Effect of sex,dietary glycerol or dietary fat during late fattening,on fatty acid composition and positional distribution of fatty acids within the triglyceride in pigs

The effect of sex, source of saturated fat (lard v. palm oil) and glycerol inclusion in the fattening diet on composition and fatty acid positional distribution in the triglyceride molecule was studied in pigs from 78 to 110 kg BW. Average daily gain and carcass characteristics, including ham and loin weight, were not affected by dietary treatment but sex affected backfat depth (P<0.01). A significant interaction between sex and glycerol inclusion was observed; dietary glycerol increased lean content in gilts but not in barrows (P<0.05 for the interaction). Individual and total saturated fatty acid (SFA) concentrations were greater in barrows than in gilts. In contrast, the concentration of total polyunsaturated fatty acids (PUFA) and of C18:2n-6, C18:3n-3, C20:3n-9 and C20:4n-6 in the intramuscular fat (IMF) was higher (P<0.05) in gilts than in barrows. Sex did not affect total monounsaturated fatty acids (MUFA) concentration in the IMF. The proportion of SFA in the subcutaneous fat (SF) was higher in barrows than in gilts (P<0.001). Within the individual SFA, sex affected only the concentrations of C14:0 and C16:0 (P<0.001). Dietary fat did not affect total SFA or PUFA concentrations of the IMF but the subcutaneous total MUFA concentration tended to be higher (P=0.079) in pigs fed lard than in pigs fed palm oil. Dietary glycerol increased total MUFA and C18:1n-9 concentration in the IMF and increased total MUFA and decreased C18:2n-6, C18:3n-3 and total PUFA concentrations in the SF. The data indicate that altering the fatty acid composition of the triglyceride molecule at the 2-position, by dietary intervention during the fattening phase, is very limited.     

Evolution of the fatty acid profile of subcutaneous back-fat adipose tissue in growing Iberian and Landrace × Large White pigs

The lipid content and fatty acid (FA) profile in pig tissues are strongly influenced by genotype and nutrient supply, with implications in meat quality. The de novo lipid synthesis and pattern of FA unsaturation could be an important cause of variation in the overall efficiency of energy utilization among breeds. To test the effects of pig genotype and CP supply on the evolution of back-fat tissue FA profile throughout the growing and finishing stages, 32 Iberian (IB) and Landrace × Large White (LR × LW) barrows were offered one of two diets differing in CP content (13% or 17% as fed). A pair-fed procedure (0.8 × ad libitum intake of IB pigs) was used. Subcutaneous fat samples were taken at the dorso-lumbar region at ∼38, 50, 65, 90 and 115 kg BW. Higher proportions of total monounsaturated FA (MUFA; P < 0.01) and lower proportions of total saturated FA (SFA; P < 0.01 to 0.05) were found in the outer back-fat layer of pigs both at 50 and 115 kg BW. Pig genotype affected the FA composition of both subcutaneous back-fat layers. The proportions of C18:0 and SFA in fat tissue were higher in IB than in LR × LW pigs from 38 to 65 kg BW, especially in the outer layer. In addition, MUFA contents were higher in IB pigs at 115 kg BW in both layers (+5% on average; P < 0.01). Increased proportions of C18:2 n-6 and polyunsaturated FA (PUFA) were found in LR × LW pigs, irrespective of the stage of growth and back-fat layer (P⩽0.02). At 50 kg BW, pigs receiving the high-protein diet presented the highest C18:2 n-6, C18:3 n-3, C20:5 n-3 and PUFA contents. A significant genotype × CP content interaction was observed for C18:3 n-3 because of the increased concentration of this FA in LR × LW pigs when offered the 17% CP diet (P < 0.05). Higher C16:0 and SFA contents (+5%; P = 0.03) were found in pigs offered the 13% CP diet and slaughtered at 115 kg BW. There was a genotype × CP interaction for MUFA concentration because of the higher MUFA content observed in IB pigs offered the highest protein content diet (P = 0.03). Our results suggest that genetic variation in de novo lipid synthesis and pattern of FA unsaturation might contribute to explain differences in back-fat FA profile of IB and LR × LW pigs under identical nutritional management. They could be also relevant to explain the low efficiency of nutrient and energy utilization in the IB pig.     

Brain protection by rapeseed oil in magnesium-deficient mice

Diets given for 30 days with various mono-(MUFA) and poly-(PUFA) unsaturated fatty acid contents were evaluated for brain protection in magnesium-deficient mice: a commercial and three synthetic diets (n-6PUFA, n-3PUFA and MUFA-based chows enriched with 5% corn/sunflower oils 1:3, with 5% rapeseed oil and with 5% high oleic acid sunflower oil/sunflower oil 7:3, respectively). Unlike magnesium deprivation, they induced significant differences in brain and erythrocyte membrane phospholipid fatty acid compositions. n-3PUFA but not other diets protected magnesium-deficient mice against hyperactivity and moderately towards maximal electroshock- and NMDA-induced seizures. This diet also inhibited audiogenic seizures by 50%, preventing animal deaths. Because, like n-6PUFA diet, matched control MUFA diet failed to induce brain protections, alpha-linolenate (ALA) rather than reduced n-6 PUFA diet content is concluded to cause n-3PUFA neuroprotection. Present in vivo data also corroborate literature in vitro inhibition of T type calcium channels by n-3 PUFA, adding basis to ALA supplementation in human anti-epileptic/neuroprotective strategies.     

Maternal grazing on stubble and Mediterranean shrubland improves meat lipid profile in light lambs fed on concentrates

Concentrates-fed lamb meat is often associated with an unfavourable lipid profile (high levels of saturated and/or n-6 polyunsaturated fatty acids; SFA and PUFA). For this reason, Spanish sheep producers from Mediterranean areas are turning to traditional grazing by ewes to obtain healthier lamb meat. The objective of this research was to determine the effects of maternal grazing on the fatty acid (FA) composition of weaned lamb meat. The ewes (Segureña breed) were allocated to two different rearing systems during pregnancy (5 months) and lactation (45 days): (i) feeding indoors on barley grain and lucerne pellets; (ii) grazing on cereal stubble, fallow land and seasonal pastures consisting of Mediterranean shrubs, herbs and trees. Two groups of 20 autumn and spring lambs were sampled. The lambs were weaned at 13.1±0.9 kg and 45.0±4.1 days age and fed on grain-based concentrates until they reached 24.8±2.1 kg live weight (light lambs slaughtered at 98.3±3.6 days of age). The FA content was determined in the intramuscular loin fat by gas chromatography using a flame ionization detector. The ewe diet did not affect the levels of the main lamb FAs (C18:1c+t, C16:0 and C18:2c), and so did not provide any additional reduction in fat saturation. Saturated fatty acids represented around 40% of total FAs determined in the meat. Ewe grazing acted as an n-3 PUFA-promoting diet, providing a lamb meat with a lower n-6/n-3 ratio. Spring lamb meat had higher proportions of n-3 PUFA (C18:3n-3, C20:5, C22:5 and C22:6) and conjugated linoleic acid (C18:2c9t11+c11t9) to the detriment of the n-6 PUFAs (C20:4, C20:2 and C22:4), while autumn lamb meat also had higher levels of C18:3n-3 and C18:3n-6, and lower level of C20:4, which points to little seasonal differences. The n-6/n-3 ratio achieved by ewe grazing fell from 8.2 to 4.1 (Spring) and from 7.6 to 5.5 (Autumn), values which are close to those recommended in human diet for good cardiovascular health. These n-6/n-3 reductions were associated with lower levels of total PUFA and C20:4n-6. Our research concluded that grazing on stubble and Mediterranean shrubland by ewes, a sustainable rearing practice involving local agro resources, contributed to obtaining weaned lamb meat with a more favourable lipid profile and so can be recommended to sheep farmers.     

Feeding level in the period previous to the late fattening phase influences fat composition at slaughter in free-ranged Iberian pigs

A group of 11 pigs was fed with 70 g feed per kg of metabolic weight (H pigs) and another group of 11 pigs was fed with 50g feed per kg of metabolic weight (L pigs). In both experimental groups (H and L pigs), it was observed that the higher initial proportion of C16:0, C18:0 and C18:2 (n-6) in backfat at the beginning of the free-range feeding period, the greater decrease rate of these fatty acid proportions regarding weight gain during the free-range fattening period took place. On the other hand, the greater initial proportion of C18:1 (n-9), the smaller increase rate in the concentration of this fatty acid was observed. The intramuscular neutral lipids from L pigs had higher C18:3 (n-3) and lower proportions of monounsaturated fatty acids (MUFA) than those from H pigs, while intramuscular polar lipids from L pigs had significantly higher proportions of C18:0, PUFA, C18:3 (n-3) and (n-3) and significantly lower MUFA and C18:1 (n-9) proportions than those from H pigs. The alpha-tocopherol concentration found in Longissimus dorsi from L pigs was significantly higher (p < 0.012) than those from H pigs.     

Fatty acid composition of membrane bilayers: Importance of diet polyunsaturated fat balance

In one of the most extensive analyses to date we show that the balance of diet n-3 and n-6 polyunsaturated fatty acids (PUFA) is the most important determinant of membrane composition in the rat under 'normal' conditions. Young adult male Sprague-Dawley rats were fed one of twelve moderate-fat diets (25% of total energy) for 8weeks. Diets differed only in fatty acid (FA) profiles, with saturate (SFA) content ranging 8-88% of total FAs, monounsaturate (MUFA) 6-65%, total PUFA 4-81%, n-6 PUFA 3-70% and n-3 PUFA 1-70%. Diet PUFA included only essential FAs 18:2n-6 and 18:3n-3. Balance between n-3 and n-6 PUFA is defined as the PUFA balance (n-3 PUFA as % of total PUFA) and ranged 1-86% in the diets. FA composition was measured for brain, heart, liver, skeletal muscle, erythrocytes and plasma phospholipids, as well as adipose tissue and plasma triglycerides. The conformer-regulator model was used (slope=1 indicates membrane composition completely conforming to diet). Extensive changes in diet SFA, MUFA and PUFA had minimal effect on membranes (average slopes 0.01, 0.07, 0.07 respectively), but considerable influence on adipose tissue and plasma triglycerides (average slopes 0.27, 0.53, 0.47 respectively). Diet balance between n-3 and n-6 PUFA had a biphasic influence on membrane composition. When n-3 PUFA<10% of total PUFA, membrane composition completely conformed to diet (average slope 0.95), while diet PUFA balance>10% had little influence (average slope 0.19). The modern human diet has an average PUFA balance ~10% and this will likely have significant health implications.     

Effect of Dietary Mono- and Polyunsaturated Fatty Acids on the Fatty Acid Composition of Pigs' Adipose Tissues

In two experiments with growing-finishing pigs six different dietary fats were added to a conventional diet (control - C) to study the effects of dietary monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) on the fatty acid composition of backfat and kidney fat at similar amounts of double bonds in feed (Exp. 1:7% pork fat - PF, 4.95% olive oil - OO, 3.17% soybean oil - SO) or a constant amount of 5% of processed fats (Exp. 2: partially hydrogenated fat - SAT, fractionated pork fats: olein - OLE, stearin - STE). Compared with the control, PUFA were only slightly increased in backfat of pigs fed PF, OLE, STE or OO, although dietary PUFA intake was up to 70% higher. With SO PUFA were significantly increased in adipose tissues, predominantly at the expense of MUFA. Consequently, a non-linear relationship was found between PUFA intake and proportion in backfat. MUFA were incorporated at the expense of SFA, therefore, adipose tissues of OO fed animals were lowest in SFA. Despite comparable amounts of double bonds in feed (Exp. 1), the degree of unsaturation measured as fat score (sum of double bonds) was in the order SO > OO > PF > C. In contrast, the proportion of SFA was C > PF = SO > OO. Regarding the decisive role of SFA for fat consistency it may be concluded that MUFA should also be considered in feeding recommendations for pigs. Furthermore, in case of a high dietary supply of MUFA, a simple index of double bonds might not be sufficiently conclusive to judge pig fat quality.     

Brain anticonvulsant protection of mice given chronic carbamazepine under various fatty acid and magnesium diet conditions

The anticonvulsant and mood stabilizer drug carbamazepine (CBZ) was evaluated for anti-seizure activity after drug pretreatment of young weaning mice given various oil-based diets. These diets had various mono-(MUFA) and poly-(PUFA) unsaturated fatty acid contents, were associated or not with magnesium deprivation, and were given over the entire experimental period (34 days). The diets included a commercial and three purified synthetic diets (n-6 PUFA, n-3 PUFA and MUFA-based chows containing 5% corn/sunflower oils 1:3, 5% rapeseed oil and 5% high oleic acid sunflower oil/sunflower oil 7:3, respectively). A 10-days CBZ treatment (50mg/kg/day fragmented in two daily intraperitoneal injections of 25mg/kg) was given 20 days after initiating diet administration and evaluations of mice was performed 4 days after arrest of CBZ in various seizure tests. In these conditions, CBZ pretreatment still exhibited anticonvulsant protection especially in magnesium-deficient animals. Ethosuximide (ESM)-like profiles under MUFA and n-3 PUFA diets and unusual GABA(A)ergic profile under n-6 PUFA diet in magnesium-deficiency dependent audiogenic seizures (MDDAS) test as well as protection against NMDA-induced seizures in all lipid (n-3 PUFA>MUFA and n-6 PUFA) diet conditions were observed in CBZ-pretreated mice. By highlighting ESM-like and anti-NMDA mechanisms previously induced by an n-3 PUFA diet, present CBZ anticonvulsant properties suggest brain protective targets common to CBZ and n-3 PUFAs.     

Feeding level in the period previous to the late fattening phase influences fat composition at slaughter in free-ranged Iberian pigs

Abstract

A group of 11 pigs was fed with 70 g feed per kg of metabolic weight (H pigs) and another group of 11 pigs was fed with 50 g feed per kg of metabolic weight (L pigs). In both experimental groups (H and L pigs), it was observed that the higher initial proportion of C16:0, C18:0 and C18:2 (n-6) in backfat at the beginning of the free-range feeding period, the greater decrease rate of these fatty acid proportions regarding weight gain during the free-range fattening period took place. On the other hand, the greater initial proportion of C18:1 (n-9), the smaller increase rate in the concentration of this fatty acid was observed. The intramuscular neutral lipids from L pigs had higher C18:3 (n-3) and lower proportions of monounsaturated fatty acids (MUFA) than those from H pigs, while intramuscular polar lipids from L pigs had significantly higher proportions of C18:0, PUFA, C18:3 (n-3) and (n-3) and significantly lower MUFA and C18:1 (n-9) proportions than those from H pigs. The α-tocopherol concentration found in Longissimus dorsi from L pigs was significantly higher (p < 0.012) than those from H pigs.     

Different fatty acid composition in central and peripheral adipose tissues of the American mink (Mustela vison)

Fatty acid (FA) composition in the intraabdominal (IAB), subcutaneous (SC) and peripheral adipose tissues of the semiaquatic American mink (Mustela vison) was examined in comparison to the diet by gas-liquid chromatography. There was a clear compositional gradient from the IAB via SC to peripheral adipose tissues and the anatomically different adipose tissues accumulated or metabolized FA selectively. The total lipids of the body appendages had smaller proportions of saturated (SFA) and larger proportions of monounsaturated (MUFA) and polyunsaturated fatty acids (PUFA) than the lipids of the trunk adipose tissues. Especially n-3 PUFA were enriched in the periphery. The appendages were also characterized with a high ratio of unsaturated FA to SFA, an increased Delta9-desaturation index and increased mean numbers of double bonds and carbon atoms in a FA molecule. The proportions of SFA and MUFA of the diet resembled the trunk adipose tissues while the dietary percentage of n-3 PUFA surpassed those of the trunk fat depots but was lower than those of the peripheral fats. These data confirm that the FA signatures of mammals reflect not only their dietary history but also metabolic modifications of ingested FA.     

Genetic parameters of backfat fatty acids and carcass traits in Large White pigs

Subcutaneous fat thickness and fatty acid composition (FAC) play an important role on seasoning loss and organoleptic characteristics of seasoned hams. Dry-cured ham industry prefers meats with low contents of polyunsaturated fatty acids (PUFA) because these negatively affect fat firmness and ham quality, whereas consumers require higher contents in those fatty acids (FA) for their positive effect on human health. A population of 950 Italian Large White pigs from the Italian National Sib Test Selection Programme was investigated with the aim to estimate heritabilities, genetic and phenotypic correlations of backfat FAC, Semimembranosus muscle intramuscular fat (IMF) content and other carcass traits. The pigs were reared in controlled environmental condition at the same central testing station and were slaughtered at reaching 150 kg live weight. Backfat samples were collected to analyze FAC by gas chromatography. Carcass traits showed heritability levels from 0.087 for estimated carcass lean percentage to 0.361 for hot carcass weight. Heritability values of FA classes were low-to-moderate, all in the range 0.245 for n-3 PUFA to 0.264 for monounsaturated FA (MUFA). Polyunsaturated fatty acids showed a significant genetic correlation with loin thickness (0.128), backfat thickness (−0.124 for backfat measured by Fat-O-Meat’er and −0.175 for backfat measured by calibre) and IMF (−0.102). Obviously, C18:2(n-6) shows similar genetic correlations with the same traits (0.211 with loin thickness, −0.206 with backfat measured by Fat-O-Meat’er, −0.291 with backfat measured by calibre and −0.171 with IMF). Monounsaturated FA, except with the backfat measured by calibre (0.068; P<0.01), do not show genetic correlations with carcass characteristics, whereas a negative genetic correlation was found between MUFA and saturated FA (SFA; −0.339; P<0.001). These results suggest that MUFA/SFA ratio could be increased without interfering with carcass traits. The level of genetic correlations between FA and carcass traits should be taken into account in dealing with the development of selection schemes addressed to modify carcass composition and/or backfat FAC.     

Effects of feeding and rearing systems on growth, carcass composition and meat quality in pigs

Animal growth performance and quality of pork depend on the interactive effects of pig genotype, rearing conditions, pre-slaughter handling, and carcass and meat processing. This paper focuses on the effects of feeding and rearing systems (feeding level and diet composition, housing, production system, etc.) on growth performance, carcass composition, and eating and technological qualities of pork. The feeding level and protein : energy ratio can be used to manipulate growth rate or composition of weight gain. Restricted feed allowance strongly reduces growth rate and carcass fatness and also intramuscular fat (IMF) level, resulting in decreased meat tenderness or juiciness. Expression of compensatory growth due to restricted followed by ad libitum feeding modifies the composition of weight gain at both carcass and muscle levels, and may improve meat tenderness due to higher in vivo protein turnover. Decreasing the protein : energy ratio of the diet actually increases IMF and improves eating quality, but gives fatter carcasses. In contrast, a progressive reduction in the protein : energy ratio leads to similar carcass composition at slaughter but with higher IMF. Technological meat traits (pH1, pHu, colour, drip loss) are generally not affected by the level or protein : energy in feed. Modification of fatty acid composition and antioxidant level in meat can be obtained through diet supplementations (e.g. vegetable sources with high n-3 fatty acids), thereby improving the nutritional quality of pork. Influences of pig rearing system on animal performance, carcass and meat traits result from interactive effects of housing (floor type, space allowance, ambient temperature, physical activity), feeding level and genotype in specific production systems. Indoor enrichment (more space, straw bedding) generally increases growth rate and carcass fatness, and may improve meat juiciness or flavour through higher IMF. Outdoor rearing and organic production system have various effects on growth rate and carcass fatness, depending on climatic conditions and feed allowance. Influence on meat quality is also controversial: higher drip and lower pHu and tenderness have been reported, whereas some studies show improved meat juiciness with outdoor rearing. Discrepancies are likely due to differences between studies in rearing conditions and physiological responses of pigs to pre-slaughter handling. Specific production systems of the Mediterranean area based on local breeds (low growth rate, high adiposity) and free-range finishing (pasture, forests), which allows pig to express their genetic potential for IMF deposition, clearly demonstrate the positive effects of genotype × rearing system interactions on the quality of pork and pork products.     

Reduced protein diets increase intramuscular fat of psoas major,a red muscle,in lean and fatty pig genotypes

The present study aims to assess the effects of pig’s genotype (lean v. fatty) and dietary protein level (control v. reduced) on intramuscular fat (IMF) content, fatty acid composition and fibre profile of psoas major, a representative red muscle in pig’s carcass scarcely studied relative to white longissimus lumborum. The experiment was conducted on 40 intact male pigs (20 Alentejana purebred and 20 Large White×Landrace×Pietrain crossbred) from 60 to 93 kg of live weight. Pigs were divided and allocated to four dietary groups: control protein diet equilibrated for lysine (17.5% of CP and 0.7% of lysine) and reduced protein diet (RPD) not equilibrated for lysine (13.1% of crude protein and 0.4% of lysine) within a 2×2 factorial arrangement (two genotypes and two diets). Alentejana purebred had higher IMF content (15.7%) and monounsaturated fatty acids (MUFA) (8.9%), whereas crossbred pigs had higher PM weight (46.3%) and polyunsaturated fatty acids (PUFA) (20.1%). The genotype also affected colour with higher lightness (15.1%) and yellowness (33.8%) and lower redness (9.9%) scores in crossbred pigs. In line with this, fatty pigs displayed more oxidative fibres (29.5%), whilst lean pigs had more glycolytic (54.4%). Relative to fatty acids, RPD increased MUFA (5.2%) and SFA (3.2%) but decreased PUFA (14.8%). Ultimately, RPD increased IMF content (15.7%) in the red muscle under study, with no impact on glycolytic to oxidative fibre type transformation.     

Tissue fatty acid composition of pigs fed different fat sources

Dietary fat influences the physico-chemical properties of meat, and fatty acid (FA) composition may have implications on human health. The objectives of the experiment were to study tissue FA partitioning and the effect of dietary fat source on tissue FA composition. Seventy crossbred gilts (61.8 ± 5.2 kg BW average) were fed one of seven treatments: a diet containing a very low level of fat (no fat (NF)) and six fat-supplemented diets (10%: tallow (T), high-oleic sunflower oil (HOSF), sunflower oil (SFO), linseed oil (LO), fat blend (FB: 55% tallow, 35% SFO, 10% LO) and fish oil blend (FO: 40% fish oil, 60% LO). Differential tissue FA depositions were observed, with flare fat being the most saturated, followed by intermuscular, and subcutaneous being the least saturated. Monounsaturated fatty acid (MUFA) deposition showed an opposite tissue pattern. Subcutaneous fat showed the highest MUFAs, intermuscular fat showed intermediate values and flare fat showed the lowest MUFAs. Intramuscular polyunsaturated fatty acid (PUFA) content was less susceptible to dietary treatment modifications compared with other depots. Significant tissue FA modifications were observed due to dietary treatments, mainly in diets rich in PUFA. The saturated fatty acids (SFA) were high in NF-fed and low in HOSF-fed animals, MUFA were high in HOSF-fed and low in SFO-, LO- and FO-fed animals, while PUFA were high in SFO- and LO-fed and low in HOSF-, T- and NF-fed animals. Pigs fed LO and FB showed detectable levels of EPA, which depended on the linolenic content of the diet. The only effective way to increase tissue DHA contents was to add DHA in the diet through FO feeding. Araquidonic acid was high in SFO diets and low in LO and FB diets, and also high in intramuscular fat compared with other tissues. EPA and DHA were also high in intramuscular fat compared with other fat depots. The deposition of oleic and linoleic acids depended on the composition of dietary fat, as their deposition varied between diets, even at similar levels of intake of each FA. The NF diet resulted in the greatest proportion of SFAs (palmitic and stearic) of all treatments tested. SFAs were less susceptible to modification than MUFA in response to the different PUFA levels supplemented in the diet. T resulted in less fat deposition in some of the fat depots and more in others, suggesting that T could partition fat differently among fat depots.     

饥饿胁迫对瓦氏黄颡鱼脂肪代谢的影响

在水温(252)℃条件下, 对初始体重为(23.652.82) g的瓦氏黄颡鱼进行30d饥饿处理, 于饥饿第0、第7、第15和第30天取样, 分析了饥饿胁迫对瓦氏黄颡鱼的生长、体成分、脂肪酸组成和脂肪代谢相关基因表达的影响. 结果表明: 饥饿胁迫显著降低了瓦氏黄颡鱼肥满度、脂体比及肝体指数(p0.05). 肌肉脂肪含量也随着饥饿时间的延长而下降(p0.05). 肝脏中的饱和脂肪酸和肌肉中的单不饱和脂肪酸显著下降, 而肝脏中多不饱和脂肪酸和单不饱和脂肪酸及肌肉中的多不饱和脂肪酸显著上升(p0.05). 此外, 肌肉中的n-6和n-3及肝脏中的n-6多不饱和脂肪酸显著上升, 而肝脏中的n-3多不饱和脂肪酸显著下降(p0.05), 表明瓦氏黄颡鱼饥饿期间主要消耗饱和脂肪酸及单不饱和脂肪酸供能, 保留多不饱和脂肪酸. 饥饿胁迫15-30d, 瓦氏黄颡鱼肝脏脂蛋白酯酶、肝酯酶及肉碱酰基转运酶mRNA表达显著高于对照组(0d)(p0.05), 而脂肪酸结合蛋白及脂肪酸合成酶mRNA的表达显著低于对照组(p0.05), 表明饥饿胁迫可能会促进肝脏脂肪分解供能, 降低脂肪的生物合成.       

Genome-Wide Association Study Singles Out SCD and LEPR as the Two Main Loci Influencing Intramuscular Fat Content and Fatty Acid Composition in Duroc Pigs

Intramuscular fat (IMF) content and fatty acid composition affect the organoleptic quality and nutritional value of pork. A genome-wide association study was performed on 138 Duroc pigs genotyped with a 60k SNP chip to detect biologically relevant genomic variants influencing fat content and composition. Despite the limited sample size, the genome-wide association study was powerful enough to detect the association between fatty acid composition and a known haplotypic variant in SCD (SSC14) and to reveal an association of IMF and fatty acid composition in the LEPR region (SSC6). The association of LEPR was later validated with an independent set of 853 pigs using a candidate quantitative trait nucleotide. The SCD gene is responsible for the biosynthesis of oleic acid (C18:1) from stearic acid. This locus affected the stearic to oleic desaturation index (C18:1/C18:0), C18:1, and saturated (SFA) and monounsaturated (MUFA) fatty acids content. These effects were consistently detected in gluteus medius, longissimus dorsi, and subcutaneous fat. The association of LEPR with fatty acid composition was detected only in muscle and was, at least in part, a consequence of its effect on IMF content, with increased IMF resulting in more SFA, less polyunsaturated fatty acids (PUFA), and greater SFA/PUFA ratio. Marker substitution effects estimated with a subset of 65 animals were used to predict the genomic estimated breeding values of 70 animals born 7 years later. Although predictions with the whole SNP chip information were in relatively high correlation with observed SFA, MUFA, and C18:1/C18:0 (0.48–0.60), IMF content and composition were in general better predicted by using only SNPs at the SCD and LEPR loci, in which case the correlation between predicted and observed values was in the range of 0.36 to 0.54 for all traits. Results indicate that markers in the SCD and LEPR genes can be useful to select for optimum fatty acid profiles of pork.     

Effect of selected plant species within biodiverse pasture on in vitro fatty acid biohydrogenation and tissue fatty acid composition of lamb

The effect of botanical diversity on supply of polyunsaturated fatty acids (PUFA) to ruminants in vitro, and the fatty acid (FA) composition of muscle in lambs was investigated. Six plant species, commonly grown as part of UK herbal ley mixtures (Trifolium pratense, Lotus corniculatus, Achillea millefolium, Centaurea nigra, Plantago lanceolata and Prunella vulgaris), were assessed for FA profile, and in vitro biohydrogenation of constituent PUFA, to estimate intestinal supply of PUFA available for absorption by ruminants. Modelling the in vitro data suggested that L. corniculatus and P. vulgaris had the greatest potential to increase 18:3n-3 supply to ruminants, having the highest amounts escaping in vitro biohydrogenation. Biodiverse pastures were established using the six selected species, under-sown in a perennial ryegrass-based sward. Lambs were grazed (~50 days) on biodiverse or control pastures and the effects on the FA composition of musculus longissimus thoracis (lean and subcutaneous fat) and musculus semimembranosus (lean) were determined. Biodiverse pasture increased 18:2n-6 and 18:3n-3 contents of m. semimembranosus (+14.8 and +7.2 mg/100 g tissue, respectively) and the subcutaneous fat of m. longissimus thoracis (+158 and +166 mg/100 g tissue, respectively) relative to feeding a perennial ryegrass pasture. However, there was no effect on total concentrations of saturated FA in the tissues studied. It was concluded that enhancing biodiversity had a positive impact on muscle FA profile reflected by increased levels of total PUFA.     

Effect of low- and high-forage diets on meat quality and fatty acid composition of Alentejana and Barrosã beef breeds

This study investigated the effects of genotype and diet on meat fat composition and palatability obtained from Alentejana (AL) and Barrosã (BA) breeds. Herein, 20 males from each breed allocated at 11 months of age were fed ad libitum a low-forage diet or a high-forage diet and slaughtered at 18 months of age. Trained sensory panel analysis found that the longissimus lumborum (Ll) muscle from BA had higher tenderness, juiciness and overall acceptability scores than the AL breed. The highest scores for those attributes were observed in the BA breed fed the high-forage diet. Regarding the semitendinosus (St) muscle, breed was a source of variation of tenderness scores. In contrast to the Ll muscle, the highest tenderness scores for the St muscle were observed in the AL breed. The intramuscular fat (IMF) content was positively correlated with tenderness, juiciness and overall acceptability in Ll muscle and negatively correlated with flavour in the St muscle. The levels of 14:0 and 16:0, 16:1c9, 18:1c9 and 18:1c11 were positively correlated to juiciness, tenderness and overall acceptability in the Ll muscle. These correlations were not observed in the St muscle, which may be related to its low IMF content. Nonetheless, negative correlations were observed for the St muscle between flavour and 14:0, 16:0 and 18:0 FA contents.The IMF varied widely in the Ll but not in the St muscle. The latter had higher levels of 16:1c9 and trans fatty acids (∑TFA) in the BA than in the AL breed. Regarding the Ll muscle, the BA had higher amounts of 14:0, 16:0, 16:1c9, 18:0, 18:1c9, 18:1c11, saturated fatty acids (∑SFA), cis monounsaturated fatty acids (∑cis MUFA), ∑TFA and n-3 polyunsaturated fatty acids (∑n-3 PUFA) than the AL breed. The diet exerted an influence on the IMF content and on the levels of 14:0, 16:0, 16:1c9, 18:0, 18:1c9, 18:1c11, ∑SFA, ∑cis MUFA and ∑TFA in both Ll and St muscles. Moreover, the levels of ∑n-3 PUFA in the Ll muscle and 18:2n-6, 20:4n-6, ∑n-6 PUFA and ∑PUFA in the St muscle were influenced by diet. The results obtained in this study, with two Portuguese breeds, confirm that genetic background plays a major role in the determination of meat eating quality.     

The fatty acid profile of muscle and adipose tissue of lambs fed camelina or linseed as oil or seeds

The objective of this study was to evaluate the impact of diets enriched with plant oils or seeds, high in polyunsaturated fatty acids (PUFA), on the fatty acid profile of sheep intramuscular and subcutaneous adipose tissue (SAT). Sixty-six lambs were blocked according to initial body weight and randomly assigned to six concentrate-based rations containing 60 g fat/kg dry matter from different sources: (1) Megalac (MG; ruminally protected saturated fat), (2) camelina oil (CO), (3) linseed oil (LO), (4) NaOH-treated camelina seed (CS), (5) NaOH-treated linseed (LS) or (6) CO protected from ruminal saturation by reaction with ethanolamine; camelina oil amides (CA). The animals were offered the experimental diets for 100 days, after which samples of m. longissimus dorsi and SAT were collected and the fatty acid profile determined by GLC. The data were analyzed using ANOVA with 'a priori' contrasts including camelina v. linseed, oil v. NaOH-treated seeds and CS v. CA. Average daily gain and total fatty acids in intramuscular adipose tissue were similar across treatments. The NaOH-treatment of seeds was more effective in enhancing cis-9, trans-11 conjugated linoleic acid (CLA) incorporation than the corresponding oil, but the latter resulted in a higher content of trans-11 18:1 in both muscle neutral and polar lipids (P < 0.01, P < 0.001, respectively). Inclusion of LS resulted in the highest PUFA:saturated fatty acid (SFA) ratio in total intramuscular fat (0.22). The NaOH-treatment of seeds resulted in a higher PUFA/SFA ratio (0.21 v. 0.18, P < 0.001) than oils and on average, linseed resulted in a higher PUFA/SFA ratio than camelina (P < 0.01). Lambs offered LS had the highest concentration of n-3 PUFA in the muscle, while those offered MG had the lowest (P < 0.001). This was reflected in the lowest (P < 0.001) n-6: n-3 PUFA ratio for LS-fed lambs (1.15) than any other treatment, which ranged from 2.14 to 1.72, and the control (5.28). The trends found in intramuscular fat were confirmed by the data for SAT. This study demonstrated the potential advantage from a human nutrition perspective of feeding NaOH-treated seeds rich in PUFA when compared to the corresponding oil. The use of camelina amides achieved a greater degree of protection of dietary PUFA, but decreased the incorporation of biohydrogenation intermediates such as cis-9, trans-11 CLA and trans-11 18:1 compared to NaOH-treated seeds.