Intramuscular Lipid Research Articles

Adiponectin resistance precedes the accumulation of skeletal muscle lipids and insulin resistance in high-fat-fed rats

High-fat (HF) diets can induce insulin resistance (IR) by altering skeletal muscle lipid metabolism. An imbalance between fatty acid (FA) uptake and oxidation results in intramuscular lipid accumulation, which can impair the insulin-signaling cascade. Adiponectin (Ad) is an insulin-sensitizing adipokine known to stimulate skeletal muscle FA oxidation and reduce lipid accumulation. Evidence of Ad resistance has been shown in obesity and following chronic HF feeding and may contribute to lipid accumulation observed in these conditions. Whether Ad resistance precedes and is associated with the development of IR is unknown. We conducted a time course HF feeding trial for 3 days, 2 wk, or 4 wk to determine the onset of Ad resistance and identify the ensuing changes in lipid metabolism and insulin signaling leading to IR in skeletal muscle. Ad stimulated FA oxidation (+28%, P < or = 0.05) and acetyl-CoA carboxylase phosphorylation (+34%, P < or = 0.05) in control animals but failed to do so in any HF-fed group (i.e., as early as 3 days). By 2 wk, plasma membrane FA transporters and intramuscular diacylglycerol (DAG) and ceramide were increased, and insulin-stimulated phosphorylation of both protein kinase B and protein kinase B substrate 160 was blunted compared with control animals. After 4 wk of HF feeding, maximal insulin-stimulated glucose transport was impaired compared with control. Taken together, our results demonstrate that an early loss of Ad's stimulatory effect on FA oxidation precedes an increase in plasmalemmal FA transporters and the accumulation of intramuscular DAG and ceramide, blunted insulin signaling, and ultimately impaired maximal insulin-stimulated glucose transport in skeletal muscle induced by HF diets.

Alterations in Muscle Attenuation following Detraining and Retraining in Resistance-Trained Older Adults

Background: Aging skeletal muscle is characterized not only by a reduction in size (sarcopenia) and strength but also by an increase in fatty infiltration (myosteatosis). An effective countermeasure to sarcopenia is resistance exercise; however, its effect on fatty infiltration is less clear. Objective: To examine in resistance-trained older persons whether muscle attenuation, a noninvasive measure of muscle density reflecting intramuscular lipid content, is altered with training status. Methods: Thirteen healthy community-dwelling men and women aged 65–83 years (body mass index 27.0 ± 1.2, mean ± SE) had computed-tomography scans of the mid-thigh performed following 24 weeks of training, 24 weeks of detraining, and 12 weeks of retraining. Training and retraining were undertaken twice weekly for several upper- and lower-body muscle groups. Skeletal muscle attenuation in Hounsfield units (HU) as well as mid-thigh muscle volume was obtained for the quadriceps and hamstrings. Muscle strength was assessed by 1-repetition maximum and physical function by a battery of tests. Results: The average change in muscle strength following training, detraining and retraining was 48.8 ± 2.9%, –17.6 ± 1.3%, and 19.8 ± 2.0%, respectively. Strength changes were accompanied by significant alterations in muscle density (p < 0.001), with the quadriceps HU decreasing by 7.7 ± 1.0% following detraining and increasing by 5.4 ± 0.5% with retraining. For the hamstrings HU measure, detraining and retraining resulted in an 11.9 ± 1.4% loss and a 5.5 ± 1.8% gain, respectively. There was no significant change in muscle volume. Conclusion: Cessation of resistance exercise in trained older persons increases the fatty infiltration of muscle, while resumption of exercise decreases it. Monitoring changes in both muscle size and fat infiltration may enable a more comprehensive assessment of exercise in combating age-related muscular changes.

Subcutaneous and intramuscular lipid traits as tools for classifying Iberian pigs as a function of their feeding background

The present work was aimed to study the feasibility of classifying Iberian pigs fattened with two different diets, acorns and grass (AG) and oleic acid enriched concentrate (HO), by means of comparing the fatty acid profile and the content of different compounds of the unsaponifiable lipid fraction (neophytadiene and α- and γ-tocopherol) of subcutaneous (SCF) and intramuscular (IMF) fat of Biceps femoris and Semimembranosus muscles. The proportions of palmitic (C16:0), stearic (C18:0) and linoleic (C18:2 n-6) acids of the three studied tissues did not show a consistent behaviour as influenced by the feeding. The proportion of oleic acid (C18:1 n-9) was significantly affected by the diet in SCF and IMF of Semimembranosus muscle but not in IMF of B. femoris. Some minor fatty acids, such as arachidonic (C20:4 n-6) and linolenic (C18:3 n-3) acids, showed the best ability for the classification of the animals according to their feeding background and the obtained values showed significant differences caused by the diet in the three studied tissues. Neophytadiene and γ-tocopherol contents were statistically higher in AG than in HO pigs, while there were not differences in the α-tocopherol levels between experimental groups. Thus, it seems that procedures based on the quantification of arachidonic (C20:4 n-6) and linoleic (C18:3 n-3) acids as well as neophytadiene and γ-tocopherol levels would be useful to differentiate Iberian pigs fattened outdoors on acorns and grass from those fed MUFA enriched diets.

Intramuscular lipid metabolism, insulin action, and obesity

With the increasing prevalence of obesity, research has focused on the molecular mechanism(s) linking obesity and skeletal muscle insulin resistance. Metabolic alterations within muscle, such as changes in the cellular location of fatty acid transporter proteins, decreased mitochondrial enzyme activity, and defects in mitochondrial morphology, likely contribute to obesity and insulin resistance. These defects are thought to play a role in the reduced skeletal muscle fatty acid oxidation and increased intramuscular lipid (IMCL) accumulation that is apparent with obesity and other insulin-resistant states such as type 2 diabetes. Intramuscular triacylglycerol does not appear to be a ubiquitous marker of insulin resistance, although specific IMCL intermediates such as long-chain fatty acyl-CoAs, ceramide, and diacylglycerol may inhibit insulin signal transduction. In this review, we will briefly summarize the defects in skeletal muscle lipid metabolism associated with obesity, and discuss the proposed mechanisms by which these defects may contribute to insulin resistance.

Carcass, meat quality, and sensory characteristics of heavy body weight pigs fed ractopamine hydrochloride (Paylean)

Carcass characteristics, meat quality traits, and sensory attributes were evaluated in late-finishing barrows and gilts, weighing between 100 to 130 kg of BW, fed 0, 5, or 7.4 mg/kg of ractopamine hydrochloride (RAC) for the final 21 to 28 d before slaughter. Carcass data were collected from carcasses from barrows and gilts (n = 168), and all primal cuts from the right sides of these carcasses were fabricated to calculate primal yields as a percentage of the HCW. Subjective (National Pork Producers Council and Japanese) color, firmness, and marbling scores were determined on the LM of each loin and the semimembranosus muscle (SM) of the ham, whereas the moisture, extractable lipid, Warner-Bratzler shear force (WBSF), and trained sensory evaluations (juiciness, tenderness, and pork flavor) were measured on the LM samples only. Gilts produced heavier (P < 0.05) HCW than barrows, whereas feeding RAC increased (P < 0.05) HCW over pigs fed diets devoid of RAC. Carcasses from gilts also had greater (P < 0.02) primal cut and lean cut (P < 0.01) yields than barrows, and dietary inclusion of 5 mg/kg of RAC increased (P < 0.05) total boneless cut and lean cut yields when compared with carcass from pigs fed 0 or 7.4 mg/kg of RAC. Warner-Bratzler shear forces values were greater (P < 0.05) in the LM of gilts than barrows, but only juiciness scores were greater (P < 0.03) in LM chops from barrows than gilts. The LM from barrows had greater intramuscular lipid (P < 0.001) than the LM from gilts, and even though the LM from pigs fed 5 mg/kg of RAC had greater (P < 0.04) WBSF values than the LM from pigs fed 0 or 7.4 mg/kg of RAC, including RAC in the late-finishing diets for 21 or 28 d did not affect sensory panel rating or percentages of moisture and intramuscular lipid. In summary, addition of RAC in the late-finishing diet improved carcass and primal cut yields when it was fed at 5 and 7.4 mg/kg without altering pork quality traits regardless of whether RAC was fed for 21 or 28 d.

Dietary vitamin A concentration alters fatty acid composition in pigs

This experiment was conducted to study the effect of vitamin A concentration in the diet on fatty acid composition in pigs. One-hundred and twenty eight Duroc × (Large White × Landrace) castrated male pigs were used. Pigs were randomly distributed and located in cages of four pigs each to the following treatment: vitamin A-enriched diet (100,000 IU/kg) ( n = 16) and control diet with a basal level (7500 IU/kg) ( n = 16). The pigs were slaughtered at an average weight of 125.9 kg. No effect of diet vitamin A level on performance, carcass traits and intramuscular fat percentage was observed. The retinol concentration in subcutaneous backfat and retinol and retinol palmitate contents in liver were higher in the pigs that were given the vitamin A enriched diet than in those receiving the control diet. However the vitamin A supplementation did not increase the retinol content in the muscle. Pigs receiving the vitamin A enriched diet showed a higher C16:0 and ∑SFA proportions in the outer layer and C18:0 and ∑SFA proportions in the inner layer. Moreover, the diet rich in vitamin A led to a reduction of C18:1 n−9 and ∑MUFA proportions in subcutaneous backfat inner layer. Dietary vitamin A concentration had not influence on main fatty acids composition of intramuscular lipids. Dietary vitamin A enrichment lead to a higher C16:0, ∑SFA concentration in liver lipids.

Free fatty acids and skeletal muscle insulin resistance

Acute exposure to fatty acids causes insulin resistance in muscle, and excess dietary lipid and obesity are also strongly associated with muscle insulin resistance. Relevant mechanisms, however, are still not fully elucidated. Here we examine the latest evidence as to why lipids might accumulate in muscle and the possible mechanisms for lipid-induced insulin resistance. Muscle lipid metabolites such as long chain fatty acid coenzyme As, diacylglycerol and ceramides may impair insulin signalling directly. Crosstalk between inflammatory signalling pathways and insulin signalling pathways, mitochondrial dysfunction and oxidative stress have also been put forward as major contributors to the development or maintenance of lipid-induced insulin resistance in muscle. Several animal models with gene deletions in pathways of fatty acid synthesis and storage also show increased metabolic rate, reduced intramuscular lipid storage and improved insulin action when challenged with a high lipid load. Studies in genetic and dietary obese animal models, genetically modified animals and humans with obesity or type 2 diabetes suggest plausible mechanisms for effects of fatty acids, lipid metabolites, inflammatory pathways and mitochondrial dysfunction on insulin action in muscle. Many of these mechanisms, however, have been demonstrated in situations in which lipid accumulation (obesity) already exists. Whether the initial events leading to muscle insulin resistance are direct effects of fatty acids in muscle or are secondary to lipid accumulation in adipose tissue or liver remains to be clarified.

A role for altered TLR gene expression in association with increased expression of CD200R in the induction of mucosal tissue CD4 + Treg in aged mice following gavage with a liver extract along with intramuscular monophosphoryl lipid A (MPLA) injection

Previous studies showed a fetal sheep liver extract (FSLE), in association with LPS, injected into aged (>20 months) mice reversed the altered polarization (increased IL-4 and IL-10 with decreased IL-2 and IFN-γ) in cytokine production seen from ConA stimulated lymphoid cells of those mice. Aged mice show a >60% decline in numbers and suppressive function of both CD4 +CD25 +Foxp3 +Treg and so-called Tr3 (CD4 +TGFβ +). Their number/function is restored to levels seen in control (8-week-old) mice by FSLE. We have reported at length on the ability of a novel pair of immunoregulatory molecules, members of the TREM family, namely CD200:CD200R, to control development of dendritic cells (DCs) which themselves regulate production of Foxp3 + Treg. The latter express a distinct subset of TLRs which control their function. We report that a feature of the altered Treg expression following combined treatment with FSLE and monophosphoryl lipid A, MPLA (a bioactive component of lipid A of LPS) is the altered gene expression both of distinct subsets of TLRs and of CD200Rs. We speculate that this may represent one of the mechanisms by which FSLE and MPLA alter immunity in aged mice.

Changes in Fatty Acid Composition of two Muscles from Three Different Iberian × Duroc Genotypes After Refrigerated Storage

The changes of the fatty acid (FA) profile of 2 muscles Longissimus dorsi and Biceps femoris from 3 Iberian × Duroc genotypes were studied: GEN1: ♂ Iberian × ♀ Duroc1, GEN2: ♂ Duroc1 × ♀ Iberian; GEN3: ♂ Duroc2 × ♀ Iberian. GEN1 and GEN2 are reciprocal crosses while the difference between GEN2 and GEN3 is the Duroc sire line. The genotype Duroc1 was selected for the production of dry-cured meat products while the genotype Duroc2 was selected for meat production. Longissimus dorsi and Biceps femoris BF from the reciprocal cross showed similar changes in FAs profile after refrigerated storage. However, the Duroc sire line affected the FA profiles of intramuscular fat (IMF) and lipid fractions since some differences were found between GEN2 and GEN3. Meat from GEN3 had the highest level of polyunsaturated fatty acids (PUFA) in IMF and lipid fractions as well as the lowest rate of plasmalogens in polar lipid fraction. After storage, meat from GEN3 showed an increase of long chain PUFA in free fatty acids fraction and the highest increase in the ratio DMA/FA [(dimethylacetals/FAs) × 100] after the refrigerated storage, which was indicative of a higher deterioration of this genotype. Therefore, the crossbreeding of Iberian pigs with Duroc selected genotypes (Duroc2) could affect the changes in the FAs profile of meat under refrigerated storage.

Lipid composition of meat and backfat from Casertana purebred and crossbred pigs reared outdoors

The study aimed to evaluate, with regard to the human nutrition, the lipid profile of meat and backfat from gilts and barrows of the Italian autochthonous genotype Casertana and its crossbreed (Casertana × Large White) slaughtered at two different live weights. Meat from the Casertana cross was nutritionally comparable to that from the purebreed and both would be considered healthy, irrespective of sex and weight, due to the relatively low levels of intramuscular lipids and cholesterol. Muscle cholesterol was considerably lower in the heavy pigs than in the light ones and, as weight increased, cholesterol decreased but only in gilts. Females supply meat with higher polyunsaturated fatty acids (PUFA) and slightly lower saturated fatty acids (SFA) respect to barrows and, thus, higher PUFA/SFA ratio. Casertana crossbreds can represent a good alternative to pure Casertana, mainly in the production of Colonnata lard, due to the better fatty acid profile of the subcutaneous adipose tissue. From the nutritional point of view, the optimal slaughtering weight was about 150 kg for both genotypes. Heavy pigs, compared to the light ones, produced loin with lower atherogenic and thrombogenic indexes, lower SFA/unsaturated fatty acids ratio, and higher PUFA/SFA ratio.

Intramuscular lipid oxidation and obesity.

There is an accumulating amount of evidence indicating that lipid oxidation is depressed in the skeletal muscle of obese individuals. Decrements in fatty acid oxidation (FAO) have been reported with obesity in models ranging from whole body measurements to isolated skeletal muscle preparations as well as in myotubes raised in culture. This reduction appears to be associated with a depression in the activities of enzymes involved in various steps of lipid oxidation, which subsequently partitions lipid entering the cell toward storage. The defect in FAO in skeletal muscle may be critical in relation to health, as a reduction in the capacity for lipid oxidation could directly or indirectly contribute to the insulin resistance commonly evident with obesity. Although less characterized, a decrement in FAO has also been linked with weight gain, which suggests that this characteristic may be an integral aspect leading to the obese state. In terms of intervention, weight loss does not seem to correct the defect in FAO with obesity. This review will provide evidence supporting a reduction in muscle FAO with obesity.

Effect of high and low glycaemic index recovery diets on intramuscular lipid oxidation during aerobic exercise

Intramyocellular lipid (IMCL) and plasma NEFA are important skeletal muscle fuel sources. By raising blood insulin concentrations, carbohydrate ingestion inhibits lypolysis and reduces circulating NEFA. We hypothesised that differences in the postprandial glycaemic and insulin response to carbohydrates (i.e. glycaemic index; GI) could alter NEFA availability and IMCL use during subsequent exercise. Endurance-trained individuals (n 7) cycled for 90 min at 70 % V O2peak and then consumed either high GI (HGI) or low GI (LGI) meals over the following 12 h. The following day after an overnight fast, the 90 min cycle was repeated. IMCL content of the vastus lateralis was quantified using magnetic resonance spectroscopy before and after exercise. Blood samples were collected at 15 min intervals throughout exercise and analysed for NEFA, glycerol, glucose, insulin, and lactate. Substrate oxidation was calculated from expired air samples. The 90 min cycle resulted in >2-fold greater reduction in IMCL in the HGI trial (3.5 (sem 1.0) mm/kg wet weight) than the LGI trial (1.6 (sem 0.3) mm/kg wet weight, P < 0.05). During exercise, NEFA availability was reduced in the HGI trial compared to the LGI trial (area under curve 2.36 (sem 0.14) mEq/l per h v. 3.14 (sem 0.28) mEq/l per h, P < 0.05 respectively). No other differences were significant. The findings suggest that HGI carbohydrates reduce NEFA availability during exercise and increase reliance on IMCL as a substrate source during moderate intensity exercise.

Productive performance and meat quality of Mouflon × Sarda and Sarda × Sarda suckling lambs

The objective of this study was to compare slaughtering performance, carcass characteristics, and meat quality in lambs of two different genotypes. Sixteen crossbred Mouflon×Sarda (M×S) and sixteen pure Sarda breed (S×S) suckling lambs were analysed. Chemical and fatty acid composition were determined on semitendinosus and longissimus dorsi muscles and perirenal and pelvic fats. Dressing percentage was higher (P<0.01) in M×S group and after histological dissection M×S carcasses had more muscle tissue (P<0.01) and less separable fat (P<0.05). Muscles of M×S had less cholesterol than the S×S lambs (P<0.01). Polyunsaturated/saturated and n−6/n−3 fatty acids ratios of the intramuscular lipids were optimal in both groups. Indexes of atherogenicity and of thrombogenicity in muscles varied between 0.9 and 1.1. The results indicated several good qualities in both the genotypes, but M×S lambs have some traits which could provide a higher market price.

Setting the stage: possible mechanisms by which acute contraction restores insulin sensitivity in muscle

It has long been known that acute exercise can dramatically improve insulin sensitivity in previously insulin-resistant muscle; however, the precise mechanisms underlying this clinically significant interaction remain unknown. Using hindlimb perfusions in obese Zucker rats, our group found that acute muscle contraction synergistically improved insulin-stimulated glucose transport in skeletal muscle, but contrary to our hypothesis, these findings were not associated with either improved insulin signaling or decreased intramuscular lipid metabolites. A further analysis revealed that the improved insulin sensitivity was associated with a robust increase in mitochondrial energy flux. These findings and reports from other labs suggest that mitochondrial energy flux and mitochondrial oxidative capacity may govern insulin sensitivity and override insulin signaling defects associated with obesity. This review will discuss the effects of acute exercise to enhance insulin sensitivity in previously insulin-resistant muscle and present possible novel mechanisms by which alterations in mitochondrial energy metabolism may play a regulatory role.

Adipose triglyceride lipase (ATGL) expression in human skeletal muscle is type I (oxidative) fiber specific

Accumulation of triacylglycerol (TAG) and lipid intermediates in skeletal muscle plays an important role in the etiology of insulin resistance and type 2 diabetes mellitus. Disturbances in skeletal muscle lipid turnover and lipolysis may contribute significantly to this. So far, knowledge on the regulation of muscle lipolysis is limited. Recently the identification of a new lipase was reported: adipose triglyceride lipase (ATGL). ATGL deficient animals show significant lipid accumulation in skeletal muscle, which may indicate that ATGL plays a pivotal role in skeletal muscle lipolysis. However, until now, it is still unknown whether ATGL protein is expressed in human skeletal muscle. Therefore, the aim of the present study was to investigate whether ATGL is expressed at the protein level in human skeletal muscle, and to examine whether its expression is fiber-type specific. To accomplish this, we established an imunohistochemical and immunofluorescent staining procedure to study ATGL protein expression in relation to fiber type in human vastus lateralis muscle of eight male subjects (BMI range: 21.0–34.5 kg/m2 and age: 38–59 years). In the present paper we report for the first time that ATGL protein is indeed expressed in human skeletal muscle. Moreover, ATGL is exclusively expressed in type I (oxidative) muscle fibers, suggesting a pivotal role for ATGL in intramuscular fatty acid handling, lipid storage and breakdown.

Influence of a severe reduction of the feeding level during the period immediately prior to free-range fattening on performance and fat quality in Iberian pigs

BACKGROUND: Restricted feeding before fattening is a common procedure in the production of Iberian pigs, but little scientific information about its consequences on productive traits and characteristics of fat is available. This work studied the effect of a severe feeding restriction previous to the free-range fattening on carcass and fat quality traits in Iberian pigs, considering two different feeding levels (high restriction: HR; versus maintenance level: M) before free-range fattening. RESULTS: Animals from the M group showed longer and higher-perimeter hams and tended (P < 0.10) to show higher slaughter and carcass weights, carcass inner length and loin and sirloin weights than HR ones. Animals from the HR group showed lower proportions of total saturated fatty acids (SFA) and higher total monounsaturated fatty acids in the backfat inner layer than those from the M group. Total polyunsaturated fatty acids in intramuscular neutral lipids were higher in HR pigs than in M ones, while stearic acid (C18:0) was lower. The average daily gain, fatty acid profile of the outer backfat layer and that of the hepatic polar and neutral lipids and the rheological features of backfat inner layer remained unaffected. CONCLUSION: A severe reduction of the feeding level previous to free-range fattening does not produce compensatory growth, tends to diminish carcass quality and to slightly increase IMF content and improves the fatty acid profile of the inner backfat layer. Copyright © 2007 Society of Chemical Industry

Effects of two supplementation levels of linseed combined with CLA or tallow on meat quality traits and fatty acid profile of adipose and different muscle tissues in slaughter pigs

Dietary linseed supply efficiently elevates the linolenic acid concentration of pork. The main problem of increasing the n-3 fatty acid tissue levels arises from a higher susceptibility to lipid oxidation. Increasing the saturation level of tissue lipids by the dietary inclusion of conjugated linoleic acids (CLA) or tallow might prevent oxidation. Thus, the aim of the study was to evaluate the impact of dietary CLA or tallow supplementation combined with extruded linseed on the growth performance, carcass characteristics and fatty acid profile of muscles (longissimus, semimembranosus, biceps femoris) and subcutaneous fat (SF). The enzyme activity of the de novo lipogenesis and stearoyl-CoA desaturase in the SF was also assessed. From 18 to 104 kg BW, 32 Swiss Large White barrows were fed a diet supplemented with either: (1) 2% linseed (L2); (2) 3% linseed (L3); (3) 2% linseed + 1% CLA (L2-C) or (4) 2% linseed + 1% tallow (L2-T). The linolenic and eicosatrienoic acid concentrations were higher (P < 0.01) and the ∑n-6/∑n-3 ratio was lower (P < 0.01) in all tissues of L3 than L2 and L2-T barrows. Only in the SF the docosapentaenoic acid concentration was increased (P < 0.01) in L3 barrows. Compared with the other three diets, feeding the L2-C diets increased (P < 0.01) the amount of myristic, palmitic, stearic and palmitoleic acid at the expense of the oleic and eicosenoic acid content in the intramuscular and SF lipids. Except for the lower (P < 0.05) eicosadienoic acid concentration in the muscles, feeding the L2-C treatment resulted in similar polyunsaturated fatty acid concentrations and ∑n-6/∑n-3 ratio than feeding L2 or L2-T diets. Both the c9,t11- and t10,c12-CLA isomers found in the CLA-supplemented diet were also detected in the tissues, but the c9,t11-isomer was more abundant than the t10,c12-isomer. De novo lipogenesis was not (P > 0.05) affected by the dietary fats, whereas Δ9-desaturase activity was depressed (P < 0.05) by CLA inclusion (L2-C). Only when oxidation was challenged by cooking and subsequent storage for 4 days at 4°C values of thiobarbituric acid-reactive substances were lower (P < 0.05) in longissimus muscle chops of L2-C compared with L2, L3 and L2-T barrows. The present findings revealed that CLA, but not tallow, combined with extruded linseed enhanced the oxidative stability of pork probably by lowering the degree of unsaturation of the lipids without affecting the improved ∑n-6/∑n-3 ratio.

Estudo da influência de diferentes alimentos sobre características quantitativas e qualitativas da gordura em porcos de raça alentejana

In this study, we tested three foodstuffs, complementary to the traditional breeding system (“montanheira”): a commercial foodstuff, a cereal (triticale) and a mixture of triticale, oats and soybean meal. Each foodstuff was given to the Alentejano pigs in order to supply the following digestible energy contents daily: 4250 kcal between 30 and 40 kg of live weight; increasing thereafter until reaching 6800 kcal at 60-70 kg of live weight; and then progressively decreasing until 4800 kcal, at 90-100 kg of live weight. After analysing the results, we found positive correlations between the percentages of palmitic acid (C16:0) and estearic acid (C18:0), both in the L. dorsi muscle and in the subcutaneous adipose tissue. We also found negative correlations between the percentages of oleic (C18:1) and linoleic (C18:2) acids in both tissues. We found significant differences between feedstuffs in what concerned total amount of fat, as well as relative values of C18:1 and C18:2 in subcutaneous fat. Triticale was the feedstuff that led to a larger amount of fat in the carcasses (16,65 ± 1,06 kg). It also led to a greater amount of intramuscular lipids in the L. dorsi muscle (5,54%), even though this difference was statistically non significant. On the other hand, this was the feedstuff that led to a higher C18:1 value (48,76%) and to a lower C18:2 value (5,52%). These characteristics, combined with the ease of production of this feedstuff at the farm, can make triticale an interesting option for organic pig farmers, as long as the amounts fed are restricted, in order not to diminish the commercial worth of carcasses because of excess of fat.

Intramuscular fat content has little influence on the eating quality of fresh pork loin chops1

Fresh pork loins (n = 290) were selected from a commercial packing facility based on subjective marbling of the intact loin and 24-h pH to determine the influence of marbling on sensory attributes. The study was designed using pigs from a similar genetic background, raised in similar production facilities, and slaughtered on a single kill day to minimize the effects of genetics, management, environment, and slaughter day. Loins were vacuum-packaged, transported to the University of Illinois Meat Science Laboratory, and aged for 7 d, after which a chop was removed from the area of the tenth rib for proximate analysis. Quality measurements, including National Pork Producers Council color, marbling, and firmness, ultimate pH, Minolta L*, a*, and b*, and drip loss, were determined after aging. After the proximate composition was completed, 150 loins were selected to provide a continuous and uniform distribution of extractable lipid, ranging from 1 to 8%, and a pH range from 5.5 to 5.8. Trained sensory panel analyses (end point cooking temperatures of 62, 71, or 80 degrees C) as well as measurement of Warner-Bratzler shear force (cooked to 71 degrees C) were performed on chops from the 150 loins. Consumer evaluation was also conducted on a subset (n = 40) of these loins, which were broken down into 5 discrete levels of intramuscular lipid, with averages of 1.6, 2.5, 3.6, 4.5, and 5.7% extractable lipid. Consumers were also asked to select the chops they would most prefer from a retail display case based on the amount of marbling present. Results from the consumer portion of the study indicated that intramuscular fat content had limited effects on perceived tenderness, juiciness, pork flavor, and oiliness; some significant differences (P < 0.05) were detectable, but they were numerically small. Most consumers also selected lean chops from the retail case, with nearly 50% selecting chops with less than 1.7% extractable lipid. Warner-Bratzler shear force was negatively related (P < 0.0001) to extractable lipid, with an R(2) value of 0.10. Results from the trained panel sensory analysis indicate that the percentage of extractable lipid did not correlate strongly with perceived tenderness, juiciness, or pork flavor for this group of pork loins that was controlled for genetics, pH, management, and day of slaughter.

Beef lipids in relation to animal breed and nutrition in Argentina

Fatty acid (FA) composition of intramuscular fat (IMF) in M. Longissimus dorsi (LD) was measured in 72 steers from Angus (A), Charolais×Angus (CHA×A) and Holstein Argentine (HA) breeds. The steers were allotted to four dietary treatments of six animals each: T1, steers grazed on pasture; T2, steers supplemented with cracked corn grain (0.7% of live-weight) daily and free access to pasture; T3, steers supplemented with cracked corn grain (1% of live-weight) daily and free access to pasture; and T4, feedlot (concentrate based on corn, alfalfa hay and soybean meal without access to pasture). At slaughter weight, samples of LD at the 11th rib were used for intramuscular lipid analysis. The diet was shown to be more important than breed in determining FA composition. Pasture beef had higher percentages of saturated fatty acids (SFA), n−3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acid (CLA) and lower percentages of IMF, monounsaturated fatty acids (MUFA), n−6 PUFA and n−6/n−3 ratios than feedlot beef. HA beef presented lower percentages of SFA and more MUFA with a higher n−6/n−3 ratio than A and CHA×A. Comparing grass and feedlot beef the amounts of FA in muscle (mg/100g) were, respectively 18:3 n−3 (44 vs. 11mg), CLA (20 vs. 12mg), 20:5 n−3 (20 vs. 11mg), 22:5 n−5 (20 vs. 11mg), 22:6 n−3 (12 vs. 6mg) and n−3 PUFA (84 vs. 32mg). Feedlot beef has more SFA (1372 vs. 1081mg), MUFA (1574 vs. 1078mg), PUFA (350 vs. 227mg) and n−6 PUFA (318 vs.143mg).