J. Anim Sci. 2007. 85:1504-1510. doi:10.2527/jas.2006-581
© 2007 American Society of Animal Science
Effects of supplemental rumen-protected conjugated linoleic acid or corn oil on lipid content and palatability in beef cattle1
M. H. Gillis*,
S. K. Duckett
,2 and
J. R. Sackmann*
* University of Georgia, Athens 30602, and
and
Clemson University, Clemson, South Carolina 29634
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Abstract
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Thirty-six Angus x Hereford heifers were used in a 3 x 2 factorial (3 dietary treatments; 2 supplementation times) to examine the effect of dietary lipid supplementation on lipid oxidation, lipid composition, and palatability of ribeye steaks and ground beef. Lipid was supplied in the diets as corn oil or a partially rumen-protected CLA salt for 2 specific treatment periods of the final 32 or 60 d on feed, corresponding to a total time on feed of 89 or 118 d. After an initial 56-d feeding period (basal diet), the heifers were fed 1 of 3 dietary treatments (DM basis): 1) a basal diet containing 88% concentrate and 12% grass hay (CON), 2) the basal diet plus 4% corn oil (OIL), or 3) the basal diet plus 2% partially rumen-protected CLA (RPCLA) containing 31% CLA. Heifers were randomly allotted to dietary treatments at the initiation of the study and fed individually. At 48 h postmortem, the right forequarter of each carcass was fabricated into retail cuts. Steaks (2.54-cm thick) were obtained from the posterior end of the ribeye roll (NAMP 112), and beef trim was ground for all subsequent analyses. Dietary treatment did not affect (P > 0.05) lipid oxidation in ground beef or ribeye steaks. Total trans-octadecenoate fat and trans-10 octadecenoic acid content in ribeye steaks increased (P < 0.05) with RPCLA compared with CON. Total CLA and the cis-9 trans-11 isomer of CLA contents in ribeye steaks were unchanged (P > 0.05) by lipid supplementation. In ground beef, RPCLA supplementation increased (P < 0.05) the amount of trans fat and trans-10 octadecenoic acid compared with CON or OIL; supplementation of RPCLA increased (P < 0.05) the amount of CLA cis-9 trans-11 isomer and total CLA. Lipid supplementation did not alter (P > 0.05) off-flavor ratings in ground beef or ribeye steaks. Supplementation of corn oil increased (P < 0.05) total PUFA content of ribeye steaks compared with CON and RPCLA. Dietary RPCLA supplementation increased the amount of trans fat per serving (85.5 g, broiled) by 110 and 88% in ribeye steak and ground beef, respectively, and CLA cis-9 trans-11 by 58% in ground beef compared with CON. Supplementing OIL or RPCLA resulted in minimal changes in lipid oxidation and sensory attributes of steaks and ground beef.
Key Words: beef • conjugated linoleic acid • sensory • trans fat
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INTRODUCTION
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The relatively low levels of PUFA and high levels of SFA found in edible beef products (Rule et al., 2002
) are of concern due to their association with negative effects on human health. Dietary saturated and trans fat consumption in humans influences serum LDL cholesterol levels and is believed to be associated with increased risk of cardiovascular disease (AHA, 2000). Mensink and Katan (1990) compared the effects of diets with oleic acid, transoctadecenoic acids, or SFA and demonstrated that trans fats have a more negative effect on serum cholesterol levels than saturated fats. The Food and Drug Administration (FDA, 2003) has amended the nutritional labeling regulations to now include levels of trans fat in food products. In cattle, dietary unsaturated fatty acids are biohydrogenated (BH) in the rumen to various intermediates and saturated end products (Bauman et al., 1999). However, this process of ruminal BH is sometimes incomplete, yielding various transoctadecenoic acids and CLA isomers. Conjugated linoleic acid, specifically the cis-9 trans11 isomer, has been shown to possess anticarcinogenic effects (Ha et al., 1987).
Alterations in adipose tissue fatty acid composition may affect meat quality attributes such as flavor, color, and lipid oxidation rates (Gray et al., 1994). As the degree of unsaturation increases, fatty acids become more susceptible to oxidation. Off-flavors and odors in beef products are related to the oxidative potential of the tissue, fatty acid composition, and the presence of anti-and prooxidants in muscle (Gray et al., 1994). Duckett et al. (1993) additionally reported negative correlations between sensory flavor ratings and PUFA, indicating lower consumer acceptance ratings from taste panelists as PUFA content increased. Thus, dietary lipid supplementation has the potential to alter lipid oxidation and palatability of the resulting end product (Gray et al., 1994).
The objective of this research was to determine the effects of dietary lipid, corn oil or rumen-protected CLA, on fatty acid composition, lipid oxidation, and palatability of ribeye steaks and ground beef from heifers supplemented for the final 32 or 60 d on feed.
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MATERIALS AND METHODS
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Experimental Design
The experimental procedures were reviewed and approved by the University of Georgia Animal Care and Use Committee. Thirty-six Angus x Hereford heifers (365 ± 60 kg of BW; 13 mo of age) were obtained from the NW Georgia Experiment Station (Calhoun) and used in a completely randomized design. The effect of dietary lipid source on subsequent fatty acid content, sensory attributes, and shelf life of ribeye steaks and ground beef was evaluated in a 3 x 2 factorial arrangement, with 3 dietary treatments supplied for 2 specific periods. For the purposes of this study, heifers were fed treatment diets for the last 32 or 60 d before slaughter, which corresponded to a total time on feed of 89 or 118 d, respectively.
Heifers were randomly allotted to dietary treatments (12 heifers per treatment) at trial initiation. After 89 d on feed (32 d of lipid supplementation), heifers (6 per treatment) that had 1.27 cm or greater fat thickness were slaughtered. The remaining heifers (6 per treatment) were fed the treatment diets to reach a similar fat thickness end point (> 1.27 cm), which required an additional 28 d on the dietary treatments, and were then slaughtered. This approach allowed us to attain the same compositional end point for each supplementation length. Additional information on experimental design, animal performance, leptin concentration, and fatty acid composition of various adipose depots has been previously reported (Gillis et al., 2004a,b).
Dietary Treatments
After an initial feeding period of 56 d (basal diet), heifers were fed 1 of 3 dietary treatments: 1) a basal diet containing 88% concentrate and 12% grass hay (CON), 2) the basal diet plus 4% corn oil (OIL), or 3) the basal diet plus 2% rumen-protected CLA salt (RPCLA), containing 31% CLA-60 (27.2% cis-9, trans-11 + 32.8% trans-10, cis-12 CLA). Corn oil was used for OIL and contained 58% linoleate, 27% oleate, 11% palmitate, 2% stearate, and 2% linolenate. The RPCLA supplement (Agribrands Purina Canada Inc., Ontario, Canada) was composed of a mixture of Ca-salts of palm oil fatty acids and CLA, which contained 22.1% palmitate, 4.8% stearate, 27.4% oleate, 7.1% linoleate, and 31% CLA (27.2% cis-9, trans-11; 32.8% trans-10, cis-12; 10.6% trans-8, cis-10; 18.95% cis-11, trans-13; and 10.5% various trans, trans CLA isomers). As supplemental lipid was included in the treatment diets, an equal proportion of concentrate was removed. Synovex-H implants (20 mg of estradiol benzoate and 200 mg of testosterone; Fort Dodge Animal Health, Fort Dodge, IA) were administered to all animals at trial initiation. Heifers were housed by treatment group in pens (6 heifers per pen) outfitted with individual Calan gate feeders (American Calan Inc., Northwood, NH). Heifers were allowed free access to diets, with fresh rations weighed and provided at 0800 daily (refusals were recorded daily).
Sample Collection
At 48 h postmortem, the forequarter from the right side of each carcass was fabricated into retail cuts. Three 2.54-cm-thick steaks were removed from the posterior end of the ribeye roll (NAMP 112), vacuum packaged, aged for 14 d at 4°C, and stored at –20°C for subsequent fatty acid analysis and sensory evaluation. Four 1.25-cm-thick steaks were then removed from the ribeye roll for lipid oxidation determination using the TBARS procedure (Jo and Ahn, 1998). Steaks for lipid oxidation were placed on Styrofoam trays in duplicate for each sample time, wrapped with oxygen permeable film, and stored in a 4°C cooler illuminated with 1,614-lx fluorescent lighting for 0, 5, 12, or 19 d. Beef trim was ground (0.635-cm plate), and 3 patties (120 g) were obtained for fatty acid analysis and sensory evaluation. Eight patties (120 g) were also obtained for lipid oxidation determination using the TBARS procedure described above. Patties were placed individually on Styrofoam trays and wrapped with oxygen permeable overwrap and placed in a 4°C cooler illuminated with 1,614-lx fluorescent lighting for 0, 2, 4, or 8 d of storage. Trays containing the steak and ground beef patties were randomly placed in the cooler at an equal distance from the lighting source and rerandomized daily.
Fatty Acid Composition
One ribeye steak and 1 ground beef patty were pulverized in liquid nitrogen before lipid extraction. Total lipids were extracted in duplicate from samples using organic solvents according to the procedures of Folch et al. (1957), except that a solvent to sample ratio of 10:1 (vol/vol) was used. Lipid extracts were stored at –80°C for subsequent determination of fatty acid composition. Lipid extracts, containing approximately 5 mg of lipid, were transmethylated according to the method of Park and Goins (1999). Analysis of FAME was performed using an Agilent 6850 GC equipped with an automatic sampler (Agilent, Wilmington, DE), according to conditions outlined by Duckett et al. (2002). Retention times were compared with those for known standards (Matreya, Pleasant Gap, PA; Nu-Chek Prep, Elysian, MN; Sigma Chemical Co., St. Louis, MO). Fatty acids were quantified based upon the inclusion of an internal standard (methyl tricosanoate) during methylation and were expressed as a percentage of total fatty acid.
Gravimetric fatty acid content (g/85.5 g serving) was calculated from the fatty acid percentage composition of the steaks and ground beef from each animal, cooking loss, and published true nutrient retention values for beef steaks (99%; Duckett and Wagner, 1998) and ground beef of similar fat percentage (65%; Hoelscher et al., 1987). These calculations are similar to those used for the USDA Nutrient Databases to estimate cooked value from raw food composition (Schakell et al., 1997). Cooking loss for steaks and hamburgers broiled on Farberware (Bronx, NY) electric grills to an internal temperature of 71°C (AMSA, 1995) was 24 and 26%, respectively.
Trained Sensory Panel
An 8-person taste panel was trained, and sensory evaluation was conducted according to American Meat Science Association (AMSA, 1995) guidelines. Ribeye steaks were cooked to an internal temperature of 71°C and cut into 1 x 1 x 2.54-cm cubes using a plastic grid (14 cm long x 12 cm wide x 4 cm deep, with slots spaced every 1.25 cm). Ground beef patties were cooked to an internal temperature of 81°C and cut into 6 wedges per patty. Samples were served immediately to each panel member. Samples were evaluated for initial and overall tenderness, juiciness, and beef flavor using an 8-point scale (1 = extremely tough, extremely dry, extremely bland, or abundant; 8 = extremely tender, extremely juicy, extremely intense, or none). Off-flavor was appraised on a 9-point scale (0 = none; 8 = extremely intense).
Statistical Analyses
Data were subjected to ANOVA for a completely randomized design using the GLM procedure (SAS Inst. Inc., Cary, NC), with individual heifer serving as the experimental unit. The model for fatty acid content and sensory analyses included the effects of dietary treatment (CON, OIL, or RPCLA), length of supplementation (32 or 60 d), and the 2-way interaction. Lipid oxidation of steaks and patties were analyzed using PROC MIXED of SAS for repeated measures of display time. Least squares means for main or interactive effects were generated and separated using the PDIFF procedure if the F-test was significant (P < 0.05). All interactions between dietary treatment and length of supplementation were nonsignificant (P > 0.05), with the exception of total CLA percentage, trans-10 cis-12 isomer of CLA amount, PUFA amount, and overall tenderness in ground beef samples, and initial tenderness, overall tenderness, and beef flavor ratings for ribeye steaks. Significance was determined at P 
0.05, whereas differences of P > 0.05 to P 0.10 were considered as trends.
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RESULTS AND DISCUSSION
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Gravimetic fatty acid content of the ribeye steaks from heifers supplemented with OIL or RPCLA is shown in Table 1. Total fatty acid content of ribeye steaks did not differ (P > 0.05) among dietary treatments. Supplementing the animal’s diet with RPCLA increased (P < 0.05) the level of trans fat and trans-10 octadecenoic acid by 110 and 117%, respectively, compared with CON with OIL being intermediate. The trans-10 octadecenoic acid isomer was present in highest concentrations and contributed from 69 to 71% of total trans fat content present in beef ribeye steaks. The predominance of the trans-10 octadecenoic acid in beef agrees with previous research evaluating the duodenal outflow of these BH intermediates in which trans-10 octadecenoic acid predominated in steers fed high concentrate diets (Duckett et al., 2002; Sackmann et al., 2003). Vaccenic acid (VA) concentration was unchanged with dietary lipid supplementation. Others (Enser et al., 1999; Dhiman et al., 2005b) have reported similar changes in transoctadecenoic acid content in beef fed diets supplemented with unsaturated lipids.
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Table 1. Effect of dietary treatment on transoctadecenoic, CLA, and fatty acid types in ribeye steaks on a gravimetric fatty acid (g/85.5 g, broiled) basis
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One serving (85.5 g broiled) of beef ribeye steak from CON would contribute 100 mg of trans fat and 69 mg of trans-10 octadecenoic acid to the human diet. The level of trans fat contributed by beef to the human diet reported in this study is much lower than that reported by the FDA (2003) for total beef, ground and not ground (590 mg/serving), but was increased with dietary lipid supplementation to beef cattle to levels of 210 mg. Mensink and Katan (1990) compared the effects of a trans or SFA-rich diet in humans and demonstrated that trans fats have a more negative effect on serum cholesterol levels than saturated fats. Clifton et al. (2004) reported high correlations (r = 0.66) between dietary trans fat intake from margarine and level of trans fat in adipose tissue, and that the level of trans fat in adipose tissue was associated with increased risk of coronary artery disease. Importantly, VA can be converted to cis-9 trans-11 isomer of CLA, which has been shown to have anticarcinogenic properties (Ha et al., 1987). Turpeinen et al. (2002) reported that on average 19% of dietary VA is converted to CLA, cis-9 trans-11 isomer, in humans. As a result, it has been suggested that dietary consequences of VA in beef products should be considered separately from other trans fatty acids (Lock et al., 2005).
Total CLA,cis-9 trans-11 isomer, cis-11 trans-13 isomer, and cis cis isomers of CLA content per serving were unchanged (P > 0.05) by lipid supplementation. Lipid supplementation increased (P < 0.05) the content of trans-10 cis-12 isomer of CLA compared with CON; however, the levels of this CLA isomer were very low ( 1 mg per serving) regardless of animal diet. Supplementation with RPCLA increased (P < 0.05) trans, trans isomers of CLA compared with CON. Other researchers (Griswold et al., 2003; Dhiman et al., 2005b) have shown similar results in that dietary lipid supplementation of cattle consuming high grain diets did not enhance CLA cis-9 trans-11 isomer of beef. These researchers also reported increased trans-10, cis-12 CLA content in steaks from loin and round with soybean oil supplementation. Ruminal by-pass studies have shown that RPCLA is largely hydrogenated in the rumen when supplemented to high concentrate feedlot diets (Gassman et al., 2000). In contrast, Bolte et al. (2002) observed higher CLA content (+61%) in lamb muscle from animals fed added high-linoleate safflower seeds. Mir et al. (2002) also reported higher CLA levels in muscle from steers fed 6% sunflower oil.
One serving of beef (3 oz. broiled) would contribute 35 mg of cis-9 trans-11 isomer of CLA in the human diet. Evidence from in vitro and rodent experiments suggests that a minimum dietary level of 0.5% CLA cis-9 trans-11 isomer is needed to help reduce the incidence of cancer (Ip et al., 1994). If the average American adult consumes a 2,200 kcal diet with about 40% of calories from fat (assuming 60% diet digestibility), we estimate that the average dietary intake for adults would be about 600 g per d and the level of CLA needed would be 300 mg of CLA cis-9 trans-11 per d. If we assume an average conversion of VA to CLA (Turpeinen et al., 2002), the amount of CLA, cis-9 trans-11 isomer contributed from 1 serving of beef muscle would be 44 mg. Levels of CLA reported here are within the range reported for ribeye steaks as summarized by Dhiman et al. (2005a). The amounts of saturated, odd-chain, monounsaturated, and polyunsaturated fatty acids in beef ribeye steaks were unchanged (P > 0.05) with dietary lipid supplementation, regardless of lipid source.
The effect of dietary treatment on fatty acid content of ground beef is shown in Table 2. Total fatty acid content of ground beef did not differ (P > 0.05) among dietary treatments; however, numerical increases in total fatty acid content were observed with lipid supplementation. Supplementation with RPCLA increased (P < 0.05) the content of total trans octadecenoic acid and trans-10 octadecenoic acid. Lipid supplementation did not alter (P > 0.05) cis-9 trans-11 isomer of CLA content in ground beef. One serving (3 oz.) of ground beef from CON would provide 156 mg of trans fat with about equal proportions of trans-10 octadecenoic acid and VA. In contrast, 1 serving of ground beef from RPCLA would provide 303 mg of trans fat with 214 mg from trans-10 octadecenoic acid and 89 mg from VA. This research shows that dietary lipid supplementation to finishing cattle increases the trans fat content of beef with the greatest changes in trans-10 octadecenoic acid, an isomer that cannot be desaturated and may be of concern related to trans fat intake (FDA, 2003).
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Table 2. Effect of dietary treatment on transoctadecenoic, CLA, and fatty acid types in ground beef on a gravimetric fatty acid (g/85.5 g, broiled) basis
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Total CLA content was 103 mg per serving for CON and increased (P < 0.05) from 36 and 71% with OIL and RPCLA supplementation, respectively. The amount of cis-9 trans-11 CLA increased (P < 0.05) with lipid supplementation by 36% with OIL and by 57% with RP-CLA. Supplementation with RPCLA increased (P < 0.05) the amount of cis-11, trans-13; cis, cis; and trans, trans isomers compared with CON or OIL. The levels of CLA reported here for ground beef samples are higher than those summarized by Dhiman et al. (2005a). Based on the CLA levels for ground beef in this study, 2 servings of ground beef from RPCLA per day would contribute 260 mg of cis-9 trans-11 CLA and approach the minimum levels for cancer prevention (Ip et al., 1994). Levels of CLA are higher in subcutaneous than intramuscular adipose tissues (Gillis et al., 2004a; Realini et al., 2005), and therefore, a higher percentage of CLA is found in ground beef, which contains subcutaneous and intramuscular fat, and also higher total fat contents.
Total amount of SFA, odd-chain fatty acids, and MUFA in ground beef did not differ (P > 0.05) by dietary treatment. Interactions between dietary lipid supplementation and length of supplementation are shown in Table 3. The amounts of trans-10, cis-12 CLA isomer and PUFA in ground beef increased (P < 0.05) with OIL supplementation length but did not change over time in CON or RPCLA. The increase in PUFA content was primarily due to linoleic acid concentrations in ground beef of OIL-supplemented animals, which would suggest that feeding corn oil 60 d before slaughter is sufficient to increase adipose tissue PUFA levels. Similarly, Bolte et al. (2002) reported a 42.3% increase in PUFA content of lamb fed high-linoleate compared with high-oleate safflower seeds as a fat source.
Lipid oxidation in ground beef and ribeye steaks was determined from levels of thiobarbituric acid reactive substances (TBARS) produced over display time. Dietary treatment and length of lipid supplementation did not alter (P > 0.05) levels of 2-TBARS over display times in ground beef or ribeye steaks (data not shown). These results are likely related to the minor changes in polyun-saturated fat content with dietary lipid supplementation. Similarly, Gassman et al. (2000) also reported no effect on shelf life of loin samples when 2.5% rumen-protected CLA salt was fed to finishing steers.
Effects of dietary treatment and length of supplementation on sensory attributes of ground beef and ribeye steaks are shown in Table 4. In ground beef, juiciness was perceived by sensory panelists to be lower (P < 0.05) for RPCLA than CON or OIL, which did not differ. Initial tenderness ratings were greatest (P < 0.05) for CON and lowest (P < 0.05) for RPCLA, with OIL being intermediate. Sensory panelist ratings of connective tissue and beef flavor did not differ by dietary treatment. Off-flavor ratings for ground beef were greater for CON (P < 0.05) compared with OIL or RPCLA, which were similar.
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Table 4. Effects of dietary treatment and length of supplementation on sensory attributes of ground beef and ribeye steaks
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Release of inorganic iron upon cooking serves to accelerate the accumulation of lipid peroxide degradation products such as alkanes, alkenes, aldehydes, ketones, and alcohols, which contribute to off-flavor formation (Gray et al., 1994). Research in lamb has shown the flavors sweet and fruity to be associated with protected lipid supplements of safflower oil. Similarly, oily flavor in lamb has been attributed to increased tissue levels of linoleic acid (Gray et al., 1994). Ground beef off-flavor ratings tended (P < 0.10) to be lower for heifers supplemented 60 d. Ratings of juiciness, initial tenderness, and beef flavor of ground beef were greater (P < 0.05) for heifers supplemented 60 d compared with 32 d. Dietary treatment and length of supplementation did not alter off-flavor ratings of ribeye steaks. Heifers fed OIL received lowest (P < 0.05) juiciness ratings for ribeye steaks, whereas CON were scored highest (P < 0.05). Juiciness of ribeye steaks did not differ by length of supplementation. The interaction of dietary treatment and length of lipid supplementation was significant (P < 0.05) for overall tenderness in ground beef and initial tenderness, overall tenderness, and beef flavor of ribeye steaks (Table 5). Ratings of overall tenderness were similar between supplementation lengths for CON. Heifers fed lipid supplements received higher (P < 0.05) overall tenderness ratings following 60 d of supplementation. Regardless of length of supplementation, heifers fed OIL had highest (P < 0.05) overall tenderness ratings for ground beef. Initial tenderness ratings of ribeye steaks increased (P < 0.05) as lipid supplementation was extended for OIL and RPCLA, whereas CON animals had reduced (P < 0.05) initial tenderness at 60 d compared with 32 d. However, for CON as well as RPCLA animals, overall tenderness scores of ribeye steaks did not differ between supplementation lengths. Similarly, Andrae et al. (2001) reported no differences in sensory properties of longissimus steaks of steers fed high-oil corn compared with typical corn varieties for 83 d. Corn oil-supplemented heifers had higher (P < 0.05) overall tenderness scores at 60 d compared with 32 d. Heifers fed CON and OIL diets had lower (P < 0.05) beef flavor scores following 60 d of supplementation, whereas those fed RPCLA received similar (P > 0.05) scores at 32 and 60 d. These changes, although statistically significant, are relatively minor and reflect minimal changes in sensory properties with oil supplementation.
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Table 5. Effects of dietary treatment x length of supplementation on sensory attributes of ground beef and ribeye steaks
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In conclusion, beef produced using traditional, high grain finishing diets contains < 160 and < 85 mg per serving of trans-octadecenoic fatty acids and cis-9 trans-11 isomer of CLA, respectively, as a result of incomplete ruminal biohydrogenation of dietary unsaturated fatty acids. Dietary lipid supplementation increased the amount of trans fat in steaks and ground beef and the amount of CLA in ground beef. Dietary lipid supplementation resulted in minimal changes in shelf life and sensory attributes of steaks and ground beef.
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Footnotes
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1 Supported in part by Cattlemen’s Beef Board and National Cattlemen’s Beef Association. 
2 Corresponding author: sducket{at}clemson.edu
Received for publication August 29, 2006.
Accepted for publication February 9, 2007.
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LITERATURE CITED
|
|---|
AHA. 2000. A statement for healthcare professionals from the nutrition committee of the American Heart Association. Circulation available from the World Wide Web: http://www.circulationaha.org Accessed Aug. 29, 2006.
AMSA. 1995. Research guidelines for cookery, sensory evaluation, and instrumental tenderness measurements of fresh meat. Am. Meat Sci. Assoc., Chicago, IL.
Andrae, J. G., S. K. Duckett, C. W. Hunt, G. T. Pritchard, and F. N. Owens. 2001. Effects of feeding high-oil corn to beef steers on carcass characteristics and meat quality. J. Anim. Sci. 79:582–588.[Abstract/Free Full Text]
Bauman, D. E., L. H. Baumgard, B. A. Corl, and M. Griinari. 1999. Biosynthesis of conjugated linoleic acid in ruminants in Proc. Am. Soc. Anim. Sci. http://jas.fass.org/misc/abstr_proc.shtml Accessed Mar. 14, 2007.
Bolte, M. R., B. W. Hess, W. J. Means, G. E. Moss, and D. C. Rule. 2002. Feeding lambs high-oleate or high-linoleate safflower seeds differentially influences carcass fatty acid composition. J. Anim. Sci. 80:609–616.[Abstract/Free Full Text]
Clifton, P. M., J. B. Keogh, and M. Noakes. 2004. Trans fatty acids in adipose tissue and the food supply are associated with Myocardial Infarction. J. Nutr. 134:874–879.[Abstract/Free Full Text]
Dhiman, T. R., S. E. Nam, and A. L. Ure. 2005a. Factors affecting conjugated linoleic acid content in milk and meat. Crit. Rev. Food Sci. Nutr. 45:463–482.[CrossRef][Medline]
Dhiman, T. R., S. Zaman, K. C. Olson, H. R. Bingham, A. L. Ure, and M. W. Pariza. 2005b. Influence of feeding soybean oil on conjugated linoleic acid content in beef. J. Agric. Food Chem. 53:684–689.[CrossRef][Medline]
Duckett, S. K., J. G. Andrae, and F. N. Owens. 2002. Effect of high oil corn or added corn oil or added corn oil on ruminal biohydrogenation and conjugated linoleic acid formation in beef steers fed finishing diets. J. Anim. Sci. 80:3353–3360.[Abstract/Free Full Text]
Duckett, S. K., and D. G. Wagner. 1998. Effect of cooking on the fatty acid composition of beef intramuscular lipid. J. Food Comp. Anal. 11:357–362.[CrossRef]
Duckett, S. K., D. G. Wagner, L. D. Yates, H. G. Dolezal, and S. G. May. 1993. Effects of time on feed on beef nutrient composition. J. Anim. Sci. 71:2079–2088.[Abstract]
Enser, M., N. D. Scollan, N. J. Choi, E. Kurt, K. Hallet, and J. D. Wood. 1999. Effect of dietary lipid on the content of conjugated linoleic acid in beef muscle. Br. J. Anim. Sci. 69:143–146.
FDA. 2003. Food Labeling: Trans fatty acids in nutrition labeling, nutrient content claims and health claims. 21 CFR Part 101. Fed. Reg. 68:41434–41506.
Folch, J., M. Lees, and G. S. H. Stanley. 1957. A simple method for the isolation and purification of lipids from animal tissues. J. Biol. Chem. 266:497–509.
Gassman, K. J., D. C. Beitz, F. C. Parrish, and A. Trenkle. 2000. Effects of feeding calcium salts of conjugated linoleic acid to finishing steers. J. Anim. Sci. 78(Suppl. 1):275–276. (Abstr.)[Abstract/Free Full Text]
Gillis, M. H., S. K. Duckett, and J. R. Sackmann. 2004a. Effects of supplemental rumen-protected conjugated linoleic acid or corn oil on fatty acid composition of adipose tissues in beef cattle. J. Anim. Sci. 82:1419–1427.[Abstract/Free Full Text]
Gillis, M. H., S. K. Duckett, J. R. Sackmann, C. E. Realini, D. H. Keisler, and T. D. Pringle. 2004b. Effects of supplemental rumen-protected conjugated linoleic acid or linoleic acid in beef cattle on feedlot performance, carcass quality, and leptin concentrations. J. Anim. Sci. 82:851–859.[Abstract/Free Full Text]
Gray, J. I., A. M. Pearson, and F. J. Monahan. 1994. Flavor and aroma problems and their measurement in meat, poultry and fish products. Pages 250–288 in Advances in Meat Research Series. Quality Attributes and their Measurement in Meat, Poultry and Fish Products. Vol. 9. A. M. Pearson and T. R. Dutson, ed. Chapman & Hall, New York, NY.
Griswold, K. E., G. A. Apgar, R. A. Robinson, B. N. Jacobson, D. Johnson, and H. D. Woody. 2003. Effectiveness of short-term feeding strategies for altering conjugated linoleic acid content of beef. J. Anim. Sci. 81:1862–1871.[Abstract/Free Full Text]
Ha, Y. L., N. K. Grimm, and M. W. Pariza. 1987. Anticarcinogens from fried ground beef: Heat altered derivatives of linoleic acid. Carcinogenesis 12:1881–1887.
Hoelscher, L. M., J. W. Savell, J. M. Harris, H. R. Cross, and K. S. Rhee. 1987. Effect of initial fat level and cooking method on cholesterol content and caloric value of ground beef patties. J. Food Sci. 52:883–885.[CrossRef]
Ip, C., M. Singh, H. J. Thompson, and J. A. Scimeca. 1994. Conjugated linoleic acid suppresses mammary carcinogenesis and proliferative activity of the mammary gland in the rat. Cancer Res. 54:1212–1215.[Abstract/Free Full Text]
Jo, C., and D. U. Ahn. 1998. Fluorometric analysis of 2-thiobarbituric acid reactive substances in turkey. Poult. Sci. 77:475–480.[Abstract/Free Full Text]
Lock, A. L., C. A. M. Horne, D. E. Bauman, and A. M. Salter. 2005. Butter naturally enriched in conjugated linoleic acid and vaccenic acid alters tissue fatty acids and improves the plasma lipoprotein profile in cholesterol-fed hamsters. J. Nutr. 135:1934–1939.[Abstract/Free Full Text]
Mensink, R. P., and M. B. Katan. 1990. Effect of dietary trans fatty acids on high-density and low-density lipoprotein cholesterol levels in healthy subjects. N. Engl. J. Med. 323:439–445.[Abstract]
Mir, P. S., Z. Mir, P. S. Kuber, C. T. Gaskins, E. L. Martin, M. V. Dodson, J. A. Elias Calles, K. A. Johnson, J. R. Busboom, A. J. Wood, G. J. Pittenger, and J. J. Reeves. 2002. Growth, carcass characteristics, muscle conjugated linoleic acid (CLA) content, and response to intravenous glucose challenge in high percentage Wagyu, Wagyu x Limousin, and Limousin steers fed sunflower oil-containing diets. J. Anim. Sci. 80:2996–3004.[Abstract/Free Full Text]
Park, P. W., and R. E. Goins. 1999. In situ preparation of fatty acid methyl esters for analysis of fatty acid composition in foods. J. Food Sci. 59:1262–1266.[CrossRef]
Realini, C. E., S. K. Duckett, N. S. Hill, C. S. Hoveland, B. G. Lyon, J. R. Sackmann, and M. H. Gillis. 2005. Effect of endophyte type on carcass traits, meat quality, and fatty acid composition of beef cattle grazing tall fescue. J. Anim. Sci. 83:430–439.[Abstract/Free Full Text]
Rule, D. C., K. S. Broughton, S. M. Shellito, and G. Maiorano. 2002. Comparison of muscle fatty acid profiles and cholesterol concentrations of bison, beef cattle, elk, and chicken. J. Anim. Sci. 80:1202–1211.[Abstract/Free Full Text]
Sackmann, J. R., S. K. Duckett, M. H. Gillis, C. E. Realini, A. H. Parks, and R. B. Eggelston. 2003. Effects of forage and sunflower oil levels on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets. J. Anim. Sci. 81:3174–3181.[Abstract/Free Full Text]
Schakell, S. F., I. M. Buzzard, and S. E. Gebhardt. 1997. Procedures for estimating nutrient values for food composition databases. J. Food Comp Anal. 10:102–114.[CrossRef]
Turpeinen, A. M., M. Mutanen, A. Antti, I. Salminen, S. Basu, D. L. Palmquist, and J. M. Griinari. 2002. Bioconversion of vaccenic acid to conjugated linoleic acid in humans. Am. J. Clin. Nutr. 75:504–510.
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Abstract
INTRODUCTION
