Effects of in ovo acrylamide injection on bone mineral composition and morphometric, geometric and mechanical parameters of femur and tibia bone of newly hatched chickens.

Acrylamide (ACR) is a recognized toxic compound that can contaminate food and animal feed and thus pose a risk of transfer to eggs. Due to the fact that this substance has a negative effect on the neural tube. We decided to test the hypothesis that ACR leads to weakening bone strength in long bones of chicken chicks and, consequently, to motor coordination disorders. Therefore, the aim of this study was to determine the effect of administration of ACR in ovo at various doses (0.25 mg, 0.5 mg, and 1 mg/egg) on the mechanical, morphometric and geometric properties of the tibia and femur, as well as indicators of mineralization/bone formation in the body (Ca, P, Ca:P, ALP) among one-day-old chicks. Chicken embryos on day 6 of incubation were divided into 6 equal experimental groups (n = 96 per group), which were injected with the following substances: (1) 0.9% saline solution (0-ACR), (2) ACR at a dose of 0.25 mg/egg (L-ACR), (3) ACR at a dose of 0.5 mg/egg (M-ACR), (4) ACR at a dose of 1 mg/egg (H-ACR), (5) ACR at a dose of 2 mg/egg and (6) ACR at a dose of 4 mg/egg. Hatchability was 74.0, 67.7, 66.7 and 49.5% in groups 0-ACR, L-ACR, M-ACR and H-ACR, respectively, whereas in the groups treated with doses of 2.0 and 4.0 mg ACR per egg, all embryos died. Statistical analysis revealed a varied and dose-dependent effect of ACR on the geometric, osteometric, and mechanical properties and mineral composition of the long bones of one-day-old chicks. The administration of ACR at a dose of 0.5 mg/egg resulted in an increase in the vertical external diameter (VED) (P = 0.025) and radius of gyration (Rg) (P = 0.034) in the tibia, the vertical internal diameter (VID) (P = 0.014) in the femur, as well as the calcium (Ca) (P = 0.020) and phosphorus (P) (P = 0.041) content in pooled femur and tibia samples relative to the control group. In addition, an increase in ultimate load (Fmax) (P = 0.022) and work to fracture (Wmax) (P = 0.036) was demonstrated, but only in the tibia in the group treated with ACR at a dose of 0.25 mg/egg compared to the group injected with 0.9% saline solution. Furthermore, elevated strains (εy and εmax) of the tibia were observed at all applied doses (0.25, 0.5, and 1 mg/egg) (P = 0.002, P = 0.003, P < 0.001 for εy, respectively, and P = 0.009, P = 0.010, P = 0.016 for εmax, respectively) and higher ultimate strain (εmax) (P = 0.032) of the femur in the M-ACR group. However, the body weight of birds as well as Ca, P, Ca:P, and alkaline phosphatase (ALP) levels in blood remained at similar levels in all experimental groups. In summary, the findings do not indicate generalized weakening of long bones at hatch. Instead, they show endpoint- and bone-specific responses whose biological persistence and mechanism remain to be established. Thus, these studies advance understanding of long bone development and bone mineralization among one-day-old chicks following ACR administration and provide a basis for continuing research beyond the hatching period to determine the likelihood of health effects later in life.