Age-related changes in muscle fiber type frequencies and cross-sectional areas in straightbred and crossbred rabbits

Abstract

This study was designed to investigate the effects of the interaction among genetic group, sex and age on the frequencies and cross-sectional areas of myofiber types in rabbits. A total of 48 straightbred and crossbred Botucatu rabbits, males and females, were involved in a split plot design with a 2 3 2 (genetic groups 3 genders) factorial arrangement. Young rabbits were weaned at 35 days of age and sequentially slaughtered, four per genetic group 3 sex combination, at 42, 63 and 84 days of age. The flexor carpi radialis muscle was dissected, histological sections (10 mm) were obtained and the frequencies and cross-sectional areas of myofiber types: I, IIA and IIB/X were determined. An effect of the genetic group 3 sex 3 slaughter age interaction was found on the frequency distribution of myofiber types. A transition from type IIA to type IIB/X fibers was observed (P , 0.01) with advancing age, except in crossbred females, but the frequency of IIA fibers was already lower (57.3%) and of IIB/X fibers numerically higher (33.7%) in this group at 42 days. The proportions of IIA fibers in straightbred males, crossbred males and straightbred females decreased from 80.1%, 89.4% and 68.8% at 42 days to 43.9%, 52.3% and 40.1% at 63 days, respectively, whereas the proportions of type IIB/X fibers, in the same groups, increased from 10.3%, 1.6% and 22.3% at 42 days to 42.2%, 37.0% and 49.8% at 63 days, respectively. In all three age points, type IIA fibers showed the largest cross-sectional areas, followed by type I and IIB/X fibers. The cross-sectional areas of IIB/X fibers were larger in crossbreds, but no differences were found between genetic groups concerning fiber types IIA and I. All three types of fibers showed positive linear association with age, but relative to the initial area type IIB/X fibers presented a higher degree of hypertrophy (144% up to 84 days) than type IIA and I fibers (86% and 85%, respectively). The flexor carpi radialis muscle was, on average, heavier in crossbred than in straightbred females, but no difference was observed between crossbred and straightbred males. Differences in the weight of flexor carpi radialis muscle were attributed to the hypertrophy of type IIB/X fibers in the crossbreds.

Effect of housing system and genotype on rabbit meat quality

“…The largest CSA were measured in MB for both types of muscle fibres, while the smallest areas were identified in MW for type I and in CB for type II. Contradictory to our results, Bianospino et al (2008) did not reveal differences between genetic groups, although the values of CSA were numerically higher in the crossbred rabbits than in the straightbred ones. A smaller area of muscle fibres is generally found in smaller rabbit breeds and it can be associated with higher meat tenderness.…”

Relationship between muscle fibre characteristics and meat sensory properties in three nutria (Myocastor coypus) colour types

“…In rabbits, the proportion of type I muscle fibres is related to live weight. Heavier rabbits have a greater proportion of type I muscle fibres (Lambertini et al 1996;Bianospino et al 2008). A relationship between live weight and number of type I fibres was found in pigs (Choi et al 2013).…”

“…However, in our previous study, colour type did not affect muscle fibre proportion in biceps femoris (Tumova et al 2015). On the other hand, in rabbits, the effect of genotype on muscle fibre percentage has been reported for type I fibres (Dalle Zotte and Ouhayoun 1998;Bianospino et al 2008;Tumova et al 2014). In rabbits, the proportion of type I muscle fibres is related to live weight.…”

Carcass and meat quality traits of rabbits under heat stress

“…They could be partially explained by the selection program to which the Botucatu rabbits have been subjected (Moura et al, 2001;Garreau et al, 2004). Long-term selection for growth rate may have influenced myofiber metabolism (Bianospino et al, 2008) and, consequently, meat color, increasing lightness and decreasing redness. Line differences with respect to meat color traits have been reported, especially when selection for fast growth was practiced (Ramírez et al, 2004;Pascual and Pla, 2007).…”