Adding nutrients when the chicken is still in the egg can increase hatching weight, growth performance, and pectoral muscle weight of broiler chickens (1).

With the increasing pressure to remove sub-therapeutic levels of antibiotics from poultry feed due to antimicrobial resistance (AMR), poultry producers have been facing new challenges to improve production. For example, considerable research has been directed toward assessments on a wide range of potential feed additives, from essential oils to synbiotics, to compensate for the reduction growth performance and immune system responses observed in poultry not fed antibiotic growth promoters, after the EU ban in 2006 (2).

A healthy gastrointestinal tract is crucial for optimum performance, better feed efficiency, and the overall health of poultry. This necessitates the need for alternative nutritional strategies to produce healthy poultry. As such, several alternatives to antibiotics have been developed with different levels of success. However, effective modulation of the gut health parameters depends on the methods and timing of the compound being available to host animals. Routinely, the alternatives to antibiotics and other nutrients are provided in feed or water to poultry. However, the gastrointestinal tract of the newly hatched poultry is functionally immature, despite going through significant morphological, cellular, and molecular changes toward the end of incubation. Thus, early growth and development of gastrointestinal tract are of critical importance to enhance nutrients utilization and optimize the growth of poultry (3).

The nutritional demand of embryos and early aged chicks has changed over decades. Early nutrition programming (in-ovo injection) is one of the latest and successful methods to feed embryos, in order to prepare chickens with a healthy gut, favourable microbiota, improved immunity, and overall improved growth performance (4).

Early feeding

The modern broiler increases its body weight by 50-fold from hatch until harvest at 35-42 days, hence, the first few critical days of “adjustment” represent a much greater proportion of the bird’s life span than in the past. Consequently, early feeding methods have a great impact on overall growth and well-being of the bird, particularly as genetic selection for increased growth performance continues in the future (5).

In-ovo injection is a method to administer exogenous substances into the amnion during embryo development with the objective of promoting positive effects on hatchability, post-hatch growth performance, immune response, and carcass quality. In comparison with the traditional method of broiler vaccination, in-ovo injection offers a less stressful, faster, and more uniform delivery of vaccines and nutrient mixtures to developing embryos (6). The in-ovo method was first used in 1982 for the vaccination of turkey hatching eggs against Marek’s disease. Recently, the in-ovo method has been investigated by researchers for administering ascorbic acid, carbohydrates, amino acids, vitamins, minerals, pollen, hormones and royal jelly (7).

In ovo nutrition is aimed at the last stage of embryonic development, something that has been shown to improve the vitality and liveability of chicks at birth. When the egg is injected with nutrients (approximately three days before hatching), the future chick is ingesting amniotic fluid. Therefore, the inoculated nutrients in that fluid will reach the embryonic intestine (8).

Although the technology of in-ovo feeding was patented more than 10 years ago, it has not been widely adopted by the poultry industry (9). In-ovo nutrient administration appears to have a significant effect on hatching weights, but the responses in terms of final weights and feed conversion efficiency are not consistent. This failure to obtain tangible benefits may be due to a lack of suitable nutritional products for administration, but there are also fears of a reduction in hatchability as a result of in-ovo feeding of some nutrients (10).

In commercial poultry rearing, getting a good start for the chick at the hatchery is a vital factor for maximizing profits. Kadam et al. (2013), indicate that chicks pip out of the egg at different times. In particular, chicks hatch over a 36–48 h time frame and are usually removed from the hatcher only when the majority (95%) has hatched. This period, added to the time required for hatchery treatments and transport to the rearing farm, means that chicks may be deprived of feed and water for up to 48–72 h. In addition, the spread in hatch causes variability in the delay in time to feed access within any batch of chicks. The weight loss between hatching and removal from the hatcher is approximately 0.18 g/h while fasting (11). During this period, the yolk, comprising mainly fat and protein, is the major source of energy for maintenance and growth. Feed deprivation after hatch demonstrates the detrimental effects of any delay in feed access on performance of the chicks with respect to growth, immune system activation, digestive enzyme stimulation and organ development. Approximately 2% to 5% of hatchlings do not survive the critical post-hatch “adjustment” period and many survivors exhibit stunted growth, inefficient feed utilization, reduced disease resistance, or poor meat yield. Improved management strategies, such as in-ovo feeding, provide an alternative in dealing with the negative effects caused by a delay in feed access (12 & 5).

Nutrients for in-ovo administration

The major intention of pre-hatch feeding is to equip the embryo with the nutrients necessary to continue intestinal development post-hatch at or close to the same rate as pre-hatch. Supplying the embryo with exogenous nutrients would allow the gastrointestinal tract to develop the structures and functionality to properly digest and absorb nutrients immediately when exogenous nutritional supplementation is provided after hatch (3 & 9). These nutrients, along with the yolk sac reserves, can contribute not only to maintaining the systems and metabolism already established but also to continuing growth, development, and proper nutritional status (13). Numerous studies have been conducted investigating the efficacy of in-ovo injection of various biologics in poultry, including nutrient supplements.

Al-Murrani (1982), was the first to attempt to improve embryo body weight by introducing amino acids into the yolk sac of chicken embryos at 7 days of incubation. Results indicated that the embryo did not use the protein until late-stage embryonic development to gain weight and they carried the additional weight through market age (10).

Also, Hou et al. (2018), demonstrated the probiotic effects of nutrients, utilizing the in-ovo feeding model of various plant origin prebiotics, peptides, isoflavones, carbohydrates, and synbiotics, which resulted in an in vivo indication of these compounds’ prebiotic effects, such as mineral absorption, gut microflora population, intestinal development, short-chain fatty acid content, and immune system response (14). 

In their review, Uni and Ferket (2004) concluded that if early feeding is beneficial for early development of post-hatch poultry, then feeding the embryo during incubation by in-ovo administration would be expected to enhance hatchability and development of the digestive tract and increase body weight and nutritional status of the hatchling (10 & 5). However, Retes et al. (2017) also performed a systematic review, in which the effect of injected carbohydrate-based solutions into embryonated eggs was evaluated, and as a result, it was proven that in-ovo feeding of carbohydrates decreases the hatch rate, improves the hatch weight, but it does not appear to influence the post‐hatch performance of broilers (15).

To date, primarily, the used materials given in early nutrition include probiotics, prebiotics, exogenous enzymes, amino acids, hormones, vaccines, and drugs. Early feeding to chicks with these nutrients and supplements has been found to improve total digestive tract development, increase hatchability (16), growth rate and feed efficiency, reduce post-hatch mortality and morbidity, promote growth of beneficial gut microbiota, improve the immune system and the response to enteric antigens (14), reduce incidence of developmental skeletal disorders (4 & 17), and increase in muscle development and breast meat yield (4).

Conclusions

In summary, the technique of delivering various nutrients, supplements, immunostimulants, vaccines, and drugs via the in-ovo route seems to be gaining wide attention among researchers worldwide for boosting production performance, immunity and safeguarding the health of poultry. The supplementation of feed additives, nutrients, hormones, probiotics, prebiotics, or their combination via in-ovo techniques has shown diverse advantages for poultry products, such as improved growth performance and feed conversion efficiency, optimum development of the gastrointestinal tract, enhancing carcass yield, decreased embryo mortality, and enhanced immunity of poultry, but also a number of negative results, such as decrease of hatch rate and weight of newly-hatched chickens (18) or no effect in the post-hatch performance of broilers.

The results, beneficial or not, depends on the kind of the injected exogenous substances, however it is admissible that supplementing the amnion fluid with appropriate nutrients is a novel way to feed critical dietary components to embryos, which provides opportunities to nutritionists to optimize poultry production, and seems to be a promising strategy. Indeed, the in-ovo feeding technology may “jump-start” development of the chick.

Further research is required to adapt the in-ovo feeding technique for application at commercial scale in farm conditions, to understand the embryonic development and nutrient metabolism process more precisely, and understand how early nutrition affects specific genes responsible for performance, intestinal health, and overall health-related traits in poultry.

References

1. Koeleman E. Effect of in-ovo feeding on broiler growth. 2017. Available at: https://www.allaboutfeed.net/Compound-Feed/Articles/2017/10/Effect-in-ovo-feeding-on-growth-broiler-chickens-199481E/
2. Roto Stephanie M., Kwon Young Min, Ricke Steven C. Applications of In Ovo Technique for the Optimal Development of the Gastrointestinal Tract and the Potential Influence on the Establishment of Its Microbiome in Poultry, Frontiers in Veterinary Science, 2016. Available at: https://www.frontiersin.org/article/10.3389/fvets.2016.00063
3. Jha Rajesh, Singh Amit Kumar, Yadav Sudhir, Berrocoso Julio Francisco Diaz, Mishra Birendra. Early Nutrition Programming (in ovo and Post-hatch Feeding) as a Strategy to Modulate Gut Health of Poultry, Frontiers in Veterinary Science, 2019. Available at: https://www.frontiersin.org/article/10.3389/fvets.2019.00082

By Niovi Kordali, Regulatory Affairs Specialist

Pen & Tec Consulting