Establishment of a physiological reference for embryonic development of three SPF duck breeds compared to SPF chickens.

Specific pathogen free (SPF) duck and chicken embryos serve as essential biological models bridging fundamental developmental biology and biomedical applications. Although morphological staging has been established for SPF ducks, systematic and standardized reference frameworks for their physiological and biochemical characteristics are still lacking. This study aimed to establish a comprehensive and quantitative reference framework for the embryonic development of three SPF duck breeds (HSM, HBW, and HJD) at different developmental stages, using SPF chickens (BM8 line) as a benchmark. By systematically analyzing exterior embryonated egg characteristics, interior nutrient reserves and microenvironmental dynamics, and embryonic growth kinetics, we constructed developmental reference data. Our results show that exterior embryonated egg characteristics remain largely stable during incubation and may be influenced by genetic background, whereas interior biochemical parameters and nutrient utilization exhibit pronounced stage and species-specific dynamics. The embryos of three SPF duck breeds display more complete yolk utilization, faster late-stage growth, compared with the SPF BM8 chickens. Furthermore, we established stage-specific reference ranges and integrated multi-parameter indicators, including physiological, biochemical, and embryonic growth and developmental parameters. These findings reveal divergent embryonic developmental strategies between ducks and chickens. Furthermore, they provide physiological and biochemical reference data for various SPF duck breeds, which are highly valuable for agricultural research.