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ANIMAL NUTRITION |
Department of Animal Science, University of Missouri, Columbia 65211
Abstract
The hypothesis of this experiment was that increasing dietary fat through the use of whole oilseeds and altering the dietary ratio of PUFA:saturated fatty acids would alter carcass composition of finishing steers. Seventy-two steers (443.6 ± 1.0 kg) were fed for 76 d one of four dietary treatments: a corn/soybean meal-based diet (NOFAT); two diets containing 16% (DM basis) whole raw soybeans; and a corn/soybean meal-based diet containing choice white grease (CWG) equal to the fat addition supplied by the soybeans. Soybeans used in the diets were either a standard variety (NORM-SB) or a variety high in oleic acid content (HO-SB). The fatty acid profile of diets differed (P < 0.05) in the degree of saturation and content of palmitic, stearic, oleic, linoleic, and linolenic acids. There were no differences in ADG (1.73 kg/d), hot carcass weight (347 kg), longissimus muscle area (79.4 cm2), yield grade (3.31), or percentage of boneless retail cuts (48.8%). Contrasts revealed differences (P < 0.05) in G:F and marbling score with the addition of fat (0.126 vs. 0.137 and 4.66 vs. 4.91, respectively, for NOFAT vs. fat). The addition of fat tended (P < 0.10) to increase backfat, and feeding NORM-SB increased (P < 0.01) dressing percent compared with the HO-SB treatment. Loin samples taken from steers fed NOFAT, NORM-SB, and HO-SB did not differ in 
-tocopherol content. Loins from the CWG treatment tended (P < 0.10) to have lower -tocopherol content than did the soybean treatments (0.79 vs. 0.99 ppm, respectively). From main-effects analysis, HO-SB loin samples had the highest (F3,8 = 32.91; P < 0.01) concentration of 
-tocopherol (0.33 ppm); this resulted in differences (P < 0.05) in -tocopherol when comparing all contrasts. When comparing loin samples from NORM-SB-fed steers with those from HO-SB-fed steers, NORM-SB samples had a greater (P < 0.05) percentage of linoleic acid and PUFA and a lower (P < 0.05) percentage of oleic acid and monounsaturated fatty acids. Furthermore, loin samples from soybean-fed steers tended (P < 0.10) to have a greater concentration of conjugated linoleic acid than samples from CWG-fed steers. These data suggest that the source of added dietary fat may affect overall carcass composition. Furthermore, dietary addition of soybeans or CWG can improve feed efficiency and marbling, whereas the addition of whole raw soybeans compared with CWG may increase unsaturation and total vitamin E content of beef.
Key Words: Carcasses • Dietary Fat • Soybeans • Steers
Introduction
Feeding fats differing in origin and degree of saturation to ruminants has resulted in a variety of responses in ruminant production. Feeding soybean soap stock or a blend of soybean oil and tallow did not affect ADFI, ADG, or feed efficiency when compared with feeding tallow or yellow grease (Zinn, 1989
; Bock et al., 1991). These sources improved ADG and efficiency in comparison to no-fat controls and increased i.m. fat deposition (Zinn, 1989; Brandt and Anderson, 1990). On the contrary, yellow grease added to feedlot diets decreased ADFI in comparison to no-fat controls (Brandt and Anderson, 1990). Furthermore, various fat sources have shown either an improvement in feed efficiency or no effect (Brandt and Anderson, 1990).
Typically, the microflora in the rumen convert the majority of dietary unsaturated fatty acids (FA) to saturated FA (SAT). As a result, stearate is the primary FA available for absorption in the digestive tract (Chang et al., 1992). However, oleate, rather than stearate, is the predominant FA in bovine muscle and adipose tissue, indicating that absorbed stearate is modified before deposition in ruminant tissues (Chang et al., 1992).
The pericarp of seeds, if left intact, may provide a margin of protection for the oil within and should provide decreased exposure of the oil to microbial interaction (Baldwin and Allison, 1983). Thus, feeding oilseeds whole may provide a means of increasing PUFA available for absorption and deposition. This was previously demonstrated with whole cottonseed and sunflower seeds fed to finishing steers and bulls (Huerta-Leidez et al., 1991; Eweedah et al., 1997). Based on the reported literature, we hypothesized that increasing dietary fat through the use of whole oilseeds and altering the dietary ratio of PUFA to SAT would alter tissue composition and carcass quality of finishing steers.
Materials and Methods
Animals and Management
Seventy-two large-frame crossbred yearling steers were randomly allotted to one of four dietary treatments in a completely randomized design. Steers were weighed on two consecutive days (initial treatment BW = 443.6 ± 1.0 kg) at initiation and conclusion of the 76-d feeding period. Steers were fed to reach an average final weight of approximately 567 kg. Steers were housed six per pen, with three pens per treatment and pen was the experimental unit. Pens were of open construction, measuring 7.3 x 24.4 m sharing a 9.8-m concrete feed bunk between two pens (4.9 m/pen). Bunks were set on concrete slabs and extended approximately 2.5 m into the pens. Frost-free waterers were shared between two pens, and feed bunks and slabs were under sloped roof shades.
Before study initiation, all steers were fed a common corn-based diet containing 25% corn silage. Steers were adapted to the treatment diets by initially feeding them at 2.0% of average BW and increasing the amount fed 4.5 kg per pen every 4 d until maximum intake was achieved. Once maximum intake was obtained, clean bunk management (zero refusal) was used throughout the remainder of the study, with amount fed being adjusted only after daily refusal level remained constant for 3 d. Steers had been previously implanted (Ralgro; Schering-Plough, Inc., Union, NJ), with the expected payout expiring before initiation of treatments and were not reimplanted. Diets were fed once daily. Treatment diets were offered for the first time immediately after all steers returned to their pens on d 2 of initial BW measurement. Steers were slaughtered within 48 h of final live weight measurement. Experimental procedures were conducted under an approved Animal Care and Use Protocol (ACUC#3278) as regulated by the University of Missouri Animal Care and Use Committee.
Treatments
Steers were fed one of four dietary treatments: a corn/soybean meal-based diet (NOFAT); two diets containing 16% (DM basis) whole raw soybeans; and a corn/soybean meal-based diet containing choice white grease (CWG) equal to the fat addition supplied by the soybeans. Soybeans used in the diets were either a standard variety (NORM-SB) or a variety high in oleic acid content (HO-SB). Treatment diets (NOFAT, NORM-SB, HO-SB, and CWG) were formulated to be similar in N, Ca, and P content (Table 1), while meeting or exceeding the beef NRC (1996) requirements for the steers used in this study. Whole raw soybeans (WRS), either NORM-SB or HO-SB, replaced all the soybean meal of the NOFAT diet and were the major source of dietary lipids. The diet containing CWG was very similar in composition to that of the NOFAT diet except that CWG replaced corn, to yield an ether extract content similar to that of the WRS diets. Thus, NORM-SB, HO-SB, and CWG diets were formulated to contain similar levels of dietary lipid, but greater lipid content than the NOFAT diet. All diets contained equal amounts of soybean hulls, corn silage, limestone, NaCl, monensin, and tylosin. Dietary treatments were randomly assigned to pens. Steers were fed treatment diets via a Harsh (model 203T; Harsh International, Inc., Eaton, CO) truck-mounted paddle mixer.
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). For FA determination, ether extracts from diet and ingredient samples were evaporated under N at 55°C to dryness (N-EVAP Analytical Evaporation; Organomation Assoc. Inc., Berlin, MA) after filtering through granular anhydrous sodium sulfate. A small aliquot of remaining oil was transferred to a 15-mL glass culture tube and mixed with 0.5 mL of benzene containing trinonadecanoin (triglyceride 19:0; 2 mg/mL) as an internal standard. Benzene was used as an aid in solublizing dietary triglycerides. Methyl esters of FA were formed by adding 4 mL of 4% (vol/vol) sulfuric acid in anhydrous methanol to the culture tubes containing samples and heating capped at 90°C for 60 min (Fritsche and Johnston, 1990). After heating, reactions were stopped by adding 3.0 mL of double-distilled H2O. Methyl esters were extracted by adding 8.0 mL of chloroform, vortexing, and centrifuging at 900 x g to aid in phase separation. The chloroform layer was transferred through a sodium sulfate-filled Pasteur pipet into 15-mL glass conical bottom tubes and evaporated to dryness under N. Fatty acid methyl esters were resuspended in heptane and quantified using a gas chromatograph equipped with a flame ionization detector and integrator (Varian model 3400; Varian Associates, Walnut Creek, CA). The column used was a fused silica capillary column with He as the carrier gas (30 m x 0.25 mm i.d., 0.25-µm film thickness; SP 2380; Supelco, Bellefonte, PA). A split injection was used at a rate of 1.0 mL/1.1 s with a back pressure of 0.8788 kg/cm2. The initial oven temperature was 150°C, held for 7 min, and increased at a rate of 2°C/min until reaching a final temperature of 220°C. The injector and detector temperatures were set at 250 and 240°C, respectively. Commercially available marine- and animal-derived FA methyl esters were used for peak identification (PUFA I and PUFA II; Supelco, Bellefonte, PA). Reported chemical analysis is the average nutrient composition of weekly diet and ingredient samples. Percentages of PUFA, SAT, and monounsaturated FA (MONO) for all discussions were calculated by summation of individual fatty acids. All chemicals used were purchased through either Fisher Scientific (Pittsburgh, PA) or Sigma Chemical (St. Louis, MO). One day after final BW determination, steers were fed 50% of the previous day’s intake (as-fed basis). Late afternoon on the same day, steers were transported from Columbia, MO, to Schuyler, NE, where they were slaughtered the following morning at a commercial processing facility (Excel Corp., Schuyler, NE). Hot carcass weight (HCW) was recorded immediately before the carcass entering the cooler. Carcass measurements (marbling scores; backfat [BF]; longissimus muscle area [LMA]; percentage of kidney, pelvic, and heart fat [KPH]; and yield grade [YG]) were taken after carcasses were allowed to chill for 48 h at 0°C by trained personnel from the University of Missouri meat sciences group. Marbling scores were coded so that 4.0 = slight00 (low Select), 5.0 = small00 (low Choice), 6.0 = modest00 (average Choice), and 7.0 = moderate00 (high Choice). Personnel responsible for carcass measurements had no knowledge of treatment association.
Samples of internal fat (perinephric) were obtained immediately before carcass ribbing. After assignment of marbling scores, an approximately 1.25-cm slice of 12th-rib facial longissimus muscle was removed from the left side of the carcass. These tissues were independently identified and immediately placed on ice and transported back to the University of Missouri. Longissimus samples were dissected free of intermuscular and s.c. fat. External fat free lean, s.c. fat, and perinephric fat were stored frozen (–80°C) until later analysis of FA profile. Muscle tissue was also analyzed for moisture, crude fat, OM (AOAC, 1984), and tocopherol content. All analyses were initiated on frozen (–80°C) samples.
In preparation for analysis of vitamin E and FA, muscle samples were wrapped in aluminum foil, submerged in liquid N for approximately 15 to 20 s and shattered with a hammer. Shattered muscle tissue and fat samples were immediately ground with additional liquid N to a fine powder using a Stein Laboratory Mill (Fred Stein Laboratories Inc., Atchison, KS). Ground tissues were immediately transferred to Whirl Pak (Nasco, Modesto, CA) freezer bags and stored at –80°C. Vitamin E preparation of samples was performed within 1 h of grinding.
For analysis of vitamin E, approximately 0.5 g of ground tissue was weighed in a 50-mL polypropylene centrifuge tube. Ten milliliters of pH 7.4 adjusted 10-mM EDTA-disodium salt and 100 µL of 1% (wt/vol) butylated hydroxytoluene in absolute ethanol were added to each tube. Samples were homogenized with a Tissue Tearor (model 985-370; Biospec Products Inc., Dremel, Racine, WI) for approximately 30 s. Two milliliters of homogenate was immediately transferred to a disposable 16- x 150-mm borosilicate glass culture tube containing 2 mL of 1% (wt/vol) ethanolic ascorbic acid along with 200 µL of a 0.15 ppm solution of 
-tocopherol (used as the internal standard). Four milliliters of hexane and 1 mL of double-distilled H2O were added to each tube. Samples were vortexed and phase-separated by centrifugation at 500 x g for 5 min at 0 to 15°C. The hexane layer was transferred into clean 15-mL conical bottom glass test tubes. Hexane extraction was repeated twice and combined with previous extract. Hexane was evaporated under N (N-EVAP Analytical Evaporation; Organomation Assoc. Inc.), and the residue was resuspended in 300 µL of MeOH. Twenty microliters of sample was injected and analyzed via a Perkin-Elmer model 250 liquid chromatograph (Boston, MA) equipped with an ISS200 autosampler, a Luna 6-cm, C18 column (3-µm particle size with a guard column), and fluorescence detection (em 330 nm and ex 295 nm) with a Hitachi F-1200 fluorescence spectrophotometer (Schaumburg, IL). The mobile phase consisted of methanol:water (97:3) and was run at 1 mL/min. Individual injections of pure -, -, and -tocopherol (Sigma Chemical) were used for peak identification. A mixture of -, -, and -tocopherol at various concentrations was used for direct calibration to calculate sample concentration.
Tissue lipids were extracted by the methods of Folch et al. (1957). Fatty acid profiles of muscle tissue extract were determined by acid methylation. Acid methylation (Fritsche and Johnston, 1990) in the presence of benzene was used due to the mixed sources of fatty acids in muscle tissue, especially the presence of cholesterol esters and FFA which do not methylate as readily under basic conditions (Christie, 1992). Briefly, methyl esters of muscle sample chloroform:methanol:acetic acid extract were prepared by using 4 mL of 4% (vol/vol) H2SO4 in anhydrous methanol. Basic methylation, which is much simpler and more rapid, was used for fat tissue extracts due to the predominate presence of tryglyceride derived fatty acids (Christie, 1992). Briefly, methyl esters of fat sample chloroform:methanol:acetic acid extracts were prepared by using 2 mL of 0.5 M NaOH in methanol. Methyl esters, including conjugated dienes of linoleic acid (CLA), were measured using a gas chromatograph equipped with a flame ionization detector and integrator (Varian model 3400; Varian Associates). The column used was a fused silica capillary column with He as the carrier gas (60 m x 0.25 mm i.d., 0.25-µm film thickness; J and W Scientific DB23, Folsom, CA). A split injection was used at a rate of 1.0 mL/0.6 s with a back pressure of 1.055 kg/cm2. The oven temperature was programmed at an initial temperature of 150°C, held for 7 min, and increased at a rate of 3°C/min until reaching a temperature of 205°C. Oven temperature was held at 205°C for 5 min and increased to 215°C at a rate of 1.5°C/min. This temperature was held for 2 min and increased to 220°C at a rate of 20°C per min and held for 9 min. Total run time was 48.24 min. The injector and detector temperatures were set at 230 and 250°C, respectively. A commercially available mixture of FA methyl esters as well as CLA methyl esters were used for peak identification (FAME 37; Supelco and CLA; Sigma Chemical) with nonadecanoate (19:0) and trinonadecanoin (triglyceride 19:0) used as internal standards. The CLA methyl esters used for peak identification consisted of a mixture of the cis- and trans-isomers of 9,11- and 10,12-octadecadienoic acid methyl esters and sample CLA content are reported as a total of these isomers.
Statistical Analyses
Performance and carcass data from this study were analyzed as a completely randomized design by the GLM procedures of SAS using the LSMEANS and orthogonal contrast statements (SAS Inst., Inc., Cary, NC). Pen was used as the experimental unit for all analyses with three pens per treatment used for replication. The model included treatment, pen replicate, and treatment x replicate with treatment x replicate used as the error term. Comparisons made were 1) NOFAT vs. fat addition (NORM-SB, HO-SB, and CWG); 2) WRS (NORM-SB and HO-SB) vs. animal fat (CWG); and 3) NORM-SB vs. HO-SB. Tissue FA composition was analyzed by GLM procedures as a split plot with the main-plot factor being treatment and the subplot factor being the site from which tissues were harvested. No treatment x site effects were detected for variables tested thus data was analyzed by site, testing only for treatment effects. Thus, a simple one-way ANOVA for a completely randomized design was conducted using the same treatment orthogonal contrasts as previously described. For tissue FA composition analysis, pen within treatment was used as the residual error term. Dietary FA profiles were analyzed by the GLM procedures of SAS testing differences in LSMEANS. For all analysis, an alpha level of 0.05 was used for significance to minimize type-I errors, with alpha levels of 0.05 to 0.10 denoting a tendency for significance.
Results and Discussion
Dietary
Dietary composition and formulated and/or analyzed chemical analysis are reported in Table 1
. Normal WRS are relatively high in PUFA (59%) and low in SAT (16%). To the contrary, high oleate soybeans, which were used in the HO-SB treatment, are a mutant strain of soybean which lacks the 6-desaturase gene resulting in very high levels of MONO (85.1%) with very low levels of PUFA (4.7%) and SAT (10.2%). Similar to high-oleic soybeans, choice white grease typically is very low in PUFA (2.8%) but moderate in MONO and SAT (41.8 and 55.5%, respectively). Thus, source of dietary fat had a major influence on overall dietary FA profile and the degree of dietary FA saturation (Table 2). Fatty acid profile and ether extract content of all dietary ingredients supplying greater than 10% of the dietary FA are reported in Table 3. As reported in Table 3, the ether extract values for corn and corn silage are much higher than values commonly reported in the beef NRC (NRC, 1996). However, values for other ingredients are consistent with those reported elsewhere. The authors have no explanation for this other than potential differences in corn variety. Fatty acid profile of the NOFAT diet was very similar to that of the NORM-SB diet except for the NORM-SB diet containing a greater (P < 0.05) percentage of -linolenic acid (18:3n3). However, the NOFAT diet was formulated to be much lower in total lipid content. As one would expect from the FA profiles of the major lipid sources used in this study, the CWG diet contained the greatest (P < 0.05) amount of SAT (52.2%), mainly palmitic (16:0) and stearic (18:0); the HO-SB diet contained the greatest (P < 0.05) amount of MONO (54.4%), predominately oleic acid (18:1n9). The NOFAT and NORM-SB diets contained similar profiles of FA but, owing to the actual level of fat fed, the NORM-SB contained the greatest amount of PUFA, mainly cis-linoleic (18:2n6) and 18:3n3.
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). Dry matter intake tended to (P < 0.10) decrease with the addition of fat whereas G:F was improved (P < 0.05). Some researchers have also reported little effect of fat feeding or source of fat on gain while improving feed efficiency through decreasing feed intake (Andrae et al., 2000; Ramirez and Zinn, 2000). Similar to the results of our study, Madron et al. (2002) showed only minor differences in feed intake with no effect on gain or finishing weight when steers were fed extruded full-fat soybeans. Others have reported no effects on performance of growing bulls with feeding different whole oilseeds (Eweedah et al., 1997).
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). Likewise, no differences were detected in calculated or assigned yield grade (3.31 and 2.59) and in the percentage of closely trimmed retail cuts (48.8%) available from the carcasses. However, fat feeding tended to increase (P < 0.10) BF, whereas the feeding of WRS tended to increase (P < 0.10) dressing percent compared with the CWG treatment. Furthermore, steers on the NORM-SB treatment had a greater (P < 0.01) dressing percent than those on the HO-SB treatment. Feeding additional fat increased (P < 0.05) marbling scores by one-fourth of a marbling score grade with no effect due to source. The results observed in this study were similar to those in which tallow, yellow grease, griddle grease, or high-oil corn were used to increase fat content of feedlot diets (Zinn and Plascencia, 1996; Andrae et al., 2001).
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) than did NOFAT-fed steers. Likewise, main effects of treatment on LS means separation (data not shown) revealed that feeding NORM-SB increased (P < 0.01) the percentage of cis-18:2n6 and PUFA of perinephric fat to nearly double that of the other dietary treatments. This response resulted in differences being detected for all contrast comparisons for cis-18:2n6 (P < 0.05) and PUFA (P < 0.06), respectively. The percentage of perinephric arachidic acid (20:0) from NORM-SB was greater (P < 0.05) than from HO-SB. There was a tendency (P < 0.10) for the content of perinephric CLA to be increased for the HO-SB treatment as compared with the NORM-SB treatment group. Likewise, there was a tendency (P < 0.10) for -linolenic to be lower for HO-SB perinephric samples when compared with NORM-SB samples. Dietary fat addition, regardless of source, did not affect any of the other long-chain FA or percentage of SAT or MONO measured in the perinephric fat.
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). The percentage of s.c. CLA tended (P < 0.10) to be decreased in the CWG treatment when compared with the other fat treatments. There was a tendency (P < 0.12) for s.c. fat from HO-SB-fed steers to be higher in cis-18:1n9 but lower in cis-18:2n6 (P < 0.01) than s.c. fat from NORM-SB-fed steers. Subcutaneous fat from CWG-fed steers had lower percentages of cis-18:2n6 (P < 0.05) and CLA (P < 0.10) than WRS-fed steers. Overall, feeding additional fat did not influence the percentage of PUFA, SAT, or MONO of s.c. fat when compared with the NOFAT treatment. However, within sources, the WRS treatments had a greater (P < 0.05) proportion of PUFA than did the CWG treatment. Additionally, the NORM-SB treatment had a greater (P < 0.05) proportion of PUFA and a lower (P < 0.05) proportion of MONO when compared with the HO-SB treatment.
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). This is to be expected with the large amount of cellular membranes and cellular activity occurring in muscle cells. The percentages of 14:0 and 16:0 were reduced (P < 0.05) with the feeding of additional fat. There was also a tendency for palmitoleic (16:1n7; P < 0.10) to be reduced with fat feeding. Longissimus samples from steers fed CWG had a lower percentage of 14:0 (P < 0.01) and tended to have lower CLA (P < 0.10) than steers fed WRS. Within the longissimus muscle of CWG-fed steers, CLA made up less than 0.1% of the total FA content. Longissimus samples from NORM-SB-fed steers in comparison to HO-SB-fed steers had a lower percentage of cis-18:1n9 (P < 0.05) and tended to have lower 17:1n7 (P < 0.10) and -18:3n3 (not detected; P < 0.10) but a higher (P < 0.05) percentage of cis-18:2n6. Feeding additional fat did not affect the percentage distribution of PUFA, SAT, or MONO of longissimus samples. However, there was an increase (P < 0.05) in PUFA and a decrease (P < 0.05) in MONO when the NORM-SB treatment was compared with the HO-SB treatment, respectively.
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) that the seed coat of canola may physically protect lipids from ruminal biohydrogenation in just such a manner. Duckett et al. (2002) further suggested that the seed coat of dry-rolled high-oil corn offered very little protection against biohydrogenation, indicating the necessity to leave the seed coat intact.
Fatty acid composition and ultimately the degree of FA saturation differed (P < 0.05) across tissues (Table 9) as has been reported elsewhere (St. John et al., 1987; Huerta-Leidenz et al., 1991) and reflect ruminal and tissue modifications of dietary FA (Beaulieu et al., 2002). As one would expect due to the greater amount of phospholipids present in muscle cells, longissimus muscle was higher (P < 0.05) in PUFA than was either perinephric or s.c. fat. Rule et al. (1994) demonstrated that muscle FA profile was more sensitive to dietary lipid when the dietary lipid was somewhat resistant to ruminal biohydrogenation. Furthermore, due to the metabolically active nature of muscle requiring the modification of PUFA for metabolic functions, muscle tissue also has a greater degree of elongase and less desaturase activity (Chang et al., 1992; Beaulieu et al., 2002). Conversely, perinephric fat was higher in total SAT and lowest in MONO when compared with longissimus and s.c. fat, which is similar to the results reported by Wood (1984) and Webb et al. (1998). These results also suggest that there is a lower activity of the desaturase enzyme for internal fat stores. Likewise, internal fat stores tend to be chronologically older than other tissue sites, potentially indicating the greater likelihood of ruminal biohydrogenation and deposition of FA encompassed before finishing (Beaulieu et al., 2002). Of the three tissues analyzed, s.c. fat contained the greatest percentage of MONO, indicating the potential for greater desaturase activity as compared with internal fat stores (Beaulieu et al., 2002). In looking at the site data, this may be important when comparing these results with those of other fat feeding studies in that the interpretation may depend on the site from which tissues are obtained.
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). However, ash content tended to be decreased (P < 0.10) with the feeding of additional fat. Dietary fat addition seemed to increase numerically the percentage of ether-extractable fat, thus decreasing the proportion of ash and protein. A lack of difference in ether-extractable fat among treatments may have been due to experimental error in tissue dissection.
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-tocopherol (vitamin E) acetate added at equal levels; -tocopherol acetate is highly absorbable and deposited as -tocopherol. Other sources of tocopherol (- and -tocopherol) are reported to be much less absorbable than - or -acetate (Combs, 1999). Soybeans are typically very high in -tocopherol; but little data exist on the availability of vitamin E in the seed when in ruminant diets. Interestingly, total tocopherol content of longissimus dorsi samples was affected by dietary treatment (Table 10). Muscle tissue from steers fed WRS was much higher (P < 0.05) in total tocopherol than were tissues from CWG-fed steers, with HO-SB-fed steers having a numerically greater total amount of tocopherol than NORM-SB-fed steers. These results reflect the fact that the CWG-fed steers had lower (P < 0.10) levels of muscle -tocopherol. Furthermore, muscle tissue from NORM-SB and HO-SB-fed steers had 1-fold and 1.5-fold increases (P < 0.01) in tissue extracted -tocopherol compared with CWG and NOFAT-fed steers. These results indicated that the vitamin E in soybeans may be quite available for absorption in ruminant diets.
Grains were not processed in this experiment as is commonly done in the feedlot industry. In addition, treatment diets contained relatively high levels of fiber from the inclusion of soybean hulls. Both of these dietary management decisions were made in order to minimize the chances of digestive upsets. Furthermore, soybean hulls were used as a carrier for the choice white grease and were used in all diets at equal inclusion levels. Thus, substantial fiber digestion may have been possible, increasing the fibrolytic bacterial species present. Several fibrolytic bacterial species commonly found in the rumen have been implicated as major organisms responsible for biohydrogenation and ruminal CLA production (Fay et al., 1990; Kim et al., 2000). However, many of these bacterial species are susceptible to the toxic effects of PUFA, and the NORM-SB diet was elevated with these. Leaving the seed coat intact for the WRS treatments could have prevented this toxicity. Furthermore, the high dietary fat level of the fat-containing diets (approaching 8%) could have coated the dietary fiber, limiting the ability of the fibrolytic bacterial populations to grow and to biohydrogenate the unsaturated fatty acids present. The effects of dietary fat source observed in this experiment may be different with unprocessed grain, processed oilseeds, and lower dietary fiber levels.
Regardless of the aforementioned, heavy-weight, large-frame yearling steers maintained feedlot performance and carcass quality when fed high-fat diets containing choice white grease, whole raw conventional, or high-oleate soybeans. The feeding of additional fat, regardless of source, improved feed efficiency at a time when intakes are typically the greatest and efficiency is the lowest. Compared with the U.S. average finished steer (Boleman et al., 1998), the control (NOFAT) steers in the present study were similar in weight but had more internal and s.c. fat with lower marbling scores. This would indicate that the steers used in this study might not have had the propensity to marble. However, as compared with their NOFAT contemporaries, the addition of fat improved marbling scores without affecting fat deposition at other sites. Thus, the addition of fat may improve the marbling capabilities of steers with poor marbling propensity.
Beyond affecting marbling scores, feeding additional fat as well as source of fat altered FA profiles in s.c. and perinephric fat and longissimus dorsi external fat-free lean. Similar to the results of Beaulieu et al. (2002), the feeding of WRS, regardless of variety, had little effect on CLA content of various tissues as compared with NOFAT controls. However, the feeding of CWG did appear to decrease the CLA content of muscle and s.c. fat tissues as compared with the WRS treatments. As the degree of dietary FA saturation decreased, the degree of tissue FA saturation also decreased, especially in edible tissues commonly consumed by the beef consumer. Likewise, the addition of WRS increased tocopherol concentration of longissimus dorsi samples mainly through increasing -tocopherol. However, the addition of CWG compared with the WRS treatments decreased total tocopherol content by decreasing -tocopherol. Typical feeding periods are much longer than the period during which cattle were fed in this study. Thus, if steers were fed treatment diets for greater periods of time than used here, the amount of tocopherol present in and the FA profile of the tissue may have been substantially different.
Implications
As long as economically feasible, the addition of fat to feedlot diets at reasonable inclusion levels can improve feed efficiency and marbling score. Furthermore, dietary fat source can alter the composition of the beef carcass by altering fatty acid profile and vitamin E content. In the selection of dietary fat sources, the use of whole raw soybeans that are high in unsaturated fat compared with choice white grease can increase the amount of unsaturated fat and total vitamin E deposited in the tissue. Additional tissue vitamin E may play an important role in protecting the additional deposited unsaturated fatty acids from lipid oxidation. These changes may have further implications for the shelf life of beef products as well as the diet of the beef consumer.
Footnotes
1 This research was supported in part by the Missouri Soybean Merchandising Council (Jefferson City, MO) and Optimum Quality Grains (West Des Moines, IA). 
2 Current address: Dept. of Anim. and Vet. Sci., West Virginia Univ., Morgantown 26506.
3 Correspondence: 111A Animal Sciences Research Center, 920 East Campus Dr. (phone: 573-882-0834; fax: 573-884-4606; e-mail: kerleym{at}missouri.edu).
Received for publication February 16, 2003. Accepted for publication February 3, 2004.
Literature Cited
AOAC. 1984. Official Methods of Analysis. 14th ed. Assoc. Offic. Anal. Chem., Washington, DC.
Aldrich, C. G., N. R. Merchen, J. K. Drackley, S. S. Gonzalez, G. C. Fahey, Jr., and L. L. Berger. 1997. The effects of chemical treatment of whole canola seed on lipid and protein digestion by steers. J. Anim. Sci. 75:502–511.
Andrae, J. G., C. W. Hunt, S. K. Duckett, L. R. Kennington, P. Feng, F. N. Owens, and S. Soderlund. 2000. Effect of high-oil corn on growth performance, diet digestibility, and energy content of finishing diets fed to beef cattle. J. Anim. Sci. 78:2257–2262.
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.
Baldwin, R. L., and M. J. Allison. 1983. Rumen metabolism. J. Anim. Sci. 57(Suppl. 2):461–472.
Beaulieu, A. D., J. K. Drackley, and N. R. Merchen. 2002. Concentrations of conjugated linoleic acid (cis-9,trans-11-octadecadienoic acid) are not increased in tissue lipids of cattle fed a high-concentrate diet supplemented with soybean oil. J. Anim. Sci. 80:847–861.
Bock, B. J., D. L. Harmon, R. T. Brandt, Jr., and J. E. Schneider. 1991. Fat source and calcium level effects on finishing steer performance, digestion, and metabolism. J. Anim. Sci. 69:2211–2224.[Abstract]
Boleman, S. L., S. J. Boleman, W. W. Morgan, D. S. Hale, D. B. Griffin, J. W. Savell, R. P. Ames, M. T. Smith, J. D. Tatum, T. G. Field, G. C. Smith, B. A. Gardner, J. B. Morgan, S. L. Northcutt, H. G. Dolezal, D. R. Gill, and F. K. Ray. 1998. National Beef Quality Audit—1995: Survey of producer-related defects and carcass quality and quantity attributes. J. Anim. Sci. 76:96–103.
Brandt, R. T., Jr., and S. J. Anderson. 1990. Supplemental fat source affects feedlot performance and carcass traits of finishing yearling steers and estimated diet net energy value. J. Anim. Sci. 68:2208–2216.[Abstract]
Chang, J. H. P., D. K. Lunt, and S. B. Smith. 1992. Fatty acid composition and fatty acid elongase and stearoyl-CoA desaturase activities in tissues of steers fed high oleate sunflower seed. J. Nutr. 122:2074–2080.
Christie, W. W. 1992. Preparation of fatty acid methyl esters. Inform 3:1031–1034.
Combs, G. F., Jr. 1999. The Vitamins: Fundamental Aspects in Nutrition and Health. 2nd ed. Academic Press. San Diego, CA.
Duckett, S. K., J. G. Andrae, and F. N. Owens. 2002. Effects of high-oil corn or added corn oil on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets. J. Anim. Sci. 80:3353–3360.
Eweedah, N., L. Rozsa, J. Gundel, and J. Varhegyi. 1997. Comparison of fullfat soybean, sunflower seed and protected fat as fat supplements for their effect on the performance of growing-finishing bulls and carcass fatty acid composition. Acta Vet. Hung. 45:151–163.[Medline]
Fay, J. P., K. D. Jakober, K. J. Cheng, and J. W. Costerton. 1990. Esterase activity of pure cultures of rumen bacteria as expressed by the hydrolysis of p-nitrophenylpalmitate. Can. J. Microbiol. 36:585–589.[Medline]
Folch, J., M. Lees, and G. H. Sloane Stanley. 1957. A simple method for the isolation and purification of total lipids from animal tissues. J. Biol. Chem. 226:497–509.
Fritsche, K. L., and P. V. Johnston. 1990. Effect of dietary alpha-linolenic acid on growth, metastasis, fatty acid profile and prostaglandin production of two murine mammary adenocarcinomas. J. Nutr. 120:1601–1609.
Huerta-Leidenz, N. O., H. R. Cross, D. K. Lunt, L. S. Pelton, J. W. Savell, and S. B. Smith. 1991. Growth, carcass traits, and fatty acid profiles of adipose tissues from steers fed whole cottonseed. J. Anim. Sci. 69:3665–3672.[Abstract]
Kim, Y. J., R. H. Liu, D. R. Bond, and J. B. Russell. 2000. Effect of linoleic acid concentration on conjugated linoleic acid production by Butyrivibrio fibrisolvens A38. Appl. Environ. Microbiol. 66:5226–5230.
Madron, M. S., D. G. Peterson, D. A. Dwyer, B. A. Corl, L. H. Baumgard, D. H. Beermann, and D. E. Bauman. 2002. Effect of extruded full-fat soybeans on conjugated linoleic acid content of intramuscular, intermuscular, and subcutaneous fat in beef steers. J. Anim. Sci. 80:1135–1143.
NRC. 1996. Nutrient Requirements of Beef Cattle. 7th rev. ed. Natl. Acad. Sci., Washington, D.C.
Ramirez, J. E., and R. A. Zinn. 2000. Interaction of dietary magnesium level on the feeding value of supplemental fat in finishing diets for feedlot steers. J. Anim. Sci. 78:2072–2080.
Rule, D. C., J. R. Busboom, and C. J. Kercher. 1994. Effect of dietary canola on fatty acid composition of bovine adipose tissue, muscle, kidney, and liver. J. Anim. Sci. 72:2735–2744.[Abstract]
St. John, L. C., C. R. Young, D. A. Knabe, L. D. Thompson, G. T. Schelling, S. M. Grundy, and S. B. Smith. 1987. Fatty acid profiles and sensory and carcass traits of tissues from steers and swine fed an elevated monounsaturated fat diet. J. Anim. Sci. 64:1441–1447.
Webb, E. C., S. DeSmet, C. Van Nevel, B. Martens, and D. I. Demeyer. 1998. Effect of anatomical location on the composition of fatty acids in double-muscled Belgian Blue cows. Meat Sci. 50:45–53.
Wood, J. D. 1984. Fat deposition and the quality of fat tissue in meat animals. Pages 407–425 in Fats in Animal Nutrition. R. J. Wiseman, ed. Butterworths, London.
Zinn, R. A. 1989. Influence of level and source of dietary fat on its comparative feeding value in finishing diets for steers: Feedlot cattle growth and performance. J. Anim. Sci. 67:1029–1037.
Zinn, R. A., and A. Plascencia. 1996. Effect of forage level on the comparative feeding value of supplemental fat in growing-finishing diets for feedlot cattle. J. Anim. Sci. 74:1194–1201.[Abstract]
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