Genetics and breeding for intramuscular fat and oleic acid content in pigs

Abstract Text:

Total fat and fatty acid content affect both food quality and human health and therefore they are becoming increasingly important to industry and consumers. The intramuscular fat (IMF) and oleic acid (C18:1) content have been favorably related to pork quality, particularly in dry-cured products. This has triggered the interest of including them in the breeding goal of pig lines producing for high-valued markets. It is known that IMF responds to selection but there is little evidence on the opportunities for genetic change in fatty acid composition. Based on research conducted on a Duroc line, we showed that C18:1, like IMF, has a moderate heritability and is genetically associated with increased IMF, BW and backfat thickness. Despite this correlation structure, we proved that there exist selection schemes leading to response scenarios where C18:1, IMF and lean content can be simultaneously improved. A limitation for implementing direct selection for C18:1 is that phenotypes are costly to obtain and cannot be measured on selection candidates themselves. Furthermore, results may depend on the reference tissue used for genetic evaluations. DNA markers and genomic selection provide a complementary approach to overcome this problem. A genome-wide association study was performed on Duroc pigs genotyped with a 60k single nucleotide polymorphism chip to detect genomic variants exhibiting influence on fat content and composition. We detected strong associations with IMF and C18:1 for two chromosomal regions co-localizing with the SCD (SSC14) and LEPR (SSC6) genes, which were then validated using a set of data from around 1000 pigs. The DNA variant at the SCD gene affected the oleic to stearic desaturation index (C18:1/C18:0), C18:1, and SFA and MUFA and was consistently detected in several muscles and subcutaneous fat, and both in raw and dry-cured pork. The association of LEPR with fatty acid composition was detected in muscle and was, at least in part, a consequence of its effect on overall fatness, with increased IMF resulting in more SFA, less PUFA, and greater SFA/PUFA ratio. With the benefits of genomic selection needing further assessment, selection combining pedigree-connected phenotypic data on IMF and C18:1 and some singled-out genetic markers is presented as a suitable alternative. However, if adopted, the response on lean growth is expected to be reduced. The extent to which it is affordable relies on how much consumers are prepared to pay for high-IMF and C18:1 pork products.

Keywords: fatty acid, intramuscular fat, meat