Intra-allantoic injection of calcium promotes hatching of chick embryos grown in shell-less culture.

The hatch rate of chick embryos cultured outside of the eggshell with 350 mg calcium l-lactate hydrate (CaL) and 3.5 mL water is fourfold greater in cultures in which the chorioallantoic membrane (CAM) surrounds the egg contents by incubation day 17.5 (E17.5) an event which occurs in ovo by E13. It was first investigated whether decreasing the volume of water added with 350 mg CaL would promote CAM expansion due to the smaller volume to enclose. When 350 mg CaL was present, the CAM did not surround the egg contents by E13. By E17.5, the CAM surrounded the egg contents in 53%-74% of cultures; however, CAM expansion was not significantly different when 0, 1, 2, or 3.5 mL water was present. The hatch rate with 2 or 3.5 mL water was greater than 50% but was not improved with less water. Second, it was investigated whether CaL or water inhibits CAM expansion. In the absence of CaL, the CAM surrounded the egg contents in up to two-thirds of cultures by E13, whether 2 mL water was present or not. Thus CaL, but not water, inhibits expansion of the CAM by E13, even though CaL promotes hatching. Finally, it was investigated whether injection of aqueous CaL into the allantoic fluid, in conjunction with not adding CaL to culture hammocks, would promote CAM expansion. Allantoic injection of CaL starting at E13 did not promote CAM expansion at E17.5 but resulted in hatch rates of approximately 30%. Allantoic injection is a novel route for supplementation of calcium in cultured chick embryos.

Shell-less culture system for chick embryos from the blastoderm stage to hatching.

Since 2014, methods have been described to hatch chick embryos from shell-less culture after egg contents are first incubated within shells for 55-70 h. The present report describes for the first time a shell-less culture system for chick embryos from the blastoderm stage to hatching. For the first 69-70 h, egg contents suspended in polymethylpentene kitchen wrap (F.O.R. Wrap, Riken Fabro, Tokyo, Japan) supported in 6.35 or 6.67 cm inside diameter tripods and covered with a disc of immobilized Milli-Wrap, were rotated back and forth through 90° at 16 or 22 cycles per minute (CPM). Subsequently, the Milli-Wrap disc was removed and culture tripods were transferred to environmental chambers, which were rocked ±20° through incubation day 8.5 (E8.5). From E9, environmental chambers were maintained in the horizontal position through to hatching with controlled O2 and CO2 . To provide supplemental calcium, an aqueous solution containing 100 mg/mL of calcium l-lactate hydrate was injected through the plastic wrap into the albumen at E9 (2.5 mL) and at E13 (1.0 mL) or E15 (1.0 mL). After incubation for 69-70 h at 16 or 22 CPM, 80%-83% of previously unincubated egg contents yielded apparently normal embryos. Hatch rate of normal embryos resulting from turntable incubation at 16 or 22 CPM was approximately 43%. Of note, egg contents remained in the same culture tripod from blastoderm stage to hatching. This technique may find use as an educational tool and in basic investigations of early embryogenesis, teratogenesis, and gene transfer experiments.

Supplemental calcium increases hatch rate but not hatchling mass of chick embryos in shell-less culture.

A method is described for culturing 64-70 h-old chicken embryos and egg contents outside of the eggshell through to hatching. Cultured egg contents were suspended in polymethylpentene kitchen wrap (F.O.R. wrap; Riken Fabro) supported in polyvinyl chloride tripods. Tripods were incubated in Plexiglas environmental chambers which were rocked automatically through an angle of ±20°. The concentration of CO2 was maintained at 2% throughout incubation, while that of O2 was increased from ambient to 50%, and relative humidity was decreased from 90%-92% to 83%-84% at incubation Day 9. Cultured embryos not supplemented with calcium did not hatch. The Hatch rate increased when supplemental calcium L-lactate hydrate was increased between 250 and 350 mg. A maximal hatch rate of 54.8% was achieved when cultures were supplemented with 350 mg of calcium L-lactate hydrate and 3.5 ml of sterile water. Adding 400 or 450 mg of calcium L-lactate hydrate did not increase the hatch rate further. The mass of cultured hatchlings (including the retracted yolk) and yolk-free carcass wet and dry mass and length of the right third toe were significantly less than the corresponding parameters observed in hatchlings in ovo. No statistically significant differences in hatchling mass, yolk-free carcass wet or dry mass, or length of the right third toe were noted among cultured hatchlings supplemented with 250-450 mg of calcium L-lactate hydrate. Failure to completely absorb albumen was the most common abnormality observed in cultures which failed to hatch. The present technique allows a unique approach to study the physiology of the developing chicken embryo.