Abstract
Among the large number of attributes that define pork quality, fat content and composition have attracted the attention of breeders in the recent years due to their interaction with human health and technological and sensorial properties of meat. In livestock species, fat accumulates in different depots following a temporal pattern that is also recognized in humans. Intramuscular fat deposition rate and fatty acid composition change with life. Despite indication that it might be possible to select for intramuscular fat without affecting other fat depots, to date only one depot-specific genetic marker (PCK1 c.2456C>A) has been reported. In contrast, identification of polymorphisms related to fat composition has been more successful. For instance, our group has described a variant in the stearoyl-coA desaturase (SCD) gene that improves the desaturation index of fat without affecting overall fatness or growth. Identification of mutations in candidate genes can be a tedious and costly process. Genome-wide association studies can help in narrowing down the number of candidate genes by highlighting those which contribute most to the genetic variation of the trait. Results from our group and others indicate that fat content and composition are highly polygenic and that very few genes explain more than 5% of the variance of the trait. Moreover, as the complexity of the genome emerges, the role of non-coding genes and regulatory elements cannot be disregarded. Prediction of breeding values from genomic data is discussed in comparison with conventional best linear predictors of breeding values. An example based on real data is given, and the implications in phenotype prediction are discussed in detail. The benefits and limitations of using large SNP sets versus a few very informative markers as predictors of genetic merit of breeding candidates are evaluated using field data as an example.
Highlights
Meat quality has always been important to consumers and critical to guarantee returning customers
Tenderness is influenced by the amount of intramuscular fat (IMF) in the meat cut as infiltrated fat gives thinner myofibrils, which facilitates chewing and reduces instrumental tenderness [2]
This review focuses on the genetic constitution of fat content and composition in pork and how novel technologies can contribute to identify markers that can be used in a pig breeding scheme
Summary
Meat quality has always been important to consumers and critical to guarantee returning customers. The two attributes more important for meat consumers are tenderness and flavor. The former is directly related to muscle fiber morphology (total number of fibers and cross-sectional area) and, most importantly, to fiber type composition. Fresh meat quality is strongly related to fiber type composition in muscle and to the aging and proteolysis of these fibers during the muscle-to-meat transformation process (reviewed in [1]). Intramuscular fat is a source of meat flavor, in dry-cured products. Intramuscular fat content and composition have an important genetic component (h2 ∼= 0.4–0.7), which means animals can be selected for more favorable content and composition and bred to improve these traits in the generation (see Section 3). After an update on the latest advances regarding phenotype-based and marker-assisted selection, an example is given with field data from a Duroc selection company aiming at quality cured products (Section 5)
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