In ovo inoculation of probiotics for broiler chickens: systematic review and meta-analysis

Abstract

The objective of this study was to evaluate the effect of probiotic inoculation in fertilized eggs on hatching and posthatching characteristics of broilers. The search for scientific articles was conducted in December 2020 in eight databases (Embase, Google Scholar, SciELO, Science Direct, Scopus, Periodicos Capes, PubMed, and Web of Science) using the following combination of keywords: ((probiotic OR synbiotic) AND "in ovo"). Only articles that evaluated the effect of in ovo inoculation of probiotics, combined or not with other compounds, on hatching parameters (number of hatched eggs and hatching weight) and/or posthatching parameters (performance and carcass yield) in broilers were included. The meta-analysis was performed using the random-effects model to calculate the confidence interval (CI) of the differences between the group inoculated with probiotics and the control (vehicle inoculation). The degree of heterogeneity was assessed by meta-regression, and publication bias was assessed by funnel plots. Wide heterogeneity was observed (P < 0.01) in all analyzes. The overall analysis showed that probiotic inoculation did not influence (P > 0.05) number of hatched eggs, hatching weight, or feed intake after hatching but increased (P < 0.01) weight gain and reduced (P < 0.05) feed conversion ratio. Subgroup analysis showed that, for performance, the Bifidobacterium as probiotic brought the best results, while the yolk was best inoculation site. We conclude that probiotics can improve posthatching performance without influencing hatching parameters, depending on the type of microorganism, inoculation site, and broiler strain used.