Variability in subcutaneous fat composition of Iberian pigs reared in free-range conditions in the southwest of the Iberian Peninsula

A total of 80 free-range Iberian pigs reared with acorns and grass in eight different free-range systems (n = 10) in the southwest of the Iberian Peninsula were used to determine the relationship between fatty acid, tocopherol, and neophytadiene subcutaneous fat composition. The pigs were fed extensively for 79.1 ± 9.5 d from 110.9 ± 11.9 kg live weight at the beginning of the final fattening phase to 175.0 ± 15.9 kg slaughtered weight. Quercus suber and Quercus rotundifolia acorns were characterised by a high content of C18:1n-9 (58.3 and 63.1%, respectively) and γ-tocopherol [43.7 and 43.0 mg kg−1 dry matter (DM), respectively], while grass exhibited a high content of C18:3n-3 (42.5%), α-tocopherol (366.5 mg kg−1 DM) and neophytadiene (136.2 relative area units). The C18:1n-9 (54.4%–57.7%) and γ-tocopherol (2.7–4.1 mg kg−1 DM) contents in subcutaneous fat from Iberian pigs differed (p < 0.001) between the free-range systems studied. Pasture intake had a significant effect (p < 0.01) on subcutaneous fat content of C18:3n-3 (0.5%–0.8%), α-tocopherol (7.8–13.1 mg kg−1 DM) and neophytadiene (2.6–6.3 relative area units). However, the results demonstrated no correlations between accumulated levels of these compounds throughout the free-range period. In conclusion, the absence of correlations corroborated the heterogeneity of extensive rearing systems, with variations between years and geographical areas where the Iberian pigs were reared.

Free-Range and Low-Protein Concentrated Diets in Iberian Pigs: Effect on Plasma Insulin and Leptin Concentration, Lipogenic Enzyme Activity, and Fatty Acid Composition of Adipose Tissue

Simple Summary

Recently, it has been shown that reducing dietary crude-protein levels during the final fattening period prior to slaughter is a suitable strategy to increase intramuscular fat content in Iberian pig meat, without affecting pig growth. Investigating the effect of a low-protein diet on the metabolism, development, and composition of the adipose tissue of Iberian pigs, and the obese porcine breed, was the objective of this study. Three groups of pigs fed under free-range conditions and in confinement with concentrated diets with low- and standard-protein contents were studied. All three groups exhibited the same backfat thickness at the end of the fattening period. The level of hormones and activities of enzymes related to adipogenic metabolism were affected by diet, with differences between free-range and intensive feeding systems. Therefore, we suggest that feeding Iberian pigs on low-protein diets did not result in fatter carcasses, and is thus a useful strategy to improve Iberian pig meat quality.

Abstract

The purpose of this study was to investigate the effect of diets with different protein contents on carcass traits, plasma hormone concentration, lipogenic enzyme activities, and fatty acid (FA) composition in the adipose tissue of Iberian pigs. Twenty-four castrated male Iberian pigs (eight per feeding diet) were fed under free-range conditions with acorns and grass (FR), and in confinement with concentrated diets with standard (SP) and low-protein contents (LP) from 116.0 to 174.2 kg live weight. Backfat thickness was not affected by diet. The plasma leptin concentration was higher (p < 0.001) in the FR group than in the LP and SP groups, while insulin concentration was higher in the SP group than in the LP and FR groups. The lipogenic enzyme activities of glucose-6-phosphate dehydrogenase, malic enzyme, and glycerol-3-phosphate dehydrogenase were lower in the FR group compared to the LP and SP pigs. The activities of these enzymes were adipose-tissue-specific. No differences were found in FA composition of adipose tissue between the SP and LP groups, while the FR pigs had lower proportions of saturated FA and higher proportions of monounsaturated and polyunsaturated FA than the SP and LP pigs. In conclusion, feeding low-protein diets in Iberian pigs does not seem to affect adipose carcass traits, strengthening previous findings that indicate that this is a good strategy to improve meat and dry-cured product quality.

Effect of Free-Range and Low-Protein Concentrated Diets on Growth Performance, Carcass Traits, and Meat Composition of Iberian Pig

Simple Summary

It is generally assumed in the Iberian pig sector that substitution of traditional free-range rearing, with acorns and grass, by mixed diets affects intramuscular fat content and fatty-acid composition, among others, causing a decrease in meat quality. As mixed diets are usually formulated with higher protein contents than those supplied by natural resources consumed by Iberian pig fed extensively, we hypothesized that the use of a low-protein diet in the final fattening period of pig could be a suitable strategy to improve meat and dry-cured product quality. However, it is also necessary to evaluate the effect of this strategy on performance and carcass traits of pigs. In this study, we found that Iberian pigs fed on low-protein diets had higher intramuscular fat content and different meat composition compared to pigs fed on concentrates with standard protein levels, which could be a suitable way of improving the Iberian pig meat and dry-cured product quality.

Abstract

The feeding system is one of the main factors influencing the Iberian pig meat quality. This experiment was undertaken to evaluate the influence of feeding diets containing different levels of protein on performance, carcass, and meat quality of Iberian pigs. To that aim, 24 castrated male Retinto Iberian pigs with an average weight of 116 kg were fed under free-range conditions with acorns and grass (FR), and on concentrated diets in confinement with standard (SP) and low protein content (LP). The crude protein content in acorns was lower than that in the grass and SP diet, but similar to that in the LP diet. FR pigs needed more time to achieve slaughter weight than LP and SP pigs. Iberian pigs fed on low-protein diet (FR and LP) had a higher intramuscular fat content in the musculus serratus ventralis than SP pigs. The influence of diet on the fatty-acid composition was reflected more markedly in subcutaneous fat than in muscles. FR pigs showed a higher level of C18:1 n-9 and total polyunsaturated fatty acids and lower total saturated fatty acids in subcutaneous fat than LP and SP. It is concluded that diets with low protein levels do not affect Iberian pig productive traits but change the meat composition, rendering them an interesting strategy to improve the quality of Iberian pig meat and dry-cured products.

Two by-products of the olive oil extraction industry as oleic acid supplement source for Iberian pigs: effect on the meat's chemical composition and induced lipoperoxidation

BACKGROUND

The objective of the present study was to evaluate the effect of two by-products of the olive oil extraction industry-olive soapstocks and olive-pomace oil-as added fat sources into feed concentrates, in two different rearing systems (free-range complemented with concentrates and intensive rearing with concentrates) on the chemical composition and oxidative stability of Iberian pig meat.

RESULTS

No differences in the chemical composition, colour and fatty acid composition of gluteobiceps m. were found due to added fat source. However, the feeding system had a significant effect on protein (P < 0.05), γ-tocopherol (P < 0.05), colour (P < 0.01) and fatty acid composition of gluteobiceps m. Neither added fat source nor the feeding system had an effect on the malondialdehyde content.

CONCLUSION

The addition of olive soapstock or olive-pomace oil as fat sources into concentrates did not influence meat composition or fatty acid profile. However, there are differences in the fatty acid composition of meat from Iberian pigs as a result of the production system used.