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Feeding strategies to improve fat partitioning and meat quality in pigs

Publication . Madeira, Marta Sofia Morgado dos Santos; Prates, José António Mestre; Bessa, Rui José Branquinho de

Modern commercial pig breeds usually produce very lean meat with poor eating quality. Thus, strategies to increase intramuscular fat (IMF) content and consequently to improve sensorial meat quality are needed. In view of this, our investigation explores the potential of feeding strategies based on reduction of dietary protein to improve intramuscular fat and carcass fat partitioning in pigs and to study the associated genetic mechanisms. In a first experiment, three diets differing in dietary protein and lysine levels (control diet with 17.5% crude protein, reduced protein diet – RPD with 13% of crude protein, and reduced protein diet adjusted with lysine – RPDL) were applied to two genetic divergent pig genotypes (30 Alentejano purebred, fatty and 30 commercial crossbred pigs, lean). In a second experiment, six diets differing in dietary protein (16 vs. 13% of crude protein) and arginine and/or leucine supplementation were applied on 54 commercial crossbred pigs. The effects of these diets on growth performance, carcass traits, IMF content, meat quality, subcutaneous adipose tissue (SAT) deposition, fatty acid composition and mRNA levels of genes controlling lipid metabolism were evaluated. The results from the first experiment showed that RPD increase IMF but decrease the productive performance in commercial crossbred pigs but not on Alentejano pigs, suggesting that lysine restriction mediates the effect of RPD on muscular lipid deposition. The effect of RPD on IMF of crossbred pigs was accompanied by an increased stearoyl-CoA desaturase (SCD) and PPARγ mRNA levels. The backfat thickness did not change with RPD, but total fatty acid content increased in both genotypes. In addition, this result reflects a tendency for higher sensory scores in crossbred pigs. The Alentejano pigs showed higher sensory scores than crossbred pigs, although RPD increased the juiciness of crossbred pigs. In the second experiment, reduced protein diet increased both IMF and backfat thickness. However, the observed increase in IMF was also accompanied by increased SCD expression but did not improved meat sensory traits. Neither arginine nor leucine dietary supplementation increased IMF content. Nevertheless, arginine introduced an off-flavour of meat. The only relevant effect of arginine was increasing the fat content of adipose tissue (and consistent up-regulation of fatty acid synthase (FASN) and SCD genes) and a slightly decrease in 20:5n-3 and of total n-3 PUFA in muscle. Leucine supplementation resulted on up-regulation of muscle SCD and FASN reflected in higher 18:1c9 and 16:0 proportions and lower PUFA proportions. The results suggested that fat partitioning can be modulated and pork quality improved with reduced protein diets without lysine adjustment.

2013-12Doctoral thesis

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Higher membrane fluidity mediates the increased subcutaneous fatty acid content in pigs fed reduced protein diets

Publication . Lopes, P. A.; Martins, A. P.; Martins, S. V.; Madeira, M. S.; Santos, N. C.; Moura, T. F.; Prates, J. A. M.; Soveral, G.

The production of pork with moderate amounts of intramuscular fat (IMF) without an increase in subcutaneous fat is highly desirable for the meat industry. Several studies indicate that dietary protein reduction during the growing-finishing period of pigs enhances IMF content, but its consequence on carcass fat deposition is still contradictory. In this study, we hypothesized that the effects of reduced protein diets (RPD), corrected or not with the limiting amino acid lysine, on subcutaneous fat deposition from pigs with distinct genotypes are mediated by adipose membranes biophysical properties. In total, 36 crossbred (Large White×Landrace×Pietrain - a lean genotype) and purebred (Alentejana breed - a fatty genotype) male pigs were randomly assigned to the control group, the RPD group or the reduced protein diet equilibrated for lysine (RPDL) group, allowing a 2×3 factorial arrangement (n=6). Backfat thickness and total fatty acid content were higher in Alentejana relative to crossbred pigs. Although dietary treatments did not change backfat thickness, RPD and RPDL increased total fatty acids content of subcutaneous fat. In order to understand this effect, adipose tissue membranes isolated from pig's subcutaneous fat were assayed for glycerol permeability and fluidity, using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-(trimethylamino)-phenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) probes. The glycerol transport across adipose membranes was not mediated by aquaglyceroporins and remained unchanged across dietary groups. Regardless of lysine correction, RPD increased membrane fluidity at the hydrocarbon region (lower DPH fluorescence anisotropy) in both genotypes of pigs. This result was associated with a lower ratio between oleic acid and linoleic acid on membrane's fatty acid composition. Adipose membrane's cholesterol content was independent from genotype and diet. Taken together, the present study shows that dietary protein reduction is successful in maintaining backfat thickness, although a negative side effect was observed on total fatty acids in subcutaneous fat, which may be due to changes in the fluidity of adipose membranes.

2017Journal article

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