Micronutrients in Eggs for the Chicken Embryo

Avian embryos develop and grow from energy and nutrients stored in the egg by the hen. In this sense, breeder male contribution is not important. Follicular deposition of nutrients occurs over a wide range of time, but becomes relevant during the week prior to ovulation. Amounts, but also forms, of nutrients deposited in the egg determine success of embryo development and hatching of a healthy chick. To support the embryo during incubation, oxygen is the only nutrient not derived from the egg; however, adequate oxygen concentrations in the surrounding air and its free passage through well-established shell membrane porosities are essential. Developmental limitations and embryo mortality are aggravated when any inadequacy in these conditions prevail. Macroscopically, the fertile egg has three components: shell, yolk, and albumen. Specific nutrients are mobilized by the embryo metabolism from each of these parts. These typically have expected compositions, which are notably affected by the hen’s nutrition. After oviposition, the egg may be submitted to changes due to in ovo injection using the vaccination equipment routinely used in hatcheries. However, these injections are limited to small amounts, and preferably done with more available forms of micronutrients. Research on this matter is recent and usually directed to metabolic interventions, such as the role of substances which stimulate or mediate enzyme transcription.