Variation in instrumental meat quality among 15 muscles from 14-month-old sheep and its relationship with fibre typing

Abstract

The aims of the present study were to describe intermuscular differences in meat-quality traits in 15 young-sheep muscles, and to study the associations between meat quality and fibre typing across all (pooled) muscles as well as in previously selected homogeneous contractile–metabolic groups of muscles (slow-oxidative, intermediate and fast-glycolytic muscles). Meat-quality traits (pH, colour, expressed juice, cooking losses, tenderness and sarcomere length) and fibre typing were evaluated after 24 h of slaughter in 15 muscles from five cross-bred young sheep. Across all the studied muscles, intermuscular differences in some meat-quality traits (pH24, a* and expressed juice) seemed to be mainly explained by muscle oxidative activity, while intermuscular variation in other meat-quality traits (L*, b* and Warner–Bratzler shear force) were mainly explained by differences in fibre sizes. Within fast-glycolytic muscles, larger fast-glycolytic fibres and reduced oxidative activity were generally associated with lower ultimate pH, higher L* values, lower a* values and longer sarcomeres. Within intermediate muscles, larger fast-glycolytic fibres and reduced oxidative activity were generally associated with lower ultimate pH, higher L* values, shorter sarcomeres and reduced meat tenderness. Within slow-oxidative muscles, larger fast-glycolytic fibres and reduced oxidative activity were generally associated with lower amounts of expressed juice, lower a* values and reduced meat tenderness. The present study has contributed to a better understanding of the influence of muscle fibre types on intermuscular meat-quality variation, suggesting that although muscle fibre diversity may explain, at least in part, intermuscular differences in meat quality, these associations can also slightly vary among muscle contractile–metabolic groups.

Comparison of transcriptomic landscapes of different lamb muscles using RNA-Seq.

“…Interestingly, MDS plots showed a very similar pattern to the principal component analysis presented by Ithurralde et al (2017), in which they study the general relationships between meat quality traits and fiber typing across muscles [ 13 ]. In agreement with the present gene expression analysis, the muscles clustered in three main categories, with SS, ST and SM clearly separated.…”

“…All animal experimental procedures were approved by the Animal Experimentation Committee (CHEA, Universidad de la República, Montevideo, Uruguay). Muscle samples were collected in a previous study by Ithurralde et al (2015, 2017) [ 12 , 13 ] from four unrelated Poll Dorset cross-bred lambs, raised on grasslands. Animals were acquired from different flocks.…”

“…Histochemical tests for fiber typing, fiber morphometric analysis and meat quality determination were performed by Ithurralde et al (2015, 2017)[ 12 , 13 ].…”

“…Eight genes that showed highly significant differential expression between ST and SS (the most contrasting muscles in terms of metabolic and histochemical properties according to Ithurralde et al, 2015, 2017 [ 12 , 13 ]) were chosen for validation of the RNA-Seq results: myozenin 2 ( MYOZ2 ), myosin light chain 2 ( MYL2 ), myosin light chain 3 ( MYL3 ), tropomyosin 3 ( TPM3 ), myosin light chain 6 ( MYL6 ), troponin T1 ( TNNT1 ), troponin C1 ( TNNC1 ) and methyl transferase-like 21C ( METTL21C ). The same muscle samples used for RNA-Seq were used for validation of differential expression.…”

“…Mammalian skeletal muscles differ in their contractile and metabolic properties, mainly related to speed of contraction and resistance to fatigue. In a previous study, Ithurralde et al (2015, 2017) studied fiber content and type among lamb muscles with different histochemical and meat quality characteristics [ 12 , 13 ]. The authors demonstrated the existence of specific intermuscular differences in fiber typing and meat quality in sheep.…”