Statistical analyses
All data are expressed as mean ± standard deviation (SD). Normality in distribution of variables was univariate tested and log or square transformed when necessary to meet normality, after they were back-transformed for tables and graphics. We used MANOVA and regression methods to examine our hypotheses on blood hematological and biochemistry parameters according to sample timing and birds’ age and sex. In analyses, we standardized hatching dates using the earliest estimated record of hatching each year as day 1 and the difference between the earliest record and each subsequent hatch date. Statistica 8.0 software statistical package was used to perform statistical procedures, and we used an alpha value of 0.05 to assess significance of results.