LAUSR

Simple Summary Poultry mortality in the embryonic stage makes it difficult to achieve one of the main objectives of the poultry sector, i.e., constant increase in productivity. If well executed with safe and efficient substances, the in ovo injection technique can be an intervention alternative to enhance the development of more resistant, healthy, quality birds, with substantial positive effects on poultry production. For the commercial implementation of any intervention, information from the vast literature must be compiled in order to understand its effects on production parameters. Thus, this review aims to assess how injecting different substances in ovo influences hatching results, including the reported effects on embryo and chick health parameters. Bibliographic mappings of co-authorship of citations, co-occurrence of keywords and bibliographic coupling were also performed for articles based on the in ovo injection technique and hatchability. Abstract Recent advances in poultry practice have produced new tools enabling the poultry industry to increase productivity. Aiming at increasing production quality, varying protocols of in ovo injection facilitate the introduction of exogenous substances into the egg to complement the nutrients that support embryonic development up to hatching, which are already available in the internal and external compartments. Due to embryonic sensitivity, adding any substance into the egg can be either advantageous or disadvantageous for embryonic survival and can influence hatch rates. Thus, understanding the relationship between poultry practices and production rates is the first step towards successful commercial application. This review aims to assess the influence on hatch rates of injecting different substances in ovo, including effects on embryo and chick health parameters where these are reported. Bibliographic mappings of co-authorship of citations, co-occurrence of keywords, and bibliographic coupling based on the in ovo injection technique and hatchability parameters were also performed. Using the Scopus database, 242 papers were retrieved, reviewed, and submitted for bibliographic mapping using the VOSviewer® software. This review provides a broad overview of just over 38 years’ research on the subject, revealing that studies have significantly increased and peaked in 2020, being produced primarily by US researchers and published primarily in the journal Poultry Science. It also reveals that despite negative reports relating to some substances in the embryo, in ovo delivery of substances may possibly change the poultry industry for the better in terms of production rates (hatchability) and/or poultry health.