Broiler embryo bone development is influenced by incubator temperature,oxygen concentration and eggshell conductance at the plateau stage in oxygen consumption1

1. Four experiments were conducted to evaluate the effects of temperature (TEM) and oxygen (O₂) concentrations during the last 4 d of incubation on bone development. Fertile eggs from two strains were obtained that either exhibited Low or High eggshell conductance (G).

2. Four experimental cabinets provided either four TEM (36, 37, 38 or 39^°C) or four O₂ concentrations (17, 19, 21 or 23% O₂). Data were analysed as a 2 × 2 factorial design. In the fourth experiment, two temperatures (36 and 39^°C), two O₂ concentrations (17 and 23%) and the same Low and High G strains were evaluated in a 2 × 2 × 2 factorial design.

3. Body weights (BW) and residual yolks were obtained, both legs were dissected. Femur, tibia and shank weights, length and thickness were recorded. Relative asymmetry (RA) of each leg section was calculated.

4. The results indicated that elevated TEM during incubation increased RA between the two legs, mainly in the Low G strain. Chickens at the lowest O₂ concentrations had lighter and shorter tibias, lighter shanks, and increased RA of femur length compared to chickens in the 23% O₂. In the fourth experiment no interactions were observed between O₂ and TEM. High TEM depressed BW of Low G broilers, but no significant effect of treatments was observed on BW of High G broilers. Nevertheless, the high TEM or low O₂ independently caused reduced femur and tibia weights and length, shank length and thickness, and both low O₂ and high TEM together increased RA in shank weight.

5. These results suggest that late incubation conditions affect long bone development in broilers.