Heritabilities of growth curve parameters and age-specific expression of genetic variation under two different feeding regimes in Japanese quail (Coturnix coturnix japonica)

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Abstract
Summary: This study investigated genetic variation in growth and final size in relationship to differences in heritabilities under good and poor feeding conditions. Heritabilities of growth and final size were estimated for several traits underad libitumand restricted feeding conditions. A 30% feed restriction from hatching to 44 days of age in Japanese quail chicks decreased body weight and tarsus length at 44 days of age and the length of the third primary covert feather at 24 days of age relative to controls fedad libitum. Wing length at 44 days of age was not significantly different forad libitumfed and restricted quail. Genetic variances for body weight and tarsus length were very large throughout growth which resulted in heritability estimates close to one for these traits. The genetic correlations among feeding treatments were low, indicating that different genes were affecting growth under the two treatments. Growth was described by the components: asymptote, growth period, and shape of the growth curve following the modified Richards growth curve model (Brisbinet al.1986). Tarsus length, which had high heritability of the parameter ‘growth period’ of the model, tended to display a higher heritability under the restriction than underad libitumfeeding. Body weight and feather length, which had either no heritable or low heritable ‘growth periods’ estimates, tended to be more heritable underad libitumfeeding. The shape parameter of the growth curve was not heritable for any trait, except tarsus length under restricted feeding.