Short Communication Effect of day-old body weight on subsequent growth, carcass perfor- mances and levels of growth-related hormones in quality meat-type chicken Einfluss der Körpergewichte von Mastküken am Schlupftag auf das Wachstum, die Schlachtleistung und die Spiegel der Wachstumshormone

Quality meat-type chickens refer to color-feathered and slow-growing chickens, are developed from local breeds and taste better than fast-growing broilers. Due to the lovely appearance and wonderful taste, quality chickens are considered as alternatives to fast-growing broilers in some regions of the world, such as in Europe and East Asia, and the output of quality chicken meat is rising each year (CHIN, 2003). Among them, the Three Yellow in China and Label Rouge in France are two famous examples. Reproductive efficiency is of great importance to the production of quality chickens. Genetic selection for high hatching egg number will result in smaller egg weight and thus decrease day-old chick weight (SHANAWANY, 1984; YANNAKOPOULOS and TSERVENI-GOUSI, 1987). However, the effect of day-old weight on juvenile growth rate and carcass performances at market age varied among different studies. Some researchers have found that day-old chick weight affects performance of broiler chicks to market age (AL-MURRANI, 1978; WHITING and PESTI, 1984; MAFENI et al., 1986), while other studies have shown that, for broiler, the advantage of initially higher chick weight diminishes rapidly during early growth period and has little influence on economic traits at market time (MORRIS et al., 1968; PINCHASOV, 1991). Information on whether and how day-old chick weight affects post-hatch growth in quality chicken is lacking. Growth hormone (GH) plays an important role in growth, skeletal muscle development, metabolism, immunity, reproduction, and regulation of other hormones in chicken and other avian species (HALEVY et al., 1996; FOSTER et al., 1997; HODIK et al., 1997). Thyroid hormones, tri-