae colonization at day-of-hatch (DOH) and day (d) 7. Furthermore, there was a significant increase in total lactic acid bacteria on DOH, body weight (BW) DOH, BW d7, and d0–d7 BW gain and reduced mortality d0–d7 was observed in the LAM group compared with that in phosphate-buffered saline (PBS) control. The bacterial composition at the family level revealed that the Enterobacteriaceae was numerically reduced, whereas the Ruminococcaceae was significantly increased in the LAM group when compared with that in the PBS control. Moreover, the bacterial genera Proteus and Butyricicoccus and unidentified bacterial genera of family Lachnospiraceae and Erysipelotrichaceae were significantly enriched in the LAM group. In contrast, the Clostridium of the family Peptostreptococcaceae and unidentified genus of family Enterobacteriaceae were significantly abundant in the PBS control group. In summary, in ovo administration of a defined LAM isolated from adult hens did not affect hatchability, improved body weight gain and reduced mortality at d7, induced variations in the cecae microbiota structure and reduced Enterobacteriaceae colonization on a virulent E. coli horizontal infection model in broiler chickens.

Synergistic effects of the early administration of Lactobacillus kefiranofaciens DN1 and Kluyveromyces marxianus KU140723-05 on the inhibition of Salmonella Enteritidis colonization in young chickens

In this study, we aimed to assess the feasibility of the lactic acid bacterium Lactobacillus kefiranofaciens DN1 (LKF_DN1) and the yeast Kluyveromyces marxianus KU140723-05 (KMA5), recently isolated from kefir, as probiotics. Specifically, we evaluated the effect of early administration of these 2 microbes on the inhibition of Salmonella Enteritidis (SE) colonization in neonatal chicks. We also examined the effects of exposure of chicks to probiotics before SE exposure on the reduction in the number of gut SE. A total of 108 1-day-old specific-pathogen-free male layer chicks were used for 3 independent experiments. The experimental chicks were randomly divided into 6 groups (negative control: basal diet [BD] without probiotics and SE; positive control: BD; probiotic group [PG] 1: BD + LKF_DN1; PG2: BD + KMA5; PG3: BD + LKF_DN1 + KMA5; and PG4: BD+ a commercial product IDF-7), all of which, except negative control, were coadministered with SE strain resistant to rifampicin (SERR). We found that the administration of LKF_DN1 and/or KMA5 reduced the number of viable cells of the SERR strain in chicks by up to 1.90 log₁₀, relative to positive control chicks. Compared with late administration (day [D] 10 and D11), early administration (D1 and D2) of the probiotics was more effective in reducing SERR cell numbers in the gut. Furthermore, we detected no significant difference in the reduction of gut SERR cell numbers in chicks from the same groups exposed to the probiotics at D10 and D11 before and after administration with SERR. Collectively, our findings indicate that, as dietary additives, LKF_DN1 and KMA5 showed potential probiotic activity in chicks. Moreover, the combination of the lactic acid bacteria and/or yeast strain was found to rapidly reduce SE numbers in the chick gut and showed a prolonged inhibitory effect against SE colonization. We, thus, propose that the administration of these 2 probiotics, as early as possible after hatching, would be considerably effective in controlling SE colonization in the guts of chicks.

Post hatch recovery of a probiotic Enterococcus faecium strain in the yolk sac and intestinal tract of broiler chickens after in ovo injection

Concerns about antibiotic-resistant bacteria and their presence in animal products grow and thus alternatives to use of antibiotics in animal production are being investigated. Probiotics have gained increased focus due to improvements in performance, immune health and pathogen reduction when provided to poultry through feed. These traits may be further improved if probiotics can be provided to the embryo before hatch, before meeting environmental pathogens. The objective was to determine the faith of a probiotic Enterococcus faecium (M74) strain in the yolk sac and intestinal tract of broiler chickens after injection into hatching eggs. E. faecium M74 (1.4 × 107 CFU/egg) was applied in ovo at day 18 of incubation. From 1- and 7-day-old chickens, 20 samples from yolk sac, caecal tonsils and rest of the intestinal tract were subjected to CFU counting. Isolates from a sample subset were typed by pulsed-field gel electrophoresis (PFGE). Enterococci were found in varying numbers: 1.0 × 104-2.2 × 1010 CFU/g. The prevalence of M74 PFGE profiles was high in 1-day-old (88%) and 7-day-old chickens (67%). This demonstrates that the embryos ingested M74 before hatching, that M74 is viable for intestinal colonization through in ovo administration, and that the strain multiplies in the chickens gastrointestinal tract post hatching.

The potential for inoculating Lactobacillus animalis and Enterococcus faecium alone or in combination using commercial in ovo technology without negatively impacting hatch and post-hatch performance

The poultry industry has recently undergone transitions into antibiotic free production, and viable antibiotic alternatives, such as probiotics, are necessary. Through in ovo probiotic inoculation, beneficial microflora development in the gastrointestinal tract may occur prior to hatch without negatively impacting chick performance. Therefore, the objective of the present study was to observe the impacts of the injection of probiotic bacteria individually or combined into fertile broiler hatching eggs on hatch and live performance characteristics. A total of 2,080 fertile broiler hatching eggs were obtained from a commercial source. On day 18 of incubation, 4 in ovo injected treatments were applied: 1.) Marek's Disease (HVT) vaccination, 2.) L. animalis (∼10⁶ cfu/50μl), 3.) E. faecium (∼10⁶ cfu/50μl), and 4.) L. animalis + E. faecium (∼10⁶ cfu & ∼10⁶ cfu/50μl each). On day of hatch, hatchability and hatch residue data were recorded. A portion of male chicks from each treatment were placed in a grow-out facility for a 21 d grow-out (18 chicks/pen × 10 pens/treatment = 720 male chicks) with a corn and soy bean meal-based diet without antibiotics or antibiotic alternatives. Performance data and gastrointestinal samples were collected on days 0, 7, 14, and 21. Results indicated no differences in all hatch parameters between treatments (P > 0.05) except for % pipped, where the L. animalis treatment had lower % pipped eggs compared to the HVT control and E. faecium treatments (P = 0.04). No differences were observed in body weight gain or mortality (P > 0.05). Probiotic treatments altered gastrointestinal tissue length, weight, and pH. This resulted in all in ovo injected probiotic treatments increasing feed conversion ratio (FCR) from days 7 to 14 as compared to the control (P = 0.01). Differences in FCR were not observed in any other week of data collection (days 0 to 7, 14 to 21, or 0 to 21; P > 0.05). Although probiotics altered live performance from days 7 to 14, these data suggest that in ovo inoculations of L. animalis and E. faecium in combination are viable probiotic administration practices that potentially improve hatch characteristics and gastrointestinal tract development.

Topical Application of Adult Cecal Contents to Eggs Transplants Spore-Forming Microbiota but Not Other Members of the Microbiota to Chicks

The intestinal microbiota plays an essential role in the metabolism and immune competence of chickens from the first day after hatching. In modern production systems, chicks are isolated from adult chickens, instead hatching in a clean environment. As a result, chicks are colonized by environmental bacteria, including potential pathogens. There is a need to investigate methods by which chicks can be exposed to a more appropriate microbial community at hatching. Such methods must be easy to apply in a hatchery and produce consistent results. The development of the intestinal microbiota of chicks hatched from eggs sprayed with dilute adult cecal content during incubation was observed at 0, 3, 7, and 14 days posthatching (dph) across two experiments. High-throughput Illumina sequencing was performed for the V4 hypervariable region of the 16S rRNA gene. A topical treatment of dilute adult cecal content was sufficient to transplant spore-forming bacteria such as Lachnospiraceae and Ruminococcaceae However, this treatment was not able to transplant other taxa that are considered to be core elements of the chicken cecal microbiota, such as Bacteroidaceae, Lactobacillaceae, Bifidobacteriaceae, and Burkholderiaceae The topical treatment significantly altered the microbiota of chicks immediately posthatching and accelerated the normal development of the microbiota with earlier colonization by Ruminococcaceae in the cecum and "Candidatus Arthromitus" in the ileum. The effect of the treatment on the cecal microbiota was maximal at 3 dph but diminished over time.IMPORTANCE Over the last 60 years poultry production has intensified in response to increased demand for meat. In modern systems, chicks hatch without contacting chickens and their gut bacteria. Consequently, they are colonized by environmental bacteria that may cause disease. The normal bacteria that live in the gut, or intestinal microbiota, play an important role in the development of the immune system. Therefore, it is essential to find easy ways to expose chicks to the more appropriate bacteria at hatching. This experiment investigated whether spraying eggs with adult cecal contents was sufficient to transfer an adult microbiota to chicks. Our findings show that spore-forming bacteria were transplanted, but other members of the microbiota were not. In this respect, the spray application was partially successful, but the timing of the spray needs to be modified to ensure that more bacteria are transferred.

Impact of in ovo administered pioneer colonizers on intestinal proteome on day of hatch

Pioneer colonization of the gastrointestinal tract (GIT) by bacteria is thought to have major influence on neonatal tissue development. Previous studies have shown in ovo inoculation of embryos with saline (S), species of Citrobacter (C, C2), or lactic acid bacteria (L) resulted in an altered microbiome on day of the hatch (DOH). The present study investigated GIT proteomic changes at DOH in relation to different inoculations. Embryos were inoculated in ovo with S or ∼10² cfu of C, C2, or L at 18 embryonic days. On DOH, the GIT was collected, and tissue proteins were extracted for analysis via tandem mass spectrometry. A total of 493 proteins were identified for differential comparison with S at P ≤ 0.10. Different levels were noted in 107, 39, and 78 proteins in C, C2, and L groups, respectively, which were uploaded to Ingenuity Pathway Analysis to determine canonical pathways and biological functions related to these changes. Three members of the cytokine family (interleukin [IL]-1β, IL6, and Oncostatin M) were predicted to be activated in C2, indicated with Z-score ≥ 1.50, which suggested an overall proinflammatory GIT condition. This was consistent with the activation of the acute-phase response signaling pathway seen exclusively in C2 (Z-score = 2.00, P < 0.01). However, activation (Z-score = 2.00) of IL-13, upregulation of peroxiredoxin-1 and superoxide dismutase 1, in addition to activation of nitric oxide signaling in the cardiovascular system of the L treatment may predict a state of increased antioxidant capacity and decreased inflammatory status. The nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress response (Z-score = 2.00, P < 0.01) was predicted to be upregulated in C which suggested that chicks were in an inflammatory state and associated oxidative stress, but the impact of these pathways differed from that of C2. These changes in the proteome suggest that pioneer colonizing microbiota may have a strong impact on pathways associated with GIT immune and cellular development.