D. Bauchart

Effect of grass or concentrate feeding systems and rate of growth on triglyceride and phospholipid and their fatty acids in the M. longissimus thoracis of lambs

Thirty-two male Ile-de-France lambs were used in a factorial 2×2 design to analyse the effects of feeding systems (grass outdoor, G, or concentrate and hay indoor: stall, S) and of growth rate (low, L, or high, H) on total lipids, triglyceride (TG) and phospholipid (PL) contents and their fatty acid composition in the longissimus thoracis muscle (L.T.). Contents were lower for TG (10.4 vs. 15.8 mg/100 g fresh tissue, P<0.05) and higher for PL (6.4 vs. 5.8 mg/100 g fresh tissue, P <0.05) in grass-fed lambs compared to stall-fed ones. TG of grass fed lambs displayed lower proportions of palmitic acid (C16:0), monounsaturated fatty acids (MUFAs), linoleic acid (C18:2n-6) and other (n-6) polyunsaturated fatty acids (PUFA) and higher proportions of stearic acid (C18:0), linolenic acid (C18:3n-3), cis 9, 11 trans C18:2 and trans monounsaturated fatty acids. In PL of the same lambs only lower MUFA, C18:2n-6 and (n-6) PUFA and higher C18:3n-3, (n-3) PUFA and cis 9, 11 trans C18:2 were observed. Growth rate had no effect on lipid, TG or PL contents of longissimus thoracis. However C18:0 proportions were higher in TG and lower in PL for low growth rate lambs. Low growth rate lambs had also lower cis 9, 11 trans C18:2 in TG. Thus, irrespective of growth rate, the muscle lipids characteristic of grass fed lambs fulfilled the recommended features of human food components much better than that of stall fed lambs, namely for CLA and C18:3n-3. The lower ratios of (n-6) to (n-3) PUFA displayed in grass fed lambs both in TG and in PL were also useful to discriminate all the grass fed lambs from all the stall fed animals.

Lipid metabolism of liquid-associated and solid-adherent bacteria in rumen contents of dairy cows offered lipid-supplemented diets

The lipid distribution and fatty acid (FA) composition of total lipids, polar lipids and free fatty acids (FFA) were determined in liquid-associated bacteria (LAB) and solid-adherent bacteria (SAB) isolated from the rumen contents of seven dairy cows fitted with rumen fistulas. Two experiments, arranged according to a 4 x 4 and 3 x 3 Latin Square design, were performed using two basal diets consisting of one part hay and one part barley-based concentrate, and five lipid-supplemented diets consisting of the basal diet plus (g/kg dry matter):53 or 94 rapeseed oil, 98 tallow, 87 soya-bean oil or 94 palmitostearin. For all diets used, total lipids were 1.7-2.2 times higher in SAB than in LAB (P less than 0.05); this probably resulted from a preferential incorporation of dietary FA absorbed onto food particles. Addition of oil or fat to the diets did not modify the polar lipid content but increased the FFA content of SAB and LAB by 150%. Lipid droplets were observed in the cytoplasm in SAB and LAB using transmission electron microscopy, which suggested that part of the additional FFA was really incorporated into the intracellular FFA rather than associated with the cell envelope by physical adsorption. Linoleic acid was specifically incorporated into the FFA of SAB, which emphasized the specific role of this bacterial compartment in the protection of this acid against rumen biohydrogenation.

Bioavailability and antioxidant capacity of plant extracts rich in polyphenols, given as a single acute dose, in sheep made highly susceptible to lipoperoxidation.

Plant extracts rich in polyphenols (PERP) could represent interesting alternative antioxidants but their use in ruminants needs further investigation since the antioxidant capacity of PERP could be altered by digestive processes. The aim of the study was to investigate the bioavailability and the antioxidant capacity of four PERP (rosemary; grape; citrus; marigold) in ruminants made highly susceptible to lipoperoxidation by a continuous linseed oil infusion (4 % DM) in the duodenum. The PERP were given, as a single acute dose (10 % DM), directly into the rumen of sheep (n 5) and blood was then collected every 3 h over a period of 30 h. Grape was particularly efficient to enhance the plasma total antioxidant status (P < 0.05). Moreover, many new polyphenols were detected in the plasma and the identification of epicatechin in the grape group suggested that, contrary to monogastrics, ruminants can benefit from the antioxidant effect of polymeric proanthocyanidins. Finally, the four PERP tested, and more especially marigold, significantly reduced plasma susceptibility to liperoxidation (mean increase of lag phase: +5.9 min, P < 0.02; mean reduction of oxidation rate: - 1.7 A234/min, P < 0.01). In conclusion, the digestive processes in ruminants do not inhibit the antioxidant properties of PERP in vivo and are beneficial by improving the biological effect of polymeric proanthocyanidins. Further experiments are now necessary to determine the optimum dose of administration and to characterize the bioactive molecules.

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.

Prediction of lamb meat fatty acid composition using near-infrared reflectance spectroscopy (NIRS).

The aim of this study was to assess the feasibility of near-infrared reflectance spectroscopy (NIRS) for predicting lamb meat fatty acid composition. We compared ground vs. intact non-ground meat samples to determine whether grinding and homogenisation of meat samples improved the performance of the predictions. We used 76 male lambs, of which 32 were pasture-fed and 44 stall-fed with concentrate and hay. The reflectance spectrum of Longissimus lumborum muscle was measured at wavelengths between 400 and 2500nm. Predictions were better with ground than with intact muscle samples. NIRS accurately predicts several individual fatty acids (FA) (16:0, 18:0, 16:1 Δ9 cis, 17:1 Δ9 cis, 18:1 Δ9 cis, 18:1 Δ11 cis and 16:1 Δ9 trans) and several FA groups (total linear saturated FA, total branched saturated FA, total saturated FA, total cis monounsaturated FA (MUFA), total trans MUFA, total MUFA and total polyunsaturated PUFA). These results show the potential of NIRS as a rapid, and convenient tool to predict the major FA in lamb meat.

Enhancing fatty acid composition of milk and meat through animal feeding

In ruminants, extensive ruminal biohydrogenation of unsaturated fatty acids (FA) results in numerous cis and trans isomers of 18:1 and of conjugated and non-conjugated 18:2, the incorporation of which into ruminant products depends on the composition of the diet (forage vs concentrate) and of dietary lipid supplements. The low amount of 18:3n-3 (α-linolenic acid) absorbed explains its limited incorporation in meat and milk lipids. Its protection against hydrogenation has been an objective for several decades, but only encapsulation in a protein matrix is efficient. In non-ruminants, the FA composition of products is determined by dietary FA, despite minor differences in digestibility and in metabolic activity. Physicochemical differences in intestinal absorption processes between ruminants and non-ruminants can explain the lower FA digestibility in non-ruminants, especially for saturated FA. Unlike in non-ruminants, FA digestibility in ruminants does not depend on FA intake, except for 18:0. The decrease in cow butterfat, especially with concentrate diets, is generally attributed to t10–18:1 or t10,c12–18:2, but the regulation is probably more complex. Differences in terms of butterfat content and FA composition of milk between cow, ewe and goat responses to the amount and composition of ingested lipids are due to between-species variations in mammary metabolism. In animals bred for meat production, dietary 18:3n-3 results in increases in this FA and in n-3 long-chain polyunsaturated FA (20:5n-3, 22:5n-3) in muscles. The extent of this increase depends both on animal and nutritional factors. Grass is a source of 18:3n-3, which contributes to increased 18:3n-3 in muscle of ruminants as well as of pigs. Conjugated linoleic acids are mainly present in fat tissues and milk due to t11–18:1 desaturation. Their concentration depends on tissue type and on animal species. Non-ruminants fed synthetic conjugated linoleic acids incorporate them in significant amounts in muscle, depending on the isomer. All dietary manipulations favouring polyunsaturated FA incorporation in milk and meat lipids increase the risk of lipoperoxidation, which can be efficiently prevented by use of dietary combined hydro- and lipophilic antioxidants in the diet. Putative effects on organoleptic and technological quality of products deserve further studies.

Contribution of mitochondria and peroxisomes to palmitate oxidation in rat and bovine tissues

Total and peroxisomal palmitate oxidation capacities and mitochondrial enzyme activities were compared in tissues from growing rats, preruminant calves and 15-month-old bulls. Total palmitate oxidation rates were 1.9-5.2-fold higher in rat than in bovine tissues and 1.7-fold higher in the heart and muscles from calves than from growing bulls. The peroxisomal contribution to palmitate oxidation was similar between rats and bovines (i.e. calves and bulls) in liver (35-51%), heart (26%) but not in muscles (14 +/- 3% in rats vs 33 +/- 4.5% in bovines, P < 0.05). Mitochondrial enzyme activities were 1.8-4.8-fold higher in rat than in bovine tissues but the citrate synthase to cytochrome-c oxidase ratio was the highest in the liver (17-38), intermediate in the heart and muscles from calves and rats (6-10) and the lowest in heart and muscles from bulls (2-3, P < 0.05). In all tissues and animal groups, palmitate oxidation rates were similar per unit cytochrome-c oxidase activity, but not always per unit citrate synthase activity. Therefore, differences in mitochondrial contents (as between rats and bovines) or in mitochondrial characteristics (as between liver and muscles) relate to the differences in palmitate oxidation capacity.

Plant polyphenols associated with vitamin E can reduce plasma lipoperoxidation in dairy cows given n-3 polyunsaturated fatty acids

Diets rich in n-3 polyunsaturated fatty acids (PUFA) improve the nutritional value of ruminant products but also increase the risk of lipoperoxidation in plasma and tissues. The relative effectiveness of dietary antioxidants such as vitamin E (vit E) given alone or with plant extracts rich in polyphenols (PERP) containing rosemary, grape, citrus, and marigold was investigated in the plasma of mid-lactation dairy cows given diets enriched in 18:3 n-3. For a 30-d period, the animals were given a maize silage-based diet (control group C, n = 6) or the same basal diet supplemented with extruded linseed rich in 18:3 n-3 [50 g of oil/kg of diet dry matter (DM); group L, n = 6], extruded linseed + vit E (375 international units/kg of diet DM; 7,500 IU/cow per day; group LE, n = 6), or extruded linseed + vit E + PERP (10 g/kg of diet DM; group LEP, n = 5). Plasma susceptibility to lipoperoxidation was evaluated using in vitro parameters of conjugated diene formation (lag phase and maximum oxidation rate). Plasma indicators of lipoperoxidation and antioxidant status were analyzed in the 4 experimental groups as well as the fatty acid (FA) composition of total plasma lipids. At d 30, group L significantly increased plasma cholesterol esters (+57%) and phospholipids (+35%) compared with group C. It also increased plasma n-3 PUFA (4.7-fold increase) to the detriment of n-6 PUFA (-30%), leading to a higher peroxidizability index (+20%). Plasma in vitro lipoperoxidation was higher in group L (rich in 18:3 n-3) than in group C. Vitamin E alone had no effect on lipoperoxidation, whereas vit E in association with PERP lowered lipoperoxidation by increasing the resistance time against peroxidation (+47%) and by decreasing the oxidation rate (-48%) compared with group L at d 30. Surprisingly, in vivo plasma lipoperoxidation estimated by the plasma level of the major lipoperoxidation product (malondialdehyde) was not significantly increased in group L. This study shows, for the first time, that PERP supplied in association with vit E were able to reduce lipoperoxidation in lactating cows given a diet rich in 18:3 n-3, thereby helping to protect cows against the deleterious consequences of lipoperoxidation and potentially ensuring antioxidant potential for 18:3 n-3-enriched dairy products.

Colour, lipid and protein stability of Rhea americana meat during air- and vacuum-packaged storage: influence of muscle on oxidative processes.

Physicochemical characteristics and oxidative stability during storage were determined in Gastrocnemius pars interna (GN) and Iliofiburalis (IF) muscles of Rhea americana. Glycolytic potential (GP) and pH decline of muscles were measured within the first 24 h post mortem. Colour, lipid and protein stability were determined during storage of meat, i.e. 5 days under air-packaging at 4°C, or 28 days under vacuum-packaging at 4°C. In parallel, anti-oxidant status of muscles was estimated by measuring α-tocopherol content and anti-oxidant enzyme activities (superoxide dismutase and catalase), while pro-oxidant status was evaluated by determining haeminic iron and long chain fatty acids (especially polyunsaturated fatty acids). The ultimate pH was similar in both muscles, but the GP value was significantly higher in IF than in GN muscle. Haeminic iron and alpha-tocopherol content differed between muscles, with 30% more haeminic iron (p<0.05) and 134% more alpha-tocopherol (p<0.001) in IF than GN muscle. The IF muscle presented higher lipid content and lower PUFA/SFA ratio (polyunsaturated fatty acids/saturated fatty acids) than GN muscle. With storage under air-packaging, lipid and protein oxidation of rhea muscles increased up to 275% and 30%, respectively. This increase was more rapidly and marked in IF muscle. The IF also showed high level of metmyoglobin accumulation after 3 days of storage (47%) and was rejected by 1 consumer out of 2 in sensorial analysis. Under vacuum-packaging, both muscles showed a high stability of colour and no oxidation of lipids and proteins.

Indoor fattening of lambs raised on pasture. Part 1: Influence of stall finishing duration on lipid classes and fatty acids in the longissimus thoracis muscle

Forty male Ile-de-France lambs (10 blocks of 4 homologous lambs) were used to study the effects of four feeding systems on muscle fatty acids (FA): raising and finishing on cool-season grasses (G), raising on the same grasses and stall-finishing, indoors, on concentrates and hay, respectively, for 22 (GSS) or 41 days (GSL), and stall-feeding indoors on concentrates and hay during both growing and finishing periods (S). Twenty-four lambs only (6 blocks) were retained for comparison of growth performances, lipid content in the longissimus thoracis muscle (LT) and their FA composition according to treatment. The 16 other lambs (4 blocks) were removed from the comparison, due to a large spread in the growth of the lambs towards the end of the trial. No significant effects of treatment were seen on the rate of growth (221, 228, 243 and 245±SE 8.0g/d, respectively, for G, GSS, GSL and S groups), and the lipid contents of the LT (2.22, 2.16, 2.17 and 2.52±SE 0.11g/100g fresh tissue). Grazing, lowered n-6 PUFA (polyunsaturated fatty acids), and increased n-3 PUFA and C18:2 c9t11 (conjugated linoleic acid cis9, trans11) compared to concentrate feeding. The main effects of grazing were not removed by a short period of finish indoors on concentrate (GSS group), but C20:4 n-6 and C22:6 n-3 contents achieved the lowest contents in this group, with significant differences from the values observed for GSL and S groups (C20:4 n-6) or from the three other groups (C22:6 n-3). After a longer period of finish on concentrate (GSL group), C18:3 n-3 (linolenic acid), C18:2 c9t11 and long chain (LC) n-3 PUFA were brought to the levels observed in the S group. In terms of adequacy for human health, the C18:2 n-6/C18:3 n-3 ratios were favourably low in the four groups (2.6, 3.6, 4.9 and 5.2±SE 0.7, respectively, for G, GSS, GSL and S groups), the level observed in the case of G group being significantly lower than for the three other groups and the level observed for GSS group being significantly lower than for the GSL and S groups.