ARS | Publication request: Breast muscle tissue characteristics in growing broilers

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 17, 2012
Publication Date: July 10, 2012
Citation: Bowker, B.C., Solomon, M.B., Vimini, B., Lee, B. 2012. Breast muscle tissue characteristics in growing broilers. Poultry Science Association Meeting Abstract. p. 472.

Technical Abstract: Muscle cell development in broilers influences growth rate, breast meat yield, and meat quality. The objective of this study was to characterize muscle tissue changes in breast muscles from two commercial lines of broilers from 21 to 56 days of age. The experiment was designed as a 2×2×6 factorial with two lines of birds (line A: sire line selected for breast yield; line B: female line selected for chick production crossed with line A), two sexes, and six ages of bird (21, 28, 35, 42, 49, and 56 days). At each age, 10 birds/sex/line were harvested and breast samples were collected for histochemical analysis. Muscle samples were sectioned and stained using a succinate dehydrogenase, myosin ATPase, hematoxylin combination staining procedure. Measurements of muscle fiber type, fiber cross-sectional area, and tissue abnormalities were recorded. In both lines and sexes, the percent of slow, oxidative fibers decreased (p<0.0001) from 9.5% of fibers at 21-28 days to <4% of fibers at 35-56 days. Cross-sectional area of fast glycolytic (FG) fibers increased (p<0.0001) with age in both lines and sexes. At 35-56 days, line A had larger (p<0.05) FG fibers than line B. Indicators of muscle fiber degeneration increased with age in both lines and sexes. Occurrence of necrotic muscle fibers was greater (p<0.001) in 49-56 day samples than in 21-42 day samples. Monocyte invasion increased (p<0.0001) with age in both lines and sexes. Occurrence of giant fibers increased (p<0.0001) with age in both sexes and lines, however, the incidence of hypercontracted fibers was greater (p<0.01) in line A. Centralized nuclei were observed in nearly 100% of fibers by 35 days in both lines. In 42-56 day samples, FG fiber size was correlated to the occurrence of necrotic fibers (r = 0.48), monocyte invasion (r = 0.39), and giant fibers (r = 0.59). Overall, data suggest that shifts in fiber type within the breast occur by 35 days of age, the growth of FG fibers continues through 56 days of age, and indicators of muscle tissue degeneration increase with age and muscle fiber size.