Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 21, 1994
Publication Date: N/A
Interpretive Summary: Broiler (chicken) meat quality is affected by many factors and muscle fiber morphology is one of the factors. Muscle fiber growth differs among muscles which are characterized by speed of contraction or energy metabolism. The sex of the chickens virtually had no influence on either the proportion or area of muscle fibers. Muscle fiber area increase in size as chickens became older; however, the rate of enlargement decreased with increasing chronological age. Fast twitch anaerobic fibers play an important role in increasing muscle deposition, as reflected by the growth of this fiber type in muscles with a high growth rate. Knowing the morphological and compositional characteristics of individual muscles in the carcass will assist in the success of developing value-added meat products.
This research characterizes the change in muscle fiber types from selected leg muscles of broiler chickens in relation to chronological age and sex. Six male and six female broilers were killed at each chronological age of 2, 4, 6, and 8 weeks. Five muscles were sampled from different locations along the leg of each bird and stained for the acid preincubation-SDH- "reverse"-ATPase reaction. Muscle fibers were classified as R, I, and W. The proportion of each muscle fiber type was calculated and the area of muscle fibers was measured. Muscle fiber area increased in size (P < .05) as chickens became older; however, the rate of area enlargement decreased with chronological age. Muscle fiber area enlargement affected the muscle fiber proportion which was due to the counting template used in our study. The sex of the chickens virtually had no influence (P > .05) on either the proportion of muscle fiber types or area of muscle fibers. However, a sex x age interaction was observed for the proportion of R and W muscle fiber types in the gastrocnemius muscle. "Giant fibers" were found in the muscles with a high proportion of W fibers. Giant fibers in our study resembled R and(or) I fibers. These data characterize the relationship of muscle fiber types in relation to muscle function as the birds mature in chronological age.