Effect of a Low-Lysine Diet Based on Newly Estimated Lysine Requirements on the Intramuscular Fat Content in the Longissimus Dorsi Muscle of Fattening Pigs.

We conducted a series of investigations in order to elucidate role of nutritional status in regulating GLUT expression and energy metabolism in porcine muscle. Firstly, the role of mild undernutrition in regulating muscle GLUT gene expression and function was studied in growing pigs (3 wk of age) on a high (H) or low (L) food intake (H = 2L) at 35°C or 26°C. Low food intake selectively upregulates GLUT1 and GLUT4 gene expression; mRNA levels were elevated in longissimus dorsi (L. dorsi) and rhomboideus muscles but not in diaphragm or cardiac muscles. Our next step was to determine whether dietary lysine, a major primary limiting amino acid in diets for pigs, affects muscle GLUT4 expression. Pigs of 6 wk of age were pair-fed a control or low lysine (LL) diet. The control diet contained optimal amounts of all essential amino acids, including 1.15% lysine. The LL diet was similar but contained only 0.70% lysine. GLUT4 mRNA expression was upregulated by the LL diet in L. dorsi and rhomboideus muscles, whereas that in cardiac muscle was unaffected. GLUT4 protein abundance was also higher in rhomboideus muscle of animals on the LL diet. We conducted another investigation in order to elucidate effects of the LL diet on post-GLUT4 glucose metabolism. Activity of hexokinase was unaffected by dietary lysine levels while that of citrate synthase was higher both in L. dorsi and rhomboideus muscles of pigs fed on the LL diet. Glucose 6-phosphate content was higher in L. dorsi msucle in the LL group. Glycogen content was higher both in L. dorsi and rhomboideus muscles in the LL group. Further, we determined the effects of dietary lysine levels on accumulation of intramuscular fat (IMF) in L. dorsi muscle of finishing pigs. A low lysine diet (lysine content was 0.40%) meeting approximately 70% of the requirement of lysine was given to finishing pigs for two months. IMF contents in L. dorsi of the pigs given the low lysine diet were twice higher than those of the pigs fed on a control diet (lysine content was 0.65%). Finally, we proved that a well known effect of breadcrumbs feeding to enhance IMF of finishing pigs could be attributed to shortage of amino acids in diets including breadcrumbs.

Intramuscular fat content in meat-producing animals: development, genetic and nutritional control, and identification of putative markers

Intramuscular fat (IMF) content plays a key role in establishing pork quality. In the present study, differential-display reverse transcription-polymerase chain reaction (DDRT-PCR) was used to identify differentially expressed (DE) genes between longissimus dorsi (LD) muscles with extremely different IMF content. A major DE gene associated with IMF content was identified as splicing factor serine-arginine rich protein (SFRS18) gene, also known as SRrp130. The gene exhibited relatively higher expression levels in LD muscles with higher IMF content. A full-length cDNA sequence of pig SFRS18 gene was obtained by in silico comparative cloning coupled with PCR target sequencing, while the current EST (expressed sequence tag) database supported two transcript variants of the pig gene. Differential expression of the SFRS18 gene was further confirmed using quantitative PCR. The mRNA levels of SFRS18 gene showed significant and positive correlation with IMF content in LD muscle (r = 0.54, P < 0.01). Collectively, these results suggest that the SFRS18 gene is involved in the regulation of IMF deposition in pig and that it may be a useful tool in selecting animals for desired amounts of fatness for high quality pork.

The aim of this study was to investigate the differentially expressed genes associated with intramuscular fat deposition in the longissimus dorsi muscle of Xinjiang Brown Bulls. The longissimus dorsi muscles of 10 Xinjiang Brown Bulls were selected under the same feeding conditions. The intramuscular fat content of muscle samples was determined by the Soxhlet extraction method, for which 5 samples with high intramuscular fat content (HIMF group) and 5 samples with low intramuscular fat content (LIMF group) were selected. It was found that the intramuscular fat content of the HIMF group was 46.054% higher than that of the LIMF group. Muscle samples produced by paraffin sectioning were selected for morphological observation. It was found that the fat richness of the HIMF group was better than that of the LIMF group. Transcriptome sequencing technology was used to analyze the gene expression differences of longissimus dorsi muscle. Through in-depth analysis of the longissimus dorsi muscle by transcriptome sequencing technology, we screened a total of 165 differentially expressed genes. The results of Gene Ontology (GO) enrichment analysis showed that the differentially expressed genes in the two groups were mainly clustered in biological pathways related to carbohydrate metabolic processes, redox processes and oxidoreductase activities. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that the differentially expressed genes were significantly clustered in 15 metabolic pathways, which mainly covered fatty acid metabolism (related to lipid metabolism and glucose metabolism), the pentose phosphate pathway, the Peroxisome Proliferator-Activated Receptor (PPAR) signaling pathway and other important metabolic processes. The three genes that were predominantly enriched in the glycolipid metabolic pathway by analysis were SCD5, CPT1C and FBP2, all of which directly or indirectly affect intramuscular fat deposition. In summary, the present study investigated the differences in gene expression between high and low intramuscular fat content in the longissimus dorsi muscle of Xinjiang Brown Bulls by transcriptome sequencing technology and revealed the related signaling pathways. Therefore, we hypothesized that SCD5, CPT1C and FBP2 were the key genes responsible for the significant differences in intramuscular fat content of the longissimus dorsi muscles in a population of Xinjiang Brown Bulls. We expect that these findings will provide fundamental support for subsequent studies exploring key genes affecting fat deposition characteristics in Xinjiang Brown Bulls.

Intramuscular fat content in different muscles, locations, weights and genotype-sexes and its prediction in live pigs with computed tomography

The pig p160 co-activator family: Full length cDNA cloning, expression and effects on intramuscular fat content in Longissimus Dorsi muscle

Cloning, expression, and polymorphism of the ECI1 gene in various pig breeds

Pigs of six weeks of age were given a control or low lysine (LL) diet for three weeks. GLUT4 mRNA expression was up‐regulated by the LL diet in l. dorsi and rhomboideus muscles. Activities of citrate synthase were higher in those two muscles of the LL group suggesting that oxidative function of the muscles was enhanced by dietary low lysine. Thus, we determined proportion of oxidative myofiber. Indeed, proportion of oxidative fiber was higher in the LL group than in the control group. As higher triglyceride and/or intramuscular fat (IMF) content are associated with higher proportion of oxidative myofiber, we hypothesized that accumulation of IMF might be promoted by dietary low lysine. To test this hypothesis, a low lysine diet was given to finishing pigs for two months. IMF contents in l. dorsi of the pigs given a low lysine diet were twice higher than those of the control group. We also elucidated effects of dietary lysine levels on expression of adipogenesis related genes in l. dorsi and rhomboideus muscles of growing pigs; abundances of mRNA of PPARγ tended to be higher in the LL group whereas dietary lysine levels did not affect that of C/EBPα. We infer that differentiation of preadipocytes to adipocytes is not involved in promoted accumulation of IMF due to dietary low lysine in porcine muscle.

ABSTRACTThe present study was conducted to elucidate the effect of dietary lysine levels on the intramuscular fat (IMF) content in the Longissimus dorsi (L. dorsi) muscles of finishing gilts. Eleven gilts in total from two litters of pigs aged 110 days were used. The average initial bodyweight of the pigs was 61.7 kg. Six pigs were assigned to the low lysine (LL) diet group (lysine content: 0.43 or 0.40%) and five pigs were assigned to the control group (lysine content: 0.65 or 0.68%). The diets were iso‐energetic and iso‐protein, and contained all essential amino acids (apart from lysine) in the recommended amounts. The pigs were fed these diets until their live weights reached 110 kg. Live weight gain and feed efficiency tended to be lower in the LL group (P = 0.118 andP = 0.052, respectively). Pigs from the LL group took 5 days longer to reach 110 kg (P &lt; 0.01). The IMF content in the L. dorsi of the LL group was twice as high as that of the control group (6.7 vs 3.5%;P &lt; 0.01). The percentage of oleic acid in the L. dorsi of the LL group tended to be higher than that of the control group (P = 0.052), whereas the percentage of linoleic acid and the total percentage of polyunsaturated fatty acids in the L. dorsi were lower (P &lt; 0.05) in the LL group. Free L‐carnitine content in the L. dorsi was lower (P &lt; 0.05) in the LL group. The average abundance of peroxisome proliferator‐activated receptor gamma mRNA in the L. dorsi of the LL group was threefold higher than that of the control group. The leptin mRNA abundance in the L. dorsi of the LL group was 3.3‐fold higher than that of the control group (P &lt; 0.01). These results suggest that a higher activity of adipogenesis may have been involved in the promoted accumulation of IMF in the L. dorsi muscles of pigs, induced by a dietary LL level.

Intramuscular fat (IMF) is an important trait that influences beef quality. In two studies, we examined the possible involvement of the Wnt/β-catenin signaling pathway in IMF deposition in Korean cattle. In study 1, using a group of bulls and steers, we found that castration, a non-genetic factor, decreased (P<0.01) the expression of both the WNT10B and CTNNB1 genes, whereas it increased the expression of the Wnt antagonist secreted frizzled-related proteins 4 (SFRP4, P<0.001) and the adipogenic CCAAT/enhancer binding protein (C/EPB), alpha (CEBPA, P<0.001) and peroxisome proliferator-activated receptor gamma (PPARG, P<0.05) genes in longissimus dorsi muscle (LM) tissue. The WNT10B and CTNNB1 mRNA levels showed strong (P<0.001) negative correlations (r=-0.68 and r=-0.73 respectively) with the IMF content, whereas the SFRP4, CEBPA and PPARG mRNA levels showed strong (P<0.01) positive correlations (r=0.70, 0.70 and 0.64 respectively) with the IMF content. Large variation still exists in the IMF content of steers, implying that genetic factors affect IMF deposition. Using a different group of steers, a correlation analysis in study 2 also showed that the expression of the WNT10B and CTNNB1 genes, and SFRP4 and adipogenic genes was negatively and positively associated with the IMF content respectively. Our findings suggest that downregulation of the Wnt/β-catenin signaling pathway genes, but upregulation of Wnt antagonist SFRP4 and adipogenic gene expression following castration, contributes to increased IMF deposition in the LM. Our results demonstrate that both non-genetic factors (castration) and genetic variation within the steer group affect the gene expression pattern of the Wnt/β-catenin signaling pathway.

We estimated heritability () and genetic and phenotypic correlations for carcass and meat quality traits of longissimus dorsi (LD) and semimembranosus (SM) muscles in 30-mo-old Hanwoo steers. Variance and covariance components were estimated using REML procedures under univariate and bivariate models. The mean carcass weight (CWT), eye muscle area (EMA), back fat thickness (BFT), and marbling score (MS) were 428.20 ± 46.30 kg, 87.38 ± 8.54 cm2, 13.00 ± 5.14 mm, and 5.21 ± 1.56, respectively. The mean CIE reflectance of meat lightness (L*), redness (a*), and yellowness (b*) were 40.01 ± 2.73, 22.37 ± 2.18, and 10.35 ± 1.46, respectively, in LD muscles and 36.33 ± 2.44, 22.91 ± 2.43, and 10.25 ± 1.65, respectively, in SM muscles. The mean Warner-Bratzler shear force (WBSF), intramuscular fat content (IMF), water-holding capacity (WHC), and protein and ash content in LD and SM muscles were 3.84 ± 0.96 and 6.52 ± 1.21 kg, 15.91 ± 4.39 and 5.10 ± 1.94%, 62.07 ± 3.38 and 71.61 ± 2.06%, 20.01 ± 1.39 and 21.34 ± 0.89%, and 0.80 ± 0.10 and 0.93 ± 0.07, respectively. The estimates of CWT, EMA, BFT, and MS were 0.51 ± 0.13, 0.45 ± 0.13, 0.29 ± 0.09, and 0.22 ± 0.08, respectively. The estimates were moderate for meat quality traits and were 0.37 ± 0.12, 0.40 ± 0.12, 0.33 ± 0.10, 0.33 ± 0.10, 0.30 ± 0.11, and 0.24 ± 0.09 for L*, WBSF, IMF, WHC, and protein and ash content, respectively, in LD muscle; estimates from SM muscle were comparatively low (0.08 ± 0.06 to 0.25 ± 0.09). Estimates of for a* and b* were also low (0.08 ± 0.06 to 0.13 ± 0.07). Carcass weight had a moderate, positive genetic correlation with EMA (0.60 ± 0.13) and a weak correlation with MS and BFT. The genetic correlations among the 3 colorimeter variants were strong and positive within and between muscles. Intramuscular fat content had moderate to strong and negative genetic correlations with WBSF (-0.49 ± 0.18), WHC (-0.99 ± 0.01), and protein (-0.93 ± 0.04) and ash content (-0.98 ± 0.06) in LD muscle, whereas the associations were less pronounced in SM muscle. In general, CWT and EMA had low genetic and phenotypic correlations with meat quality traits, which suggests that the traits are independent and have distinct genetic contributions in each muscle. Conversely, with few exceptions, meat quality traits had genetic and phenotypic correlations with MS and BFT. In conclusion, the estimated genetic parameters for carcass and meat quality traits could be used for genetic evaluation and breeding programs in Korean Hanwoo cattle populations.

Meat quality characteristics of springbok ( Antidorcas marsupialis). 2: Chemical composition of springbok meat as influenced by age, gender and production region

The effects of DGAT1 and DGAT2 mRNA expression on fat deposition in fatty and lean breeds of pig

The objective of this study was to investigate the effect of dietary supplementation with thiazolidinedione (TZD) on growth performance and meat quality of finishing pigs. In Experiment 1, 80 castrated finishing pigs (Large White×Landrace, BW = 54.34 kg) were randomly assigned to 2 treatments with 5 replicates of 8 pigs each. The experimental pigs in the 2 groups were respectively fed with a diet with or without a TZD supplementation (15 mg/kg). In Experiment 2, 80 castrated finishing pigs (Large White×Landrace, BW = 71.46 kg) were divided into 2 treatments as designed in Experiment 1, moreover, carcass evaluations were performed. The results from Experiment 1 showed that TZD supplementation could significantly decreased the average daily feed intake (ADFI) (p<0.05) during 0 to 28 d, without impairing the average daily gain (ADG) (p>0.05). In Experiment 2, the ADG was significantly increased by TZD supplementation during 14 to 28 d and 0 to 28 d (p<0.05) and the feed:gain ratio (F:G) was significantly decreased by TZD supplementation during 0 to 28 d (p<0.05). Compared with the control group, TZD group had significantly higher serum triglyceride (TG) concentration at 28h and serum high-density lipoprotein (HDL) levels at 14 d (p<0.05). Moreover, there was an apparent improvement in the marbling score (p<0.10) and intramuscular fat (IMF) content (p<0.10) of the longissimus dorsi muscle in pigs treated by TZD supplementation. Real-time RT-PCR analyses demonstrated that pigs of TZD group had higher mRNA abundance of PPARγ coactivator 1 (PGC-1) (p<0.05) and fatty acid-binding protein 3 (FABP3) (p<0.05) than pigs of control group. Taken together, these results suggested that dietary TZD supplementation could improve growth performance and increase the IMF content of finishing pigs through regulating the serum parameters and genes mRNA abundance involved in fat metabolism.

The genetic variations of the 5′-upstream region and the second intron of the porcineH-FABPgene were investigated by polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) in 256 pigs, including Duroc, Large White, Landrace, Neijiang, Rongchang, Bamei pig, Hanjiang Black, Hanzhong White, and wild pigs. The effect of theH-FABPgene on intramuscular fat (IMF) content was analysed by the least square method. Results showed aHinfI-RFLP in these eight pig breeds and wild pigs, among which Large White, Bamei pig, Hanjiang Black, Hanzhong White and wild pigs presented low polymorphism, while the other breeds had intermediate polymorphism. There were noHaeIII orMspI-RFLPs in the four Chinese local pig breeds tested, but Duroc, Landrace, Large White, Hanzhong White and wild pig displayed polymorphism. Landrace, Large White and wild pigs had low levels ofHaeIII- andMspI-RFLP, while the others had intermediate polymorphism. H-FABP genotypes significantly affected IMF content (P&lt;0.05). IMF content according to H-FABP genotypes wereHH&gt;Hh&gt;hh,DD&lt;Dd&lt;dd,AA&lt;Aa&lt;aa. The genetic effect values were 3.95 (HH), 3.48 (Hh), 3.23 (hh), 2.33 (DD), 2.55 (Dd), 2.97 (dd), 2.34 (AA), 2.76 (Aa) and 3.01 (aa). Results suggest that porcine meat quality may be improved by increasing the frequency of genotypeaa-dd-HHin pig breeds.