In ovo feeding of L-arginine alters energy metabolism in post-hatch broilers

L-arginine alters myogenic genes expression but does not affect breast muscle characteristics by in ovo feeding technique in slow-growing chickens

In ovo feeding (IOF) of nutrients is a viable method for increasing muscle mass through hyperplasia and hypertrophy. The objective of this study was to evaluate the effects of IOF of L-arginine (Arg) on breast muscle weight, muscle morphology, amino acid profile, and gene expression of muscle development in slow-growing chickens. Four hundred eighty fertilized eggs were randomly divided into two groups: the first group was the non-injected control group, and the second group was the Arg group, injected with 1% Arg (0.5 mL) into the amnion on day 18 of incubation. After hatching, 160 birds from each group were randomly divided into four replicates of 40 birds each. This experiment lasted for 63 days. The results showed that IOF of Arg did not affect (P > 0.05) breast muscle weight, muscle morphology, and mRNA expression of mammalian target of rapamycin (mTOR) signaling pathway in slow-growing chickens. However, the amino acid profile of breast muscle was altered (P < 0.05) on the day of hatching (DOH), day 21 (D21), and day 42 (D42) post-hatch, respectively. Myogenic factor 5 (Myf5) mRNA expression was upregulated (P < 0.05) on D21 post-hatch. Myogenic regulator 4 (MRF4) mRNA expression was increased (P < 0.05) on DOH. And myogenin (MyoG) was increased (P < 0.05) on DOH and D21 post-hatch, in the Arg group compared to the control group. Overall, IOF of 1% Arg improved the expression of myogenic genes but did not influence muscle morphology and BMW. These results indicate that in ovo Arg dosage (0.5 mL/egg) has no adverse effect on breast muscle development of slow-growing chickens.

Intestinal microbiota of layer hens and its association with egg quality and safety

The intestinal microbiota has attracted tremendous attention in the field of the poultry industry due to its critical role in the modulation of nutrient utilization, immune system, and consequently the improvement of the host health and production performance. Accumulating evidence implies intestinal microbiota of laying hens is a potential mediator to improve the prevalent issues in terms of egg quality decline in the late phase of laying production. However, the regulatory effect of intestinal microbiota on egg quality in laying hens remains elusive, which requires consideration of microbial baseline composition and succession during their long lifespans. Notable, although Firmicutes, Bacteroidetes, and Proteobacteria form the vast majority of intestinal microbiota in layer hens, dynamic intestinal microbiota succession occurs throughout all laying periods. In addition to the direct effects on egg safety, intestinal microbiota and its metabolites such as short-chain fatty acids, bile acids, and tryptophan derivatives, are suggested to indirectly modulate egg quality through the microbiota-gut-liver/brain-reproductive tract axis. These findings can extend our understanding of the crosstalk between intestinal microbiota and the host to improve egg quality and safety. This paper reviews the compositions of intestinal microbiota in different physiological stages of laying hens and their effects on egg quality and proposes that intestinal microbiota may become a potential target for modulating egg quality and safety by nutritional strategies in the future.

Developmental changes of free amino acids in amniotic, allantoic fluids and yolk of broiler embryo

1. A study was conducted to evaluate the developmental changes of protein and free amino acid concentrations in amniotic, allantoic fluids and yolk during the incubation period of broiler eggs.2. A total of 120 Cobb 500 fertile eggs were individually weighed and then placed in incubator. On incubation day: 8, 11, 13, 14, 16, and/or 18, amniotic, allantoic fluids and yolk were collected from 20 eggs for analysis of protein content and free α-amino acid concentration in allantoic and amniotic fluids and yolk.3. The total protein concentration in amniotic fluid increased from d 11 of incubation, and reached a peak at d 16 (69.85 g/l; P<0.01), then declined at d 18 (P<0.05). The total protein concentration in allantoic fluid increased with age of the embryo (P<0.01). Crude protein concentration in yolk decreased (P<0.05) from d 0 to 8, then increased gradually from d 8, and reached a peak at d 16 (P<0.05). The concentration of most free amino acids in amniotic and allantoic fluids and yolk was related to embryo weight. Amniotic fluid amino acids gradually increased from d 13 to 18, with arginine being the most abundant at d 11 and 14. Glutamate was the most predominant amniotic fluid amino acid at d 16 and 18. From d 13 to 18, the concentrations of most α-amino acids in allantoic fluid increased, and reached a peak at d 18 (aspartate, 373 μmol/l; asparagine, 519 μmol/l; glutamine, 1230 μmol/l; threonine, 537 μmol/l; citrulline, 112 μmol/l; arginine, 2747 μmol/l; alanine, 276 μmol/l; tyrosine, 330 μmol/l; tryptophan, 212 μmol/l; valine, 140 μmol/l; phenylalanine, 102 μmol/l; isoleucine, 92.39 μmol/l; lysine, 1088 μmol/l; P<0.05). Glutamine was the second most abundant amino acid in allantoic fluid at d 13 and 18. Glutamate was the most abundant α-amino acids at d 8, and 13 in the yolk.4. These results demonstrated that the concentration of free α-amino acids in chicken embryo fluid was related to embryo weight. Arginine, glutamine and glutamate were abundant free α-amino acid in chicken embryo fluid, to support the higher rates of tissue protein synthesis and growth for the embryo.

Influences of L-Arginine In Ovo Feeding on the Hatchability, Growth Performance, Antioxidant Capacity, and Meat Quality of Slow-Growing Chickens

Simple Summary

The nutrition and health status of the embryo in the hatching process directly influence the hatchability and chicken performance post-hatch in poultry production. The in ovo feeding (IOF) technique provides a viable way to improve the embryonic development and chicken performance post-hatch. Thus, the hypothesis of this study was that supplementing L-arginine (Arg) into embryos could positively affect the hatchability, growth performance, antioxidant capacity, and meat quality of slow-growing chickens. The results of this study demonstrate that IOF of Arg positively affected the antioxidant capacity of the breast muscle in the starter period, and there was no effect on the hatchability, growth performance, carcass traits, and meat quality. Overall, our findings suggest that IOF of Arg may have beneficial effects on chicken health without compromising the hatchability, subsequent growth, and meat quality.

Abstract

The aim of this study was to evaluate the effects of in ovo feeding (IOF) of L-arginine (Arg) on the hatchability, growth performance, antioxidant capacity, and meat quality of slow-growing chickens. A total of 480 eggs were randomly divided into a non-injected control group (NC group) and a 1% Arg-injected group (Arg group). On day 18 of incubation, 0.5 mL of Arg solution was injected into the embryonic amnion in the Arg group. Upon hatching, 160 mixed-sex chickens were randomly assigned to two groups, with four replicates per group. This experiment lasted for 63 days. The results showed that the hatchability, growth performance, carcass traits, and meat quality were not significantly different (p > 0.05) between the two groups. However, the malondialdehyde (MDA) content was lower (p < 0.05), and the glutathione (GSH) level was higher (p < 0.05) on day of hatching in the Arg group. The total antioxidant capacity (T-AOC) activity was increased (p < 0.05) on day 21 post-hatch in the Arg group compared to that in the NC group. In conclusion, IOF of Arg increased the antioxidant capacity of the breast muscle in the starter period, which may have a positive effect on health status of slow-growing chickens post-hatch.

Effects of low eggshell temperatures during incubation, in ovo feeding of L-arginine, and post-hatch dietary guanidinoacetic acid on hatching traits, performance, and physiological responses of broilers reared at low ambient temperature

This study aimed to investigate the effect of eggshell temperature (ET) manipulations during incubation, in ovo feeding (IOF) of arginine, and post-hatch dietary supplementation with guanidinoacetic acid (GAA) on hatching traits and subsequent growth and physiological performance of hatched broiler chicks reared under subnormal temperature. In experiment 1, from d 8 of incubation onward, a total of 2,160 hatching eggs were randomly arranged in a 2 × 3 factorial design, in which the eggs were exposed to 2 ET (37.8°C or periodically low ET), and 3 IOF treatments (noninjected, diluent-injected, and 1% arginine solution-injected). In experiment 2, a total of 576 one-day-old male broiler chicks from 2 temperature conditions and 2 IOF treatment groups (noninjected and Arg-injected) were reared for 42 d with or without GAA supplementation in a 2 × 2 × 2 factorial design. Each treatment had 6 replicates with 12 birds each. A subnormal ambient temperature (17°C) was applied from 15 d onward to induce ascites. Results from experiment 1 showed a 2-way interaction between ET and IOF for embryonic mortality rate during 19 to 21 d of incubation and residual yolk weight at hatch (P < 0.05). A periodically low ET significantly increased yolk free body mass, first-grade chicks, and relative heart weight than an ET of 37.8°C. In the second experiment, overall average daily gain (ADG) was increased, but feed conversion ratio (FCR), ascites mortality, and serum thyroid hormones and corticosterone were reduced in the low ET group (P < 0.05). There were also IOF × GAA interactions for ADG and FCR (P < 0.05). IOF of arginine or dietary GAA increased serum nitric oxide concentration and jejunal villus height, but decreased ascites mortality (P < 0.05). In conclusion, a periodically low ET accompanied by IOF of arginine during incubation and posthatch dietary supplementation with GAA could be a useful strategy for improving the chick quality at hatch and subsequent improvements in post-hatch performance and ascites indices in cold-stressed broilers.

Effect of Muscle Extract and Graphene Oxide on Muscle Structure of Chicken Embryos

Simple Summary

Genetic selection of broilers increased muscle growth; however, very fast growth can lead to pathological conditions caused by the deficiency of nutrients. The number of muscle cells is mainly formed during the embryonic period, and consequently, in ovo supplementation of proteins to embryos may impact future muscle structure. We hypothesized that proteins from chicken embryo muscle extract (CEME) caused by the unique, natural composition and biocompatibility can supply additional proteins. However, supplemented proteins are actively metabolized, which may reduce their utilization for improved muscle synthesis. Nevertheless, CEME can be transported and protected by graphene oxide (GO). The objective of the present work was to investigate the effects of in ovo-injected CEME and the complex of GO-CEME on embryonic cell cultures and the growth of chicken embryo hind limb muscle. Toxicity and cell proliferation were measured in vitro with cell cultures and mortality, morphology, histology, and blood biochemistry in vivo with embryos. CEME increased the number of cells and nuclei in muscle, but the complex GO-CEME did not further improve the muscle structure. The results indicate a vital role of CEME as in ovo enhancer of muscle development in broilers.

Abstract

The effects of CEME and it complex with GO injected in ovo on the growth and development of chicken embryo hindlimb muscle were investigated. First, the preliminary in vitro study on primary muscle precursor cell culture obtained from a nine-day-old chicken embryo was performed to assess toxicity (MTT assay) of CEME, GO (100 ppm) and it complex with different concentrations (1, 2, 5, and 10 wt.%). The effect on cell proliferation was investigated by BrdU assay. CEME at concentrations 1–5% increased cell proliferation, but not the complex with GO. In vitro cytotoxicity was highest in 10% and GO groups. Next, the main experiment with chicken embryos was performed with CEME, GO and it complex injected in ovo on day one of embryogenesis. On day 20 of embryogenesis survival, morphological development, histological structure of the muscle, and biochemical parameters of blood serum of the embryos were measured. No negative effect on mortality, body weight, or biochemistry of blood after use of CEME or GO-CEME complexes was observed. Interestingly, the slight toxicity of GO, observed in in vitro studies, was not observed in vivo. The use of CEME at the levels of 2% and 5% improved the structure of the lower limb muscle by increasing the number of cells, and the administration of 2% CEME increased the number of nuclei visible in the stained cross-section of the muscle. The complex GO-CEME did not further improve the muscle structure. The results indicate that CEME can be applied as an in ovo enhancer of muscle development in broilers.

Supplemental L-Arginine Improves the Embryonic Intestine Development and Microbial Succession in a Chick Embryo Model

Early colonization of intestinal microbiota plays an important role in intestinal development. However, the microbial succession at an embryonic stage and its assembly patterns induced by prenatal nutrition are unknown. In the present study, we used a chick embryo model to investigate the effects of in ovo feeding (IOF) of L-arginine (Arg) on the intestinal development and microbial succession of embryos. A total of 216 fertile eggs were randomly distributed into 2 groups including the non-injected control group and IOF of Arg group with 7 mg/egg. The results showed that IOF Arg increased the intestinal index, absolute weight of jejunum, and improved jejunal morphology in terms of villus width and surface area (p < 0.05). The relative mRNA expressions of mTOR and 4E-BP1 were up-regulated and accompanied by higher contents of Mucin-2 in the Arg group (p < 0.05). There was a significant elevation in contents of serum glucose and high-density lipoprotein cholesterol, whereas there was a decreased low-density lipoprotein cholesterol in the Arg group (p < 0.05). Additionally, Proteobacteria and Firmicutes were major intestinal bacteria species at the embryonic stage. However, Arg supplementation targeted to shape assembly patterns of microbial succession and then changed microbial composition (p = 0.05). Meanwhile, several short-chain fatty acids (SCFAs)-producing bacteria, such as Roseburia, Blautia, and Ruminococcus were identified as biomarkers in the Arg group (LDA > 3, p < 0.05). Accordingly, significant elevated concentrations of SCFAs, including lactic acid and formic acid, were observed in the Arg group (p < 0.05), accompanied by the higher concentration of butyric acid (0.05 < p < 0.10). In conclusion, prenatal Arg supplementation improved embryonic intestine development by regulating glucose and lipid homeostasis to supply more energy for chick embryos. The possible mechanism could be the roles of Arg in shaping the microbial assembly pattern and succession of the embryonic intestine, particularly the enrichment of potential probiotics. These findings may contribute to exploring nutritional strategies to establish health-promoting microbiota by manipulating prenatal host-microbe interactions for the healthy development of neonates.

In ovo feeding of vitamin C regulates splenic development through purine nucleotide metabolism and induction of apoptosis in broiler chickens

Nutrition in early life has a long-term influence on later health. In order to the explore effects of in ovo feeding (IOF) of vitamin C on splenic development, splenic metabolism and apoptosis were detected in embryo, adult chickens and in vitro. A total of 360 fertile eggs were selected and randomly assigned to control (CON) and vitamin C (VC) groups which were injected with saline and vitamin C on embryonic day 11, respectively. Functional enrichment of differentially expressed genes by transcriptome on embryonic day 19 suggested that purine nucleotide metabolism might be a potential pathway for the IOF of vitamin C to regulate spleen development. Additionally, the IOF of vitamin C significantly increased splenic vitamin C content on post-hatch day 21. Meanwhile, the splenic expression of adenosine deaminase, serine/threonine kinase 1 and proliferating cell nuclear antigen was down-regulated, whereas the expression of cysteinyl aspartate specific proteinase 9 was up-regulated in the VC group. On post-hatch day 42, the IOF of vitamin C significantly down-regulated the splenic expression of B-cell lymphoma 2 and increased the mRNA level of cysteinyl aspartate specific proteinase 9. The IOF of vitamin C could regulate the expression of genes related to adenylate metabolism and increased the apoptosis rate in vitro, which is consistent with the result in vivo. In conclusion, the IOF of vitamin C regulated splenic development and maturation by affecting purine nucleotide metabolism pathway and promoting apoptosis.

Chicken embryo development: metabolic and morphological basis for in ovo feeding technology

Broiler embryonic development depends on the nutrients that are available in the egg, which includes mostly water, lipids, and proteins. Carbohydrates represent less than 1%, and free glucose only 0.3%, of the total nutrients. Considering that energy requirements increase during incubation and metabolism is shifted toward the use of glycogen stores and gluconeogenesis from amino acids, extensive muscle protein degradation in the end of incubation can compromise chick development in the initial days after hatch. Significant prehatch changes occur in embryonic metabolism to parallel the rapid embryonic development. Oral consumption of the amniotic fluid begins around 17 d of incubation and promotes rapid development of the intestinal mucosa, which is characterized by morphological changes and increased expression and activity of enzymes and transporters. Furthermore, ingested substrates are stored as nutritional reserves to be used during hatching and in the first week after hatch. At hatch, this limited-nutrient store is directed to the functional development of the gastrointestinal tract to enable assimilation of exogenous nutrients. In ovo feeding is an alternative to deliver essential nutrients to chick embryos at this critical and challenging phase. The improved nutritional status and physiological changes triggered by in ovo feeding can resonate throughout the entire rearing period with significant health and economic gains. The present review addresses the main changes in metabolism and intestinal development throughout incubation, and also addresses scientific advances, limitations and future perspectives associated with the use of in ovo feeding that has been regarded as an important technology by the poultry industry.

Effects of In Ovo Supplementation with Nanonutrition (L-Arginine Conjugated with Ag NPs) on Muscle Growth, Immune Response and Heat Shock Proteins at Different Chicken Embryonic Development Stages

Simple Summary

In this study, we have analyzed the effects of in ovo supplementation of inorganic and organic synthesized silver nanoparticles (Ag NPs) conjugated with L-arginine (L-Arg) that were injected in chicken embryo at three different embryonic development stages (8th d, 14th d and 18th d). We investigated the effects of both conjugated Ag NPs on the survival, hatchability and body weight on hatching day (1 d old chicks). The expression of muscle growth related proteins, mainly myoblast determination protein (myoD), myogenin and heat-shock proteins (HSPs) were analyzed in pectoral muscles. The serum level of immunoglobulin M (IgM), serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) were also examined. Our study shows that 14th day of injection of both types of conjugated Ag NPs promoted survival rate and hatching rate at 8 d and 18 d from injection. The immunoglobulin (IgM) levels in serum and the expression of muscle growth related proteins (myoD and myogenin) were dramatically improved; in addition, HSP-60 and HSP-70 expression were declined at 14th d of injection. The serum levels of SGOT and SGPT were decreased at 14d injection when compared to 8 d and 18 d injection. Hence, the 14th day would be suitable day for injection of L-Arg with Ag NPs to promote the survival rate, hatching rate, immune system and muscle growth. Our results illustrated that plant mediated synthesis of Ag NPs at 1000 μg and chemically synthesized Ag NPs at 100 μg concentration would be a better choice to make nanonutrition with L-Arg (100 μg) to carry the nutrients without any toxicity at 14 d injection.

Abstract

The aim of the study was to analyze the in ovo injection of inorganic and organic synthesized silver nanoparticles (Ag NPs) using Brassica oleracea L. var. capitate F. rubra (BOL) conjugation with L-Arginine (L-Arg) on the immune, muscle growth, survivability and hatchability of broiler chickens. The conjugation of L-Arg (100 μg) with 1000 µg of Ag NPs synthesized by (BOL)-extract and L-Arg (100 μg) conjugated with 100 µg of Ag NPs inorganic synthesized were injected into fertile eggs at 8 d, 14 d and 18 d of incubation. Survival and hatching rate were significantly improved in the dose of L-Arg (100 μg) with 1000 µg (BOL-Ag NPs) and L-Arg (100 μg) with 100 µg (C-Ag NPs) on 14 d injection whereas it was decreased on 8 d or 18 d injection. Moreover, the protein expression of muscle development markers such as myogenin and myoD were significantly uprelated in 14 d of incubation whereas the heat shock proteins (HSPs), such as HSP-60 and HSP-70, were significantly upregulated in 18 d incubation. In addition, the liver function marker of serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) were significantly decreased and the immunoglobulin (IgM) levels were increased in a 14 d incubation period in serum at the same concentration.

Dynamic alterations in early intestinal development, microbiota and metabolome induced by in ovo feeding of L-arginine in a layer chick model

Background

Prenatal nutrition is crucial for embryonic development and neonatal growth, and has the potential to be a main determinant of life-long health. In the present study, we used a layer chick model to investigate the effects of in ovo feeding (IOF) of L-arginine (Arg) on growth, intestinal development, intestinal microbiota and metabolism. The treatments included the non-injected control, saline-injected control, and saline containing 2, 6, or 10 mg Arg groups.

Results

IOF Arg increased early intestinal index and villus height, and enhanced uptake of residual yolk lipid, contributing to subsequent improvement in the early growth performance of chicks. Prenatal Arg supplementation also increased the early microbial α-diversity, the relative abundance of Lactobacillales and Clostridiales, and decreased the relative abundance of Proteobacteria of cecum in chicks. Furthermore, the shift of cecal microbiota composition and the colonization of potential probiotics were accelerated by IOF of Arg. Simultaneously, metabolomics showed that metabolisms of galactose, taurine-conjugated bile acids and lipids were modulated to direct more energy and nutrients towards rapid growth of intestine at the beginning of post-hatch when embryos received IOF of Arg.

Conclusions

Prenatal Arg supplementation showed beneficial effects on the early intestinal development, cecal microbiota and host metabolism of layer chicks, contributing to subsequent improvement in the early growth performance. These findings provide new insight into the role of IOF of Arg in the establishment of the gut microbiota of newly-hatched layer chicks, and can expand our fundamental knowledge about prenatal nutrition, early bacterial colonization and intestinal development in neonate.

Dietary N-carbamylglutamate and l-arginine supplementation improves intestinal energy status in intrauterine-growth-retarded suckling lambs

This study explores the roles of l-arginine (Arg) and N-carbamylglutamate (NCG) supplementation in the diet in intestine damage, energy state, as well as the associated protein kinase signaling pathways activated by AMP in intrauterine growth retarded (IUGR) suckling lambs. A total of 48 newborn Hu lambs with a normal birth weight (CON) and those with IUGR were randomly divided into four groups, CON, IUGR, IUGR + 1% Arg, and IUGR + 0.1% NCG, with 12 animals in each group. All animals were fed for 21 days, from day 7-28, following birth. Our results indicated that the IUGR suckling Hu lambs in the Arg or NCG groups were associated with reduced (P < 0.05) plasma diamine oxidase (DAO) and d-lactic acid levels compared with IUGR suckling lambs. In addition, IUGR suckling Hu lambs in the Arg or NCG group were also linked with a higher (P < 0.05) villous height : crypt depth ratio (VCR), as well as villous height in the duodenum relative to those obtained for IUGR suckling Hu lambs. Relative to IUGR suckling Hu lambs, IUGR suckling Hu lambs in the Arg or NCG groups were found to have higher (P < 0.05) ATP, ADP and TAN contents, and AEC levels, and smaller (P < 0.05) AMP : ATP ratios in the duodenum, jejunum and ileum. Moreover, IUGR suckling Hu lambs in the Arg or NCG group were also linked with higher citrate synthase, isocitrate dehydrogenase and alpha-oxoglutarate dehydrogenase complex activities in the duodenum, jejunum and ileum compared with those found for IUGR suckling Hu lambs (P < 0.05), except for the activity of isocitrate dehydrogenase in the ileum. IUGR suckling Hu lambs in the Arg or NCG group were linked with a lower ratio of pAMPKα/tAMPKα and protein expression of Sirt1 and PGC1α in the ileum relative to those of the IUGR suckling Hu lambs (P < 0.05). Taken together, these findings show that supplementation of NCG and Arg in the diet can ameliorate intestinal injury, improve energy status, motivate key enzyme activities in the tricarboxylic acid (TCA) cycle, and also inhibit the AMP-activated protein kinase signaling pathways in IUGR suckling Hu lambs.

In ovo feeding of creatine pyruvate alters energy metabolism in muscle of embryos and post-hatch broilers

Objective

This study was conducted to investigate the effects of in ovo feeding (IOF) of creatine pyruvate (CrPyr) on the energy metabolism in thigh muscle of embryos and neonatal broilers.

Methods

A total of 960 eggs were randomly assigned to three treatments: i) non-injected control group, ii) saline group injected with 0.6 mL of physiological saline (0.75%), and iii) CrPyr group injected with 0.6 mL of physiological saline (0.75%) containing 12 mg CrPyr/egg on 17.5 d of incubation. After hatching, 120 male chicks (close to the average body weight of the pooled group) in each group were randomly assigned to eight replications. The feeding experiment lasted 7 days.

Results

The results showed that IOF of CrPyr increased glucose concentrations in the thigh muscle of broilers on 2 d after injection (p<0.05). Compared with the control and saline groups, the concentration of creatine in CrPyr group was increased on 2 d after injection and the day of hatch (p<0.05). Moreover, IOF of CrPyr increased the creatine kinase activity at hatch and increased the activities of hexokinase and pyruvate kinase on 2 d after injection and the day of hatch (p<0.05). Chicks in CrPyr group showed higher mRNA expressions of glucose transporter 3 (GLUT3) and GLUT8 on the day of hatch (p<0.05).

Conclusion

These results demonstrated that IOF of CrPyr was beneficial to enhance muscle energy reserves of embryos and hatchlings.

In ovo applications in poultry: A review,

The various methods employed for the in ovo administration of different materials for promoting the health and productivity of poultry are discussed in this review article. The amnion has proven to be an effective site for injection and the timing of in ovo injection has commonly occurred at transfer. However, the volumes and dosages or concentrations of the materials administered vary depending on bird type, egg size, timing and site of injection, incubation system and regimen, and the type of material. Both manual and automated injections have been shown to be effective. Nevertheless, commercial application mandates automation. Materials described in the literature over the past 20 years or more for in ovo use in avian species include vaccines, drugs, hormones, competitive exclusion cultures and prebiotics, and supplemental nutrients. Vaccines approved for in ovo delivery include those for Marek's disease, infectious bursal disease, fowl pox, Newcastle disease, and coccidiosis. Some of the materials listed above have been shown to be viable candidates for enhancing immunity and for promoting embryonic and posthatch development. Several reports have indicated that probiotics may be effectively used to fight intestinal bacterial infections, and folic aid, as well as egg white protein and various amino acids, including L-arginine, L-lysine, L-histidine, HMB, and threonine alone or in combination, have been shown to benefit embryonic development or posthatch performance. Furthermore, CpG oligodeoxynucleotides, vitamins C and E, and thyme and savory have the potential to enhance immunity, carbohydrates can be used to increase tissue glycogen stores, and creatine can be used to promote muscle growth. Trace minerals and vitamin D3 have shown potential to improve bone strength, and potassium chloride may be an effective alternative electrolyte in vaccine diluent. The in ovo application of these and other materials will continue to expand and provide further benefits to the poultry industry.