Intramuscular fat (IMF) and oleic acid (C18:1) content in pork are important issues for the pig industry and consumers, according to R. Ros-Freixedes of Spain's University of Lleida and co-authors there and at Selección Batallé S.A. in Riudarenes.

In a paper published in Journal of Animal Science, they explain that data from a purebred Duroc line were used to:

1. estimate the genetic parameters of IMF and C18:1 and their genetic correlations with lean growth components, and
2. evaluate the opportunities for genetically improving C18:1 in IMF.

The data set used for estimating genetic parameters consisted of 93,920 pigs, from which 85,194 had at least one record for bodyweight or backfat thickness at 180 days and 943 for intramuscular fat and oleic acid at 205 days. Intramuscular fat content and oleic acid, expressed as percentage of total fatty acids, were determined in the gluteus medius muscle by gas chromatography.

Genetic parameters for oleic acid were estimated under a Bayesian four-trait multivariate animal mixed model.

Heritability of oleic acid was 0.50, with a probability of 95 per cent of being greater than 0.37.

Genetic correlations of oleic acid with bodyweight, backfat thickness and intramuscular fat were 0.11, 0.22 and 0.47, respectively (with a probability of 95 per cent of being greater than –0.07, 0.04 and 0.27, respectively).

Genetic responses were evaluated by deterministic simulation using a half-sib recording scheme for oleic acid and the previously estimated parameters.

The oleic acid content is expected to exhibit only minor changes in selection programmes directed at growth rate but to decrease in those focusing on lean content. Maximum expected response in oleic acid at no lean growth loss (i.e. at no change in bodyweight and backfat thickness) was 0.44 per cent, with a resulting correlated response in intramuscular fat of 0.15 per cent. However, because lean growth is emphasised in the breeding goal, the resulting response scenarios are more constrained.

Ros-Freixedes and co-authors concluded that there is evidence to support the idea that oleic acid in intramuscular fat is genetically determined and defined selection strategies can lead to response scenarios in which oleic acid, intramuscular fat, backfat thickness and bodyweight can be simultaneously improved.

However, they added, if adopted, the potential for lean growth would be reduced. The extent to which it is affordable relies on how much consumers are prepared to pay for high-oleic acid pork products.

Reference

Ros-Freixedes R., J. Reixach, M. Tor and J. Estany. 2012. Expected genetic response for oleic acid content in pork. J Anim Sci. 90(12):4230-4238. doi: 10.2527/jas.2011-5063

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January 2013