Rui J.B. Bessa

Effect of genotype, feeding system and slaughter weight on the quality of light lambs: II. Fatty acid composition of meat

One hundred and eight Merino Branco and crossbred Ile de France×Merino Branco ram lambs were used to evaluate the effects of genotype, feeding system and slaughter weight on fatty acid composition of meat (longissimus thoracis muscle). At 60 days of age, lambs were assigned to the experimental feeding systems: P—pasture with dams; SP—pasture with dams, plus concentrate ad libitum; C—weaning and concentrate ad libitum. Lambs were slaughtered at 24 and 30 kg live weight. The meat had a low fatty acid content. Intramuscular fatty acid (FA) composition was not affected by genotype. Pasture raised lambs (P and SP) showed higher proportion of n-3 FA, conjugated linoleic acid (CLA) and trans-octadecenoic FA, and lower n-6:n-3 ratio, than C lambs. When slaughter weight increased, total FA content increased. Palmitic acid and monoenoic FA increased and polyunsaturated FA decreased with slaughter weight. The CLA proportion increased with slaughter weight, but only for lambs raised on pasture (P and SP). Fatty acid profile was effective in the identification of lamb feeding systems.

The effect of genotype, feeding system and slaughter weight on the quality of light lambs 1. Growth, carcass composition and meat quality

One-hundred and eight Merino Branco (MB) and crossbred Ile de France x Merino Branco (IFxMB) ram lambs were used to evaluate the effects of genotype, feeding system and slaughter weight on growth, carcass composition and meat quality traits. At an average age of 53 days, lambs were randomly assigned to three feeding systems: P, pasture with dams; SP, pasture with dams, plus concentrate ad libitum; C, weaning, and concentrate ad libitum. Lambs were slaughtered at 24 or 30 kg live weight. The carcass left sides were partially dissected and the Longissimus thoracis and Longissimus lumborum muscles were used for meat quality determinations. Genotype had only minor effects on lamb growth as well as on carcass composition and meat traits. Growth rate was higher, and muscle proportion was lower in C than in SP, and in SP than in P. When lambs were fed only pasture (P), carcasses were mainly classified as very lean (class 1), especially when lambs where slaughtered at 24 kg. For SP and C, carcasses were mainly graded in class 2. Lambs in P, showed lower water-holding capacity. When slaughter weight increased, muscle proportion decreased but carcasses were still considered to be lean (class 2). Meat colour became darker and redness increased with slaughter weight, but shear force remained unchanged.

Reticulo-rumen biohydrogenation and the enrichment of ruminant edible products with linoleic acid conjugated isomers

Abstract Conjugated linoleic acid (CLA) is presently under extensive research because of its potent anticarcinogenic effects and also because of its effects on the immune system and on lipid metabolism. The biological effects of these acids are briefly reviewed. Ruminant edible products are the richest natural sources of CLA because they are supposed to be mainly derived from rumen biohydrogenation of linoleic acid. The end product of the main and more effective linoleic acid biohydrogenation pathway is the trans -11 C18:1. The contents of CLA and trans C18:1 acids are positively correlated in rumen contents, fat depots and milk, although their ratio ( trans C18:1/CLA) varies. Nutritional strategies for the enrichment of ruminant products with CLA will currently be achieved by increasing the supply of linoleic acid in reticulo-rumen metabolism, although this will also result in an increase in trans -11 C18:1. The inclusion in the diet of soybean oil up to 12% does not greatly affect the trans C18:1/CLA ratio. The potential deleterious effects of trans octadecenoic acids on human health have been considered even if no consensus is reached. Therefore it will be important to manipulate rumen biohydrogenation in order to increase CLA output with a low trans C18:1/CLA ratio. Although further investigation is needed, scarce data already suggest this could be achieved by increasing the supply of linoleic rich fat and modifying the basal diet or include ionophores.

Effect of cooking methods on fatty acids, conjugated isomers of linoleic acid and nutritional quality of beef intramuscular fat

The effect of boiling, microwaving and grilling on the composition and nutritional quality of beef intramuscular fat from cattle fed with two diets was investigated. Longissimus lumborum muscle from 15 Alentejano young bulls fed on concentrate or pasture was analyzed. Cooking losses and, consequently, total lipids, increased directly with the cooking time and internal temperature reached by meat (microwaving>boiling>grilling). The major changes in fatty acid composition, which implicated 16 out of 34 fatty acids, resulted in higher percentages in cooked beef of SFA and MUFA and lower proportions of PUFA, relative to raw meat, while conjugated linoleic acid (CLA) isomers revealed a great stability to thermal processes. Heating decreased the PUFA/SFA ratio of meat but did not change its n-6/n-3 index. Thermal procedures induced only slight oxidative changes in meat immediately after treatment but hardly affected the true retention values of its individual fatty acids (72-168%), including CLA isomers (81-128%).

Rumen biohydrogenation-derived fatty acids in milk fat from grazing dairy cows supplemented with rapeseed, sunflower, or linseed oils

The effects of supplementation with rapeseed, sunflower, and linseed oils (0.5 kg/d; good sources of oleic, linoleic, and linolenic acids, respectively) on milk responses and milk fat fatty acid (FA) profile, with special emphasis on rumen-derived biohydrogenation intermediates (BI), were evaluated in a replicated 4 x 4 Latin square study using 16 grazing dairy cows. The dietary treatments were 1) control diet: 20-h access to grazing pasture supplemented with 5 kg/d of corn-based concentrate mixture (96% corn; CC); 2) RO diet: 20-h access to grazing supplemented with 4.5 kg/d of CC and 0.5 kg of rapeseed oil; 3) SO diet: 20-h access to grazing supplemented with 4.5 kg/d of CC and 0.5 kg of sunflower oil; and 4) LO diet: 20-h access to grazing supplemented with 4.5 kg/d of CC and 0.5 kg of linseed oil. Milk fatty acids were converted to methyl esters and analyzed by gas-liquid chromatography and silver-ion HPLC. Dietary treatments had no effect on milk production or on milk protein content and milk protein production. Supplementation with rapeseed and sunflower oils lowered milk fat content and milk fat production, but linseed oil had no effect. Inclusion of dietary vegetable oils promoted lower concentrations of short-chain (including 4:0) and medium-chain FA (including odd- and branched-chain FA) and 18:3n-3, and higher concentrations of C(18) FA (including stearic and oleic acids). The BI concentration was higher with the dietary inclusion of vegetable oils, although the magnitude of the concentration and its pattern differed between oils. The RO treatment resulted in moderate increases in BI, including trans 18:1 isomers and 18:2 trans-7,cis-9, but failed to increase 18:1 trans-11 and 18:2 cis-9,trans-11. Sunflower oil supplementation resulted in the highest concentrations of the 18:1 trans-10, 18:1 cis-12, and 18:2 trans-10,trans-12 isomers. Concentrations of 18:1 trans-11 and 18:2 cis-9,trans-11 were higher than with the control and RO treatments but were similar to the LO treatment. Concentration of BI in milk fat was maximal with LO, having the highest concentrations of some 18:1 isomers (i.e., trans-13/14, trans-15, cis-15, cis-16), most of the nonconjugated 18:2 isomers (i.e., trans-11,trans-15, trans-11,cis-15, cis-9,cis-15, and cis-12,cis-15), and conjugated 18:2 isomers (i.e., trans-11,cis-13, cis-12,trans-14, trans-11,trans-13, trans-12,trans-14, and trans-9,trans-11), and all conjugated 18:3 isomers. The LO treatment induced the highest amount and diversity of BI without decreasing milk fat concentration, as the RO and SO treatments had, suggesting that the BI associated with 18:3n-3 intake may not be the major contributors to inhibition of mammary milk fat synthesis.

Fatty acid composition, conjugated linoleic acid isomers and cholesterol in beef from crossbred bullocks intensively produced and from Alentejana purebred bullocks reared according to Carnalentejana-PDO specifications

The purpose of this study was to characterise and compare the nutritional value of Portuguese Carnalentejana-PDO beef, obtained from Alentejana purebred bullocks reared in a semi-extensive system, with the meat from Alentejana×Charolais crossbred bullocks produced in a conventional intensive concentrate-based system. In addition, seasonal changes in Carnalentejana-PDO beef quality were assessed, by analysing meat samples from animals slaughtered in early autumn and late spring. The results showed that beef-PDO has different intramuscular fat characteristics in comparison with meat from crossbred bullocks fed intensively with concentrate. However, the finishing period of Alentejana purebred bullocks with concentrate seems to attenuate most of the typical grass-fed characteristics of meat fat. Nevertheless, from a human nutrition perspective, Carnalentejana-PDO beef seems to be healthier than that from intensively reared animals since it has a lower n-6/n-3 ratio, although always above the recommended guidelines for human diet, and higher proportions of c9,t11 conjugated linoleic acid (CLA) isomer and total CLA relative to saturated fatty acids plus total cholesterol (CLA/SFA+CHR). Furthermore, no seasonal variation in the nutritional quality of beef-PDO was apparent. Taken together, the data indicate that Carnalentejana-PDO beef is of greater nutritional value than intensively produced beef from crossbred bullocks throughout the year.

Effect of dietary replacement of sunflower oil with linseed oil on intramuscular fatty acids of lamb meat

The effect of stepwise replacement of dietary sunflower oil (SO) with linseed oil (LO) on carcass composition, meat colour and fatty acid (FA) composition of intramuscular lipids of lamb meat was investigated. Thirty-six lambs were fed one of four diets consisting of pellets of lucerne with oil (60g/kg): the diet varied in the composition of oil added and were: 100% SO; 66.6% SO plus 33.3% LO; 33.3% SO plus 66.6% LO and 100% LO. The experimental period was 7weeks. Live slaughter weight, hot carcass weight and intermuscular fat percentage of chump and shoulder increased linearly with replacement of SO by LO. Total FA content of longissimus dorsi muscle and polar and neutral lipids were not affected by the treatments. Replacement of SO with LO increased the content of 18:3n-3 and total n-3 long chain (⩾C(20)) PUFA (LC-PUFA) and decreased the 18:2n-6, total n-6 LC-PUFA and 18:2 cis-9, trans-11 in meat lipids. Maximum CLA concentration (42.9mg/100g fresh muscle) was observed with 100% of SO, decreasing linearly by SO with LO replacement. Maximum n-3 LC-PUFA was predicted to be 27mg/100g of fresh muscle at 78% of SO with LO replacement. Considering both CLA and n-3 LC-PUFA, the maximum levels were estimated to be reached at 52% of replacement of SO with LO. The utilization of blends of SO and LO is a good approach for obtaining lamb meat enriched with both CLA and n-3 LC-PUFA.

Effect of Dietary Dehydrated Pasture and Citrus Pulp on the Performance and Meat Quality of Broiler Chickens

Some feedstuffs containing significant levels of fiber may be a good source of bioactive compounds that may contribute to improving broiler meat quality. However, high fiber level can have a negative impact on broiler performance. A study was undertaken to investigate the impact of incorporating citrus pulp (5 or 10%) or dehydrated pasture (5 or 10%) on the performance, carcass yield, and characteristics of broiler chickens. A diet containing neither citrus pulp nor dehydrated pasture was used as control. The results on growth performances showed that daily weight gain was reduced by 26% in birds of the 10% citrus pulp treatment (P<0.05). Compared with the control treatment, increases in feed intake occurred in birds consuming diets with 5 or 10% citrus pulp, which resulted in significantly higher feed conversion rates with the 10% level. Under the same incorporation rate, dehydrated pasture had effects less evident on the performances of broiler chicken. In addition, diets containing citrus pulp, displaying higher percentages of soluble nonstarch polysaccharides, increased small intestine relative length, and reduced carcass yield. Inclusion of 10% dehydrated pasture in diets resulted in improved breast skin yellowness (P<0.05). Finally, the results revealed that incorporation of the nonstarch polysaccharide-rich feedstuffs had a major impact on the fatty acid profile (affected 16 of 21 fatty acids) of broiler meat. Polyunsaturated fatty acids content in meat was higher in birds consuming the highest levels of both citrus pulp and dehydrated pasture, leading to increased ratios of polyunsaturated to saturated fatty acids. Together, the results suggest that incorporation of moderate levels of dehydrated pastures in poultry diets has a minor impact on broiler performance and can contribute significantly to improve breast skin yellowness and fatty acid composition of meat.

Effect of slaughter season on fatty acid composition, conjugated linoleic acid isomers and nutritional value of intramuscular fat in Barrosã-PDO veal

This paper describes the influence of slaughter season on lipid content, fatty acid composition, conjugated linoleic acid (CLA) isomeric profile and nutritional value of fat in Barrosã veal from calves reared according to the specifications of the Protected Designation of Origin (PDO). Barrosã purebred calves (n=27) were raised in a traditional production system and slaughtered in early autumn (October) and late spring (June). Barrosã-PDO veal only presented seasonal differences in the levels of some minor fatty acids and CLA isomers, as well as in the PUFA/SFA ratio. Based on the analysed grass intake indicators, it was shown that veal-PDO has similar values to pasture-fed cattle for both slaughter seasons. From a human nutrition perspective, intramuscular fat in Barrosã-PDO veal has a high nutritional value throughout the year, since CLA contents and the percentages of the c9,t11 isomer are relatively high, and the n-6/n-3 ratios are within the recommended values for the human diet.

Comparison of two gas-liquid chromatograph columns for the analysis of fatty acids in ruminant meat

Two gas-liquid chromatograph capillary columns for the analysis of fatty acids (FA) in ruminant fat are compared. Those columns are the CP-Sil 88 of 100 m long with a highly polar stationary phase and the Omegawax 250 of 30 m long with a stationary phase of intermediate polarity. Fatty acid methyl ester (FAME) patterns of branched-chain, cis and trans octadecenoate isomers, as well as conjugated and non-conjugated 18:2 and 18:3 isomers are fairly different between columns, even though most of the FAME could be separated on either column. However, the CP-Sil 88 showed better resolution of 18:1 isomers than Omegawax 250. The analysis of 96 samples of ruminant meat fat in both chromatographic systems showed that averages obtained for total FA content and for most of the individual FA did not differ between columns. Moreover, regression analysis of Omegawax and CP-Sil 88 data is highly correlated. Quantitative differences between chromatographic systems were detected for samples containing more than 66 mg fatty acids per gram of muscle dry matter.