Gradual increase of CO2 during first stages of incubation with late change of O2 partial pressure, modifies the hatch trajectory of broiler chicks.

Abstract

This work was conducted to determine the effect of non-ventilation (NV) during the first 10 days of incubation on car­bon dioxide (CO2) concentrations and its effects on embryonic development (ED). Two studies were done on fertile hatch­ing eggs from breeder hens (Ross 308) of 30 and 45 weeks of age. In the first study, two different incubation conditions were created, one incubator was non-ventilated (NV) during the first ten days of incubation, allowing the CO2 to rise and a second incubator was kept under standard conditions, with adequate ventilation (V). After the first 10 days, both incuba­tions were kept under standard conditions. NV group at 10 days of incubation showed 11 600 ppm of [CO2], with 48% of hatchability from fertile eggs, higher (P < 0.05) than 2 100 ppm of [CO2], and 41% of hatchability from fertile eggs of V group. Day-old chicks from NV were longer and heavier tan chicks from V group. For the second study, two different in­cubation conditions were created, one incubator was moderately non-ventilated (MNV), and the second one was strictly non-ventilated (SNV). At transfer time, a hole of 1.3 mm in diameter was done over eggshell air cell, every incubator had two groups: with hole (H) and without hole (NH). MNV group at ten days of incubation showed 15 000 ppm of [CO2], and SNV group showed 17 000 ppm of [CO2], with 82% and 77% of hatchability, respectively. The induced hypercap­nia during the early development stage improved hatchability parameters, weight and length of chicks. In 45 week-old breeder hens, an optimal hatching profile at high height above sea level with a limit of 15 000 ppm of [CO2] was de­termined. The eggshell hole helps to reduce embryonic mortality at 19.8 days; however, under this type of NV incuba­tion, it is very important to take into account egg-mass loss, height above sea level and eggshell conductance constant, since all these factors contribute to generate the optimal partial pressure of [O2] and [CO2] before and during hatching.