Abstract
The aim of this study was to analyze the effects on growth and muscle development during the growing period of the sex-linked dwarf gene in the background of a Taiwan Country chicken strain, L2, selected for egg production. Eight crossbred males, heterozygous for the DW*DW mutation, were each backcrossed to six females of the L2 strain to produce two genotypes of BC females, either normal (DW*N + /-) or dwarf (DW*DW/-). The experiment included 251 normal and 207 dwarf pullets. The effect of the dwarf gene on body weight and shank length was highly significant from 2 weeks of age. The reduction of body weight by the dwarf gene reached 34.8% and 37.4% as compared to normal sibs at 16 and 20 weeks of age, respectively. Parameters of the growth curve were estimated: the age at inflection (TI) was higher in normal pullets (66.9 days) than in dwarf pullets (61.2 days). A significant effect of the dwarf gene on single muscle fiber cross-section area was found from 12 weeks of age onwards, whereas the dwarf gene had no effect on the total number of muscle fibers. Comparing the effect of the dwarf gene on shank length at different ages revealed an earlier effect on skeleton growth, observed from 2 weeks of age, than on muscle development, which was affected from 8 to 12 weeks of age. (Key Words : Growth Curve, Muscle Development, Sex-linked Dwarf Gene, Chicken)
Highlights
It is known that some genes could reduce the chicken’s body size
The other gene, described by Hutt (1959), and known as the dwarfism gene resulted in a reduction of body weight, representing about 30-40% of the normal female weight, depending on age and genetic background, as reviewed by Mérat, 1984
As muscle tissue constitutes over 40% of lean body weight, growth and development of skeletal muscle tissue are a
Summary
It is known that some genes could reduce the chicken’s body size. The thyroid dwarfism (td) gene was a hypothyroidism (Landauer, 1929). The creeper (Cp) gene was a form of chondrodystrophy caused by an abnormal cartilage growth (Landauer and Dunn, 1930). Two sexlinked genes are known to cause dwarfism. A recessive gene for smaller body size in Bantam breeds (dwB) was found by Godfrey (1953). The increase in skeletal muscle mass is mainly due to muscle fiber hypertrophy. This process is accompanied by the proliferating activity of satellite cells (Rehfeldt et al, 2000; Nierobisz and Mozdziak, 2008). As muscle tissue constitutes over 40% of lean body weight, growth and development of skeletal muscle tissue are a
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