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 stearoyl-CoA desaturase (SCD) 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 SCD genotype (AY487830: g.2228T>C) 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 SCD 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 (P < 0.01) and 4-fold more SCD gene expression in the liver (P = 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%; P = 0.07) and MUFA (18.3 vs. 22.5%; P = 0.01) in the liver, less IMF (5.4 vs. 8.3%; P = 0.04) in the GM, and more fat content (90.4 vs. 87.9%; P = 0.09) and MUFA (48.0 vs. 46.6%; P = 0.04) in SF. The TT genotype at the SCD gene increased MUFA (P < 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-trans retinoic acid, indicating a saturation point at relatively low all-trans retinoic acid content. The results obtained provide evidence for a complementary role between dietary PVA and SCD 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.