Assessing the role of the stearoyl-CoA desaturase gene on the fatty acid profile of pork
Fecha de publicación2017-04-05
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This PhD dissertation is framed on a line of research aimed at improving pork quality and, particularly, intramuscular fat (IMF) and monounsaturated fatty acid (MUFA) content as two of the main traits affecting nutritional and sensorial pork attributes. Several strategies have been investigated to enhance IMF and MUFA without increasing the rest of fat depots, but one of the most promising approaches is to find out genetic markers specifically associated to them. There is a variant in the promoter of the stearoyl-CoA desaturase (SCD) gene (AY487830:g.2228T>C used as tag single nucleotide polymorphism) that specifically enhances MUFA. This polymorphism localizes in the core sequence of a putative retinoic acid response element. The primary objective of the thesis was to assess the impact of this SCD polymorphism in different production and commercial scenarios. The thesis comprises four studies. The first one was intended to show whether the effect of this SCD polymorphism is maintained at different market carcass weights. The second and third study examined whether the effect of the SCD polymorphism is still evident in dry-cured products from purebred Duroc and Duroc-sired Iberian crossbreds, respectively. The fourth study investigated the impact of carotenoid intake as a source of dietary retinoic acid on IMF and MUFA in pigs from opposite genotypes at the SCD gene polymorphism. Four experiments, one per objective, were designed. The first consisted of a series of 1-4 repeated samples of m. longissimus thoracis and subcutaneous fat of 214 Duroc barrows collected at 160, 180, 210 and at 220 days of age. The second and third experiments were based, respectively, on 125 dry-cured hams from purebred Duroc pigs (53 traced throughout curation and 72 randomly sampled) and on 74 dry-cured hams from Duroc × Iberian pigs (taken from sliced trays randomly purchased from the same supplier). Dry-cured hams were from barrows and gilts. The fourth experiment consisted of 32 Duroc barrows which were allocated in a 2 x 2 split-plot design consisting of two finishing diets (from 165 to 195 days of age) differing in pro-vitamin A carotenoid content and the two SCD homozygotes. The diets were identical except the corn line used in the feed. The carotenoid-rich diet was formulated with 20% of a carotenoid-fortified corn while the carotenoid-restricted diet used instead 20% of its near isogenic line, which did not contain pro-vitamin A carotenoids. The positive effect of the T allele at the SCD gene on fat desaturation and MUFA content was confirmed throughout the growing-finishing period and after the curing process on both purebred Duroc and Duroc × Iberian dry-cured hams. A strong relationship between MUFA in green and dry-cured samples was found, with TT pigs being more effective in retaining increased MUFA in green hams until the end of the curing period. Moreover, the SCD polymorphism had a greater impact on MUFA than using hams from barrows instead of gilts. The results of the last experiment indicated that pigs fed with the carotenoid-rich diet had 2.8-fold more retinoic acid and 4.5-fold more SCD gene expression in liver, around one fifth less fat and MUFA in liver and one third less IMF in m. gluteus medius. The TT genotype at the SCD gene increased MUFA in all tissues. Liver fat and MUFA content declined non-linearly with liver all-trans retinoic acid, suggesting a saturation point at relatively low all-trans retinoic acid content. The results obtained support that a pro-vitamin A carotenoid restricted diet at finishing and the TT genotype at the SCD gene complement well each other to simultaneously increase IMF and MUFA without increasing total fat content. The leptin receptor (LEPR) NM_001024587:g.1987C>T polymorphism was also segregating in Duroc, with the T allele positively affecting IMF and the saturated fatty acid (SFA) content. Selection for the SCD T allele, particularly in combination with selection for the LEPR C allele, is confirmed as a good strategy to enhance the MUFA/SFA ratio and therefore to produce healthier meat.
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- Tesis Doctorals 
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A polymorphism in the stearoyl-CoA desaturase gene promoter increases monounsaturated fatty acid content in dry-cured ham Henriquez Rodriguez, Eliana; Tor i Naudí, Marc; Pena i Subirà, Ramona Natacha; Estany Illa, Joan (Elsevier, 2015)Data on 125 dry-cured hams from purebred Duroc pigs were used to examine whether the favorable effect of the T allele in the promoter region of the stearoyl-CoA desaturase gene (AY487830:g.2228T>C) on monounsaturated fatty ...
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