Conjugated linoleic acid affects lipid composition, metabolism, and gene expression in gilthead sea bream (Sparus aurata L)

To maximize growth, farmed fish are fed high-fat diets, which can lead to high tissue lipid concentrations that have an impact on quality. The intake of conjugated linoleic acid (CLA) reduces body fat in mammals and this study was undertaken to determine the effects of dietary CLA on growth, composition, and postprandial metabolic variables in sea bream. Fish were fed 3 diets containing 48 g/100 g protein and 24 g/100 g fat, including fish oil supplemented with 0 (control), 2, or 4% CLA for 12 wk. Feed intake, specific growth rate, total body fat, and circulating somatolactin concentration were lower in fish fed CLA than in controls. Feed efficiency was greater in fish fed 2% CLA than in controls. Liver triglyceride concentrations were higher in fish fed 4% CLA and muscle triglyceride concentrations were lower in fish fed both CLA diets than in controls. Hepatic fatty acyl desaturase and elongase mRNA levels in fish fed CLA were lower than in controls. Metabolic differences between controls and CLA-fed fish were observed at 6 h but not at 24 h after the last meal, including lower postprandial circulating triglyceride concentrations, higher hepatic acyl-CoA-oxidase, and lower L-3-hydroxyacyl-CoA dehydrogenase activities in CLA-fed fish than in controls. Dietary CLA did not affect enzymes involved in lipogenesis including hepatic fatty acid synthase and malic enzyme, but it decreased glucose 6-phosphate dehydrogenase activity at 24 h, but not at 6 h after feeding. The data suggest that CLA intake in sea bream has little effect on hepatic lipogenesis, channels dietary lipid from adipose tissue to the liver, and switches hepatic mitochondrial to peroxisomal beta-oxidation.     

Effect of dietary tung oil on the growth and lipid metabolism of laying hens

The influence of dietary tung oil, containing a high level of alpha-eleostearic acid (cis-9, trans-11, trans-13-octadecatrienoic acid, EA) on growth, egg production, and lipid and fatty acid compositions in tissues and egg yolks of laying hens was studied in White Leghorn hens. Forty-week-old hens were divided into three groups of eight birds each and fed diets containing 0, 0.5, or 1.0% tung oil for 6 wk. The average body weight, feed consumption, rate of egg production, and weights of eggs and yolks were not affected. The weight of adipose tissue was remarkably small in hens fed tung oil, whereas the yolk lipid content did not change. Triglyceride level in heart and adipose tissue decreased in hens fed tung oil, and the level of linolenic acid (C18:3) in all tissues was decreased. Alpha-EA was not almost deposited in the tissues and egg yolk of hens fed tung oil, but conjugated linoleic acid (CLA) was detected in all tissues and egg yolks. The level of CLA in the tissues was significantly higher with increased dietary tung oil. The order of CLA level in tissue lipids was adipose tissue>liver>heart>breast muscle. Especially, the level of CLA in the lipids of adipose tissue and egg yolks of hens fed 1.0% tung oil was 2.0% of the total fatty acid. These results supposed that dietary tung oil affected the lipid metabolism of laying hens and could modify the lipid and fatty acid composition in tissues and eggs.     

Dietary choline requirement of juvenile yellow perch (Perca flavescens)

We conducted an 11-wk feeding trial to determine the dietary choline requirement of juvenile yellow perch (Perca flavescens) and to investigate whether dietary phosphatidylcholine (PC) could meet this requirement. Six dietary treatments contained choline concentrations of <0.11, 0.23, 0.34, 0.75, 1.22 or 3.37 g/kg diet. Two additional diets contained 31 g of lecithin/kg diet, with or without supplemental choline chloride (4.0 g choline/kg diet). The total sulfur amino acid concentration was maintained at 1.0 g/100 g diet (methionine/cyst(e)ine, 49:51). Diets were fed to satiation twice daily to triplicate groups of yellow perch initially weighing 16.0 g/fish. Weight gain, feed intake and carcass proximate composition were significantly affected by dietary choline. Weight gains and feed intakes increased as dietary choline increased from 0 to 0.75 g/kg. Both values tended to plateau in fish fed dietary choline levels above 0.75 g/kg. Broken-line analyses of weight gain and feed intake data indicated the dietary choline requirement was 0.598 and 0.634 g/kg diet, respectively. Hepatic lipid concentrations and feed efficiency values were not significantly different. Whole-body fat concentrations increased significantly, whereas ash levels decreased significantly in fish fed increasing levels of dietary choline. Weight gain and feed intake of fish fed diets containing PC were not significantly different from fish fed 0.75 g/kg of dietary choline. However, hepatic lipid concentrations were significantly higher in fish fed the diet containing PC and no choline chloride. Thus, yellow perch require a maximum of 0.598-0.634 g of choline/kg diet for maximum growth and this requirement may potentially be met with 31 g of lecithin/kg diet.     

Replacement of fish oil with rapeseed oil in diets of Atlantic salmon (Salmo salar) affects tissue lipid compositions and hepatocyte fatty acid metabolism

Duplicate groups of Atlantic salmon post-smolts were fed five practical-type diets in which the added lipid was 100% fish oil [FO; 0% rapeseed oil (0% RO)], 90% FO + 10% RO (10% RO), 75% FO + 25% RO (25% RO), 50% FO + 50% RO (50% RO) or 100% RO, for a period of 17 wk. There were no effects of diet on growth rate or feed conversion nor were any histopathological lesions found in liver, heart, muscle or kidney. The greatest accumulation of muscle lipid was in fish fed 0% RO, which corresponded to significantly lower muscle protein in this group. The highest lipid levels in liver were found in fish fed 100% RO. Fatty acid compositions of muscle lipid correlated with RO inclusion in that the proportions of 18:1(n-9), 18:2(n-6) and 18:3(n-3) all increased with increasing dietary RO (r = 0.98-1.00, P < 0.013). The concentrations of eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] in muscle lipid were significantly reduced (P < 0.05), along with total saturated fatty acids, with increasing dietary RO. Diet-induced changes in liver fatty acid compositions were broadly similar to those in muscle. Hepatic fatty acid desaturation and elongation activities, measured using [1-(14)C] 18:3(n-3), were increased with increasing dietary RO. Limited supplies of marine fish oils require that substitutes be found if growth in aquaculture is to be maintained such that fish health and product quality are not compromised. Thus, RO can be used successfully as a substitute for fish oil in the culture of Atlantic salmon in sea water although at levels of RO >50% of dietary lipid, substantial reductions occur in muscle 20:5(n-3), 22:6(n-3) and the (n-3)/(n-6) polyunsaturated fatty acid (PUFA) ratio, which will result in reduced availability of the (n-3) highly unsaturated fatty acids that are beneficial for human health.     

Substituting fish oil with crude palm oil in the diet of Atlantic salmon (Salmo salar) affects muscle fatty acid composition and hepatic fatty acid metabolism

Supplies of marine fish oils (FO) are limited and continued growth in aquaculture production dictates that substitutes must be found that do not compromise fish health and product quality. In this study the suitability of crude palm oil (PO) as a replacement for FO in diets of Atlantic salmon was investigated. Duplicate groups of Atlantic salmon post-smolts were fed four practical-type diets in which the added lipid was either 100% FO and 0% crude PO (0% PO); 75% FO and 25% PO (25% PO); 50% FO and 50% PO (50% PO); and 100% PO, for 30 wk. There were no effects of diet on growth rate or feed conversion ratio nor were any histopathological lesions found in liver, heart or muscle. Lipid deposition was greatest in fish fed 0% PO and was significantly greater than in fish fed 50% and 100% PO. Fatty acid compositions of muscle total lipid were correlated with dietary PO inclusion such that the concentrations of 16:0, 18:1(n-9), 18:2(n-6), total saturated fatty acids and total monoenoic fatty acids increased linearly with increasing dietary PO. The concentration of eicosapentaenoic acid [20:5(n-3)] was reduced significantly with increasing levels of dietary PO but the concentration of docosahexaenoic acid [22:6(n-3)] was significantly reduced only in fish fed 100% PO, compared with the other three treatments. Similar diet-induced changes were seen in liver total lipid fatty acid compositions. Hepatic fatty acid desaturation and elongation activities were approximately 10-fold greater in fish fed 100% PO than in those fed 0% PO. This study suggests that PO can be used successfully as a substitute for FO in the culture of Atlantic salmon in sea water. However, at levels of PO inclusion above 50% of dietary lipid, significant reductions in muscle 20:5(n-3), 22:6(n-3) and the (n-3):(n-6) PUFA ratio occur, resulting in reduced availability of these essential (n-3) highly unsaturated fatty acids to the consumer.     

Conjugated linoleic acid differentially modifies fatty acid composition in subcellular fractions of muscle and adipose tissue but not adiposity of postweaning pigs

This study examined the interaction between conjugated linoleic acid (CLA) and dietary fat type on the enrichment of subcellular fractions, the Delta(9) desaturase index and adiposity in pigs. Early weaned piglets (n = 6/group) were fed for 35 d diets supplemented with 15 g/100 g diet beef tallow or corn oil, or 12 g/100 g tallow or corn oil plus 3 g CLA. There were no effects of dietary fat or CLA on the mass of dissected skin, bone, muscle or adipose tissue of the 7th to 9th thoracic rib sections. Medial subcutaneous adipose tissue of pigs fed tallow had smaller adipocytes than that of pigs fed corn oil. The lateral subcutaneous site was unaffected by dietary fat type. Microsomes accumulated <50% the concentration of trans-10,cis-12, cis-11,trans-13, and cis-9,trans-11 CLA as membrane and nonmembrane fractions of adipose tissue and longissimus muscle. There was no evidence of preferential incorporation of any CLA isomer into any of the subcellular fractions. Addition of CLA to the diets reduced adipose tissue nonmembrane monounsaturated fatty acids (MUFA; g/100 g total fatty acids) by 15% in corn oil-fed pigs and by 19% in tallow-fed pigs. Total saturated fatty acids (SFA) were increased by CLA commensurately in this lipid fraction. This resulted in a reduced Delta(9) desaturase index [MUFA/(SFA + MUFA)] in the nonmembrane lipid fraction of pigs fed either the corn oil or tallow diets. Thus, in spite of marked effects on fatty acid composition and the Delta(9) desaturase index, CLA had no effect on adiposity in early weaned piglets fed high fat diets.     

Detrimental effects of a high fat diet in early renal injury are ameliorated by fish oil in Han:SPRD-cy rats

Dietary fish oils containing (n-3) fatty acids can modulate renal inflammatory injury. We previously demonstrated that a high fat (HF) diet worsens early renal disease progression in the Han:SPRD-cy rat model of polycystic kidney disease (PKD). Therefore, using HF (20 g/100 g diet) and low fat (LF; 5 g/100 g diet) diets, we compared the effects of menhaden oil (MO), soybean oil (SO) and cottonseed oil (CO) on renal function and histology in male Han:SPRD-cy rats fed the diets for 6 wk in the early stages of renal disease. Overall, rats fed HF compared with those fed LF diets had larger kidneys, more renal fibrosis and lower creatinine clearance (main effects of fat level).Rats fed MO rather than CO and SO diets had significantly lower kidney weights, kidney water content, cyst volumes and serum cholesterol and triglyceride concentrations (main effects of fat type). Rats fed MO diets also had less renal fibrosis than those fed CO diets, but the least fibrosis was in rats fed SO diets. Analysis of simple effects (due to interactions between fat level and type) revealed that HF diets increased renal inflammation in rats fed CO diets, but reduced inflammation was present in those fed SO and MO diets; HF diets also increased compared with LF diets serum urea nitrogen concentrations in rats fed the MO and CO diets, but not the SO diet. These results confirm that high dietary fat worsens early disease progression in this model of renal disease, and further demonstrate that diets with oils containing (n-3) fatty acids ameliorate some of the detrimental effects of a high fat diet.     

Dietary gamma-linolenic acid suppresses aortic smooth muscle cell proliferation and modifies atherosclerotic lesions in apolipoprotein E knockout mice

The present study was conducted to evaluate the antiatherogenic effects of dietary gamma-linolenic acid (GLA) (primrose oil) in apolipoprotein E (apoE) genetic knockout mice. Five-wk-old male mice were fed cholesterol-free diets containing 10 g/100 g lipid as corn oil (CO) [control diet, 0 mol/100 mol GLA and (n-3) polyunsaturated fatty acids (PUFA)], primrose oil (PO, 10 mol/100 mol GLA), fish oil-CO mix [FC; 9:1 wt/wt, 0 mol/100 mol GLA and 17 mol/100 mol (n-3) PUFA] or fish oil-PO mix [FP, 1:3 wt/wt, 8 mol/100 mol GLA and 5 mol/100 mol (n-3) PUFA] for 15 wk. Subsequently, diets were supplemented with cholesterol (1.25 g/100 g) and sodium cholate (0.5 g/100 g) and fed for an additional 10 and 16 wk. Plasma cholesterol and triglyceride levels generally did not differ among groups at 20, 30 and 36 wk of age. Mice fed GLA-containing diets (PO and FP) had significantly (P < 0.05) higher liver phospholipid levels of dihomo-gamma-linolenic acid, the elongated product of GLA, relative to CO and FC groups. Consumption of GLA (PO and FP diets) significantly reduced (P < 0.05) aortic vessel wall medial layer thickness at 20 and 30 wk. A parallel GLA-dependent suppression in the number of proliferating (proliferating cell nuclear antigen positive) aortic smooth muscle cells was also observed. Diets containing either GLA or (n-3) PUFA reduced (P < 0.05) atherosclerotic lesion size in 30-wk-old mice. These results indicate that dietary GLA can suppress smooth muscle cell proliferation in vivo and retard the development of diet-induced atherosclerosis in apoE knockout mice.     

Influence of dietary fats and vitamin e on plasma and hepatic vitamin a and β‐carotene levels in rats fed excess β‐carotene

Effects of different dietary lipids and excess vitamin E on plasma and hepatic concentrations of β‐carotene were evaluated in rats fed diets containing a large excess (0.2%) of β‐carotene. Male weanling Wistar Kyoto rats were fed β‐carotene‐supplemented diets containing various dietary lipids as follows: Group I, a saturated fat (coconut oil); Group II, a monounsaturated fat (olive oil); Group III, a polyunsaturated fat rich in ω‐6 fatty acids (safflower oil); Group IV, same as Group III plus vitamin E; and Group V, a polyunsaturated fat rich in ω‐3 fatty acids (menhaden oil). All diets contained 2% saf flower oil to provide sufficient amounts of linoleic acid (an essential fatty acid). Rats were killed after six weeks of feeding the various diets, and the concentrations of Q‐carotene and vitamin A were determined in plasma and liver. Plasma vitamin A levels were not altered by any of the dietary lipids or by an excess of vitamin E. The concentrations of β‐carotene in plasma were the lowest in rats fed the diet containing menhaden oil. The feeding of the diet containing an excess of vitamin E also resulted in a significant decrease in plasma β‐carotene concentration. Similarly, the hepatic β‐carotene concentration was also reduced to about one‐half in rats fed the diet containing an excess of vitamin E. Liver β‐carotene concentration was higher in Groups II and III than in the other three dietary groups. Hepatic vitamin A concentrations were also affected by the type of dietary fat. The highest levels were observed in rats fed the coconut oil diet; the lowest level of vitamin A was in rats fed menhaden oil (Group V). The results of this study suggest that the type of dietary fat and an excess of vitamin E can have a significant effect on 0‐carotene and vitamin A stores in liver and on β‐carotene content of plasma.     

Effects of dietary n-3 polyunsaturated fatty acids, breed and dietary vitamin E on the fatty acids of lamb muscle, liver and adipose tissue

The effect of feeding n-3 PUFA on the fatty acid composition of muscle, adipose tissue and liver of lambs was investigated. Groups of eight ram lambs per breed, SuffolkxLleyn (24 kg live weight) and Scottish Blackface (18 kg live weight), were each fed one of six diets containing one of three fat sources (50 g fatty acids/kg DM; Megalac((R)) (calcium soap of palm fatty acid distillate; Volac Ltd, Royston, Herts., UK) and formaldehyde-treated whole linseed (Trouw Nutrition UK, Northwich, Ches., UK) either alone or with fish oil (1:1, w/w) and either 100 or 500 mg alpha-tocopheryl acetate/kg DM. Feed was offered ad libitum until slaughter at approximately half breed mature live weight. The type of dietary fat had no effect on intake, growth rate or feed conversion ratio. The 3.0-fold higher concentration of 18 : 3n-3 in the linseed compared with the Megalac((R)) diet approximately doubled (P<0.001) the concentration in the neutral and polar lipid fractions of musculus semimembranosus and liver, and in adipose tissue it increased 2.5-fold. Feeding protected linseed also increased (P<0.001) concentrations of 20 : 5n-3 and 22 : 5n-3 in muscle polar lipids and both lipid fractions of liver. The linseed-fish oil raised the 20 : 5n-3 concentrations above those for the linseed diet and also increased 22 : 6n-3. Scottish Blackface lambs had lower concentrations of 18 : 3n-3 in all lipids compared with Suffolk x Lleyn lambs, but more 20 : 5n-3 in the polar lipids of muscle and liver. High levels of dietary vitamin E were associated with small decreases in the concentration of monounsaturated fatty acids and increases in PUFA. Linseed raised the PUFA : saturated fatty acid ratios in liver and adipose tissue but not in muscle, and improved the n-6 : n-3 fatty acid ratio, as did the linseed-fish oil. Different combinations of dietary fatty acids and better protection against rumen biohydrogenation are required to improve muscle PUFA : saturated fatty acids ratios.     

Effects of fish oil and conjugated linoleic acids on expression of target genes of PPAR alpha and sterol regulatory element-binding proteins in the liver of laying hens

In mammals, (n-3) PUFA and conjugated linoleic acids (CLA) act as activators of PPAR alpha and alter nuclear concentrations of sterol regulatory element-binding proteins (SREBP) in the liver, and thereby influence hepatic lipid catabolism and synthesis. In this study, we investigated the hypothesis that (n-3) PUFA and CLA exert similar effects in the liver of laying hens. Thirty hens (64 weeks old) were fed diets containing 30 g/kg of sunflower oil (control), fish oil (salmon oil) or CLA in TAG form (containing predominantly cis-9, trans-11 CLA and trans-10, cis-12 CLA) for 5 weeks. Hens fed fish oil had a higher expression of some PPAR alpha target genes and a lower nuclear concentration of SREBP-2 in the liver and lower concentrations of cholesterol and TAG in plasma than control hens. Nuclear concentration of SREBP-1 and its target genes involved in lipogenesis were not altered in hens fed fish oil. Hens fed CLA had increased concentrations of TAG and cholesterol in the liver. However, their mRNA levels of PPAR alpha target genes and nuclear concentrations of SREBP-1 and SREBP-2 as well as mRNA levels of their target genes in the liver were largely unchanged compared to control hens. The results of this study suggest that (n-3) PUFA cause a moderate activation of PPAR alpha and lower cholesterol synthesis but do not impair fatty acid synthesis in the liver of laying hens. CLA lead to an accumulation of TAG and cholesterol in the liver of hens by mechanisms to be elucidated in further studies.     

The deposition of conjugated linoleic acids in eggs of laying hens fed diets varying in fat level and fatty acid profile

The objective of this study was to investigate the incorporation of conjugated linoleic acid (CLA) into eggs and its effect on the fatty acid metabolism when layers are fed diets with different fat sources and fat levels. Layers were fed either a low fat diet (LF) or one of three high fat diets based on soybean oil (SB), animal fat (AF) or flaxseed oil (FSO). CLA was added at a concentration of 1 g/100 g feed from two different CLA premixes with a different CLA profile. For the trial, 144 laying hens were allocated to 12 treatments (4 basal fat sources x 3 CLA treatments) with 3 replicates of 4 hens each. No significant differences were observed in feed intake, egg weight, feed conversion or laying rate between chickens fed control and CLA-supplemented diets. Differences in yolk fat, cholesterol or yolk color were not clearly related to the dietary CLA. However, the supplementation of CLA to the diets had clear effects on the fatty acid composition, i.e., a decrease in monounsaturated fatty acids (MUFA) and an increase in saturated fatty acids (SFA) was observed, whereas the polyunsaturated fatty acids (PUFA) content were essentially unaffected. The results suggest that CLA may influence the activity of the desaturases to a different extent in the synthesis of (n-6) and (n-3) long-chain fatty acids. These effects of CLA depend on the level of (n-6) and (n-3) fatty acids available in the feed. The apparent deposition rate (%) is clearly higher for the c9, t11 isomer than for the t10, c12 isomer. Adding CLA to layers diets rich in (n-3) fatty acids produces eggs that could promote the health of the consumer in terms of a higher intake of (n-3) fatty acids and CLA.     

Dietary conjugated linoleic acid consumption during pregnancy and lactation influences growth and tissue composition in weaned pigs

We evaluated the effects of conjugated linoleic acid (CLA) on growth performance, tissue fatty acid composition and ex vivo lipogenic enzyme activity in piglets (n = 40) reared on sows fed diets supplemented with CLA or linoleic acid (LA). Weaned offspring of both sow groups were offered either a CLA- or LA-enriched starter diet for 35 d. The starter diets were formulated to contain 2 g CLA (containing 58.9 g CLA/100 g total fatty acids) or LA per 100 g feed. All piglets were slaughtered at 70 d of age and tissue samples of the back fat, omental fat and longissimus dorsi were collected. Irrespective of the dietary fat supplied in the starter period, piglets reared on the CLA sows had greater final body and warm carcass weights (P: < 0.01), and greater feed intake (P: = 0.02) than piglets reared on the LA sows. The dietary effect on the fatty acid composition was similar for the adipose and muscle tissues. Compared with the LA-enriched diets, CLA increased the level of total saturated fatty acids (P: < 0.05), whereas that of monounsaturated fatty acids was decreased (P: < 0.05). Dietary CLA increased glucose-6-phosphate dehydrogenase (P: < 0.01) and malic enzyme activities (P: < 0.06) in the fat tissues, but did not affect fatty acid synthase activity. The shift toward a higher deposition of saturated fatty acids and a lower deposition of monounsaturated fatty acids is the result of down-regulation of Delta9-desaturase activity that was induced by CLA rather than an altered rate of de novo synthesis.     

Influence of dietary fats and vitamin E on plasma and hepatic vitamin A and beta-carotene levels in rats fed excess beta-carotene

Effects of different dietary lipids and excess vitamin E on plasma and hepatic concentrations of beta-carotene were evaluated in rats fed diets containing a large excess (0.2%) of beta-carotene. Male weanling Wistar Kyoto rats were fed beta-carotene-supplemented diets containing various dietary lipids as follows: Group I, a saturated fat (coconut oil); Group II, a monounsaturated fat (olive oil); Group III, a polyunsaturated fat rich in omega-6 fatty acids (safflower oil); Group IV, same as Group III plus vitamin E; and Group V, a polyunsaturated fat rich in omega-3 fatty acids (menhaden oil). All diets contained 2% safflower oil to provide sufficient amounts of linoleic acid (an essential fatty acid). Rats were killed after six weeks of feeding the various diets, and the concentrations of beta-carotene and vitamin A were determined in plasma and liver. Plasma vitamin A levels were not altered by any of the dietary lipids or by an excess of vitamin E. The concentrations of beta-carotene in plasma were the lowest in rats fed the diet containing menhaden oil. The feeding of the diet containing an excess of vitamin E also resulted in a significant decrease in plasma beta-carotene concentration. Similarly, the hepatic beta-carotene concentration was also reduced to about one-half in rats fed the diet containing an excess of vitamin E. Liver beta-carotene concentration was higher in Groups II and III than in the other three dietary groups. Hepatic vitamin A concentrations were also affected by the type of dietary fat.(ABSTRACT TRUNCATED AT 250 WORDS)     

Replacing dietary fish oil by vegetable oils has little effect on lipogenesis, lipid transport and tissue lipid uptake in rainbow trout (Oncorhynchus mykiss)

In order to investigate the effects of dietary lipid sources on mechanisms involved in lipid deposition, two groups of rainbow trout were fed from first-feeding to the commercial size of 1 kg (for 62 weeks) with two diets differing only by lipid source: 100% fish oil or 100% blend of vegetable oils (55% rapeseed oil, 30% palm oil, 15% linseed oil). The activities and levels of gene expression of lipogenic enzymes (fatty acid synthetase, glucose-6-phosphate dehydrogenase and malic enzyme) in liver and of lipoprotein lipase in perivisceral adipose tissue, white muscle and liver were determined. Transport of lipid was studied by determining lipid composition of plasma and lipoprotein classes. We also examined the clearance of LDL by assaying the level of LDL receptor gene expression in several tissues. Total replacement of dietary fish oil by the blend of vegetable oils did not affect growth of rainbow trout and did not modify muscle lipid content. Hepatic lipogenesis and lipid uptake in perivisceral adipose tissue, white muscle and liver were also not modified by dietary treatments. Diets containing the blend of vegetable oils induced a decrease in plasma cholesterol and LDL. In trout fed the vegetable oils diet, expression of LDL receptor gene in the liver was down-regulated.     

Effects of conjugated linoleic acid on growth performance, feed conversion efficiency, and subsequent carcass quality in broiler chickens

The effect of dietary conjugated linoleic acid isomers (CLA) on growth performance, carcass composition, fatty acid composition of adipose and muscle tissues, and serum lipoproteins was investigated in broiler chickens. A total of 160 (eighty male and eighty female) chickens were allocated to four dietary treatments (0.0, 0.5, 1.0, and 1.5 % CLA) and fed a standard starter diet from 8 to 21 d, and a grower-finisher diet from 22-42 d. When determined for the total period 8-42 d, feed intake and body weight gains of broiler chickens were significantly reduced (from 3.31 to 3.12 kg and from 1615 to 1435 g respectively; P < 0.05), particularly at the 1.5 % dietary CLA level. Feed conversion efficiency and carcass yield values showed no significant effects of dietary CLA. Abdominal fat deposition was significantly reduced (from 2.68 to 1.78 %; P < 0.05), the relative proportion of breast muscles was unaffected, and that of leg muscles significantly increased (from 19.0 to 20.6 %; P < 0.05). The concentration of CLA isomers (% of total methyl esters of fatty acids) increased linearly in tissue samples from broilers fed 0.5, 1.0, and 1.5 % dietary CLA. The relative proportions of saturated fatty acids (16:0, 18:0) were significantly (P < 0.01) increased, and those of monounsaturated (16:1, 18:1) and polyunsaturated fatty acids (18:2, 20:4 in muscle tissues) significantly (P < 0.05) reduced. Total serum cholesterol concentrations reached a maximum in broilers fed 1.0 % CLA and then decreased slightly (from 141.73 to 136.47 mg/dl; P < 0.01). The same was true also for HDL-cholesterol (from 113.58 to 109.97 mg/dl; The HDL cholesterol:total cholesterol ratio and serum triacylglycerol concentration was unaffected. In conclusion, feeding CLA to broiler chickens resulted in substantial incorporation of CLA isomers into their tissue lipids, thus providing a potential CLA-rich source for human consumption.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phosphlipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Growth and lipid metabolism responses in rats fed different dietary fat sources

An experiment with male albino rats was conducted to examine the effect of dietary fat sources on growth performance and apparent digestibility of total fat and fatty acids. The effect on plasma and organ cholesterol concentrations as well as lipoproteins cholesterol and fatty acid profile of hepatic phospholipids was also examined. Forty 3 week old rats were fed purified diets containing 0.041% cholesterol and 7% fat (wt/wt) from soy oil (SO), or cow ghee (GH), or 25% fish oil (FO) plus soy oil (SF) or 25% fish oil plus 75% ghee (GF), or 50% soy oil plus 50% ghee (SG) for a period of 35 days. Final body weight, weight gain, organ weights and feed efficiency ratio showed no significant differences (P < 0.05) among the dietary treatments. The apparent digestibility of total dietary fat and saturated fatty acids in the animals fed diet containing cow ghee only or in combination with fish oil or soy oil was significantly lower than the other dietary groups. Consumption of ghee with combination of fish oil or soy oil lead to significant improvement in the fat apparent digestibility of dietary fat. Total cholesterol and triglyceride concentrations of plasma and organs as well as lipoprotein cholesterol levels were higher in animals fed diets containing ghee. For rats fed diet containing cow ghee in combination with fish oil or soy oil, the cholesterol content of total plasma, lipoprotein fractions (VLDL, LDL and HDL) and organs was decreased significantly. Furthermore, dietary fats altered the fatty acids composition of hepatic phospholipid fatty acids composition. Feeding dietary fish oil reduced arachidonic acid (20:4) and increased linoleic acid (18:2) and eicosapentaenoic acid (20:5) contents. The reduction in the arachidonic acid was being more pronounced in animals fed dietary ghee with combination of fish oil.     

Manipulating the fatty acid composition of muscle and adipose tissue in beef cattle

Enhancing the n-3 polyunsaturated fatty acid (PUFA) content of beef is important in view of the generally saturated nature of fatty acids in ruminant meats and the negative effect this can have on human health. This study examined the effects of different sources of dietary n-3 PUFA on the performance of steers and the fatty acid composition of m. longissimus thoracis muscle and associated subcutaneous adipose tissue. Animals were fed ad libitum on grass silage plus one of four concentrates (60:40 forage:concentrate on a DM basis) containing differing sources of lipid: Megalac (16:0), lightly bruised whole linseed (18:3n-3), fish oil (20:5n-3 and 22:6n-3) and a mixture of linseed and fish oil (1:1, on an oil basis). Diets were formulated so that total dietary oil intake was 6 %, approximately half of which was from the experimental test oil. Linseed feeding not only increased the levels of 18:3n-3 in muscle phospholipid from 9.5 to 19 mg/100 g muscle but also enhanced the synthesis of 20:5n-3, the level of which increased from 10 to 15 mg/100 g muscle. Linseed also increased the proportion of 18:3n-3 in muscle neutral lipid and in adipose tissue lipids by a factor of 1.64 and 1.75 respectively. Fish oil feeding doubled the proportion of 20:5n-3 and 22:6n-3 in muscle phospholipids. The proportion of 18:1 trans in muscle neutral lipid was higher on the n-3 PUFA diets than the control diet, 0.04 and 0.02 respectively. Despite the implied modification to rumen metabolism, lipid source did not affect feed intake, growth rate, cold carcass weight or carcass fatness, but carcass conformation score was higher on fish oil treatments (P < 0.05). However, total muscle fatty acid content was not different between treatments and ranged from 3.5-4.3 % of tissue weight. The increase in n-3 PUFA in the meat produced by feeding linseed or fish oil lowered the n-6:n-3 ratio but had little effect on the P:S ratio.     

Dose-response relationships between dietary (n-3) fatty acids and plasma and tissue lipids, steroid excretion and urinary malondialdehyde in rats.

For a 28-d experimental period, rats were fed a nonpurified, cereal-based diet containing 9.1% supplemental beef tallow or fish oil or one of the following beef tallow:fish oil blends: 95:5; 90:10; 80:20 and 50:50. All diets provided between 21.3 and 22.7 g linoleic acid/kg. Higher fish oil intake was paralleled by elevated incorporation of long-chain (n-3) fatty acids in plasma total lipid, mainly at the expense of arachidonic acid. Significant inverse relationships were found between plasma total (n-3) fatty acid concentration and plasma triglyceride, cholesterol or free fatty acid concentrations. Fish oil intake did not lead to a shift of triglycerides or cholesterol from the plasma to the tissues (liver, heart, kidneys). Reduced plasma cholesterol concentrations in the fish oil-fed rats could not be explained by higher fecal excretion of neutral sterols and bile acids. In vivo lipid peroxidation, assessed by urinary malondialdehyde excretion, was enhanced when diets containing greater than 1.8% fish oil were fed.