Are there consistent relationships between major connective tissue components, intramuscular fat content and muscle fibre types in cattle muscle?

Intramuscular connective tissue (IMCT) is mainly composed of several fibrils (known as total collagen (TCol)) linked between each other by different chemical cross-links (CLs), the whole being embedded in a matrix of proteoglycans (PGs). In the field of beef quality, there is limited information on the role of CLs and PGs. Accordingly, several authors suggest that, to investigate the role of IMCT, it is important to investigate them just like TCol and insoluble collagen (ICol). In muscle, there are two other components, the muscle fibres and intramuscular fat (IMF) content. There are limited data on the relationships between these three components of muscle and then on possibility to independently manipulate these characteristics in order to control the final quality of meat. The present study aimed to investigate whether consistent relationships exist between these different components of muscle. Therefore, the present study compared four muscles of two cattle types (dairy and beef) to determine associations between TCol, ICol, CLs and PGs. Data were analysed across and within muscle (M) and animal type (AT) based on residuals. There was a strong M and AT effect for all muscle characteristics and an interaction M × AT for type I muscle fibres and IMF. Correlations between TCol, ICol and their CLs were M- and AT-independent. Total proteoglycans were positively correlated with TCol and ICol in a muscle-dependent manner irrespective of AT, but no correlation was found with CLs. On the contrary, CLs were negatively correlated with the ratio TPGs : TCol in an M-dependent manner, irrespective of AT. TCol, ICol and CLs were positively and negatively correlated with type IIA and IIB+X muscle fibres only in longissimus thoracis (LT) muscle, regardless the AT. Insoluble collagen was the only parameter of IMCT to be correlated with type I muscle fibres but only in LT muscle, irrespective of AT. There was no correlation between PGs and muscle fibre types, but PGs were the only IMCT component to be related with IMF in an M-dependent manner, irrespective of AT. Finally, there was no correlation between muscle fibre types and IMF content within M and AT. This study revealed that there is a strong relationship between IMCT components irrespective of M, an M-dependent relationship between the IMCT components and muscle fibre types and few (only with PGs) or no relationship between IMF and IMCT and muscle fibres.

Comparison of muscle fatty acid composition and lipid stability in lambs stall-fed or pasture-fed alfalfa with or without sainfoin pellet supplementation.

Currently, consumers are increasingly interested in obtaining high-quality and healthy lamb meat. Compared to grain-based diets, dietary forage legumes such as alfalfa and condensed tannin (CT)-rich sainfoin increase the levels of polyunsaturated fatty acids (PUFAs) that are beneficial for health in lamb meat thanks to their high content in PUFA and/or their impact on ruminal biohydrogenation. However, they can therefore adversely affect its oxidative stability. Thus, the impact of dietary forage legumes on lamb longissimus thoracis (LT) muscle FA composition and their stability to peroxidation was studied in 36 Romane lambs grazing alfalfa (AF; n = 12) or alfalfa plus daily supplementation with CT-rich sainfoin pellets (AS; n = 12; 15 g DM/kg BW, 42 g CT/kg DM) or stall-fed concentrate and grass hay indoors (SI; n = 12). Lambs were slaughtered at a mean age of 162 ± 8.0 days after an average experimental period of 101 ± 8.1 days. Forage legumes-grazing lambs outperformed SI lambs in LT nutritional quality, with more conjugated linoleic acids and n-3 PUFAs, especially 18:3n-3, eicosapentaenoic and docosahexaenoic acids (P < 0.001), and thus lower n-6 PUFA/n-3 PUFA and 18:2 n-6/18:3 n-3 ratios (P < 0.001). Peroxidizability index was higher (P < 0.001) in LT muscle of forage legumes-grazing lambs. Concurrently, two endogenous antioxidant enzyme activities, superoxide dismutase and glutathione peroxidase, were, respectively, similar and lower (P < 0.001) for forage legumes-grazing compared with SI lambs. A lower vitamin E level in SI lambs compared with forage legumes-grazing lambs (1.0 v. 3.8 mg/g, P < 0.001) could explain that malondialdehyde content, a marker of lipid oxidation intensity, was 0.63 µg/g in SI after 8 days in aerobic packaging conditions, whereas it remaining steady at 0.16 µg/g in forage legumes-grazing lambs. Dietary forage alfalfa thus improved FA composition of lamb LT muscle and their stability to oxidation when compared to SI lambs. However, supplementation of alfalfa-grazing lambs with CT-rich sainfoin pellets did not affect the nutritional quality of LT muscle FAs.

Prediction of beef meat fatty acid composition by visible-near-infrared spectroscopy was improved by preliminary freeze-drying.

The aim of this study was to compare visible-near-infrared spectroscopy (VIS/NIRS) models developed from fresh or freeze-dried samples for predicting the fatty acid (FA) composition of beef samples. The hypothesis tested is that the removal of water from samples could improve the VIS/NIRS model performance. A total of 454 beef samples obtained from different bovine muscles were used. No significant differences were found in the performance of VIS/NIRS models developed from fresh or freeze-dried samples for predicting both major individual FAs and families of FAs and for some FAs (16:0, 18:0, 18:1 n-9, 18:2 n-6, 20:4 n-6, 22:5 n-3, 22:6 n-3, saturated, mono-unsaturated FA, and total n-3 long chain poly-unsaturated FAs (PUFA)). In contrast, the standard error of predictions for total PUFAs, total n-3 PUFAs, total conjugated linoleic acid, 20:5 n-3, and 18:3 n-3 were improved (by 21% on average; P < .05) in freeze-dried samples compared with fresh samples.

Performance of fluorescence spectroscopy for beef meat authentication: Effect of excitation mode and discriminant algorithms.

This study evaluated the performance of classical front face (FFFS) and synchronous (SFS) fluorescence spectroscopy combined with Partial Least Square Discriminant Analysis (PLSDA), Support Vector Machine associated with PLS (PLS-SVM) and Principal Components Analysis (PCA-SVM) to discriminate three beef muscles (Longissimus thoracis, Rectus abdominis and Semitendinosus). For the FFFS, 5 excitation wavelengths were investigated, while 6 offsets were studied for SFS. Globally, the results showed a good discrimination between muscles with Recall and Precision between 47.82 and 94.34% and Error ranging from 6.03 to 32.39%. For the FFFS, the PLS-SVM with the 382nm excitation wavelength gave the best discrimination results (Recall, Precision and Error of 94.34%, 89.53% and 6.03% respectively). For SFS, when performing discrimination of the three muscles, the 120nm offset gave the highest Recall and Precision (from 57.66% to 94.99%) and the lowest Error values (from 6.78 to 8.66%) whatever the algorithm (PLSDA, PLS-SVM and PCA-SVM).

An innovative approach combining Animal Performances, nutritional value and sensory quality of meat.

This work sets out a methodological approach to assess how to simultaneously control together Animal Performances, nutritional value, sensory quality of meat. Seventy-one young bulls were characterized by 97 variables. Variables of each element were arranged into either 5 homogeneous Intermediate Scores (IS) or 2 Global Indices (GI) via a clustering of variables and analysed together by Principal Component Analysis (PCA). These 3 pools of 5 IS (or 2 GI) were analysed together by PCA to established the links existing among the triptych. Classification on IS showed no opposition between Animal Performances and nutritional value of meat, as it seemed possible to identify animals with a high butcher value and intramuscular fat relatively rich in polyunsaturated fatty acids. Concerning GI, the classification indicated that Animal Performances were negatively correlated with sensory quality. This method appeared to be a useful contribution to the management of animal breeding for an optimal trade-off between the three elements of the triptych.

Potential of fluorescence spectroscopy to predict fatty acid composition of beef.

The present study aimed to evaluate and compare the ability of front face (FFFS) and synchronous fluorescence spectroscopy (SFS) to predict total fat and FA composition of beef LT muscles coming from 36 animals of 3 breeds (Angus, Limousin and Blond d'Aquitaine). The regression models were performed by using Partial Least Square (PLS) method. In spite of the low number of samples used, the results of this preliminary study demonstrated the ability of fluorescence spectroscopy to predict meat lipids. Nonetheless, the results suggested that the fluorescence spectroscopy is more suited to measure SFA (R(2)p≥0.66; RPD≥2.29) and MUFA (R(2)p≥0.48; RPD≥1.49) than PUFA (R(2)p≤0.48; RPD≤1.63). Moreover, R(2) and RPD factors obtained with FFFS were greater compared to the ones obtained with SFS suggesting that FFFS is more adapted to measure lipid composition of beef meat.

Breeds and muscle types modulate performance of near-infrared reflectance spectroscopy to predict the fatty acid composition of bovine meat.

This study aims to assess near-infrared reflectance spectroscopy feasibility for predicting beef fatty acid (FA) composition. Experimental scheme included four breeds (Angus, Blond d'Aquitaine, Charolais, Limousin) and three muscles, Longissimus thoracis (LT), Rectus abdominis (RA), Semitendinosus (ST). The results showed that 1) increasing FA content variability with several breeds increased calibration model reliability (R(2)CV>0.86) for the major individual and groups of FA unless polyunsaturated FAs, 2) Longissimus thoracis FAs were better predicted than RA FAs while no ST FAs were correctly predicted (R(2)CV<0.71). This difference could be explained by FA content, FA variability or specific muscle physico-chemical characteristics.

A grass-based diet favours muscle n-3 long-chain PUFA deposition without modifying gene expression of proteins involved in their synthesis or uptake in Charolais steers.

N-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) are subject of growing interest as they are of particular relevance for meat quality and human health. However, their content in the muscles of cattle is generally low probably as the complex result of their biosynthesis from dietary n-3 PUFA in the muscle and/or in other tissues/organs and of their subsequent uptake by the muscle. In view of this, this study aimed at understanding whether the changes in the muscle n-3 LCPUFA content, depending on the diet (maize silage v. grass) or the muscle type (Rectus abdominis, RA v. Semitendinosus, ST) in 12 Charolais steers, were related to variations in the gene expression of proteins involved in n-3 LCPUFA biosynthesis or cellular uptake. Tissue fatty acid composition was analysed by gas-liquid chromatography and mRNA abundance of proteins by quantitative real-time PCR. The grass-based diet resulted in a 2.3-fold (P < 0.0002) increase in both RA and ST n-3 LCPUFA content compared with the maize silage-based diet, whereas no difference in the expression of genes involved in n-3 LCPUFA biosynthesis and uptake was observed between diets. ST exhibited a 1.5-fold higher n-3 LCPUFA content than RA (P < 0.003), whereas the gene expression of proteins involved in n-3 LCPUFA biosynthesis and uptake was 1.3- to 18-fold higher in RA than in ST (P < 0.05). In conclusion, diet- or muscle type-dependent changes in the muscle n-3 LCPUFA content of Charolais steers did not seem to be mediated by the gene expression regulation of proteins involved in the biosynthesis or uptake of these fatty acids.

Breed and dietary linseed affect gene expression of enzymes and transcription factors involved in n-3 long chain polyunsaturated fatty acids synthesis in longissimus thoracis muscle of bulls.

N-3 long-chain (LC) PUFA are known to be beneficial for human development and health. These properties explain the increasing interest in promoting n-3 LC PUFA deposition in bovine muscles, leading to healthier meats. In this context, this study aimed to identify possible limiting steps in the bioconversion of 18:3n-3 into n-3 LC PUFA in the longissimus thoracis (LT) muscle of 36 Aberdeen Angus, Limousin, and Blond d'Aquitaine bulls (n = 12 per breed) that were fed, for the 105-d finishing period, either a concentrate-based diet (25% molasses straw to 75% concentrate, on a raw basis; CON) or the same CON diet supplemented with extruded linseed (44.5 g lipid/kg diet DM) mixed into the concentrate (LINS). The fatty acid (FA) composition of the LT muscle was determined by GLC, and the mRNA abundances for enzymes and transcription factors involved in n-3 LC PUFA synthesis were determined by quantitative real-time PCR. The total lipid concentration in the LT muscle was approximately 2.4-fold greater (P < 0.001) in Angus bulls than in the other breeds and composed of the greatest n-3 PUFA content (P < 0.001) including 18:3n-3 (P < 0.001) and n-3 LC PUFA (P < 0.02), primarily 20:5n-3 (P < 0.007) and 22:5n-3 (P < 0.04). These data were associated with a lesser gene expression (P < 0.02) of 2 enzymes [acyl-CoA oxidase 1 (ACOX1) and L-bifunctional protein (L-PBE)] and 2 transcription factors [liver X receptors (LXR) α and ß] in the LT muscle of Angus bulls compared with gene expression in Limousin bulls. Moreover, the mRNA of elongase 5 was only present in trace amounts in the LT muscle of the 3 breeds. The addition of linseed to the diet resulted in greater deposition of 18:3n-3 (P < 0.001) in the LT muscles of the 3 breeds, without any major changes (P > 0.34) in the n-3 LC PUFA content. Dietary linseed stimulated (P < 0.04) the gene expression of all enzymes and transcription factors involved in n-3 LC PUFA synthesis except elongases 2 and 5 (P > 0.19), the expression of which remained weak and was not inducible. These results reveal a limited capacity for n-3 LC PUFA synthesis from 18:4n-3 (substrate of elongase 5) in the LT muscles of Blond d'Aquitaine, Limousin, and Angus bulls. Therefore, further investigations on the cellular regulation of elongase gene expression are needed to identify the physiological or nutritional factors that efficiently stimulate elongase expression in beef cattle.

Effects of fish oil and additional starch on tissue fatty acid profile and lipogenic gene mRNA abundance in lactating goats fed a diet containing sunflower-seed oil.

In dairy cattle, diet supplementation with oils affects the lipid metabolism in body tissues via changes in the partitioning and deposition of fatty acids (FAs) and lipogenic gene expression; however, limited data are available in goats. Eight Alpine goats were fed a grassland hay diet supplemented with 90 g/day of sunflower-seed oil or 90 g/day of sunflower-seed oil and fish oil (2 : 1) plus additional starch. The goats were slaughtered on day 21 of the treatments and samples of the mammary secretory tissue, liver, omental and perirenal adipose tissues (ATs) were collected to characterise their FA composition and the mRNA abundance of lipogenic genes and transcription factors involved in their regulation, and to examine the impact of the diet composition on the same parameters. The results are in agreement with the specific physiological adaptation in the lipid metabolism of body tissues that is likely to occur during late lactation because of the coexistence of an active lipogenesis in the mammary secretory tissue and a significant anabolic activity in the ATs. These latter tissues were characterised by high concentrations of saturated FA and very low polyunsaturated FA (PUFA) levels. The content of PUFA was relatively higher in the mammary secretory tissue, in particular in the case of polyunsaturated C18. The highest PUFA contents were found in the liver, in accordance with the greater mRNA abundances of the genes that encode the necessary enzymes for very long-chain n-3 and n-6 PUFA synthesis. However, substantial differences between n-3 and n-6 pathways would most likely exist in the goat liver. Overall, differences in diet composition induced limited changes in the mRNA abundance of genes involved in lipid metabolism, and these were not associated with the few variations observed in tissue FA composition.

Distinct metabolism of linoleic and linolenic acids in liver and adipose tissues of finishing Normande cull cows.

Feeding strategies based on the addition of plant lipids rich in polyunsaturated fatty acids (PUFAs) in diets of bovines during the finishing period are common to enhance the nutritional value of meat. However, following rumen biohydrogenations, these FAs could still be metabolised in various tissues/organs involved in the FA metabolism such as the liver and adipose tissues (ATs), thus affecting their subsequent deposition in muscles. In this context, the objective of this study was to characterise the various metabolic pathways of linoleic acid (LA) and α-linolenic acid (ALA) in the liver and ATs (subcutaneous (SC) and inter-muscular (IM)) of Normande cull cows fed a diet supplemented (LR) or not (C) with extruded linseeds and rapeseeds, using the ex vivo incubated tissue slice method. Hepatic uptake of both FAs was higher with the LR than with the C diet (P = 0.02). For the two diets, ALA uptake was higher than that of LA (+46%, P = 0.04). ALA was much more degraded by ß-oxidation (>50% of ALA present in cells) than LA (∼27%) with both diets (P = 0.015). Whatever the diet, ALA was not converted into longer and/or more unsaturated FA, whereas about 14% of LA was converted into 20:4n-6. The intensity of the esterification pathway was higher (+70%, P = 0.004) with the LR than with the C diet, for both FAs. Hepatic secretion of ALA as part of the very-low-density lipoprotein particles was lower than that of LA (-58% and -23% for C and LR diets respectively, P = 0.02). In SC and IM ATs, dietary lipid supplementation did not alter metabolic pathways of LA and ALA. They were efficiently taken up by ATs (>68% of FA present in the medium), with uptake being higher for IM than for SC AT (+12%, P = 0.01). Moreover, LA uptake by ATs was higher than ALA uptake (+10.7%, P = 0.027). Both FAs were mainly esterified (>97% of FA present in adipocytes) into neutral lipids (>85% of esterified FA). Around 9.5% of LA was converted into 20:4n-6, whereas only around 1.3% of ALA was converted into 20:5n-3. We concluded that, in our experimental conditions, liver was highly active in ALA catabolism limiting its subsequent deposition in muscles. However, bovine liver and ATs were inefficient at converting ALA into long-chain n-3 PUFA, but actively converted LA into 20:4n-6.

Nitrogen- and energy-imbalanced diets affect hepatic protein synthesis and gluconeogenesis differently in growing lambs.

The aim of this study was to assess the metabolic fate of AA (endogenous or export protein synthesis, gluconeogenesis, or oxidation) after an imbalanced supply of energy and N in the diet of growing lambs. Eighteen INRA 401 lambs (3 mo old, 29.7 +/- 0.45 kg of BW) were fed 3 experimental diets, one providing a N and energy supply according to recommended allowances (control), one with 23% less N supply relative to energy (LN), and one with 19% less ME supply relative to N (LE). Animals were assigned to 6 blocks of 3, with each animal receiving 1 of the 3 diets, and the animals from each block were slaughtered on the same day. Liver slices from these lambs were incubated in a minimum salt medium (Krebs-Henseleit) containing physiological concentrations of propionate and AA as energy and N sources, similarly across all 3 treatments. Protein synthesis (endogenous and export) using [U-(14)C]valine and [(35)S]methionine, gluconeogenesis from [1-(14)C]propionate and [U-(14)C]alanine, and oxidation were measured. A relative sparing of AA at the liver level was observed with the LN diet because of reduced urinary N (-42%, LN vs. control, P < 0.001). The AA were also directed toward anabolic purposes in the LN diet via an increased endogenous and total export protein synthesis (+51%, LN vs. control, P = 0.01; also observed for fibrinogen synthesis, but not for albumin or transferrin) associated with a tendency for increased gluconeogenesis from alanine (+58%, LN vs. LE, P = 0.08). On the other hand, the LE diet resulted in a marked loss of N in urine (+24%, LE vs. control, P < 0.05), but no notable effect of the LE diet was demonstrated for protein synthesis or gluconeogenesis ex vivo. These data demonstrate a more efficient utilization of AA for anabolic purposes in the lambs fed LN, probably via an activation of some AA transport systems, to address the shortage of nitrogenous nutrients in the LN diet. By contrast, no such adaptation occurred in the LE lambs, probably because the regulatory mechanisms that prevailed in this case were the nutrient supply or hormones, which were not altered in our ex vivo experimental model.

9 cis,11 trans conjugated linoleic acid (CLA) is synthesised and desaturated into conjugated 18:3 in bovine adipose tissues.

Although endogenous synthesis of conjugated linoleic acid (CLA) in the mammary gland of lactating cows has been already well documented, no study has determined so far as to which tissue and/or organ is involved in CLA synthesis in the growing ruminant except one study showing that CLA synthesis does not occur in ruminant liver. In this context, adipose tissue appears to be a good candidate for endogenous synthesis of CLA in the growing ruminant. The aim of this study was to compare the respective metabolisms of 11trans 18:1 (vaccenic acid, VA) and 9cis,11trans 18:2 (rumenic acid) to that of stearic acid (the preferential substrate of Δ9 desaturase) in adipose tissues (subcutaneous, SC and intermuscular, IM) of six Charolais steers by using the in vitromethod of incubated tissue slices. Samples of SC and IM adipose tissues were incubated at 37°C for 16 h under an atmosphere of 95% O2/5% CO2 in a medium supplemented with 0.75 mM of fatty acid (FA) mixture (representative of circulating non-esterified FA) and 186 µM [1-14C]-18:0 or 58.6 µM [1-14C]-VA or 56 µM [1-14C]-9cis,11trans CLA. Viability of explants was verified by measuring metabolic functions (glucose uptake and glucose-6-phosphate dehydrogenase activity). After 16 h of incubation, FA uptake was similar for all FA (18:0, VA and 9cis,11trans 18:2) in both SC and IM adipose tissues (around 40%). Once in adipose tissue, all FA were preferentially esterified (>80% of cell FA) favouring neutral lipid synthesis (around 90% of esterified FA). Stearic acid was highly (27%) desaturated into oleic acid in SC adipose tissue whereas this desaturation was much lower (6.8%) in IM adipose tissue (P < 0.0001). VA was desaturated into 9cis,11trans CLA at a low extent of about 2.5% to 4.4% in both adipose tissues probably because of a limited affinity of Δ9 desaturase for VA. 9cis,11trans CLA was itself converted by desaturation into 6cis, 9cis,11trans 18:3 at the intensity of 10.8% and 14.5% of cell 9cis,11trans CLA in SC and IM adipose tissues, respectively. In conclusion, bovine adipose tissues of the growing ruminant were especially involved in the endogenous synthesis of CLA from VA and in its desaturation into conjugated derivative, mainly 6cis, 9cis,11trans 18:3, of which biological properties need to be elucidated.

Food restriction and refeeding in lambs influence muscle antioxidant status.

Compensatory growth, a frequent phenomenon observed in ruminants due to seasonal variation in food availability, affects protein metabolism including protein oxidation. These oxidation processes may have an impact on animal health as well as on meat protein degradation during post mortem aging (ie meat maturation). Sixteen male lambs were randomly divided into four groups. One group was fed ad libitum (C) and one group was food-restricted to 60% of the intake of the C group (R). The last two groups were restricted similarly to the R group and refed either ad libitum (RAL) or similarly to the C group (pair-feeding) (RPF). Muscles samples were taken immediately after slaughter. The present study showed that the restriction/refeeding pattern had no effect on protein oxidation in the muscles studied (longissimus dorsi (LD), semitendinosus (ST) and supraspinatus (SP)). However, total antioxidant capacity decreased after food restriction (-51%, -43%, P < 0.01 for ST and LD muscles, respectively) and re-increased only after ad libitum refeeding. This alteration in the total antioxidant status can partially be explained by the similar pattern of change observed in the glutathione concentration of the muscles (-25%, P < 0.05 for ST muscle and NS for the other muscles). However, none of the concentrations of other water-soluble antioxidants studied (carnosine, anserine, glutathione peroxidase and superoxide dismutase) were altered during compensatory growth. This study showed that an inappropriate feeding level following a nutritional stress induced alterations in the total antioxidant status (particularly that of glutathione), which may have consequences on animal health. Other consequences of a decrease of the animal antioxidant status in vivo could be an alteration of the protein oxidation processes during meat maturation.

Butters rich either in trans-10-C18:1 or in trans-11-C18:1 plus cis-9, trans-11 CLA differentially affect plasma lipids and aortic fatty streak in experimental atherosclerosis in rabbits.

Dairy fat contains high amounts of saturated fatty acids (FA), which are associated with cardiovascular disease (CVD) risk. Manipulation of dairy cows nutrition allows to decrease the saturated FA content of milk fat, and is associated with increases either in conjugated linoleic acid (CLA) and trans-11-C18:1 contents, or in trans-10-C18:1 content. CLA putatively exhibits beneficial properties on CVD risk, whereas trans FA are suspected to be detrimental. The present study compared the effects of a trans-10-C18:1-rich butter (T10 butter), a trans-11-C18:1+CLA-rich butter (T11-CLA butter) and a standard butter (S butter) on lipid parameters linked to the CVD risk and fatty streaks. Thirty-six White New Zealand rabbits were fed one of the three butters (12% of the diet, plus 0.2% cholesterol) for 6 (experiment 1) or 12 (experiment 2) weeks. Liver lipids, plasma lipids and lipoprotein concentrations (experiments 1 and 2) and aortic lipid deposition (experiment 2) were determined. The T10 butter increased VLDL-cholesterol compared with the two others, and total and LDL-cholesterol compared with the T11-CLA butter ( P < 0.05). The T10 butter also increased non-HDL/HDL ratio and aortic lipid deposition compared with the T11-CLA butter ( P < 0.05). The T11-CLA butter non-significantly reduced aortic lipid deposition compared with the S butter, and decreased HDL-cholesterol and increased liver triacyglycerols compared with the two other butters ( P < 0.05). These results suggest that, compared with the S butter, the T10 butter had detrimental effects on plasma lipid and lipoprotein metabolism in rabbits, whereas the T11-CLA butter was neutral or tended to reduce the aortic lipid deposition.

Factors influencing proportion and composition of CLA in beef.

Bovine meat is criticised for the bad nutritional image of its lipids and fatty acids. However, with dairy products, beef is the major source of conjugated linoleic acid (CLA) which could have several human health benefits. The present study compared, from data of five nutritional experiments on bovine animals performed by the laboratory, the impact of factors linked to the animals (breed, age, sex, type of muscle) and to feeding conditions (basal diet, lipid supplements) on the CLA proportion and composition in muscles. Among these factors, linseed supplementation was an efficient way to increase CLA proportion in beef (+22% to +36%) but was highly modulated by the nature of the basal diet, and by intrinsic factors (breed, age/sex, type of muscle) since these ones could modulate CLA proportion in beef from 24% to 47%. Moreover, these factors modified also the proportion of cis,trans-CLA, related to cis,cis- and trans,trans-isomers. Specific biological properties of these latter isomers should be determine to understand the consequences of intramuscular CLA isomer variations for the health of consumers.

Effects of dietary n-6 or n-3 polyunsaturated fatty acids protected or not against ruminal hydrogenation on plasma lipids and their susceptibility to peroxidation in fattening steers.

Two experiments were conducted using crossbred Salers x Charolais fattening steers fed diets enriched with no supplemental oilseeds or oils rich in either n-6 PUFA (from sunflower seeds) or n-3 PUFA (from linseeds) provided either as seeds incorporated in the diet (i.e., not protected from ruminal bacterial hydrogenation) or by chronic infusion into the duodenum (protected form). In the Sunflower experiment, animals (initial age = 454 +/- 20 d; initial BW = 528 +/- 36 kg) received a control diet for 70 d (CS, n = six) consisting of hay and concentrate, or the same basal diet supplemented with sunflower oil (4% of dietary DM), either fed as seeds (SS, n = six) or infused into the duodenum (ISO, n = six). The same experimental design was applied to animals (initial age = 412 +/- 33 d; initial BW = 536 +/- 33 kg) used in the Linseed experiment (CL, LS, and ILO; n = 8 per group). For all animals, blood was sampled every 15 d during 70 d. In both trials, a significant diet x time interaction (P < 0.001) was detected for plasma concentrations of apolipoprotein A-I, phospholipids, and free and esterified cholesterol, with values increasing with time during administration of the PUFA-rich diets being more evident with ISO and ILO diets. Plasma fatty acids were altered with oil infusions, with increased concentrations of n-6 (1.6-fold; P < 0.05) and n-3 PUFA (4.5-fold; P < 0.05) and of their respective indicies of peroxidizability (1.2- and 1.5-fold with Diets ISO and ILO, respectively; P < 0.05). In vitro copper-induced peroxidation of lipids revealed a decreased length of the lag phase in the process of conjugated diene generation by 48% (P < 0.005) with the ILO diet, indicating less resistance against peroxidation than in control steers. Compared with CS, the ISO treatment increased plasma alpha-tocopherol (x2.5; P < 0.05) leading to similar resistance against peroxidation. After depletion of this vitamin, the rates of peroxidation and production of conjugated dienes were greater (twofold; P < 0.05) with the ISO and ILO diets than with the others. In conclusion, infusion of sunflower or linseed oil into the duodenum altered the composition and distribution of plasma lipids and increased the plasma concentration of PUFA. The sensitivity of plasma PUFA to peroxidation depends on the plasma level of antioxidants, especially vitamin E, a nutrient important both for the health of animals and for the stability of the blood lipids until their tissue deposit.

Small intestine and liver microsomal triacylglycerol transfer protein in the bovine and rat: effects of dietary coconut oil.

The bovine liver is characterized by a chronic low capacity to secrete triacylglycerols (TAG). In situations favoring their hepatic synthesis, such as coconut oil feeding, TAG accumulate, leading to a lipid infiltration in the liver of preruminant calves. To assess the possible role of the microsomal TAG transfer protein (MTP) in this phenomenon and to put into evidence a tissue-specific regulation in the bovine species, we compared by Western blot the content in both MTP subunits in the liver and in different portions of the small intestine in preruminant calves and in growing rats receiving coconut oil or beef tallow as the sole source of fat in the diet. The pattern of MTP distribution was similar between calf and rat tissues, the jejunum being the major site for both MTP expression and intestinal absorption of dietary lipid endproducts. Concentrations of the MTP large and small subunits were 10- to 20-fold lower and 2- to 3-fold lower, respectively, in calf than in rat tissues, including the liver. Coconut oil in the diets of calves and rats did not significantly affect the expression of MTP large subunits even though TAG content was strongly increased 12-fold in the calf liver. These results clearly indicated that calf liver handled fat metabolically in a manner different from rat liver. However, present experimental conditions did not allow proof that MTP was directly related to the accumulation of fat in calf liver.

Fatty acid metabolism and very low density lipoprotein secretion in liver slices from rats and preruminant calves.

The liver of bovine animals possesses a low ability to secrete triglycerides (TG) as part of the very low density lipoproteins (VLDL) compared with rat liver. We compared hepatic fatty acid (FA) metabolism between rat and calf in order to determine the limiting steps of TG-VLDL secretion in bovine animals. Liver slices from young Sprague-Dawley rats and preruminant Holstein x Friesian calves were incubated for 7 h with increasing concentrations (0.1, 0.2, 0.4, and 0.8 mM) of [14C]oleate. The oxidation of oleate to CO2 and acid-soluble products was 2- to 3-fold higher in rat than in calf liver slices. Since oleate uptake was 2-fold higher in rat than in calf, the oxidation rate represented 20-29% of oleate uptake in both animal species. Oleate was essentially incorporated into the neutral lipids (75-87% of total lipids) that were stored mainly in the cytosol in both animal species (81-90% of neutral lipids). The accumulation of neutral lipids in the cytosol was 3.4-fold higher while VLDL secretion was 6- to 18-fold more efficient in rat than in calf liver slices. Our results indicate that the slow rate of VLDL secretion by bovine liver is probably due to the limited availability of TG for VLDL packaging rather than to the preferential oxidation of FA.

Developmental changes in apolipoprotein B gene expression in the liver of fetal calves.

Changes in apolipoprotein (apo B) gene expression in the liver were determined in fetal calves from 90 to 260 days of intrauterine life. Results were compared with those obtained from the livers of 1-month-old calves and adult cows. By Western blot analysis using a rabbit antiserum to bovine apo B, apo B100 was detected from 90 days of intrauterine life. Apo B100 was shown to be the only form of apo B detected in the liver of fetal calves whatever the gestational age indicating the lack of editing process during the prenatal period. Hepatic apo B contents were stable during intrauterine life and comparable to those of calves and lower than those of cows. Hepatic contents of apo B mRNA increased with the gestational age similarly to total RNA. Values of apo B mRNA at 260 days of intrauterine life were comparable to those in the liver of 1-month-old calves and adult cows. These results suggested that hepatic synthesis of calf apo B during fetal development is specifically regulated at a posttranscriptional level, either by a decrease in the rate of translation and/or by an increase in the rate of intracellular apo B degradation.