Advances in research on the prenatal development of skeletal muscle in animals in relation to the quality of muscle-based food. II – Genetic factors related to animal performance and advances in methodology

Abstract

Selective breeding is an effective tool to improve livestock. Several selection experiments have been conducted to study direct selection responses as well as correlated responses in traits of skeletal muscle growth and function. Moreover, comparisons of domestic with wild-type species and of extreme breeds provide information on the genetic background of the skeletal muscle phenotype. Structural muscular components that differed with increasing distance in lean growth or meat quality in mammals were found to be myofibre number, myofibre size, proportions of fibre types as well as the numbers and proportions of secondary and primary fibres. Furthermore, markers of satellite cell proliferation, metabolic enzyme activities, glycogen and fat contents, the expression of myosin heavy chain isoforms, of activated AMPKa and other proteins in skeletal muscle tissue and circulating IGF1 and IGF-binding proteins have been identified to be involved in selection responses observed in pigs, cattle and/or chicken. The use of molecular methods for selective breeding of fish has only recently been adopted in aquaculture and studies of the genetic basis of growth and flesh quality traits are scarce. Some of the molecular markers of muscle structure/metabolism in livestock have also been identified in fish, but so far no studies have linked them with selection response. Genome scans have been applied to identify genomic regions exhibiting quantitative trait loci that control traits of interest, for example, muscle structure and meat quality in pigs and growth rate in chicken. As another approach, polymorphisms in candidate genes reveal the relationship between genetic variation and target traits. Thus, in large-scale studies with pigs' associations of polymorphisms in the HMGA2, CA3, EPOR, NME1 and TTN genes with traits of carcass and meat quality were detected. Other studies revealed the significance of mutations in the IGF2 and RYR1 genes for carcass lean and muscle fibre traits in pigs. Mutations in the myostatin (MSTN) gene in fish were also examined. Advances in research of the genetic and environmental control of traits related to meat quality and growth have been made by the application of holistic 'omics' techniques that studied the whole muscle-specific genome, transcriptome and proteome in relation to muscle and meat traits, the development of new methods for muscle fibre typing and the adaptation of biophysical measures to develop parameters of muscle fibre traits as well as the application of in vitro studies. Finally, future research priorities in the field are defined.Keywords: farm animal, fish, skeletal muscle, animal performance, genetic effects ImplicationsSkeletal muscle development in different animal species has been an important topic of scientific research for many years.*Authoring on behalf of all members of the COST action 925: http://www. agrsci.dk/costaction925/index.html -E-mail: rehfeldt@fbn-dummerstorf.de 718The main aim of this review is to present recent knowledge on the genetic components of skele...

Epigenetics and developmental programming of welfare and production traits in farm animals

“…There are numerous reviews (e.g. Brameld and Daniel 2008;Rehfeldt et al 2011b) describing this process and the factors that regulate it, including cross-species comparisons (Rehfeldt et al 2011a), and only a brief summary is provided here.…”

“…The main difference between species is the time at which these phases of fibre formation take place, with fibre formation in most large mammals (including sheep, cattle and humans) completed by the middle of gestation; in pigs, formation completes towards late gestation, whereas in poultry and small mammals (e.g. rats) fibre formation continues for a limited period after hatching or birth (see Brameld and Daniel 2008;Rehfeldt et al 2011a).…”

“…double muscling in cattle) or environmental (e.g. maternal nutrition or administration of hormones) factors, but only if the environmental insults take place at specific times during gestation (see Brameld and Daniel 2008;Rehfeldt et al 2011aRehfeldt et al , 2011b. Tables S4 and S5 summarise studies investigating the effects of maternal nutrition on muscle fibre formation in sheep and pigs.…”

Skeletal muscle development in vertebrate animals

“…This process starts with the commitment of an embryonic precursor to the myogenic lineage followed by proliferation of those committed myoblasts which are differentiated into post-mitotic myocytes (Knight and Kothary, 2011) and lastly fuse to form a multinucleated myotube. It was proved from several studies that there is no net increase in the number of muscle fibers after hatch or birth (Zhu et al, 2004 andVelleman, 2007), in addition, development of skeletal muscle in this stage has long term effects on postnatal growth and physiological function (Rehfeldt et al, 2011b) both in animals and in human beings. Muscle fibers are produced from two distinct phases which include myoblast fusion to primary myoblast as initial phase and later primary myoblast to secondary myoblast by the second web of differentiation (Beermann et al, 1978;Miller et al, 1993 andRehfeldt et al, 2000).…”

Advances in research on the prenatal development of skeletal muscle in animals in relation to the quality of muscle-based food. I. Regulation of myogenesis and environmental impact

“…Moreover, this review will identify the main gaps and open questions in this field of research. The present part 1 of the review focuses on the regulation of myogenesis and the impact of environment on muscle development and related changes in animal performance (for part 2, see Rehfeldt et al, 2011).…”