Effect of age on fat thickness, adipocyte morphology and fatty acid content of subcutaneous fat in Nero di Parma swine

During the last 4 months of fattening, subcutaneous fat characteristics of 8 Nero di Parma pigs (4 females, 4 castrated males) were evaluated. The animals were reared in the same environmental conditions and under the same feeding programmes. At 570 and 641 days of age, by biopsy, and at slaughter (mean age: 683 d), a withdrawal of subcutaneous fat at point P2 was made. At the same moments, thoracic circumference, BW and backfat thickness (P2) were estimated. The fatty acid content (GC HP 6890; Agilent Technologies Italia, Milano) was analysed and also adipocyte morphometric analyses, by digital camera (Zeiss Axiocam MRc5), were assessed on fat samples. The images were processed with Axio Vision software (rel. 4.5). Data were submitted to analysis of variance, using a mixed model including fixed effects of sampling (3 levels), sex (2 levels), interaction and the random effect of individual within sex (6 levels). At the experimental ages, differences were observed for weight (kg 159.77a, 177.00b, 187.61c, resp.), thoracic circumference (cm 135.88a, 142.25b, 146.00c, resp.) and backfat thickness (mm 21.25a, 36.75b, 45.50c, resp.) (P<0.05) but not in ADG (P>0.05). The fatty acid composition showed a generalized reduction of short and medium-long chain (up to C18) and an increase of long-chain (> C18) fatty acids. At 641 and 683 d of age SFA decreased (P<0.05) and PUFA increased (P<0.05), as compared to 570 d. The atherogenic index [(4*C14+C12+C16)/(MUFA+PUFA)] decreased from the first to the last sampling (0.489c, 0.459b, 0.420a, resp.) (P<0.05). An age related increase (P<0.05) in the area of adipocytes (μ2 17387a, 16566a, 22837b, resp.) as well as in the measures of the major axis (μ 153a, 143a, 173b, resp.) was showed as the minor axis was not different among ages (P>0.05) and the perimeter (μ 567b, 481a, 566b, resp.) was lower at 641 d (P<0.05). In conclusion, in Nero di Parma pig, similarly to what occurs in other pig breeds, adipose tissue has a dynamic in its quantitative and qualitative composition, characterized not only by an increase in the thickness of the subcutaneous fat but also by changes in adipocytes morphology and fatty acid composition.