Effect of sunflower seed supplementation on the fatty acid composition of muscle and adipose tissue of pasture-fed and feedlot finished beef J. A. Basarab1, P. S. Mir2, J. L. Aalhus3, M. A. Shah2, V. S. Baron3, E. K. Okine4, and W. M. Robertson3 1Alberta Agriculture, Food and Rural Development, Western Forage Beef Group, Lacombe Research Centre, 6000 C & E Trail, Lacombe, Alberta, Canada T4L 1W1 (e-mail:
[email protected]); 2Agriculture and AgriFood Canada, Lethbridge Research Centre, 5403-1 Avenue South, PO Box 3000, Lethbridge, Alberta, Canada T1J 4B1; 3Agriculture and Agri-Food Canada, Lacombe Research Centre, 6000 C & E Trail, Lacombe, Alberta, Canada T4L 1W1; 4Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5. Received 25 May 2006, accepted 30 September 2006.
Basarab, J. A., Mir, P. S., Aalhus, J. L., Shah, M. A., Baron, V. S., Okine, E. K. and Robertson, W. M. 2007 Effect of sunflower seed supplementation on the fatty acid composition of muscle and adipose tissue of pasture-fed and feedlot finished beef. Can. J. Anim. Sci. 87: 71–86. This study examined the effects of whole sunflower seed (WSS) supplementation on pasture and in finishing diets on the fatty acid profile of muscle [gastrocnemius (GN), longissimus thoracis (LT), intercostals (IC)] and adipose tissue [subcutaneous (SQ), intermuscular (IM)]. Ninety-six yearling steers averaging 410 kg were randomly allocated to three pasture (P) dietary treatments: (1) supplemented with WSS (P-WSS, n = 48); (2) supplemented with cracked barley grain (P-BAR, n = 24), and (3) not supplemented (P-CON, n = 24). Steers rotationally grazed meadow bromegrass-alfalfa pasture for 66 d. After 66 d on pasture, half the steers from each dietary treatment were trucked to a feedlot where they were adjusted to finishing diets. The remaining 48 steers continued with their dietary treatment on stockpiled pasture for an additional 47 d (SD = 11) until they were slaughtered directly off pasture. In the feedlot, half the steers from each pasture dietary treatment were fed either a control (83% rolled barley, 10% alfalfa hay, 5% barley silage, 1% molasses and 1% vitamin/mineral premix; F-CON) or a WSS supplemented diet (68% rolled barley, 15% WSS, 10% alfalfa hay, 5% barley silage, 1% molasses and 1%; F-WSS). Provision of WSS to steers grazing pasture for 113 d followed by direct slaughter increased cis-9, trans-11 CLA content in the muscles by 17.0 to 29.1% (GN, 0.570 vs. 0.467; LT, 0.515 vs. 0.399; IC, 0.531 vs. 0.454 mg 100 mg–1 fat) and in adipose tissue by 32.0% in IM (0.636 vs. 0.482 mg 100 mg–1 fat) and 40.3% in SQ (0.839 vs. 0.598 mg 100 mg–1 fat) fat depots compared with control steer slaughtered directly off pasture. On pasture supplementation of WSS also increased C18:1 trans-11 content in muscle by 20.1 to 40.8% and in IM adipose tissue by 55.0%. The inclusion of WSS in finishing diets increased CLA cis-9 trans-11 content in muscle by 31.5 to 209.0% and in adipose tissue by 40.7% in the SQ fat and 25.6% in the IM fat. It also increased C18:1 trans-11 content in muscle by 80.0 to 207.3% and in adipose tissue by 181% in the IM fat and 224% in the SQ fat. Strong, positive relationships were observed between tissues in the concentration of CLA cis-9 trans-11, C18:1 trans-11 and C18:3 (R2, 0.69–0.88; P < 0.0001). The results indicate that increasing the dietary polyunsaturated fatty acids in beef cattle diets increased the levels of CLA cis-9 trans-11 and C18:1 trans-11 in muscle and fat tissues. Key words: Beef, pasture, feedlot, fatty acid profile, conjugated linoleic acids, vaccenic acid Basarab, J. A., Mir, P. S., Aalhus, J. L., Shah, M. A., Baron, V. S., Okine, E. K. et Robertson, W. M. 2007. Effets d’un supplément de graines de tournesol sur la composition des acides gras dans les tissus musculaire et adipeux des bovins de boucherie engraissés à l’herbe ou finis en parquet. Can. J. Anim. Sci. 87: 71–86. Les auteurs ont examiné l’incidence des régimes de paissance et de finition enrichis de graines de tournesol entières (WSS) sur la composition des acides gras dans les muscles (gastrocnemius [GN], longissimus thoracis [LT], intercostaux [IC]) et le tissu adipeux (sous-cutané [SQ], intermusculaire [IM]). À cette fin, ils ont réparti au hasard 96 bouvillons d’un an d’un poids moyen de 410 kg entre trois régimes de paissance (P) : 1) enrichi de WSS (P-WSS, n = 48); 2) enrichi de grosses cassures d’orge (P-BAR, n = 24) et 3) sans supplément (P-CON, n = 24). Les bouvillons ont été mis à l’herbe en rotation pendant 66 jours, dans un pâturage de brome et de luzerne. Au bout de ce laps de temps, la moitié des sujets de chaque traitement ont été conduits par camion à un parc d’engraissement où ils ont reçu la ration de finition. Les 48 bouvillons restants ont continué de recevoir des herbages pendant 47 jours (É.-T. = 11), jusqu’à leur abattage. Au parc d’engraissement, la moitié des sujets de chaque régime de paissance ont reçu soit une ration témoin (83 % de flocons d’orge, 10 % de foin de luzerne, 5 % d’ensilage d’orge, 1 % de mélasse et 1 % de prémélange de vitamines et de minéraux; F-CON), soit une ration enrichie de WSS (68 % de flocons d’orge, 15 % de WSS, 10 % de foin de luzerne, 5 % d’ensilage d’orge, 1 % de mélasse et 1 % de prémélange de vitamines et de minéraux; F-WSS). Chez les bouvillons engraissés à l’herbe pendant 113 jours avec supplément de WSS puis abattus directement, la concentration d’ALC cis-9, trans-11 dans les muscles avait augmenté de 17,0 à 29,1 % (GN, 0,570 c. 0,467; LT, 0,515 c. 0,399; IC, 0,531 c. 0,454 mg par 100 mg de gras); d’autre part, elle avait
Abbreviations: BAR, cracked barley grain; CLA, conjugated linoleic acid; GN, gastrocnemius; IC, intercostals; IM, intermuscular; LT, longissimus thoracis; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; SQ, subcutaneous; TFA, total fatty acids; WSS, whole sunflower seed 71
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CANADIAN JOURNAL OF ANIMAL SCIENCE augmenté de 32,0 % dans les dépôts de graisse IM (0,636 c. 0,482 mg par 100 mg de gras) et de 40,3 % dans le tissu adipeux SQ (0,839 c. 0,598 mg par 100 mg de gras), comparativement aux résultats obtenus avec les sujets témoins abattus directement après engraissement à l’herbe. L’enrichissement du régime de paissance par des WSS accroît aussi la teneur en C18:1 trans-11 dans les muscles de 20,1 à 40,8 % et de 55,0 % dans le tissu adipeux IM. L’addition de WSS à la ration de finition relève la concentration d’ALC cis-9 trans-11 de 31,5 à 209,0 % dans le tissu musculaire et de 40,7 % dans le gras SQ ainsi que de 25,6 % dans le gras IM. Enfin, ce supplément augmente la teneur en C18:1 trans-11 de 80,0 à 207,3 % dans le muscle ainsi que de 181 % dans le tissu adipeux IM et de 224 % dans le tissu adipeux SQ. La concentration d’ALC cis-9 trans-11, de C18:1 trans-11 et de C18:3 présente de fortes corrélations positives entre les tissus (R2, 0,69-0,88; P < 0,0001). Ces résultats donnent à penser qu’en augmentant la quantité d’acides gras polyinsaturés dans la ration des bovins de boucherie, on accroît la teneur d’ALC cis-9 trans-11 et de C18:1 trans-11 dans les tissus musculaire et adipeux. Mots clés: Bœuf, pâturage, parc d’engraissement, composition des acides gras, acides linoléiques conjugués, acide vaccénique
Conjugated linoleic acids (CLA) are isomers of linoleic acid and these CLA are produced in the rumen (Kepler et al. 1966) and in the tissues where they are deposited. Thus, they are available to consumers when they eat ruminant products such as milk, muscle (as beef or lamb) and fat. There are two forms of CLA that have known biological activity. Anticarcinogenic properties have been demonstrated in animal models for C18:2 cis-9 trans-11 (Ip et al. 1999) and for it its precursor C18:1 trans-11 (Banni et al. 2001). The second isomer, the C18:2 trans-10 cis-12 has been shown to protect against hypercholestrolemea and arrests fat deposition in adipose tissue (Brown et al. 2004). Although the mode of action of these compounds has not been delineated, the methods to increase their levels in foods of ruminant origin have been explored (Bauman et al. 2000; Mir et al. 2000; Beaulieu et al. 2002, Madron et al. 2002; Sackmann et al. 2003). Dietary sunflower (Helianthus annus L.) oil at 6% of dry matter in backgrounding and finishing diets increased muscle CLA concentrations from 28 to 128% (Mir et al. 2002) and inclusion of sunflower seeds increased muscle concentrations of both isomers of CLA and C18:1 trans-11 (Gibb et al. 2004; Shah et al. 2006). Pasturing cattle has also been shown to increase CLA content of the beef (French et al. 2000; Rule et al. 2002). The extent of CLA increase may be related to the high content of polyunsaturated fatty acids in forages, which can be as high as 60% of the total fatty acids (TFA) (Boufaied et al. 2003). The availability of these fatty acids for biohydrogenation can be high if the pasture is in the vegetative stage (Mir et al. 2005). However, the total fat content of pasture forages declines rapidly and is dependent upon the relative maturity of the forage, the species and proportion of leaves in the forage (Harfoot 1981). As a result, the extent of CLA increase can vary among trials and among animals within a trial based on forage lipid content and perhaps the genetic potential of individual animals to convert the rumen produced C18:1 trans-11 to CLA. In order to overcome the large variation, supplementation on pasture with whole soybeans containing high levels of the substrate fatty acid C18:2 cis-9 cis-12 was attempted (Duynisveld et al. 2002). However, dairy studies have indicated that raw, whole soybeans are not an efficient way to increase the CLA concentrations in milk (Dhiman et al. 2000). Furthermore, it is now established that oil seeds containing C18:2 cis-9 cis-12 such as sunflower seed lead to the highest increases in CLA (Dayani et al. 2003; Shah et al. 2006). Thus it was essential to deter-
mine the effect of supplementation with sunflower seed on pasture. The hypothesis was that the provision of a supplementary source of the C18:2 cis-9 cis-12 on pasture would increase the CLA concentration in beef tissue, which would be retained even if withdrawn from pasture and finished in a feedlot, especially if the feedlot diet was supplemented with sunflower seeds. Thus, the objective was to determine the effect of raising beef steers on pasture without or with sunflower seeds or barley, or the effect of subsequent finishing of these pasture supplemented steers in a feedlot without and with sunflower seeds, on muscle and fat content of CLA and other bioactive fatty acids. MATERIALS AND METHODS Animals and Experimental Design All animals through each aspect of this study were cared for under the guidelines established by the Canadian Council on Animal Care (1993). Basarab et al. (2007) previously described animal management on pasture and in the feedlot and slaughtering procedures. Briefly, 96 non-implanted crossbred yearling steer calves averaging 410 kg (SD = 44 kg) were randomly allocated to three pasture (P) dietary treatments: (1) supplemental whole sunflower seed ((Helianthus annus L.; P-WSS, n = 48), (2) supplemental cracked barley (Hodeum vulgare L.) grain (P-BAR, n = 24), and (3) no supplementation (P-CON, n = 24). Samples of the supplemental whole sunflower seeds and cracked barley were collected weekly, pooled monthly and stored at –20°C until processed for fatty acid analysis. Steers rotationally grazed meadow bromegrass (Bromus riparius Rehm.)-alfalfa (Medicago sativa L.) pasture during the summer period (66 d). At the end of the summer grazing period, half the steers from each pasture treatment group were moved to a feedlot where they were fed a high barley-based diet until finished. The remaining 48 steers continued with their dietary treatments on stockpiled pasture for an additional 47 d (SD = 11) until they were slaughtered directly off pasture on 2003 Sep. 16, Sep. 23, Oct. 07 and Oct. 14. Animals were stratified to kill dates based on their weights and backfat levels, with equal numbers of animals from each feeding treatment on each kill date. Representative samples of the grass consumed by the cattle were collected 2 d after the animals entered a new paddock. Immediately after collection the samples were stored at –20°C until processed for fatty acid analysis. The nutrient composition of pasture, supplemental barley grain and whole sunflower seed and feedlot
BASARAB ET AL. — ENHANCING CLA CONTENT OF BEEF
finishing diets, and forage yield and animal utilization rate for pasture are given by Basarab et al. (2006). In the feedlot (F), half the steers from each pasture dietary treatment were randomly assigned to either a no supplementation (F-CON) or a whole sunflower seed supplementation (F-WSS) group such that six feedlot dietary groups were formed [P-CON, F-CON (n = 6); P-CON, F-WSS (n = 6); P-BAR, F-CON (n = 6); P-BAR, F-WSS (n = 6); P-WSS, F-CON (n = 12); P-WSS, F-WSS (n = 12)]. Animals were assigned to individual feeding pens and adjusted from a backgrounding to a finishing diet over a 30-d adjustment period. The control finishing diet consisted of 83% rolled barley, 10% alfalfa hay, 5% barley silage, 1% molasses and 1% vitamin/mineral mix, while the WSS diet consisted of 68% rolled barley, 15% WSS, 10% alfalfa hay, 5% barley silage, 1% molasses and 1% vitamin/mineral mix (DM basis). Samples of the total mixed ration were collected weekly, pooled by weigh period and stored at –20°C until processed for fatty acid analysis. Upon completion of the feeding periods, the steers were processed at the Lacombe Research Centre abattoir. The carcasses were chilled for 24 h, and then the left side of the carcass was broken down into primals and subsequently dissected into subcutaneous fat, intermuscular fat, body cavity fat, lean and bone. Fat depots were labeled, bagged and held in tubs in a cooler at –2°C with wind speeds of 0.5 m s–1 until 72 h. At 72 h, individual fat depots were ground [Butcher Boy Meat Grinder Model A42 with a 1/4inch grind plate (Lasar Manufacturing Co., Los Angeles, CA)], hand mixed and sub-sampled. Two 100-g samples from the subcutaneous (SQ) and intermuscular (IM) fat depots were collected, bagged and stored at –80°C for fatty acid determination. The left longissimus thoracis (LT), intercostals (IC) and gastrocnemius (GN) were collected during the course of cutout, labeled, vacuum packaged [Multivac AGW (Multivac Inc., Kansas City, MO)] and stored in a cooler until 6 d postmortem. At 6 d, the LT muscle was removed from the cooler and a portion was ground three times [Butcher Boy Meat Grinder Model TCA22 with a 1/8-inch grind plate (Lasar Manufacturing Co., Los Angeles, CA)]. The GN and IC muscles were ground in a similar manner. Two 100-g samples of each muscle were bagged and stored at –80°C for fatty acid determination. Detailed results on the production parameters, carcass characteristics and composition, distribution of wholesale cuts, meat sensory parameters, and meat quality and retail attributes are given by Basarab et al. (2007). Fatty Acid Analysis of Forages The frozen forage samples were freeze-dried. Immediately prior to grinding, each sample was frozen in liquid N. Each sample was then ground through a Wiley mill (Thomas® Wiley® Mini-Mill; Arthur H. Thomas Co., Philadelphia, PA) with a 50-mesh (0.5 mm) screen. To minimize heating during grinding the grinder was cleaned and cooled using Super Cold 134. The method of Sukhija and Palmquist (1988) was used for fatty acid analysis of the frozen forage and barley samples except toluene was substituted for benzene for fatty acid methyl ester extraction. For sunflower
73
seed samples, this method was initially used but levels of fatty acids appeared 25% low, so seeds (200 mg ground sample) were first extracted with 27 mL 2/1 chloroform/ methanol, filtered, dried, re-suspended in 15 mL chloroform and a 2 mL aliquot was dried, suspended in 1 mL benzene and methylated with 4 mL 5% methanolic HCl for 1 h at 80°C. One mL of water was then added, and fatty acid methyl esters were extracted with 3 mL of hexane three times and analyzed as per extracts in Sukhija and Palmquist (1988). The dried feed samples for the two feedlot diets were further combined over 2-mo periods and analyzed for ether extract (He et al. 2005). The extracted fat was recovered by evaporating the ethyl ether under nitrogen and used for fatty acid analysis after methylation with tetramethylguanidine (Shanta et al. 1993). Approximately 10–20 mg of the fat was weighed, to which 400 µL methanol and 100 µL tetramethylguanidine were added and placed in a boiling water bath for 10 min. To this, 5 mL saturated NaCl and 2 mL petroleum ether were added, mixed for 10 min in a rocker mixer and centrifuged at 640 × g for 10 min. After that, the top petroleum ether layer was transferred to another clean tube and dried under nitrogen. Then, 5 mL hexane was added, vortexed and a portion of the solution (containing fatty acids) was put into a 2 mL gas chromatography vial, capped and stored at –20ºC until they were separated by gas chromatography. Muscle and Adipose Tissue Fatty Acid Analysis Lipid extraction from muscle and fat tissue samples was carried out according to procedures of Jiang et al. (1996) with modifications. Briefly, 15 ml of isopropanol was added to a test tube containing 8.0 ± 0.5 g of finely chopped muscle tissue or 1.0 ± 0.5 g of adipose tissue. This mixture was then homogenized (Polytron PT 1-35, Kinematic AG, Switzerland) at high speed for about 15 s. After adding 10 mL of hexane to the homogenate, the mixture was again homogenized at high speed for 15 s, and the homogenized mixture was filtered through a Whatman filter paper (No. 1) into a second test tube. Fifteen mL of hexane:isopropanol solution (10:14) was twice added to the first tube, and both times it was filtered into the second tube after vigorous mixing with a vortex mixer. Finally, the filtrate (filter paper and residue) was rinsed with 5 mL of hexane:isopropanol (10:14). Then 8 mL of aqueous sodium sulfate (66.8 g Na2SO4 per liter distilled H2O) solution was added to the filtrate and thoroughly mixed by inversion for 30 s before centrifuging at 1100 rpm (640 × g) for 10 min. The hexane layer was collected into a pre-weighed test tube, and evaporated under nitrogen. The residual fat in the pre-weighed test tube was weighed once the tube was completely dried and the fat content of the sample was calculated. Fatty acid methyl esters were prepared by the double methylation procedure of Lock and Garnsworthy (2002), and stored at –40°C until analyzed. Fatty acid methyl esters were quantified by a gas chromatograph (Hewlett Packard GC System 5890; Mississauga, ON) equipped with a flame ionization detector
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CANADIAN JOURNAL OF ANIMAL SCIENCE
and SP-2560 fused silica capillary column (100 m with 0.2µm film thickness; Supelco Inc., Oakville, ON). Samples were loaded on to the column via 1 µL splitless injections. The initial oven temperature (120°C) was held for 15 min and then ramped at 5°C min–1 to 160°C, where it was held for 15 min. Next it was ramped at 4°C min–1 to 240°C and held for 30 min. Inlet and detector temperatures were maintained at 220°C, and 275°C, respectively. Helium carrier gas flow rate through the column was 1.7 mL min–1. Hydrogen flow to the detector was 34 mL min–1, airflow was 320 mL min–1 and helium make-up gas flow rate was 29 mL min–1. Peaks in the chromatograms were identified and quantified using pure methyl ester standards (Sigma-Aldrich Inc., Oakville, ON). Nonadecanoic acid methyl ester (C19:0) was used as a reference standard to determine recoveries and correction factors for individual fatty acids. Identification of fatty acids was based on comparison to retention times of known FAME standards. Prior to sample analysis FAME standards, ranging from C6:0 (caproic acid methyl ester) to C22:6 (docosahexaenoic acid methyl ester; Sigma-Aldrich , Oakville, ON) were individually run on the gas chromatograph to determine retention times. Using these procedures, the 18:1 trans-11 (trans vaccenic acid) peak was not separated from 18:1 trans-10. In addition, the CLA cis-9, trans11 peak could contain some CLA trans-7, cis-9, possibly as much as 10% (Cruz-Hernandez et al. 2004). Proportions of fatty acids were determined as weight percentages of TFA and concentration of the fatty acids were converted to content per 100 g of tissue as the product of fat content and fatty acid concentration (Dhiman et al. 2000). Fatty acids were grouped into saturated (SFA; C10:0, C12:0, C14:0, C15:0, C16:0, C17:0, C18:0, C20:0, C21:0, C22:0, C23:0, C24:0), monounsaturated (MUFA; C14:1 cis, C14:1 trans, C16:1 cis, C16:1 trans, C17:1, C18:1 cis-9, C18:1 cis-11, C18:1 trans-9, C18:1 trans-11), n-6 polyunsaturated (n-6 PUFA; C18:2 cis cis, C18:2 trans trans, C20:4), n-3 PUFA (C18:3, C20:5, C22:5, C22:6) and PUFA (n-6 PUFA, n-3 PUFA). Statistical Analysis The data from one steer were excluded from the final analysis due to injury that occurred during the later part of the pasture phase. Data were analyzed as a completely randomized design using PROC MIXED in SAS (SAS Institute, Inc. 1996). In the initial model all possible factors [dietary treatment groups (P-CON, F-CON; P-CON, F-WSS; PBAR, F-CON; P-BAR, F-WSS; P-WSS, F-CON; P-WSS, F-WSS), source of origin, slaughter date, all interaction terms, and on pasture weight as a covariate] were included. Source of origin, slaughter date and the interaction terms were not significant (P > 0.05) and were subsequently excluded from the final model. In addition, no differences were observed between the P-CON, F-CON (n = 6) and PBAR, F-CON (n = 6) dietary treatment groups or between the P-CON, F-WSS (n = 6) and P-BAR, F-WSS (n = 6) dietary treatment groups. These groups were combined to make the P-CON, F-CON (n = 12), and the P-CON, F-WSS (n = 12) feedlot dietary treatment groups. Thus, the final statistical model was dietary treatment and on pasture weight
as a covariate. The LSMEANS and PDIFF options were used for generating least squares means and comparison of treatments (SAS Institute, Inc. 1996). The relationships between the LT muscle content of CLA cis-9 trans-11, C18:1 trans-11 or C18:3 (independent variables) and their concentrations (dependent variables) in other tissues (GN, IC, SQ, IM) were determined using the GLM procedure of SAS Institute, Inc. (1996). ). Significance and trend were declared at P ≤ 0.05 and 0.10, respectively. In addition, the relationships between the consumption of C18:2 and C18:3 fatty acids (independent variable) and the concentration of CLA cis-9 trans-11 (dependent variable) or C18:1 trans-11 (dependent variable) in muscle and adipose tissues were also determined. The general model fitted was Yij = β0 + β1FAi + β2FA2j + eij, where Yij is the tissue content for the selected fatty acid (e.g., CLA cis-9 trans-11) for animal ij, β0 is the regression intercept, β1FAi is the linear regression coefficient, β2FA2j is the quadratic regression coefficient, and eij is the residual error. If the quadratic effect was not significant (P > 0.1) then the model was reprocessed with only the linear effect. RESULTS Fatty Acid Profile of Feeds The C18:3, C18:2 and C16:0 were the most abundant fatty acids in pasture samples and they averaged, respectively, 55.0, 17.1 and 17.2% of TFA in summer and 56.9, 15.9 and 16.7% of TFA in fall pasture (Table 1). The TFA concentration averaged 17.8 mg g–1 DM in summer and 21.5 mg g–1 DM in fall pasture. The primary fatty acid in barley grain was C18:2 at 52.5% of TFA. The C16:0, C18:1 and C18:3 were less abundant and averaged 22.1, 16.0 and 5.0% of TFA, respectively. The most abundant fatty acids in whole sunflower seed were C18:2, C18:1, C16:0 and C18:0 at 75.3, 11.8, 6.7 and 4.4% of TFA, respectively. These results agree with Gibb et al. (2004) who reported the fatty acid concentration for high-linoleic sunflower seed at 72.9, 13.8, 6.8 and 2.4% of TFA for C18:2, C18:1, C16:0 and C18:0, respectively. Fatty Acid Composition of Muscle Fat Gastrocnemius The gastrocnemius muscle was the leanest muscle examined and had an average fat content of 1.33% (SD = 0.62) or 13.3 mg g–1 of fresh muscle. Diet affected total muscle fat content, with steers fed WSS on pasture and in the feedlot having more total muscle fat than all other dietary treatment groups (Table 2; 1906 vs. 889–1400 mg 100 g–1). Supplementation of WSS on pasture increased the content of C18:1 trans-11, C18:2 trans trans and CLA cis-9 trans11 and decreased the content of C14:1 trans, C15:0, C17:0, C18:3, C20:5 and SFA in the gastrocnemius muscle from PWSS compared with P-CON steers slaughtered directly off pasture (Table 2). In addition, the provision of WSS in the finishing diets, increased C18:0, C18:1 trans-11, C18:2 cis cis and n-6:n-3 ratio and decreased C17:0, C17:1, C18:1 cis-
0.12 10.3 4.8 17.0 64.7 0.92 0.35 0.23 0.83
6.8
Mean
0.88 26.6 2.2 16.6 44.2 6.4 0.37 0.83 0.40 0.01 0.01 0.01 0.07 0.09 0.01 0.01 0.01 0.02
n SD
1.0
0.05 6.68 4.37 11.83 75.32 0.17 0.33 0.13 0.77 5 5 5 5 5 5 5 5 5 0.01 0.65 0.08 0.63 1.15 0.07 0.02 0.03 0.01 0.36 22.06 1.37 16.01 52.52 5.03 0.31 0.86 0.33 5 5 5 5 5 5 5 5 5
SD Mean
0.10 1.74 0.68 1.11 2.67 5.43 0.42 0.07 0.34
18 18 18 18 18 18 18 18 18
0.63 16.65 2.22 1.92 15.88 56.90 1.71 0.04 1.39 0.58 17.18 1.77 2.76 17.09 55.00 1.68 0.11 1.19 Fatty acid, % of total fatty acids (FAME) C14:0 34 C16:0 34 C18:0 34 C18:1 34 C18:2 34 C18:3 34 C20:0 34 C20:1 34 C22:0 34
0.25 1.91 0.87 0.30 3.16 6.35 0.31 0.01 0.29
5
n SD
0.10 2.16
Mean n
5 0.34 18 0.37
SD
2.15
Mean
1.78
Fatty acid composition
Total fatty acid, % (DM basis)
n Mean n
34
SD
40.39
n
Mean 0.65
Sunflower seed diet Control diet Whole sunflower seed
Pasture diets
Barley grain Meadow bromegrass-alfalfa Aug. 15–Oct. 10 Meadow bromegrass-alfalfa Jun. 12–Aug. 15
Table 1. Fatty acid composition of summer and fall pasture, supplemental barley grain and whole sunflower seed and feedlot finishing diets
Feedlot finishing diets
SD
BASARAB ET AL. — ENHANCING CLA CONTENT OF BEEF
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9 and MUFA relative to P-CON F-CON steers. Finishing cattle on high barley-silage (P-CON F-CON steers) based diets had a large impact on the fatty acid composition of intramuscular fat relative to steers slaughtered directly off pasture after grazing alfalfa meadow bromegrass pasture for 113 d (P-CON P-CON). For example, in P-CON steers the content of C10:0, C14:0, C14:1 trans, C14:1 cis, C15:0, C16:1 trans, C18:0, C18:1 trans-11, C20:0, C18:3, CLA cis-9 trans-11, C22:0, C20:5, SFA and n-3 PUFA were increased, while the content of C17:1, C18:1 cis-9, C18:1 cis-11, MUFA and n-6:n-3 ratio were consistently decreased in the gastrocnemius muscles relative to feedlot CON steers. Provision of WSS on pasture for 65 d before feedlot finishing had no effect on the fatty acid composition of the gastrocnemius intramuscular fat at the completion of the feedlot finishing phase (P-CON F-CON vs. P-WSS F-CON; PCON F-WSS vs. P-WSS F-WSS). Longissimus thoracis The longissimus thoracis muscle was also lean and had an average fat content of 3.46% (SD = 1.73) or 34.6 mg g–1 of fresh muscle. Regardless of dietary treatment, steers finished in the feedlot had a higher total muscle fat content than steers slaughtered directly off pasture (Table 3; 4.10–5.00% vs. 2.09–2.56%). No differences were detected within the pasture or feedlot dietary treatments for total muscle fat. Supplementation of WSS on pasture increased the content of C18:1 trans-11 and CLA cis-9 trans-11 and decreased the content of C15:0, C17:0, C17:1, C18:3, C20:5 and n-3 PUFA in the longissimus thoracis muscle from P-WSS compared with P-CON steers slaughtered directly off pasture (Table 3). In addition, the provision of WSS in the finishing diets increased C18:0, C18:1 trans-11, C18:2, CLA cis-9 trans-11, n-6 PUFA and n-6:n-3 ratio and decreased C15:0, C16:1 cis, C17:0, C17:1, C18:1 cis-9 and C18:1 cis-11 relative to F-CON steers. Steers slaughtered directly off pasture (P-CON) had increased contents of C12:0, C14:1 trans, C14:1 cis, C15:0, C16:1 trans, C18:0, C18:1 trans-11, C18:2, C18:3, CLA cis-9 trans-11, C22:0, C20:4, C20:5, C22:5, SFA, n-6 PUFA and n-3 PUFA and decreased contents of C14:1 cis, C16:1 cis, C17:0, C17:1, C18:1 cis-9, C18:1 cis-11, MUFA and n-6:n-3 ratio in the longissimus thoracis muscle relative to feedlot CON steers. Again, provision of WSS on pasture for 65 d before feedlot finishing had no effect on the fatty acid composition of the longissimus thoracis intramuscular fat at the completion of the finishing phase (P-CON F-CON vs. P-WSS F-CON; P-CON F-WSS vs. P-WSS F-WSS). Intercostal The intercostal muscle had the highest fat content of the three muscles examined, and it averaged 11.12% (SD = 2.94) or 111.2 mg g–1 of fresh muscle. As was observed in the longissimus thoracis muscle, steers finished in the feedlot had a higher total fat content in the intercostal muscle than steers slaughtered directly off pasture (Table 4; 12.5–13.4% vs. 9.2-9.5%). No differences were detected within the pasture or feedlot dietary treatments for total muscle fat.
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Table 2. Effect of whole sunflower seed supplementation on the fatty acid content of the gastrocnemius muscle of steers slaughtered directly off pasture and after a feedlot finishing period Slaughtered directly off pasturez Compositional traits
P-CON P-CON
Number of steers Fat, mg 100 g–1 fresh muscle
12 899c
P-BAR P-BAR 12 1192cb
Fatty acids, mg 100 mg–1 fatty acid methyl esters C10:0 0.026a 0.014bc C12:0 0.010 0.007 C14:0 2.694a 2.459a C14:1 trans 0.195a 0.139b C14:1 cis 0.833a 0.659ab C15:0 0.581a 0.409bc C16:0 26.941a 25.942ab C16:1 trans 0.535a 0.599a C16:1 cis 4.224 4.027 C17:0 1.251a 1.027b C17:1 0.925b 0.917b 12.612a 12.128ab C18:0 C18:1 trans–11 2.218b 1.908b C18:1 cis- 9 36.931c 38.482c C18:1 cis-11 1.306c 1.907b C18:2 trans trans 0.178bc 0.210ab C18:2 cis,cis 3.993bc 4.140bc C20:0 0.051a 0.044a C20:1 0.099 0.083 C18:3 1.404a 0.957b CLA cis- 9 trans-11 0.467b 0.420b CLA trans-10 cis-12 0.000 0.000 C22:0 0.142a 0.125a C20:4 1.418 2.720 C20:5 (EPA) 0.439a 0.263c C22:5 (DPA) 0.480 0.428 SFA 44.309a 42.156b MUFA 47.267c 48.720c n-6 PUFA 5.588 7.061 n-3 PUFA 2.831a 2.062b n-6:n-3 ratio 1.89d 3.46c
Slaughtered after finishing in a feedlotz
P-WSS P-WSS 23 1246bc
P-CON F-CON 12 1379bc
0.018ab 0.020 2.570a 0.151b 0.754a 0.470b 25.873ab 0.515a 4.436 1.045b 0.881b 12.258a 2.663a 37.581c 1.573bc 0.239a 4.692b 0.041a 0.090 1.056b 0.570a 0.000 0.120a 1.493 0.313b 0.441 42.415b 48.767c 6.424 2.391ab 2.69cd
P-WSS F-CON 12 1400b
0.004c 0.001 2.106b 0.046c 0.574c 0.319c 25.800ab 0.340b 4.492 1.313a 1.479a 10.522c 1.212c 43.396a 2.564a 0.089c 3.062c 0.000b 0.217 0.281c 0.254c 0.000 0.060b 1.323 0.127d 0.315 40.124c 54.321a 4.474 1.078c 3.86bc
0.009bc 0.006 1.940b 0.046c 0.491c 0.338c 25.311bc 0.314b 3.820 1.308a 1.371a 11.358bc 1.335c 43.612a 2.074ab 0.126c 3.475c 0.023b 0.107 0.320c 0.296c 0.000 0.068b 1.580 0.173cd 0.395 40.360c 53.268ab 5.180 1.191c 5.40b
P-CON F-WSS 12 1321bc 0.005c 0.009 2.015b 0.044c 0.528c 0.288c 24.460c 0.308b 3.922 1.083b 1.006b 12.059a 1.967b 41.250b 2.240ab 0.147c 5.665a 0.018b 0.052 0.288c 0.322c 0.000 0.049b 1.738 0.140cd 0.363 39.986c 51.316b 7.550 1.147c 5.81bc
P-WSS F-WSS 12 1906a 0.011bc 0.006 2.136b 0.037c 0.507c 0.292c 24.883bc 0.321b 4.221 1.085b 0.997b 12.513a 2.182b 41.624b 2.052ab 0.136c 4.520ab 0.018b 0.060 0.264c 0.334c 0.003 0.018b 1.466 0.108d 0.184 40.963bc 52.002b 6.122 0.909c 7.67a
SEM 169 0.003 0.007 0.144 0.013 0.074 0.045 0.491 0.038 0.245 0.043 0.071 0.365 0.137 0.686 0.184 0.024 0.436 0.010 0.059 0.077 0.040 0.001 0.024 0.455 0.051 0.068 0.710 0.741 0.735 0.188 0.29
P value 0.013 0.002 0.397
