Age Evolution of Lipid Accretion Rate in Boars Selected for Lean Meat and Duroc Barrows

SIMPLE SUMMARY: Fat deposition profile and fatty acid biosynthesis in adipose tissues are two relevant metabolic processes for breeding companies as the fat content of meat relates to its technological, organoleptic, and nutritional quality. Age, breed, and sex have a great impact on fat metabolism. Therefore, in the present experiment, a labeled saturated fatty acid was added to the diet of pigs belonging to three different producing types during two growth phases, to define the rate of its incorporation into body fat. In addition, the activity of the enzyme stearoyl-CoA desaturase, which promotes the conversion of some saturated fatty acids into monounsaturated, was analyzed. In the growing phase, direct incorporation of fat from diet was higher than biosynthesis in most adipose tissues, whereas in the fattening phase it was higher only in the liver, revealing the changing roles of organs in fat metabolism with age. The leaner pigs also obtained a higher fat incorporation, denoting higher reliance on dietary fatty acids for fat deposition; overall, real stearoyl-CoA desaturase activity was higher in the fattening phase. ABSTRACT: Fatty acid (FA) deposition in growing–fattening pigs is mainly based on endogenous lipid synthesis, but also direct FA incorporation from the diet. To evaluate the direct fat incorporation rates and the endogenous desaturation action of the stearoyl-CoA desaturase (SCD) enzyme, a deuterium (D)-labeled saturated FA (d(35)-C18:0) was added to the diet. Sixteen three-way (3W) crossbred boars, and thirty-two purebred Duroc barrows homozygous for the SCD single nucleotide polymorphism rs80912566 (16 CC/16 TT), were used. Half of the animals of each genotype belonged to the growing and fattening phases. The fractional incorporation rate (FIR) of dietary fat in growing pigs was generally higher in adipose tissues, whereas in fattening pigs it was higher in the liver. Duroc pigs exhibited lower FIRs than 3W pigs, suggesting lower rates of endogenous synthesis by 3W pigs. Real fractional unsaturation rates (FURs) increased with age by the higher FIRs in 3W pigs and the de novo synthesis pathway in Duroc genotypes. Moreover, pigs carrying the SCD_T allele showed more enhanced oleic acid biosynthesis than Duroc CC pigs. In conclusion, suitable feeding protocols should be designed for each pig type to optimize production traits, considering that the metabolic pathway of FA for its deposition may differ.