In Ovo Administration of Vitamin D Sources: A Review

In ovo injection has emerged as a targeted strategy for delivering essential nutrients or vaccines during avian embryogenesis, yet the effects of vitamin D (VitD) metabolites delivered prior to hatch remain incompletely understood. This review summarizes the available evidence describing the embryonic and post-hatch responses of broilers when VitD is administered in ovo and highlights the opportunities and limitations for improving their performance in association with each VitD source, including vitamin D3 (VitD3), 25-hydroxyvitamin D3 (25OHD3), 1α-hydroxyvitamin D3 (1α-OHD3), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and 24,25-dihydroxyvitamin D3. Greater post-hatch improvements in broiler performance and skeletal development have been observed when in ovo 25OHD3 was combined with dietary 25OHD3 or minerals. The in ovo delivery of 1.2 to 2.4 µg of water-soluble 25OHD3 alone or in combination with Marek’s disease vaccine between 17.5 and 18 days of incubation (doi), has been found to be effective in improving hatchability, post-hatch performance, bone mineralization, meat yield, intestinal histomorphology, and immune function. In contrast, in ovo administration of 1α-OHD3 and 1,25(OH)2D3 at low doses has resulted in inconsistent performance and remains unsuitable for practical in ovo application. The physiological responses to in ovo VitD sources are highly dependent on metabolite form, dose, solubility, vehicle, embryonic age at administration and post-hatch environmental conditions. Nevertheless, 25OHD3 is a promising candidate for integration into commercial in ovo platforms. Furthermore, knowledge gaps remain for defining optimal dose ranges, understanding metabolite interactions, and evaluating long-term impacts across different production systems.