Abstract
The month of hatching and the rearing management, especially temperature and photoperiod, are important factors for pullets and hens reared outdoors. The yield performance and egg quality of dual-purpose chicken breeds from the Veneto region (Italy), Pepoi (PP), Ermellinata di Rovigo (ER), Robusta Maculata (RM) and Robusta Lionata (RL), with different adult body weights (ABW, kg, PP = 1.3; ER = 2.3, RM and RL = 3.1), were studied, using a factorial model (4 × 2), considering breed and age (26-33 weeks, first age, summer-autumn, under decreasing natural photoperiod-on average, 12L:12D, and 42-53 weeks, second age, winter, under implemented photoperiod-14L:10D) as the main effects and interaction. The chicks hatched in spring, and they started laying at the end of summer/beginning of autumn. Significant (p < 0.05) results were shown for many traits. ER showed higher hen-day egg production than that of PP, and RM and RL were the lowest; ER, RM and RL showed medium-size eggs and PP showed small-size eggs. RM produced the most spherical eggs and ER the most ovoid, and they showed the highest and the lowest eggshell thickness, respectively. RM showed the highest yolk to albumen ratio, and RL showed the lowest. The age increased the laying rate and the egg weight in all the groups. At 26-33 weeks, ER and PP showed higher hen-day egg production (on average 24%) than RM and RL (on average, less than 10%). The onset of laying (at least 10% laying rate) was shown, at different ages, according to the % ABW the breeds had reached: PP was the first, followed by ER, then RM, and RL was the last. At 42-53 weeks, the hen-day egg production ranged, on average, from 38 to 52%, according to the breeds; orthogonal contrasts on two-weekly data showed, at first age, increasing linear (ER) and quadratic (other groups) trends, and at second age, positive linear (ER, RM) and cubic (PP, RL) trends. Age (32 vs. 53 weeks) affected almost all the eggshell traits in PP and ER, whereas in RL, and especially RM, fewer traits changed. The age increased the yolk to albumen ratio (unchanged in PP). These results may be useful for the effective management of local purebred chickens, with the purpose to ensure the wellbeing of the hens and for supplying eggs of different quality throughout the year.