Chicken embryos injected in ovo with acrylamide at 2 mg or 4 mg per egg all died before hatch, according to a December 2026 study in Poultry Science that tracked femur and tibia development in chicks from lower-dose groups.

The trial, led by J. Wojciechowska-Puchałka and collaborators at Polish institutions, tested whether acrylamide (ACR)—a recognized contaminant that forms during high-temperature feed processing and can transfer into eggs—also weakens long bones in newly hatched chicks. Researchers also flagged ACR's known disruption of neural tube development.

Six experimental groups of 96 embryonated eggs each received a single injection on incubation day 6. Treatments were 0.9% saline control or acrylamide at 0.25, 0.5, 1, 2, or 4 mg per egg.

Hatchability fell in a clear dose pattern across the four surviving groups: 74.0% in saline controls, 67.7% at 0.25 mg, 66.7% at 0.5 mg, and 49.5% at 1 mg.

Both 2-mg and 4-mg groups produced zero live chicks.

What did the surviving chicks show?

The team measured morphometric, geometric, and mechanical parameters of the femur and tibia at hatch, plus blood markers of bone formation: Ca, P, Ca:P ratio, and alkaline phosphatase. Body weight and serum markers stayed similar across all surviving groups. Bone changes were endpoint- and bone-specific rather than uniform weakening.

Key reported findings included:

• Tibia VED (vertical external diameter) and radius of gyration rose at 0.5 mg/egg (P = 0.025 and P = 0.034).
• Femur VID (vertical internal diameter) rose at the same 0.5-mg dose (P = 0.014).
• Pooled femur-tibia calcium and phosphorus content increased at 0.5 mg/egg (P = 0.020 and P = 0.041).
• Tibia ultimate load (Fmax) and work to fracture (Wmax) rose at the lowest 0.25-mg dose (P = 0.022 and P = 0.036).
• Tibia yield and ultimate strains rose at every surviving dose: εy P = 0.002, 0.003, < 0.001 across 0.25, 0.5, and 1 mg/egg; εmax P = 0.009, 0.010, 0.016.
• Femur εmax rose in the 0.5-mg group (P = 0.032).

What does this mean at the hatchery bench?

The authors concluded the findings do not indicate generalized long-bone weakening in day-old chicks. They stated the response is "endpoint- and bone-specific" with biological persistence and mechanism that "remain to be established."

Some geometric and mechanical parameters actually rose at sub-lethal doses, particularly 0.25 and 0.5 mg/egg. That pattern complicates any direct read-through to on-farm leg weakness, tibial dyschondroplasia, or valgus deformity risk in commercial broilers.

Why feed-mill and hatchery managers should care

Acrylamide can transfer into eggs laid by exposed hens, a food- and feed-safety route the authors flagged.

The 0.25–1 mg/egg range tested sits well above typical environmental exposure, but the study now offers toxicologists and skeletal-development researchers a defined dose-response curve for hatching success and a battery of long-bone endpoints.

Day-6 in ovo injection emerges as a tool for probing how contaminants shape skeletal development from the embryonic window.

The limitation is straightforward: only day-old chicks were examined. There is no follow-up into grow-out.

Whether these geometric shifts translate into clinical lameness, fracture risk, or processing yield loss is unknown.

Feed-mill quality control and breeder-hen exposure to acrylamide precursors remain the operational levers while longer-term data accumulate. The authors call for continued research beyond hatching to determine later-life effects.