C. J. López-Bote

Sustained utilization of the Iberian pig breed.

The Iberian pig is one of the scarce non-improved swine breeds which survives the modern techniques of pig production based on improved genotypes. This is attributed both to its perfect adaptation to the Mediterranean natural ecosystem and the high quality of its products. The production of meat products from Iberian pigs has very little in common with that of meat products obtained from selected pigs raised under intensive conditions, and it constitutes an example of the preparation of high quality meat products, comparable to the most exquisite food products in the world. The production of Iberian pig is deeply bound to the Mediterranean ecosystem. It is a rare example in the world swine production where the pig contributes so decisively to the preservation of the ecosystem. The aim of this review is to describe in detail the traditional feeding of the Iberian pigs in La Dehesa and to discuss some aspects of the use of alternatives to this production system. Some of the experience in the formulation of compounds feeds for Iberian pigs and in the processing of meat products could be useful in the feeding of other pig genotypes and in different meat processing strategies.

Effect of dietary administration of oil extracts from rosemary and sage on lipid oxidation in broiler meat

1. Oxidation of meat and membrane from broilers fed on a diet containing 500 mg/kg rosemary and sage extracts was compared to meat and membrane oxidation from broilers receiving a control diet (not enriched with antioxidants) and a diet enriched in alpha-tocopheryl acetate (200 mg/kg). 2. After 9 d of refrigerated storage, thiobarbituric acid reactive substances of white meat from broilers fed on the control and the alpha-tocopheryl acetate-enriched diets were 0.51 and 0.25 mg malonaldehyde/kg meat, respectively. Values for meat from broilers fed on the diets containing the rosemary and sage extracts were in the range 0.30 to 0.35 mg malonaldehyde/kg meat, significantly lower than those from birds fed on the control diet. A similar trend was observed in the dark meat but differences were not significant at 9 d of storage. Similar trends were observed in raw samples stored at -20 degrees C for up to 4 months and in samples cooked at 70 degrees C and kept stored under refrigeration for up to 4 d. 3. The meat from broilers fed on the diet containing spice extracts had smaller concentrations of total cholesterol oxidation products (COPS) than meat from the control group (P < 0.05). Supplemental alpha-tocopheryl acetate reduced the COPS concentrations to a greater extent than did spice extracts (P < 0.05). 4. A similar trend was observed in microsomal fraction isolates, in which the rate of metmyoglobin/hydrogen peroxide-catalysed lipid peroxidation was lower in animals receiving spice extracts than in those fed on the basal diet.

Volatile components of dry cured Iberian ham

Abstract A study was conducted to identify the volatile compounds in aged Iberian hams, processed in the traditional way. The volatiles from aged hams were entrained in cold traps after distillation under high vacuum. The distillate was collected with dichloromethane and analysed by gas-chromatography-mass-spectrometry (GC-MS). Seventy-seven compounds were tentatively identified in the volatile fraction. Alkanes (12), branched alkanes (14), aldehydes (13), and aliphatic alcohols (9) dominated the volatiles. Small amounts of lactones (5), esters (9) and ketones (7) and other miscellaneous compounds were also present. The possible origins of these compounds and their relationship with the characteristic flavour of this product are discussed.

Lipid oxidative changes in the processing of Iberian pig hams

Attempts to identify the compounds responsible for the particular flavour of Iberian pig ham indicate that many derive from lipid oxidation. In the present work, the evolution of the degree of acidity, the peroxide value and the content of certain aldehydes was followed to assess the extent of the lipid oxidation in the Biceps femoris and Semimembranosus muscles of Iberian pig hams. Lipolysis occurs continuously throughout the process, being especially intense immediately after salting and during drying. The peroxide value was higher after salting and in the first stage in the cellar. Aldehyde content rose continuously in the first stages, but the sharpest rise took place before drying. Saturated aldehydes were more abundant than unsaturated. During the last stage, autoxidation seems to be considerably reduced.

Adaptation of lipid metabolism, tissue composition and flesh quality in gilthead sea bream ( Sparus aurata ) to the replacement of dietary fish oil by linseed and soyabean oils

Linseed (LO) and soyabean (SO) oils were evaluated as fish-oil (FO) substitutes in the diets of marketable-sized gilthead sea bream (Sparus aurata). Practical diets were designed factorially with the lipid added as follows (%): FO 100, LO 60+FO 40, LO 80+FO 20, SO 60+FO 40, SO 80+FO 20. The effects of experimental diets on growth, fatty acids patterns in liver and muscle, flesh quality variables and activities of selected enzymes involved in lipid synthesis and catabolism were determined at the end of a 7-month trial. Fatty acid composition of liver and muscle generally reflected the fatty acid composition of the diets. The n-3 PUFA levels were significantly reduced by the inclusion of vegetable oils. This tendency was more pronounced for EPA than for docosahexaenoic acid. The n-3:n-6 fatty acid ratio reached the lowest values in fish fed the SO diets; this was associated with a higher liver lipid deposition. No differences were found in fillet texture and pH. However, under conditions of forced peroxidation, muscles from fish fed the SO diets had lower peroxidation levels. Vegetable oil substitution decreased lipogenesis in liver and this effect was greatest at the highest substitution level. In contrast, muscle beta-oxidation enzymes had increased activities with vegetable oil substitution. Thus, the lower hepatic lipogenesis was correlated with an increased lipid utilisation in muscle. It is concluded that growth and lipid metabolism were affected by experimental diets.

Growth, digestibility and fatty acid utilization in large Atlantic salmon (Salmo salar) fed varying levels of n-3 and saturated fatty acids

Dietary fatty acids strategies of metabolic relevance were studied in large Atlantic salmon. Fish with an average weight of 1.8 kg were fed four experimental diets with the same basal composition but coated with different oils, according to a 2 x 2 factorial design. The two factors were the level of saturated fatty acids (SAFA) in the diet (30% or 19% of the total fatty acids) and the level of n-3 fatty acids (35% or 20%). The oils used were a pure fish oil (herring oil), or combinations of the fish oil with a n-3 fatty acid concentrate and/or palm stearin rich in SAFA. All diets contained the same concentration of fat, protein and carbohydrates. Productive measurements were recorded and apparent digestibility coefficients (ADC) of fat and selected fatty acids calculated. Heart muscle mitochondrial L-3-hydroxyacyl-CoA dehydrogenase (L3HOAD), and liver glucose 6-phosphate dehydrogenase (G6PD) and malic enzyme (ME) were used as markers to determine the effects of dietary fat type on fat catabolism and synthesis, respectively. Significant differences in growth were observed among fish fed the different diets, with the specific growth rate (SGR) being higher in the groups fed diets with low levels of n-3 fatty acids (P<0.003). Fat digestibility was highest in fish fed the low saturated-low fatty acid n-3 diet (93.31%) and lowest in fish fed the high saturated-high n-3 diet (79.11%). All enzymatic activities were higher in the groups fed the diets with low levels of n-3 fatty acids. Dietary polyunsaturated fatty acids (PUFA) were negatively correlated with all enzymatic activities. Monounsaturated fatty acids (MUFA) positively correlated with both the ME and L3HOAD activities, especially 16:ln-7, 20:1 and 22:1, which showed the highest Pearson correlation coefficients. Dietary SAFA negatively correlated with enzymatic activities, except 14:0, which positively correlated with ME (r=0.95; P<0.0001), and L3HOAD (r=0.81; P<0.0002). The results of this study suggest that the lipid metabolism of large Atlantic salmon is readily influenced by the fatty acids supplied in the diet according to their unsaturation and chain length. Dietary 16: In-7, 20:1 and 22:1 are preferred substrates for heart mitochondrial β-oxidation.

Short-term modulation of lipogenesis by macronutrients in rainbow trout ( Oncorhynchus mykiss ) hepatocytes

Rainbow trout (Oncorhynchus mykiss) hepatocytes were cultured under simulated conditions of varying nutritional status to explore the short-term modulation by dietary substrates of the main lipogenic enzymes: glucose-6-phosphate dehydrogenase (G6PD), malic enzyme (ME), ATP-citrate lyase (ACL), acetyl-CoA carboxylase (ACoAC) and fatty acid synthetase (FAS). Primary cultures were individually exposed to varying amounts of glucose, hydrolysed casein and long-chain polyunsaturated fatty acids (PUFA) for 12 h. A second set of experiments was designed to evaluate the effects of mixing different relative amounts of these macronutrients in the culture medium. Glucose concentrations of up to 20-25 mm showed a stimulatory effect on G6PD, ME, ACL and ACoAC activity while an earlier inhibitory effect on FAS was observed at 10-20 mm glucose The use of hydrolysed casein as a nutritional source of amino acids inhibited the activity of FAS and ME and stimulated G6PD, ACoAC and ACL activity Low levels of linolenic acid exerted a stimulatory effect on all the lipogenic enzymes assayed with the exception of FAS, and increased amounts showed some inhibition of lipogenic activities Eicosapentaenoic acid and docosahexaenoic acid showed a similar effect, although the former strongly inhibited FAS activity while the latter showed greater potential to inhibit ACoAC and G6PD. A complete change in the relative levels of glucose, hydrolysed casein and PUFA in turn led to changes in the enzyme activity patterns observed. The present study shows the feasibility of exploring the direct regulation of lipogenesis in isolated fish cells by varying the relative amounts of main macronutrients, mimicking in vivo dietary conditions. It is felt that such an approach may serve to investigate the macronutrient regulation of other metabolic pathways.

THE METABOLIC USE OF ENERGY FROM DIETARY FAT IN BROILERS IS AFFECTED BY FATTY ACID SATURATION

1. Two experiments were performed to evaluate the effect of dietary fat on performance and fat and protein accretion in broiler chickens according to the degree of saturation. 2. The first experiment was designed to test 2 sources of dietary fat and 3 levels of dietary energy using a factorial (2 × 3) experimental design. The foods were formulated to maintain a constant ratio of energy to protein (and other nutrients). There were no significant differences in weight gain, intake, final body weight or food to gain ratio between broilers fed on diets differing solely in the degree of fat saturation. Broilers fed on diets containing animal fat showed higher whole-body fat retention (P = 0.02) and lower protein accretion (P = 0.03) than those fed on diets containing vegetable oils. 3. In the second experiment, only 1 concentration of fat (tallow, lard or sunflower oil) was incorporated into the experimental diets, providing different energy to protein ratios. The carcase protein content was not affected by dietary fat source, while total fat accretion (P = 0.01) and energy retention (P = 0.14) were highest in broilers fed on a diet containing tallow. 4. The findings suggest that the degree of saturation of dietary fats affects their metabolic use and fat accumulation in broiler chickens.

Feeding Iberian pigs with acorns and grass in either free-range or confinement affects the carcass characteristics and fatty acids and tocopherols accumulation in Longissimus dorsi muscle and backfat

The experiment was undertaken to provide information on the influence of grass intake in a high fat diet based on acorns, in either free-range or confinement, on the carcass yield and characteristics, and on the accumulation of fatty acids and tocopherols. Groups raised free-range or with acorns and grass in confinement had the highest total backfat. Grass addition to the feed did not significantly modify the carcass weight and cut yield. However, outdoor raising produced lower carcass weights and yield, Longissimus dorsi muscle and ham weights than those fed the formulated diet or acorns and grass in confinement. Neither grass intake nor outdoor rearing did modify significantly the proportion of saturated fatty acids of the backfat. However, a lower proportion of saturated fatty acids was found in the intramuscular neutral lipids from pigs fed outdoors. Pigs reared free-range had significantly (P=0.0001) higher proportions of C18:1n-9 in the inner layer and in the intramuscular neutral lipids than the other groups. The grass intake significantly (P=0.0001) increased the proportion of C18:3n-3 in the inner and outer fat layers and intramuscular neutral lipids, while the outdoor rearing system not only affected on the proportion of linolenic acid but also C22:5 and C22:6 of the inner backfat layer and intramuscular polar lipids. These results suggest that the outdoor rearing allows a higher accumulation of n-3 fatty acids maybe due to an increased activity of the desaturase and elongase enzymes. On the other hand, the accumulation of tocopherols was not significantly modified neither by the grass intake nor the outdoor rearing, while differences were detected by the type of feeding (diet vs. acorns/acorns and grass). It is concluded, that the outdoor rearing system affects the nutritional value of meat, mainly by improving the fatty acid composition.

Effects of feeding in free-range conditions or in confinement with different dietary MUFA/PUFA ratios and α-tocopheryl acetate, on antioxidants accumulation and oxidative stability in Iberian pigs

The experiment was undertaken to provide information of the influence of feeding either free-range or in confinement with different dietary MUFA/PUFA ratios and α-tocopheryl acetate supplementation (40 vs. 200 mg/kg) on tocopherol content and susceptibility to lipid oxidation of muscle and microsomes in Iberian pigs. The grass provided to the pigs had a similar α-tocopherol concentration to that observed for diets supplemented with 200 mg/kg α-tocopheryl acetate, and acorns supplied fourfold higher content of γ-tocopherol than the experimental diets. The α- and γ-tocopherol contents of muscle reflected the tocopherol concentration of the diets. Mono and Medium diets produced a similar MUFA/PUFA ratio in neutral and polar lipids of pig muscle to those fed outdoors. The lowest TBARS numbers were found in muscle samples from pigs fed a MUFA-enriched diet in confinement. No significant influence of free-range feeding or dietary fat on drip loss was found. However, α-tocopheryl acetate supplementation reduced (P<0.05) drip loss. Dietary vitamin E supplementation decreased the membrane lipid oxidation by 18% after 120 min. However, free-range feeding decreased the extent of microsome oxidation by 20%, 56% and 82% after 120 min when compared with those groups fed in confinement with high, medium and low MUFA/PUFA ratios, respectively. The hexanal concentration of muscle showed a similar trend to that observed for microsome induced-oxidation, suggesting, that hexanal determination is a more accurate method to measure lipid oxidation in iberian pig muscle than the thiobarbituric acid test.