Seasonal Variation in Pasture Availability During the Fattening Period Influences Lipid Profile and Nutritional Quality in the Semi-Extensive Production of Iberian Pigs

Iberian pigs reared in a semi-extensive outdoor system, known as cebo de campo, have their commercial feed supplemented with natural pasture. However, the availability and quality of pastures vary seasonally under the Mediterranean conditions of the southwestern Iberian Peninsula. This study evaluates the effect of the seasonal fattening period on fatty acid content and nutritional quality indices (atherogenic index, thrombogenic index, hypocholesterolemic/hypercholesterolemic ratio, and healthy fatty index) in subcutaneous adipose tissue and intramuscular fat from 258 purebred Iberian pigs raised under the cebo de campo system during three periods: winter–spring (December–April, n = 63), spring–summer (May–August, n = 99), and summer–autumn (August–November, n = 96). Winter–spring pigs exhibited significantly higher monounsaturated and polyunsaturated fatty acids and lower saturated fatty acids compared to spring–summer and summer–autumn groups in subcutaneous adipose tissue. Nutritional quality indices were more favorable in winter–spring pigs, indicating superior cardiovascular health benefits. Principal component analysis revealed clear seasonal group separation, with the first two components explaining 88.51% of the variance in subcutaneous fat. Significantly higher neophytadiene concentrations, a biomarker of pasture intake, in winter–spring pigs confirmed greater pasture consumption. These findings demonstrate that seasonal factors significantly influence the nutritional quality of meat produced in cebo de campo Iberian pig systems. This influence is much clearer in subcutaneous adipose tissue than intramuscular fat, as winter–spring fattening is associated with a more favorable lipid profile.