SPAIN - Intramuscular fat is known to affect the eating quality of pork, and researchers at IRTA have been examining what we can do to affect it.
"We can affect the level of intramuscular fat (IMF) in pork - but only some of the time," according to Dr Enric Esteve, Director of Monogastric Nutrition research at IRTA.
Speaking at a conference at IRTA Mas de Bover in Constantí (Tarragona, Spain) on 16 May 2014, he presented a review of published literature and studies at IRTA on the theme 'Does genetic origin condition the response of pigs to nutritional modification?'. A link to a video clip of his presentation is given below.
Firstly, he outlined the characteristics of meat that influence eating quality of meat: colour, tenderness, juiciness and flavour. IMF affects all but the first of these characteristics, he said.
Piglets are born with very little body fat. A 100-kg pig, on the other hand, will be between 20 and 35 per cent fat; nearly all of it is under the skin (subcutaneous fat) and less than one per cent is in the form of IMF in modern genotypes.
Consumer preferences regarding pork fatness were found to be complex in an IRTA consumer study, explained Dr Estevez. Some preferred the look of marbled pork loin and others chose the leaner one - but both groups preferred the pork with more IMF when they tasted it.
Factors affecting fat deposition in pigs include genetics, liveweight, gender and environmental temperature, he said.
In his presentation, Dr Estevez explained the effects of various nutrients in the feed on IMF, using IRTA's own results as well as other sources.
In summary, he said, supplementation of the pig's diet with conjugated linoleic acid (CLA) or the amino acid, leucine, tended to increase the level of IMF, as did reducing the levels of protein or lysine. However, the effects were highly variable, as were the responses to vitamin A and arginine supplementation.
Offering a possible explanation for the wide variation in the results, he said that the pigs in the IRTA studies were different crosses; those in the one study were Landrace × Duroc, while a (Landrace × Duroc) × Pietrain was used in the other experiment.
"It seems that the Pietrain genes are blocking the effect," added Dr Estevez. "So we can affect IMF through nutrition - but only some of the time."
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