Both the rooster and incubation temperature affect embryonic metabolism and day-old chicken quality in laying hens

During incubation, the main factors driving embryonic metabolism and developmentare nutrient availability, oxygen availability and embryo temperature. Both nutrient andoxygen availability are expected to be particularly affected by the hen and thus the henis thought to majorly determining embryonic metabolism and day-old chicken quality.However, in wild birds it has been suggested that the rooster is of influence on offspringquality, directly or via affecting egg size and egg composition. In poultry, the role of therooster in embryonic development and metabolism is hardly investigated. In case therooster affects egg composition, this can mean that the incubation temperature needs to be adjusted to obtain optimal embryo temperature. The role of incubation temperatureon embryonic metabolism and development in the broiler chicken is extensivelyinvestigated, but much less information is available regarding laying hen chickens.The aim of the experiment was to investigate the role of the rooster and the incubationtemperature on laying hen embryonic development and chicken quality. Eggs of twogenetic crossbreds (AB and BB; 51 to 59 weeks of age) were used. Hens originated fromthe same breeder flock, were housed at the same farm, obtained the same managementand diet but were mated with a different rooster. In six consecutive batches, eggs ofboth crossbreds (59.0 to 61.0 gram) were incubated at an eggshell temperature (EST) of37.8oC during the first 14.5 days and at an EST of 36.7, 37.8 or 38.9oC from day 14.5 ofincubation onward. In all batches, eggs of both crossbreds were used, but EST differedamong batches. Egg composition was determined in fresh eggs, heat production wasdetermined between day 14.5 and 18.5 of incubation and day-old chicken quality wasdetermined at 6 hours after hatching or at pulling. Yolk weight tended to be higher(Δ=0.28 gram; P=0.08) in AB than in BB crossbreds, whereas other egg components didnot differ. Heat production between day 14.5 and 18.5 of incubation was higher in theAB than in the BB crossbred (Δ=2.61%; P<0.001). At pulling, AB chickens were lighter,had less red hocks, more red beaks and worse navel scores than BB chickens. An ESTof 36.7oC resulted in later hatching time, higher heart weight and higher intestineweight than an EST of 38.9oC. It can be concluded that both the rooster and incubationtemperature appears to affect embryonic metabolism and day-old chicken quality.