Divergent selection for shape of growth curve in Japanese quail. 2. Embryonic development and growth

Abstract

1. Embryonic growth and development were analysed using meat type lines of Japanese quail, HG and LG, divergently selected for shape of the growth curve. A total of 1020 embryos of generations 9, 10 or 13 were used for analysis. 2. Considerable inter-line differences were observed in the rate of embryonic development. When compared to HG, LG embryos appeared to be developmentally accelerated during the first 42 h of incubation (larger blastoderm diameter, more somites and higher frequency of more advanced Hamburger-Hamilton stages) as well as at the end of the prenatal period (more embryos with the yolk sac inside the body cavity, shorter incubation period). This corresponded with the trend in postnatal development. 3. Embryonic growth of both lines exhibited an exponential trend. However, considerable inter-line differences were noted in the rate of embryonic growth. Initial growth retardation compensated subsequently by a higher growth rate of HG vs LG quail, characterised the lines after hatching. The same growth pattern repeated three times during the prenatal period (between d 0 and 3, 3 and 8, and 8 and 16). 4. The repeated occurrence of transient decreases in growth rate of the developmentally delayed HG line could be associated with a delayed onset of genetically determined physiological functions mediating utilisation of nutrient supply. 5. Hence, different shapes of growth curves in two genotypes with similar growth potential reveal inter-line differences in physiological age persisting during the whole ontogenesis.

Divergent selection for shape of growth curve in Japanese quail. 6. Hatching time, hatchability and embryo mortality

“…Whereas LG quail hatched about 4 h earlier than HG quail in generation 9 (Hyánková et al, 2004), in generation 39, the LG quail incubation period was about 15 h shorter than that of HG quail under similar storage and incubation conditions. These results thus confirmed the findings of other authors (Siegel et al, 1968;Dunnington et al, 1992), that the direct selection for growth traits modifies the length of incubation period.…”

“…Differences in hatching time within commercial broiler populations can be explained in the same way. Comparing prenatal physiological parameters in relation to postnatal growth pattern, the recent study of Tona et al (2010) demonstrates that the differences between the Ross and Cobb strains follow the same trend as those between HG and LG quail (Hyánková et al, 2004). Ross exhibited in comparison with Cobb a slower development in the first part of the incubation period, a higher growth rate during the medium phase of incubation, a lower physiological age at the end of the prenatal period, and simultaneously, later hatching and slower growth rate immediately after hatch (Tona et al, 2010).…”

“…LG embryos are developmentally accelerated in comparison with HG embryos during the first 12 h of incubation (Hyánková et al, 2004). Because the storage temperature of about 14 C stops all embryonic development, as detected by microscopic techniques (Fasenko et al, 1992), it is possible that the developmental acceleration of LG vs. HG embryos exists also at the time of oviposition.…”

“…In early generations (9 to 13), the line differences in development were apparent during the first 42 h of incubation (Hyánková et al, 2004). The greater blastoderm diameter at 12 and 24 h of incubation, higher frequency of more advanced developmental stages at 24 and 42 h of incubation and increased number of somites at 42 h after egg setting demonstrated the developmental acceleration of LG in comparison with HG embryos.…”

“…In addition, it was demonstrated that these line differences resulted from line divergence in physiological age. The LG line was developmentally accelerated in comparison with HG counterparts during the whole growth phase of ontogenesis (Hyánková et al, 2004(Hyánková et al, , 2008Hyánková and Novotná, 2007).…”