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Abstract
BackgroundThe proportion of muscle fibre types and their size affect muscularity as well as functional properties of the musculature and meat quality. We aimed to identify QTL for microstructural muscle properties including muscle fibre size, their numbers and fibre type proportions as well as biophysical parameters of meat quality and traits related to body composition, i.e. pH, conductivity, area of M. longissimus dorsi and lean meat content. A QTL scan was conducted in a porcine experimental population that is based on Duroc and Berlin Miniature Pig.ResultsLeast square regression interval mapping revealed five significant and 42 suggestive QTL for traits related to muscle fibre composition under the line-cross model as well as eight significant and 40 suggestive QTL under the half-sib model. For traits related to body composition and biophysical parameters of meat quality five and twelve significant plus nine and 22 suggestive QTL were found under the line-cross and half-sib model, respectively. Regions with either significant QTL for muscle fibre traits or significant QTL for meat quality and muscularity or both were detected on SSC1, 2, 3, 4, 5, 13, 14, 15, and 16. QTL for microstructural properties explained a larger proportion of variance than did QTL for meat quality and body composition.ConclusionMicrostructural properties of pig muscle and meat quality are governed by genetic variation at many loci distributed throughout the genome. QTL analysis under both, the line-cross and half-sib model, allows detecting QTL in case of fixation or segregation of the QTL alleles among the founder populations and thus provide comprehensive insight into the genetic variation of the traits under investigation. Genomic regions affecting complex traits of muscularity and meat quality as well as microstructural properties might point to QTL that in first instance affect muscle fibre traits and by this in second instance meat quality. Disentangling complex traits in their constituent phenotypes might facilitate the identification of QTL and the elucidation of the pleiotropic nature of QTL effects.
Highlights
The proportion of muscle fibre types and their size affect muscularity as well as functional properties of the musculature and meat quality
Muscle fibre type composition varies considerably due to inherited factors and environmental effects that contribute to phenotypic variation at 45 and 40%, respectively, while the remaining 15% is explained by the error component related to muscle sampling and technical variance [2]
A genome scan was performed in a F2 experimental crossbred population using a marker set covering more than 80% of the porcine linkage map (USDA-MARC v2, ArkDB [17]) for traits related to muscle fibre type composition and meat quality applying line-cross and half-sib analysis
Summary
The proportion of muscle fibre types and their size affect muscularity as well as functional properties of the musculature and meat quality. We aimed to identify QTL for microstructural muscle properties including muscle fibre size, their numbers and fibre type proportions as well as biophysical parameters of meat quality and traits related to body composition, i.e. pH, conductivity, area of M. longissimus dorsi and lean meat content. The number and size of the muscle fibres are major factors determining growth and weight of each muscle. The proportion of type I and II fibres (slow and fast twitch fibres) has been related to insulin resistance and diabetes II predisposition, obesity and body mass index, as well as fat catabolism and capacity to gain or loss weight, i.e. the constitution [3,4,5]. Muscle fibre composition is to some extent predictive of obesity [6]
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