Effect of a high dose of CLA in finishing pig diets on fat deposition and fatty acid composition in intramuscular fat and other fat depots

Conjugated linoleic acids inhibit lipid deposition in subcutaneous adipose tissue and alter lipid profiles in serum of pigs

Conjugated linoleic acids (CLAs) have served as a nutritional strategy to reduce fat deposition in adipose tissues of pigs. However, the effects of CLAs on lipid profiles in serum and how these lipid molecules regulate fat deposition are still unclear. In this study, we explored the effects of CLAs on regulating lipid deposition in adipose tissues in terms of lipid molecules and microbiota based on a Heigai pig model. A total of 56 Heigai finishing pigs (body weight: 85.58 ± 10.39 kg) were randomly divided into two treatments and fed diets containing 1% soyabean oil or 1% CLAs for 40 d. CLAs reduced fat deposition and affected fatty acids composition in adipose tissues of Heigai pigs via upregulating the expression of the lipolytic gene (hormone-sensitive lipase, HSL) in vivo and in vitro. CLAs also altered the biochemical immune indexes including reduced content of total cholesterol (TChol), high-density lipoprotein (HDL-C), and low-density lipoprotein (LDL-C) and changed lipids profiles including decreased sphingolipids especially ceramides (Cers) and sphingomyelins (SMs) in serum of Heigai pigs. Mechanically, CLAs may decrease peroxisome proliferator-activated receptorγ (PPARγ) expression and further inhibit adipogenic differentiation in adipose tissues of pigs by suppressing the function of Cers in serum. Furthermore, Pearson's correlation analysis showed HSL expression was positively related to short-chain fatty acids (SCFAs) in the gut (P ≤ 0.05) but the abundance of Cers was negatively related to the production and functions of SCFAs (P ≤ 0.05). CLAs altered the distribution of the lipid in serum and inhibited adipogenic differentiation by suppressing the function of Cers and further decreasing PPARγ expression in adipose tissues of Heigai pigs. Besides, the HSL expression and the abundance of Cers are associated with the production and functions of SCFAs in the gut.

Comparative Transcriptome Analysis Provides Insight into Spatio-Temporal Expression Characteristics and Genetic Regulatory Network in Postnatal Developing Subcutaneous and Visceral Fat of Bama Pig

The depot differences between Subcutaneous Fat (SAF) and Visceral Fat (VAF) are critical for human well-being and disease processes in regard to energy metabolism and endocrine function. Miniature pigs (Sus scrofa) are ideal biomedical models for human energy metabolism and obesity due to the similarity of their lipid metabolism with that of humans. However, the regulation of differences in fat deposition and development remains unclear. In this study, the development of SAF and VAF was characterized and compared in Bama pig during postnatal development (infancy, puberty and adulthood), using RNA sequencing techniques (RNA-Seq). The transcriptome of SAF and VAF was profiled and isolated from 1-, 3- and 6 months-old pigs and identified 23,636 expressed genes, of which 1,165 genes were differentially expressed between the depots and/or developmental stages. Upregulated genes in SAF showed significant function and pathway enrichment in the central nervous system development, lipid metabolism, oxidation-reduction process and cell adhesion, whereas genes involved in the immune system, actin cytoskeleton organization, male gonad development and the hippo signaling pathway were preferentially expressed in VAF. Miner analysis of short time-series expression demonstrated that differentiation in gene expression patterns between the two depots corresponded to their distinct responses in sexual development, hormone signaling pathways, lipid metabolism and the hippo signaling pathway. Transcriptome analysis of SAF and VAF suggested that the depot differences in adipose tissue are not only related to lipid metabolism and endocrine function, but are closely associated with sexual development and organ size regulation.

Supplementing conjugated linoleic acid (CLA) in breeder hens diet increased CLA incorporation in liver and alters hepatic lipid metabolism in chick offspring

This experiment was designed to investigate the effect of supplementing conjugated linoleic acid (CLA) in breeder hens diet on development and hepatic lipid metabolism of chick offspring. Hy-Line Brown breeder hens were allocated into two groups, supplemented with 0 (CT) or 0.5% CLA for 8 weeks. Offspring chicks were grouped according to the mother generation and fed for 7 days. CLA treatment had no significant influence on development, egg quality, and fertility of breeder hens, but darkened the egg yolks in shade and increased yolk sac mass compared to CT group. Addition of CLA resulted in increased body mass and liver mass, and decreased deposition of subcutaneous adipose tissue in chick offspring. The serum triglyceride (TG) and cholesterol (TC) levels of chick offspring were decreased in CLA group. CLA treatment increased the incorporation of both CLA isomers (c9t11 and t10c12) in liver of chick offspring, accompanied by the decreased hepatic TG levels, related to the significant reduction of fatty acid synthase (FAS) and acetyl-CoA carboxylase (ACC) enzyme activities and the increased of carnitine palmitoyltransferase-1 (CPT1) enzyme activity. Meanwhile, CLA treatment reduced the mRNA expression of genes related to fatty acid biosynthesis (FAS, ACC, and sterol regulatory element-binding protein-1c), and induced the expression of genes related to β-oxidative (CPT1, AMP-activated protein kinase, and peroxisome proliferator-activated receptor α) in chick offspring liver. In summary, the addition of CLA in breeder hens diet significantly increased incorporation of CLA in liver of chick offspring, which further regulate hepatic lipid metabolism.

Effects of Combined Supplementation of Conjugated Linoleic Acid, Methionine Chromium, Betaine, and Cysteamine on Meat Tenderness of Rats

A systemic design was carried out to investigate the optimal combination of BET, Met-Cr, CLA, and CS for improving the meat tenderness in rats. A total of 104 six-week old male Sprague-Dawley rats were randomly assigned to 13 treatments with 4 replicates of 2 rats each. The experiments lasted for 5 weeks. The results showed that inclusion of Met-Cr decreased the contents of intramuscular fat (IMF), fat among muscle cells, and lipid droplets inside muscle cells (P < 0.05), and inclusion of CLA or Met-Cr increased the contents of IMF, fat among muscle cells, and lipid droplets inside muscle cells (P < 0.05). CS increased the contents of total collagen (TC) and soluble collagen (SC), and CLA decreased the contents of TC and SC (P < 0.05). The combination of BET and CLA increased IMF and SC contents and decreased TC contents (P < 0.05). The combination of BET and CS could increase fat contents among muscle cells and decrease TC and SC contents (P < 0.05). The combination of CLA and Met-Cr decreased IMF contents (P < 0.05). The combination of CLA and CS, as well as Met-Cr and CS, decreased fat contents among muscle cells (P < 0.05). These combinations may regulate lipogenesis and decrease the deposition of fat in muscles. There existed a significant positive correlation between IMF and SC content, which might indicate that IMF content improves meat's tenderness partly by increasing SC content in muscle.

Effects of dietary n-6/n-3 polyunsaturated fatty acids ratio on growth performance, apparent digestibility, blood lipid profiles, fecal microbiota, and meat quality in finishing pigs

The effects of dietary omega-6 (n-6) to omega-3 (n-3) polyunsaturated fatty acid (PUFA) ratios on growth performance, digestibility, blood lipid profiles, fecal microbial counts, and meat quality in finishing pigs were examined by using linseed and fish oil. A total of 140 crossbred finishing pigs [(Landrace × Yorkshire) × Duroc] were used in a 10 wk trial. Pigs were blocked based on body weight (BW) and sex and randomly allotted to four dietary treatments formulated to have n-6/n-3 ratios of 5/1, 10/1, 15/1, and 17/1 (control). Throughout the experiment, BW, average daily gain, and average daily feed intake were significantly (P < 0.05) increased with a decreased ratio of n-6/n-3 PUFA. Energy digestibility and fecal Lactobacillus count showed a linear (P < 0.05) increase in week 10. The high-density lipoprotein cholesterol and blood triglyceride concentrations increased (P < 0.1) during week 10. However, low-density lipoprotein cholesterol was reduced (P < 0.05) linearly during week 5 and week 10 with a reduction in dietary n-6/n-3 ratio. This study provides a basis for future research on altering n-6/n-3 ratio by using linseed oil and refined fish oil in finishing pigs.

Knockdown of CTRP6 reduces the deposition of intramuscular and subcutaneous fat in pigs via different signaling pathways

The regulation of porcine subcutaneous (SC) and intramuscular (IM) fat deposition significantly affects pork quality and the lean meat percentage of the carcass, respectively. The adipokine C1q/tumor necrosis factor-related protein 6 (CTRP6), plays a significant role in regulating animal fat deposition. The purpose of this study was to understand the effects of CTRP6 gene knockdown in IM and SC adipocytes by RNA-seq analysis. A total of 1830 and 2936 differentially expressed genes (DEGs) were identified in SC and IM adipocytes, respectively. 844 were down- and 2092 were upregulated in SC adipocytes, while 648 were down- and 1182 were upregulated in IM adipocytes. Furthermore, 1778 DEGs were detected only in SC adipocytes, 672 DEGs only in IM adipocytes, and 1158 DEGs in both types of adipocytes. GO analysis indicated that DEGs involved in adipocyte differentiation were significantly enriched in both SC and IM adipocytes following treatment with CTRP6-siRNA. Moreover, KEGG pathway enrichment analysis revealed differences of metabolic regulation between IM and SC adipocytes. With CTRP6-silencing, the signaling pathways related to Ras and arachidonic acid metabolism were significantly enriched in IM adipocytes, while four other signaling pathways, encompassing the TNF, MAPK, p53 and adipokine pathway were specifically enriched in SC adipocytes. Interestingly, the effect of CTRP6-siRNA treatment was attenuated by the specific Ras activator ML-097 in IM adipocytes, while the specific p53 activator SJ-172550 had the corresponding effect in SC adipocytes. Altogether, we suggest that CTRP6 may be a differential regulator of the development and metabolism of IM and SC adipose tissues.

Current feeding strategies to improve pork intramuscular fat content and its nutritional quality

Pork, one of the most consumed meats worldwide, has been facing major challenges regarding its low sensory quality and unhealthy image of fat. This chapter addresses current feeding strategies to ameliorate pork sensory attributes and nutritional quality by increasing intramuscular fat deposition and improving fatty acid composition, respectively. Dietary protein reduction, alone or combined with some components, contributes to satisfy consumer requirements and enhances the competitiveness of the meat industry with higher pork quality and lower production costs. In addition, feeding sources of n-3 polyunsaturated fatty acids to pigs, mainly from marine origin (rich in eicosapentaenoic and docosahexaenoic acids), increases their content in pork, thus improving the health value of its fatty acid profile. In the near future, the inclusion of microalgae and seaweeds in feed represents a promising approach for the maintenance and development of the livestock sector, as an environmental friendly alternative to balance food and feed industries.

Dietary Supplementation with Pioglitazone Hydrochloride and Chromium Methionine Improves Growth Performance, Meat Quality, and Antioxidant Ability in Finishing Pigs

This work was designed to investigate the synergistic effects of pioglitazone hydrochloride (PGZ) and chromium methionine (CrMet) on meat quality, muscle fatty acid profile, and antioxidant ability of pigs. Pigs in four groups were fed a basic diet or basic diet supplemented with 15 mg/kg of PGZ, 200 μg/kg of CrMet, or 15 mg/kg of PGZ + 200 μg/kg of CrMet. In comparison to the control group, the average daily feed intake, feed/gain ratio, and serum high-density lipoprotein level decreased in the PGZ + CrMet group. Dietary PGZ + CrMet supplementation increased carcass dressing percentage, intramuscular fat, and marbling score. The percentages of C18:1ω-9c, C18:2ω-6c, C18:3ω-3, and polyunsaturated fatty acid (PUFA) in the longissimus thoracis muscle were increased in the PGZ + CrMet group. Greater superoxide dismutase and glutathione peroxidase activities were observed in the PGZ + CrMet group compared to the control group. Collectively, these findings suggested that feed with PGZ and CrMet improved the growth performance and meat quality, especially for PUFA proportions and antioxidant ability.

Effects of different dietary n-6:n-3 PUFA ratios on growth performance, blood lipid profiles, fatty acid composition of pork, carcass traits and meat quality in finishing pigs

A total of 72 crossbred pigs [(Landrace × Yorkshire) × Duroc] with an average initial BW of 51.59±1.59 kg were used in this 10-wk feeding trial to investigate the effects of different dietary n-6:n-3 polyunsaturated fatty acids (PUFA) ratios in finishing pigs. Pigs were randomly allotted to 3 dietary treatments (each n=24) with 6 replications and 4 pigs per pen (2 barrows and 2 gilts). Pigs were fed a corn-soybean meal-based diets formulated by replacing soybean oil with linseed oil to achieve n-6:n-3 close to 5:1, 10:1 and 15:1, respectively. The growth performance, carcass traits and meat quality parameters (meat color, sensory evaluation, cooking loss, drip loss, pH, longissimus muscle area and water holding capacity) were not influenced (P>0.10) by various dietary n-6:n-3 ratios. Pigs fed dietary n-6:n-3 PUFA ratios of 5:1 had a lower (P<0.05) serum total cholesterol, LDL cholesterol and triglyceride levels. The concentrations of n-3 PUFA , including C18:3n-3, C22:5n-3 and C22:6n-3 were improved (P<0.05) in the longissimus dorsi muscles of pigs fed dietary n-6:n-3 PUFA ratios of 5:1. Furthermore, pigs fed dietary n-6:n-3 PUFA ratio of 5:1 decreased (P<0.05) the n-6 concentrations (C18:2n-6 and C20:4n-6) of longissimus dorsi muscles. In conclusion, lowering the dietary n-6:n-3 ratios to 5:1 could be beneficial for the blood lipid profiles, and improve the nutritional value of pork, without adverse effect on growth performance and meat quality parameters that are related to the consumer acceptance.

Enhancement of porcine intramuscular fat content by overexpression of the cytosolic form of phosphoenolpyruvate carboxykinase in skeletal muscle

Intramuscular fat (IMF) content has been generally recognized as a desirable trait in pork meat because of its positive effect on eating quality. An effective approach to enhance IMF content in pork is the generation of transgenic pigs. In this study, we used somatic cell nuclear transfer (SCNT) to generate cloned pigs exhibiting ectopic expression of phosphoenolpyruvate carboxykinase (PEPCK-C) driven by an α-skeletal-actin gene promoter, which was specifically expressed in skeletal muscle. Using qRT-PCR and Western blot analysis, we demonstrated that PEPCK-C was functionally expressed and had a significant effect on total fatty acid content in the skeletal muscle of the transgenic pigs, while the n-6/n-3 polyunsaturated fatty acid (PUFA) ratio showed no difference between transgenic and control pigs. Thus, genetically engineered PEPCK-C^mus pigs may be an effective solution for the production of IMF-enriched pork.

M, Laudanović M, Teodorović V, Bošković M, Peurača M, Marković R. Effect of Sunflower, Linseed and Soybean Meal in Pig Diet on Chemical Composition, Fatty Acid Profile of Meat and Backfat, and Its Oxidative Stability

The aim of this study was to examine the effect of added sunflower, linseed or soybean meal to a standard pig fattening diet on the chemical composition, fatty acid profiles of meat and backfat, and on the oxidative stability of backfat from pigs. The content of saturated (SFA) and monounsaturated fatty acids (MUFA) was significantly lower (P<0.01), while content of polyunsaturated fatty acids (PUFA) was significantly higher (P<0.01) in the diet with added linseed. The feeding study was conducted on 30 pigs, with groups of 10 pigs fed one of the three different diets for 46 days before slaughter. There were no differences in the chemical composition (protein, water, fat, minerals) of meat from pigs fed the different diets. The content of SFA and MUFA was significantly higher, while the average PUFA content was significantly lower (P<0.01) in meat and backfat of pigs fed diet with added linseed. The content of n-6 fatty acids was significantly lower and n-3 fatty acids significantly higher, with more desirable n-6/n-3 ratio, in meat and backfat of pigs fed diet with added linseed. Malondialdehyde in the backfat of pigs fed diet with added linseed was significantly lower than that in the other two diet groups after the tissue was stored frozen at −20°C for 3, 6, 9 and 12 months.

Transcriptomic Analysis Identifies Candidate Genes Related to Intramuscular Fat Deposition and Fatty Acid Composition in the Breast Muscle of Squabs (Columba)

Despite the fact that squab is consumed throughout the world because of its high nutritional value and appreciated sensory attributes, aspects related to its characterization, and in particular genetic issues, have rarely been studied. In this study, meat traits in terms of pH, water-holding capacity, intramuscular fat content, and fatty acid profile of the breast muscle of squabs from two meat pigeon breeds were determined. Breed-specific differences were detected in fat-related traits of intramuscular fat content and fatty acid composition. RNA-Sequencing was applied to compare the transcriptomes of muscle and liver tissues between squabs of two breeds to identify candidate genes associated with the differences in the capacity of fat deposition. A total of 27 differentially expressed genes assigned to pathways of lipid metabolism were identified, of which, six genes belonged to the peroxisome proliferator-activated receptor signaling pathway along with four other genes. Our results confirmed in part previous reports in livestock and provided also a number of genes which had not been related to fat deposition so far. These genes can serve as a basis for further investigations to screen markers closely associated with intramuscular fat content and fatty acid composition in squabs. The data from this study were deposited in the National Center for Biotechnology Information (NCBI)’s Sequence Read Archive under the accession numbers SRX1680021 and SRX1680022. This is the first transcriptome analysis of the muscle and liver tissue in Columba using next generation sequencing technology. Data provided here are of potential value to dissect functional genes influencing fat deposition in squabs.

Dietary vitamin A restriction affects adipocyte differentiation and fatty acid composition of intramuscular fat in Iberian pigs

The aim of this study was to investigate whether dietary vitamin A level is associated with differences in adipocyte differentiation or lipid accumulation in Iberian pigs at early growing (35.8kg live weight) and at finishing (158kg live weight). Iberian pigs of 16.3kg live weight were allocated to two feeding groups, one group received 10,000IU of vitamin A/kg diet (control); the other group received a diet with 0IU of vitamin A (var) for the whole experimental period. The dietary vitamin A level had no effect on growth performance and carcass traits. The early suppression of vitamin A increased the preadipocyte number in Longissimus thoracis (LT) muscle in the early growth period (P<0.001) and the neutral lipid content and composition (higher MUFA and lower SFA content) at the end of the finishing period (P<0.05). Vitamin A restriction in young pigs increases their lipogenic potential without affecting carcass traits.

Effect of reducing dietary protein and lysine on growth performance, carcass characteristics, intramuscular fat, and fatty acid profile of finishing barrows

Intramuscular fat is an important quality trait in pork. Lysine and protein have been reported to influence this trait, but most studies have modified both factors simultaneously. In this study, the effects of dietary Lys and protein were investigated in finishing pigs to determine if either of the 2 factors alone or in combination influence the deposition of intramuscular fat. One hundred and four barrows (Landrace × Duroc) were fed 1 of 4 experimental diets, including control protein-control Lys (CPCL), control protein-low Lys (CPLL), low protein-control Lys (LPCL), and low protein-low Lys diets (LPLL) with 10 pens per treatment and 2 or 3 pigs per pen. Pigs fed CPLL showed a trend to decrease feed efficiency (P < 0.10) compared with those fed CPCL, but pigs fed LPLL performed similarly to the CPCL pigs, indicating that CP levels can be reduced to 12% for pigs between 62 and 97 kg and to 9.8% afterward without negative effects on performance. In the longissimus thoracis, intramuscular fat increased in pigs fed LPCL or CPLL (P < 0.05) compared with CPCL. In the semimembranosus muscle, intramuscular fat was reduced in pigs fed LPLL compared with those fed CPLL (P < 0.05), and the same trend was observed in the longissimus thoracis (P < 0.10). Dietary protein reduction tended to increase back fat thickness (P < 0.10) and reduced SFA and MUFA (P < 0.05) and PUFA, particularly in subcutaneous fat (P < 0.05), whereas the effect on MUFA in the longissimus thoracis was less pronounced. A reduction of n-3 FA (P < 0.05) and PUFA (P < 0.01) in the semimembranosus muscle and in the liver, respectively, was observed when the level of dietary protein was reduced. These results indicate that the effect of a reduction of dietary protein and Lys on growth and intramuscular fat is not independent, and reduction of protein, while maintaining Lys, may improve meat quality without impairing performance.