Sixty entire male pigs from 2 distinct genotypes (30 Alentejano purebred, an autochthonous fatty genotype, and 30 commercial crossbred pigs, a lean genotype) were used to investigate the effects of dietary CP reduction and low-Lys levels on growth performance, carcass traits, and meat quality. Pigs with 59.9 ± 2.0 kg BW were randomly assigned within each genotype to 1 of 3 diets [normal CP diet (control), reduced CP diet adjusted for Lys (RPDL), and reduced CP diet not adjusted for Lys (RPD)] as a 2 × 3 factorial arrangement of treatments with 10 individually fed pigs per treatment. Pigs were slaughtered at 93.4 ± 2.4 kg BW. The results showed that intramuscular fat (IMF) content of longissimus lumborum muscle was greater in Alentejano than crossbred pigs (5.0 vs. 2.4%). The RPDL had no effect on IMF content, ADG, backfat thickness, and loin weight in both genotypes. The RPD promoted the increase (P < 0.05) in IMF content in crossbred (∼50%) but not Alentejano pigs, which indicates that Lys restriction can mediate the effect of RPD. Within crossbred pigs, meat obtained from pigs fed RPD had an increased IMF content (+1.3%) and a tendency for greater sensory scores (tenderness, juiciness, flavor, and acceptability) than those fed the control. The IMF content was positively correlated to flavor in Alentejano genotype (P < 0.05) but not in crossbred pigs. Alentejano and crossbred pigs had a greater tendency to deposit 18:1c9 and SFA, respectively. Despite the contribution of fatty acid composition to flavor, its influence on pork acceptability was more noticeable in crossbred than Alentejano pigs. In conclusion, the increased IMF promoted by dietary CP reduction in lean but not in fatty pig genotypes during the growing-finishing period is likely due to Lys limitation, which seems to enhance eating quality of pork. Copyright © 2013. American Society of Animal Science .

The present study assessed the effect of pig genotype (fattyv.lean) and dietary protein and lysine (Lys) levels (normalv.reduced) on intramuscular fat (IMF) content, subcutaneous adipose tissue (SAT) deposition, fatty acid composition and mRNA levels of genes controlling lipid metabolism. The experiment was conducted on sixty intact male pigs (thirty Alentejana purebred and thirty Large White × Landrace × Pietrain crossbred), from 60 to 93 kg of live weight. Animals were divided into three groups fed with the following diets: control diet equilibrated for Lys (17·5 % crude protein (CP) and 0·7 % Lys), reduced protein diet (RPD) equilibrated for Lys (13·2 % CP and 0·6 % Lys) and RPD not equilibrated for Lys (13·1 % CP and 0·4 % Lys). It was shown that the RPD increased fat deposition in the longissimus lumborum muscle in the lean but not in the fatty pig genotype. It is strongly suggested that the effect of RPD on the longissimus lumborum muscle of crossbred pigs is mediated via Lys restriction. The increase in IMF content under the RPD was accompanied by increased stearoyl-CoA desaturase (SCD) andPPARGmRNA levels. RPD did not alter backfat thickness, but increased the total fatty acid content in both lean and fatty pig genotype. The higher amount of SAT in fatty pigs, when compared with the lean ones, was associated with the higher expression levels ofACACA,CEBPA,FASNandSCDgenes. Taken together, the data indicate that the mechanisms regulating fat deposition in pigs are genotype and tissue specific, and are associated with the expression regulation of the key lipogenic genes.

Fifty-four entire male pigs (Duroc × Pietrain × Large White × Landrace) from a commercial crossbred operation were used to investigate the effect of dietary Arg supplementation, protein reduction (PR), and Leu supplementation on performance, carcass traits, and meat quality. Pigs weighing 58.9 ± 1.6 kg BW were randomly assigned to 1 of 6 treatments (n = 9). The 6 dietary treatments were normal CP diet (16% CP, NPD), reduced CP diet (13% CP, RPD), reduced CP diet with Leu addition to 2.0% (RPDL), normal CP diet supplemented with 1% Arg (16% CP, Arg-NPD), reduced CP diet supplemented with 1% Arg (13% CP, Arg-RPD), and reduced CP diet with Leu addition to 2.0% and supplemented with 1% Arg (13% CP, Arg-RPDL). Pigs were slaughtered at 91.7 ± 1.6 kg BW. Dietary Arg supplementation had no effect on intramuscular fat (IMF) content but produced meat off-flavor and increased meat tenderness and overall acceptability. The PR increased (P < 0.001) IMF content (45% to 48%) but negatively affected the growth performance of pigs. In addition, PR increased (P < 0.05) back fat thickness and decreased loin weight. Leucine addition did not affect IMF content, back fat thickness, or loin weight. There was an increase of juiciness with PR and Leu addition, which accompanied the increase of IMF content with the low-CP diet. The PR increased meat deposition of 18:1c9, SFA, MUFA, and PUFA, which were not correlated with any pork sensory trait. The main combined effect of Arg was an increased tenderness and overall acceptability of pork. In conclusion, it was confirmed that dietary CP reduction enhances pork eating quality but negatively affects growth performance and carcass characteristics of pigs. Copyright © 2014. American Society of Animal Science .

The cumulative effects of dietary arginine, leucine and protein levels on fat content, fatty acid composition and mRNA levels of genes controlling lipid metabolism in pig longissimus lumborum muscle and subcutaneous adipose tissue (SAT) were investigated. The experiment was performed on fifty-four intact male pigs (Duroc × Pietrain × Large White × Landrace crossbred), with a live weight ranging from 59 to 92 kg. The pigs were randomly assigned to one of six experimental treatments (n9). The treatments followed a 2 × 3 factorial arrangement, with two levels of arginine supplementation (0v.1 %) and three levels of a basal diet (normal protein diet, NPD; reduced protein diet, RPD; reduced protein diet to achieve 2 % of leucine, RPDL). The results showed that dietary arginine supplementation did not affect the intramuscular fat (IMF) content and back fat thickness, but increased the total fat in SAT. This effect was associated with an increase in fatty acid synthase (FASN) and stearoyl-CoA desaturase (SCD) mRNA levels in SAT, which suggests that arginine might be involved in the differential regulation of some key lipogenic genes in pig muscle and SAT. The increase in IMF content under the RPD, with or without leucine supplementation, was accompanied by increasedFASNandSCDmRNA levels. Arginine supplementation did not influence the percentage of main fatty acids, while the RPD had a significant effect on fatty acid composition in both tissues. Leucine supplementation of RPD did not change IMF, total fat of SAT and back fat thickness, but increased 16 : 0 and 18 : 1cis-9 and decreased 18 : 2n-6 in muscle.

Forty entire male pigs from a commercial crossbreed (Duroc × Large White × Landrace) were used to investigate the individual or combined effects of betaine and Arg supplementation in Lys-deficient diets on growth performance, carcass traits, and pork quality. Pigs with 59.9 ± 1.65 kg BW were randomly assigned to 1 of 5 dietary treatments (n = 8). The 5 dietary treatments were normal Lys and CP diet (0.51% Lys and 16% CP; control), reduced Lys and CP diet (0.35% Lys and 13% CP), reduced Lys and CP diet with betaine supplementation (0.33%), reduced Lys and CP diet with Arg supplementation (1.5%), and reduced Lys and CP diet with betaine and Arg supplementation (0.33% betaine and 1.5% Arg). Pigs were slaughtered at 92.7 ± 2.54 kg BW. The Lys-deficient diets (–35% Lys) increased intramuscular fat (IMF) content by 25% (P = 0.041) and meat juiciness by 12% (P = 0.041) but had a negative effect on growth performance (P < 0.05) of pigs. In addition, Lys-deficient diets increased L* (P = 0.005) and b* (P = 0.010) muscle color parameters and perirenal fat deposition (P < 0.001) and decreased both HCW (P = 0.015) and loin weight (P = 0.023). Betaine and Arg supplementation of Lys-deficient diets had no effect on IMF content but increased (P < 0.05) overall pork acceptability. Arginine supplementation also increased (P = 0.003) meat tenderness. Differences in fatty acid composition of pork were not detected among dietary treatment groups. However, oleic acid was positively correlated (P < 0.05) with IMF content, juiciness, flavor, and overall acceptability of meat. Data confirm that dietary CP reduction enhances pork eating quality but negatively affects pigs' growth performance. Moreover, it is suggested that betaine and Arg supplementation of Lys-deficient diets does not further increase IMF content but improves some pork sensory traits, including overall acceptability.