164 JATURASITHA ET AL.
Table 3. Muscle fiber1 counts and size in the chickens2
Chicken genotype
Black-
Item boned Thai Bresse Rhode SEM P-value
Breast muscle
Fiber count (% of total)
Type I and IIA 5.7 7.2 3.9 5.5 0.18 0.135
Type IIB 94.3 92.8 96.1 94.5 0.31 0.860
Cross-sectional area (diameter, m2)
Type I and IIA 21.5c 17.7d 26.3b 36.5a 0.03 0.001
Type IIB 47.8c 45.7d 52.5a 48.9b 0.00 0.001
Thigh muscle
Fiber count (% of total)
Type I and IIA 34.0ab 39.0a 31.2bc 25.8c 0.35 0.001
Type IIB 66.0b 61.0c 68.8b 74.2a 0.34 0.001
Cross-sectional area (diameter, m2)
Type I and IIA 31.8d 33.9c 41.1a 36.4b 0.01 0.001
Type IIB 54.8b 55.5b 60.3a 59.9a 0.00 0.001
a–dMeans within a row with no common superscripts are significantly different (P < 0.05).
1Type I = slow-twitch oxidative (red); type IIA = fast-twitch oxidative-glycolytic (intermediate); type IIB =
fast-twitch glycolytic (white).
2n = 10.