Prebiotics and synbiotics - in ovo delivery for improved lifespan condition in chicken

Abstract

Commercially produced chickens have become key food-producing animals in the global food system. The scale of production in industrial settings has changed management systems to a point now very far from traditional methods. During the perinatal period, newly hatched chicks undergo processing, vaccination and transportation, which introduces a gap in access to feed and water. This gap, referred to as the hatching window, dampens the potential for microflora inoculation and as such, prevents proper microbiome, gastrointestinal system and innate immunity development. As a consequence, the industrial production of chickens with a poor microbial profile leads to enteric microbial infestation and infectious disease outbreaks, which became even more prevalent after the withdrawal of antibiotic growth promoters on many world markets (e.g., the EU).This review presents the rationale, methodology and life-long effects of in ovo stimulation of chicken microflora. In ovo stimulation provides efficient embryonic microbiome colonization with commensal microflora during the perinatal period. A carefully selected bioactive formulation (prebiotics, probiotics alone or combined into synbiotics) is delivered into the air cell of the egg on day 12 of egg incubation. The prebiotic penetrates the outer and inner egg membranes and stimulates development on the innate microflora in the embryonic guts. Probiotics are available after the mechanical breakage of the shell membranes by the chick's beak at the beginning of hatching (day 19). The intestinal microflora after in ovo stimulation is potent enough for competitive exclusion and programs the lifespan condition. We present the effects of different combinations of prebiotic and probiotic delivered in ovo on day 12 of egg incubation on microflora, growth traits, feed efficiency, intestinal morphology, meat microstructure and quality, immune system development, physiological characteristics and the transcriptome of the broiler chickens.We discuss the differences between in ovo stimulation (day 12 of egg incubation) and in ovo feeding (days 17-18 of egg incubation) and speculate about possible future developments in this field. In summary, decades of research on in ovo stimulation and the lifelong effects support this method as efficient programming of lifespan conditions in commercially raised chickens.

Keywords: Broilers; Day 12 of egg incubation; Embryonic development; Gene expression; Hatching window; Intestinal morphology; Microflora; Performance; Synbiotics.

Fig. 1

Model of in ovo delivery and penetration of the bioactive solution through the chorioallantoic membrane into the circulatory system of the chicken embryo. For in ovo injection, 0.2 ml of a blue dye (E132, indigotine, artificial dye used for food coloring) at a concentration of 0.01 g/ml was injected in ovo on day 12 of egg incubation. Blue dye was deposited into the air cell. The eggs were sealed and incubation was continued until 19 of egg incubation. Penetration of the dye through chorioallantoic membrane was observed daily by dissecting permeable outer shell membrane from semi-permeable inner cell membrane. After 3 days (i.e., from 15 of egg incubation onwards) the dye was transferred to the blood vessel on the inner shell membrane. The stained vessel is marked with an arrow Steady influx of the dye through the chorioallantoic membrane was observed until 19 of egg incubation, when the experiment was terminated

Fig. 2

Concept of early microbial programming in ovo. Prebiotic or probiotic given on day 12 of egg incubation influences embryonic factors (microbiome, GALT development and function, gene expression, nutrient absorption) which are critical for future phenotype of the broiler chicken. Two critical perinatal moments are shown (hatch window and fasting post-hatching), when the newly hatched chicken is the most receptive to environmental stressors