Carotenoid intake and SCD genotype exert complementary effects over fat content and fatty acid composition in Duroc pigs.

Nutritional and genetic strategies are needed to enhance intramuscular fat (IMF) and MUFA content without altering carcass leanness. Dietary vitamin A restriction has been suggested to specifically promote IMF, whereas a polymorphism of the () gene has shown to specifically increase MUFA. The purpose of this study was to investigate the combined effects of provitamin A (PVA) carotenoid intake and genotype (>) on hepatic retinoid content and on the liver, muscle (LM and gluteus medius [GM]), and subcutaneous fat (SF) content and fatty acid composition. Following a split-plot design, 32 castrated Duroc pigs, half of each of the 2 homozygous genotypes (CC and TT), were subjected from 165 to 195 d of age to 2 finishing diets differing in the PVA carotenoid content (an enriched-carotene diet [C+] and a control diet [C-]). Both diets were identical except for the corn line used in the feed. The C+ was formulated with 20% of a carotenoid-fortified corn (M37W-Ph3) whereas the C- instead used 20% of its near isogenic M37W line, which did not contain PVA carotenoids. No vitamin A was added to the diets. The C- was estimated to provide, at most, 1,300 IU of vitamin A/kg and the C+ to supply an extra amount of at least 800 IU vitamin A/kg. Compared with the pigs fed the C-, pigs fed with C+ had 3-fold more retinoic acid ( < 0.01) and 4-fold more gene expression in the liver ( = 0.06). The diet did not affect performance traits and backfat thickness, but pigs fed the C+ had less fat (4.0 vs. 5.0%; = 0.07) and MUFA (18.3 vs. 22.5%; = 0.01) in the liver, less IMF (5.4 vs. 8.3%; = 0.04) in the GM, and more fat content (90.4 vs. 87.9%; = 0.09) and MUFA (48.0 vs. 46.6%; = 0.04) in SF. The TT genotype at the gene increased MUFA ( < 0.05) in all tissues (21.4 vs. 19.5% in the liver, 55.0 vs. 53.1% in the LM, 53.9 vs. 51.7% in the GM, and 48.0 vs. 46.7% in SF for TT and CC genotypes, respectively). Liver fat and MUFA content nonlinearly declined with liver all- retinoic acid, indicating a saturation point at relatively low all- retinoic acid content. The results obtained provide evidence for a complementary role between dietary PVA and genotype, in the sense that the TT pigs fed with a low-PVA diet are expected to show higher and more monounsaturated IMF without increasing total fat content.

The effect of SCD and LEPR genetic polymorphisms on fat content and composition is maintained throughout fattening in Duroc pigs.

The effects of the stearoyl-CoA desaturase (SCD; AY487830:g.2228T>C) and leptin receptor (LEPR; NM_001024587:g.1987C>T) polymorphisms on fat content and fatty acid (FA) composition were investigated throughout fattening. Samples of Longissimus thoracis (LT) and subcutaneous fat (SF) from 214 Duroc barrows were collected from 160days to slaughter age (220days) using a longitudinal design. Results indicated that the positive effect of the T allele at the SCD gene on monounsaturated FA and of the T allele at the LEPR gene on saturated FA are maintained throughout the growing-finishing period, both in LT and SF. In LEPR, however, compositional changes, particularly in SF, are a result of increased fatness. There is very limited evidence of genotype by age interaction, and thus it is concluded that the combined selection for the SCD T and LEPR C alleles is a good strategy to increase the MUFA/SFA ratio regardless of the age at slaughter.

A polymorphism in the stearoyl-CoA desaturase gene promoter increases monounsaturated fatty acid content in dry-cured ham.

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 acid (MUFA) content in green ham is maintained after the curing process. It is shown that pigs carrying the T allele produced dry-cured hams with increased C16:1, C18:1n-9, C18:1n-7, and MUFA and decreased C18:0 and saturated fatty acid (SFA) content. The TT pigs had 1.39% more MUFA and 1.62% less SFA than the CC animals, while gilts had 0.74% more MUFA and 0.34% less SFA than barrows. The correlation between MUFA in green and dry-cured hams (n=53) was high (r=0.88), with TT pigs being more effective in retaining increased MUFA in green hams until the end of the curing period. It is concluded that increasing the presence of the T allele could have more impact than gender to produce hams with a high level of MUFA.