Chix in Space

“Chix in Space”

On the 13 March 1989 aboard Discovery STS-29 launched a total of 32 fertilized eggs from broiler hens (Gallus gallus domesticus) were launched into space for a five-day tour of weightlessness in an incubator.

They were divided into two groups: younger embryos, having first undergone two days of terrestrial incubation, followed by the five-day exposure to microgravity and a set of more mature embryos, having first undergone nine days of incubation on Earth, followed by the five days in the onboard incubator. Half in number of each group were allowed a full term (approximately 21 days) of incubation upon return to Earth, while the other half were dissected upon landing for histological, morphological, and in the case of mineralized tissues, elemental analysis.

Of those incubated for the full term, in the young embryo group, not a single egg hatched, while all of the eight more mature eggs, subjected to the nine-day pre-incubation on Earth, hatched and proved to be viable.R.L. Hullinger Dissection revealed that in the younger embryos, development ceased at varied stages during exposure to microgravity conditions aboard Discovery STS-29.

Preliminary analysis of the viable, more mature embryos indicated that microgravity conditions did not significantly affect development. The mineral content and histo-morphoplogy of long bones of the sacrificed mature embryos did not differ from that of the bones sampled from embryos of the synchronous control group incubated on Earth, suggesting that bone modelling and osteoblastic activity in ovo were not affected by microgravity.M.F. Holick et al. Eggshell mineralization studies revealed that in those younger embryos that failed to hatch, the shell was substantially thicker and contained more magnesium, while the eggshell sampled from the more mature embryos that hatched did not differ from the that of the control set.P.Y. Hester et al. Morphology of otoconia from sacrificed embryos subjected to weightlessness, examined by Scanning Electron Microscopy (SEM), did not exhibit any deformity or systematic size difference compared to otoconia of embryos subjected to Earthly incubation. R.V. Kenyon et al. Generally, microgravity had adverse effects only on the younger embryos, while the more mature embryos of chickens seemed not to be vulnerable. This result implicated a possible threshold after which the gravity field factor becomes irrelevant to the microenvironment of embryogenesis.

Furthermore, post-hatch behavior of the chicks and chickens from those embryos that survived the flight evaluated in terms of feeding, growth, perching, sexual maturation, ovulation, and various reproductive parameters did not differ from the assessments of terrestrially incubated control group.P.Y. Hester et al. Vestibular reflex behavior of the chicks hatched from embryos incubated inflight was not significantly distinguishable from that of chicks subjected to terrestrial incubation.R.V. Kenyon et al. Scientists even tried to test for second generation effects. They artificially inseminated the hens who had endured space flight as embryos with sperm of the males who had endured the same and reported no effects.P.Y. Hester et al.

After this pilot experiment, NASA scientists launched chicken embryos again in late 1992 aboard Endeavor STS-47 for collaborative study with Japan, and the research of chicken embryos in space is ongoing worldwide, evidently. For NASA, the “Chix in Space” hardware served as the prototype of the “Avian Development Facility” in projects led by J.D. Dickman and S.B. Doty to study vestibular and musculoskeletal development of Japanese Quail embryos in microgravity, but Americans were certainly not the first in the poultry space race . . .