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J. Anim. Sci. 2002. 80:3353-3360
© 2002 American Society of Animal Science

Effect 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

S. K. Duckett*,1, J. G. Andrae* and F. N. Owens{dagger}

* The University of Georgia, Athens, 30602 and and {dagger} Pioneer Hi-Bred International, Inc., Johnston, IA, 50131

1 Correspondence:
Animal and Dairy Science Complex (E-mail:
sduckett{at}arches.uga.edu).


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 
Three Angus steers (410 kg) cannulated in the proximal duodenum were used in a replicated 3 x 3 Latin square to evaluate the effects of dietary lipid level and oil source on ruminal biohydrogenation and conjugated linoleic acid (CLA) outflow. Dietary treatments included: 1) typical corn (TC; 79.2% typical corn), 2) high-oil corn (HOC; 79.2% high-oil corn), and 3) the TC diet with corn oil added to supply an amount of lipid equal to the HOC diet (OIL; 76.9% TC + 2.4% corn oil). Duodenal samples were collected for 4 d following 10-d diet adaptation periods. Data were analyzed with animal, square, period, and treatment in the model and planned, nonorthogonal contrasts were used to test the effects of dietary lipid content (TC vs HOC and OIL) and oil source (HOC vs OIL) on ruminal biohydrogenation. Intake and duodenal flow of total long-chain fatty acids were increased (P < 0.05) by over 63% for diets containing more lipid regardless of oil source. Apparent ruminal dry matter and long chain fatty acid digestibilities were not altered (P > 0.05) by dietary lipid level or oil source. Ruminal biohydrogenation of total and individual 18-carbon unsaturated fatty acids was greater (P < 0.05) for diets with higher lipid content. Biohydrogenation of oleic acid was greater (P < 0.05) for HOC than OIL, but biohydrogenation of linoleic acid was lower (P < 0.05) for HOC than OIL. Duodenal flows of palmitic, stearic, oleic, linoleic, and arachidic acids were more than 30% greater (P < 0.05) for diets containing more lipid. Flow of all trans-octadecenoic acids was greater (P < 0.05) for diets containing more lipid. Corn oil addition increased (P < 0.05) the flow of trans-10 octadecenoic acid and the trans-10, cis-12 isomer of CLA by threefold compared to feeding high-oil corn. Feeding high-oil corn or adding corn oil to typical corn rations increased intake, biohydrogenation, and duodenal flow of unsaturated long-chain fatty acids. Compared with high-oil corn diets, addition of corn oil increased duodenal flow of trans-10, trans-12 and cis-12 isomers of octadecenoic acid and the trans-10, cis-12 isomer of CLA. The amount of cis-9, trans-11 isomer of conjugated linoleic acid flowing to the duodenum was less than 260 mg/d, a value over 20 times lower than flow of trans-11 vaccenic acid indicating the importance of tissue desaturation for enhanced conjugated linoleic acid content of beef.

Key Words: Beef • Biohydrogenation • High-Oil Corn


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 
Through selection, corn grain hybrids containing 7% ether extract, nearly twice the amount found in typical corn, have been developed and are commercially available. Previous research (Andrae et al., 2001) has shown that feeding high-oil corn to steers in finishing rations increased the percentages of linoleic (C18:2) and arachidonic (C20:4) acids in i.m. lipid. Because linoleate is not synthesized in the body, enrichment in tissue indicates that more linoleic acid reached the small intestine for absorption and deposition when high-oil corn was substituted for typical corn. This increased intestinal supply of linoleic acid could be from reduced ruminal biohydrogenation of fatty acids, an increased dietary supply of unsaturated fat, or both.

Conjugated linoleic acid (CLA) and trans-octadecenoic acid are produced in the rumen as intermediates in the biohydrogenation of dietary linoleic acid to stearic acid (Bauman et al., 1999). Conjugated linoleic acid is an anticarcinogen, which reduced tumor proliferation when topically applied to mice with experimentally induced epidermal carcinogenesis (Ha et al., 1987). Chin et al. (1992) reported that CLA concentrations in ground beef are 3.8 to 4.3 mg/g of lipid with about 84% being cis-9, trans-11 CLA isomer. Concentrations of CLA in milk fat increase with dietary supplementation of unsaturated vegetable oils (McGuire et al., 1996; Kelly et al., 1998) or oilseeds (Stanton et al., 1997; Lawless et al., 1998). However, little research is available on the flow of CLA to the duodenum in cattle fed high-concentrate diets. The hypothesis of this research was to determine if dietary lipid levels or sources increased the flow of unsaturated fatty acids to the small intestine. The objective of this research project was to determine the effect of dietary lipid level or oil source on ruminal biohydrogenation and CLA outflow in beef steers fed finishing diets.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results and Discussion
 Implications
 Literature Cited
 
Animals.
Three Angus steers (410 kg) cannulated in the proximal duodenum were fed one of three diets in a replicated 3 x 3 Latin square. The polyethylene T-type cannulae (Ankom, Fairport, NY) were inserted by a clinical veterinarian into the proximal duodenum of steers while under general anesthesia. The Animal Care and Use Committee approved the surgical procedures and use of animals in this study. The experiment began after a 4-wk recovery period. Steers were housed in covered pens with concrete floors without bedding. Rubber mats were provided in each pen for animal comfort. Steers weighed 410 kg at the beginning of the first square and 480 kg at the beginning of the second square, which started 42 d later. All feeding conditions and animal management practices were similar for each square.

Diets.
The three dietary treatments were: 1) typical corn (TC; 79.2% typical corn; 14% hay; 3.0% fatty acid content; DM basis), 2) high-oil corn (HOC; 79.2% high-oil corn; 14% hay; 5.2% fatty acid content; DM basis), and 3) the TC diet in which corn oil replaced corn so that it contained the same amount of lipid as HOC (OIL; 76.9% typical corn, 14% hay, 2.4% corn oil, and 5.2% fatty acid content; DM basis). Corn was processed by dry rolling, which was similar to the previous feeding experiment of Andrae et al. (2000). Bromegrass hay was coarsely chopped to approximately 5 cm in length. The TC and HOC diets were identical except for the grain source. The typical corn and high-oil corn were supplied by Pioneer Hi-Bred International, Inc. (Johnston, IA) from a TopCross hybrid with the female (ear bearing) parent being the same as for the typical corn. Grain sources were grown in adjacent fields. Ingredient and chemical composition of the diets are presented in Table 1Go. Diets were designed to be isonitrogenous. No ionophore was included in diets because ionophores might reduce the benefit of added fat (Clary et al., 1993) and alter ruminal biohydrogenation (Dhiman et al., 1999). Total lipid content of typical and high-oil corn was 4.25% and 7.25%, respectively. The amount of corn oil added to the OIL diet was calculated to make the OIL diet equal in lipid to the HOC diet. Animals were individually fed twice daily at 0800 and 1700 with total daily intake being 95% of intake determined during a preliminary period in which feed supply was unlimited to eliminate refusals during the sampling period. Chromic oxide (5 g per animal per day) was added to the diets as an external marker for calculating duodenal flow.


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  		Table 1. Ingredient and chemical composition (percentage of diet dry matter) of diets fed to steersa
 
Sample Collection and Analyses.
Experimental periods lasted 14 d with 10 d for diet adaptation and 4 d for sample collection. Following the 10-d adaptation period, duodenal samples (200 mL) were taken 12 times over 4 d, with sampling at 8-h intervals and sampling times shifted ahead by 2 h each day, such that samples represented duodenal contents from 12 equally spaced intervals over a 24-h day. Feed samples were collected once daily during each sampling period. Feed samples were immediately frozen after collection. Duodenal samples were composited on an equal liquid volume basis for each steer within each period and frozen for later processing. Later, duodenal digesta and feed samples were thawed, lyophilized, ground through a Wiley mill (1-mm screen), and frozen at -20°C for subsequent analyses.

Prior to transmethylation of the samples, four CLA standards (free fatty acids; Matreya, Pleasant Gap, PA) were each methylated in triplicate using three methods to examine conversion of CLA isomers to methyl esters. The three methods tested were those of Sukhija and Palmquist (1988), Yurawecz et al. (1999), and Park and Goins (1994). Retention times of the CLA isomers were determined for methyl esters of CLA isomers obtained from Nu-Chek-Prep (Elysian, MN). Results from these method comparisons are presented in Table 2Go. The method of Sukhija and Palmquist (1988) resulted in lower recoveries of the specific CLA isomers than for the standard. Acid catalyzed transmethylation reactions can alter the trans and cis double bonds present in CLA, which in turn will invalidate results (Shantha et al., 1993; Yurawecz et al., 1999). The method of Yurawecz et al. (1999) did not convert free fatty acids to methyl esters. Others (Luddy et al., 1968; Glass, 1971; Park and Goins, 1994) have reported that base-catalyzed reactions can result in transesterification, but do not convert free fatty acids to methyl esters. The method of Park and Goins (1994) combines the use of sodium methoxide followed by boron trifluoride for a complete conversion of fatty acids to methyl esters. The percentages of the CLA isomers obtained after using the method of Park and Goins (1994) were similar to those reported by the supplier for each CLA standard. Kramer et al. (1997) reported similar results when comparing acid, base, or combination catalysts for methylation of milk and rumen fatty acids.


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  		Table 2. Comparison of transmethylation procedures for conversion conjugated linoleic acid (CLA) isomers to methyl esters (reported as a percentage of total fatty acids)
 
Fatty acid composition of feed and duodenal samples was determined by the direct transmethylation procedure of Park and Goins (1994). Fatty acid methyl esters (FAME) were analyzed using a HP6890 (Hewlett-Packard, San Fernando, CA) gas chromatograph equipped with a HP7673A (Hewlett-Packard, San Fernando, CA) automatic sampler. Separations were accomplished using a 100-m SP2560 (Supelco, Bellefonte, PA) capillary column (0.25 mm i.d. and 0.20 µm film thickness). Column oven temperature was programmed to increase from 150 to 160°C at 1°C per min, from 160 to 167°C at 0.2°C per min, from 167 to 225°C at 1.5°C per min, and then held at 225°C for 5 min. The injector and detector were maintained at 250°C. Sample injection volume was 1 µL. Hydrogen was the carrier gas at a flow rate of 1 mL per min. In order to resolve both the individual trans- and cis-octadecenoic acids and CLA isomers, FAME had to be analyzed twice with GLC at different concentrations and split ratios. For the trans- and cis- octadecenoic fatty acids and the major long-chain fatty acids, FAME with a concentration of 5 µg/µL were injected into the gas-liquid chromotograph with the above temperature program and a split ratio of 1:20. For CLA isomers, FAME were concentrated to 50 µg/µL by reducing solvent volume to 100 µL in a limited vial insert and injected into the gas-liquid chromotograph with the above temperature program and a split ratio of 1:1. Peaks were identified by comparison to reference standards from Supelco. Conjugated linoleic acid isomers were identified by using available standards from Matreya and Nu-Chek-Prep, and by methylating Tonalin, a dietary supplement containing numerous CLA isomers at various levels, as described by Benito et al. (2001). Available standards (Sigma, St. Louis, MO) were used to identify trans- and cis-octadecenoic acids and compared to published chromatograms (Precht et al., 2001; Griinari et al., 1998). Fatty acids were quantified by incorporating an internal standard, methyl tricosanoate (C23:0) into each sample prior to methylation.

Chromium concentration in digesta was measured by inductively coupled plasma spectrometry (ICP; Thermo Jarrell Ash Corp., Franklin, MA) using the sample preparation method of Williams et al. (1962). Concentrations of Cr and fatty acids in the feed, refusals, and digesta were used to calculate digestibility and duodenal flow of fatty acids (Schneider and Flatt, 1975). The percent biohydrogenation of total and individual unsaturated 18-carbon fatty acids were calculated according to Wu et al. (1991). Data were analyzed using the GLM of SAS (SAS Inst., Inc., Cary, NC) with animal, square, period, and treatment included as class variables in the model. Preplanned, nonorthogonal contrasts were used to test the effects of dietary lipid level (TC vs HOC and OIL) and oil source (HOC vs OIL) on ruminal digestion, ruminal biohydrogenation, fatty acid intake, and flow of long-chain fatty acids to the small intestine.


   Results and Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
Implications
 Literature Cited
 
The fatty acid composition of typical corn, high-oil corn, and corn oil is presented in Table 3Go. High-oil corn contained a greater percentage of total fatty acids as oleic acid (C18:1), but a lower percentage as linoleic acid. These differences in fatty acid composition between high-oil corn and typical corn are similar to those reported by Crum and Stilborn (1997). Corn oil had a similar oleic acid percentage, but was richer in linoleic acid and poorer in palmitic acid (C16:0) concentrations than typical corn.


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  		Table 3. Fatty acid profiles of typical corn, high-oil corn, and corn oil
 
Dry matter intake for all three diets was similar (P > 0.05) and averaged 10.57 kg per animal per day (2.2% BW; Table 4Go). Similarly, Eibs et al. (2000) found no reduction in DMI when feeding HOC to finishing steers. Zinn et al. (2000) reported that intakes by finishing cattle were not changed when 2 to 6% yellow grease or 2 to 4% formaldehyde-protected fat was added to the diet. In contrast, Andrae et al. (2000) reported that DMI was lower for cattle fed HOC than when cattle were fed TC. Daily intake of total long-chain fatty acids was 78% greater (P < 0.05) for high-lipid (HOC and OIL) diets compared to low-lipid (TC) diets, but intake was not different (P > 0.05) between oil sources (HOC and OIL). Dry matter flow of duodenal digesta and apparent ruminal dry matter digestibility were not different (P > 0.05) between dietary lipid levels or oil sources. Long chain fatty acid flow (g/d) at the duodenum was 63% greater (P < 0.05) with the higher lipid diets, but was not different (P > 0.05) for HOC and OIL diets. Apparent ruminal long chain fatty acid digestibility was similar (P > 0.05) between dietary lipid levels and oil sources. These values for apparent ruminal digestibility of long-chain fatty acids in the rumen are within the range of those reported by other researchers, as summarized by Jenkins (1993).


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  		Table 4. Dry matter and long-chain fatty acid intake and ruminal digestion by steers fed typical corn (TC), high-oil corn (HOC), or typical corn plus corn oil (OIL)
 
Intakes of long-chain fatty acids are shown in Table 5Go. Steers consuming the two diets with higher lipid levels had greater (P < 0.05) intakes for each of the fatty acids measured. Intake of several of the saturated fatty acids (myristic [C14:0], stearic [C18:0], and arachidic [C20:0] acids) and oleic acid was greater (P < 0.05) for HOC than OIL, whereas intakes of other saturated (palmitic) and unsaturated fatty acids (palmitoleic [C16:1], linoleic, and linolenic [C18:3] acids) were lower (P < 0.05) for HOC than OIL. Diets containing higher lipid levels from substituting with high-oil corn or supplementing corn oil increased (P < 0.05) dietary intake of unsaturated fatty acids by 193 g/d compared to the low-lipid diet. Intake of total unsaturated fatty acids did not differ (P > 0.05) between oil sources.


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  		Table 5. Long-chain fatty acid intake (g/d) by steers fed diets containing typical corn (TC), high-oil corn (HOC) or corn oil (OIL)
 
Ruminal biohydrogenation was calculated simply by comparison of dietary intake with duodenal flow of individual 18-carbon fatty acids according to Wu et al. (1991). By this calculation, ruminal biohydrogenation of total and individual 18-carbon unsaturated fatty acids was greater (P < 0.05) for diets with higher lipid levels (Table 6Go). Bolte et al. (2001) also reported that ruminal biohydrogenation of total 18-carbon fatty acids was increased when high-oil corn was fed. Oil source did not alter (P > 0.05) overall 18-carbon unsaturated fatty acid biohydrogenation level, but differences were observed for the individual fatty acids by oil source. Biohydrogenation of oleic acid was greater (P < 0.05) for HOC than OIL diets, but biohydrogenation of linoleic acid was lower (P < 0.05) for HOC than OIL diets. Linolenic acid biohydrogenation tended to be greater (P > 0.05) for OIL than HOC diets. Aldrich et al. (1997) suggested that the seedcoat of canola may physically protect lipids from ruminal biohydrogenation. However, similar overall biohydrogenation levels of unsaturated 18-carbon fatty acids between HOC and OIL diets suggests that the seedcoat of dry-rolled high-oil corn did not offer any protection against biohydrogenation.


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  		Table 6. Effects of high-oil corn (HOC) or added corn oil (OIL) on ruminal biohydrogenation (%) of individual and overall unsaturated 18-carbon fatty acids
 
Biohydrogenation percentages were highest for linolenic (91%), intermediate for linoleic (80%), and lowest for oleic (70%) acids. Scollan et al. (2001) reported similar levels of biohydrogenation for the linolenic and oleic acids in cannulated steers given free choice access to silage with a barley/sugarbeet supplement (40 to 60% of DMI) containing rumen-protected lipid, linseed oil, or fish oil. Zinn et al. (2000) reported biohydrogenation percentages for cattle consuming wheat-based finishing diets containing 2, 4, or 6% yellow grease that were quite similar to our values. Elizalde et al. (1999) reported higher values (82%) for ruminal biohydrogenation with diets containing white grease (2.5 or 5%) and 52% roughage. Zinn et al. (2000) reported lower biohydrogenation values for steers fed protected fat sources with high-concentrate diets. These biohydrogenation levels for the individual 18-carbon fatty acids indicate that oils rich in oleic acid have the greatest potential for altering tissue composition due to its lower level of biohydrogenation.

The effect of diet on duodenal flow (g/d) of long-chain fatty acids is shown in Table 7Go. Duodenal flows of palmitic, stearic, oleic, linoleic, and arachidic acids were more than 30% greater (P < 0.05) for diets containing more lipid. Similarly, Bolte et al. (2001) reported greater duodenal flow of stearic, oleic, linoleic, and linolenic acids for steers consuming high-oil corn diets compared to typical corn. Andrae et al. (2000) reported that tissue concentrations of linoleic and arachidonic acids were increased when steers were fed high-oil corn. Presumably, the greater percentages of the essential fatty acids in adipose tissue of cattle fed high-oil corn previously observed is the result of greater intake and flow of these unsaturated fatty acids to the small intestine and not a result of reduced biohydrogenation.


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  		Table 7. Flow (g/d) of long-chain fatty acid and biohydrogenation intermediates at the duodenum of steers fed diets containing typical corn (TC), high-oil corn (HOC), or added corn oil (OIL)
 
Biohydrogenation of dietary linoleic acid to stearic acid is sometimes incomplete, yielding several intermediates, including various CLA isomers and trans- or cis-octadecenoic acids (Bauman et al., 1999). Duodenal flow of all trans-octadecenoic acids was greater (P < 0.05) for diets containing greater lipid content. Flow of cis-octadecenoic acids did not differ (P > 0.05) by dietary lipid level. High-oil corn feeding increased (P < 0.05) the flow of trans-11 vaccenic acid by 73% and cis-11 octadecenoic acid by 39% compared to OIL. The trans-10 octadecenoic acid flow was 3.4-fold greater (P < 0.01) for OIL than HOC. Duodenal flows of trans-12 and cis-12 octadecenoic acids were greater (P < 0.05) for OIL than HOC. Similarly, Griinari et al. (1998) reported increased levels of trans-10 octadecenoic acid in milk fat from cows fed low-fiber diets containing 4% corn oil. Beaulieu et al. (2002) reported increased levels of trans-octadecenoic acids in rumen contents of steers fed high-concentrate diets supplemented with increasing soybean oil levels.

The predominant CLA isomers identified in duodenal contents were trans-9, trans-11/trans-10, trans-12; cis-9, trans-11; and trans-10, cis-12 isomers, which accounted for more than 77% of the total CLA present. Duodenal flow of trans-10, cis-12 CLA isomer and total CLA was greater (P < 0.05) for diets with higher lipid content. Dietary lipid level did not alter (P > 0.05) the flow of other CLA isomers including the cis-9, trans-11 isomer. Similarly, Beaulieu et al. (2002) reported no change in cis-9, trans-11 CLA isomer level in ruminal contents or tissues of finishing cattle fed varying levels of soybean oil. McGuire et al. (1998) and Dhiman et al. (1999) found no change in beef i.m. fat or milk fat concentrations of cis-9, trans-11 CLA when high-oil corn was fed to finishing steers or lactating dairy cows, respectively. In contrast, Bolte et al. (2001) reported greater duodenal flow of cis-9, trans-11 CLA when finishing steers were fed dry-rolled high-oil corn.

Corn oil addition increased (P < 0.05) the flow of trans-10, cis-12 isomer of CLA by 3.4-fold compared to feeding high-oil corn. Beaulieu et al. (2002) also reported linear increases in trans-10, cis-12 CLA isomer of ruminal contents from finishing steers supplemented with increasing levels of soybean oil. Others (Griinari et al., 1998; 1999) have shown that feeding low-fiber diets containing unsaturated fats to dairy cows increased the proportion of trans-10, cis-12 CLA isomer in milk fat. Griinari and Bauman (1999) have proposed pathways for the formation of trans-10, cis-12 CLA. Flow of trans-9, trans-11/trans-10, trans-12 CLA isomers and total CLA was greater (P < 0.05) for OIL than HOC. Oil addition also tended (P = 0.07) to increase the flow of cis-11, cis-13 isomer of CLA to duodenum. Flows of other CLA isomers (cis-9, trans-11; cis-11, trans-13; cis-9, cis-11; trans-11, trans-13/trans-9, trans-10) were unchanged (P > 0.05) by oil source. Duodenal flow of trans-10, trans-12 and cis-12 octadecenoic acids and trans-10, cis-12 CLA isomers were over threefold greater for OIL than HOC diets suggesting that oil source may alter microbial populations that favor the trans-10 pathway of linoleic acid biohydrogenation.

Flow of trans-octadecenoic acids (trans-10 and trans-11) and CLA isomers (trans-10, cis-12 and cis-9, trans-11) as a percentage of linoleic acid intake by dietary treatment is shown in Figure 1Go. Flow of cis-9, trans-11 CLA and trans-11 vaccenic acids as a percentage of linoleic acid intake did not differ (P > 0.05) for diets with higher lipid content. Flow of cis-9, trans-11 CLA as a percentage of linoleic acid intake did not differ (P > 0.05) by oil source. Duodenal flow of trans-10, cis-12 CLA and trans-10 octadecenoic acid as a percentage of linoleic acid intake was greater (P > 0.05) for OIL than HOC. Percentage of dietary linoleic acid flowing to the duodenum as trans-11 vaccenic acid was greater (P < 0.05) for HOC than OIL. More importantly, duodenal flow of cis-9, trans-11 or trans-10, cis-12 CLA isomer was less than 0.12% of linoleic acid intake, whereas flow of trans-10 or trans-11 octadecenoic acid ranged from 1.5 to 6.3% of linoleic acid intake. The percentage of linoleic acid intake flowing to the duodenum as trans-11 vaccenic acid was 20- to 39-fold greater, depending on dietary treatment, than that of the cis-9, trans-11 isomer of CLA. Santora et al. (2000) have shown that feeding trans-11 vaccenic acid to rodents increases accumulation of cis-9, trans-11 CLA isomer in adipose tissue, which suggests an important contribution of {delta}9-desaturase to CLA tissue accumulation. In lactating dairy cows, infusion of trans-vaccenic acid into the abomasum also increased the concentrations of cis-9, trans-11 CLA in milk fat (Griinari et al., 2000), whereas infusion of sterculic acid, an inhibitor of {delta}9-desaturase enzyme, reduced cis-9, trans-11 levels in milk fat. From these experiments, Griinari et al. (2000) estimated that 64% of the cis-9, trans-11 CLA present in milk fat came from the desaturation of infused trans-vaccenic acid by {delta}9-desaturase enzyme in mammary tissue. Bovine adipose tissues also contain {delta}9-desaturase and can convert stearic acid to oleic acid (St. John et al., 1991). The very small duodenal flow of cis-9, trans-11 CLA suggests that conversion of trans-11 vaccenic acid to cis-9, trans-11 CLA in adipose tissue by {delta}9-desaturase also serves as major source of CLA in beef fat.



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  		Figure 1. Flow of trans-octadecenoic acids (trans-10 and -11) and conjugated linoleic acid (CLA; trans-10, cis-12 and cis-9, trans-11) isomers by dietary treatment as a percentage of linoleic (C18:2) acid intake.

 

   Implications
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 Implications
Literature Cited
 
Feeding high-oil corn or adding corn oil to typical corn rations increased both intake and duodenal flow of unsaturated long-chain fatty acids. Higher lipid diets, from added corn oil or high-oil corn increased ruminal biohydrogenation of 18-carbon unsaturated fatty acids. Compared with high-oil corn diets, the addition of corn oil to a typical corn diet increased linoleic acid biohydrogenation and duodenal flow of specific isomers of octadecenoic and conjugated linoleic acids. However, the amount of cis-9, trans-11 isomer of conjugated linoleic acid flowing to the duodenum was less than 260 mg/d, a value more than 20 times lower than the flow of trans-11 vaccenic acid, indicating the importance of tissue desaturation for enhanced conjugated linoleic acid content of beef.

Received for publication April 16, 2002. Accepted for publication July 26, 2002.


   Literature Cited
Top
 Abstract
 Introduction
 Materials and Methods
 Results and Discussion
 Implications
 Literature Cited
 


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.[Abstract/Free Full Text]

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]

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.[Abstract/Free Full Text]

Bauman, D. E., L. H. Baumgard, B. A. Corl, and J. M. Griinari. 1999. Biosynthesis of conjugated linoleic acid in ruminants. Proc. Am. Soc. Anim. Sci. Available: http://www.asas.org/jas/journal.asp?Society=asas&month=0&year=0. Accessed March 3, 2001.

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.[Abstract/Free Full Text]

Benito, P., G. J. Nelson, D. S. Kelley, G. Bartolini, P. C. Schmidt, and V. Simon. 2001. The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans. Lipids 36:229–236.[Medline]

Bolte, M. R., E. J. Scholljegerdes, B. W. Hess, J. Gould, D. C. Rule, and F. N. Owens. 2001. Long-chain fatty acid flow in and digestion by beef steers fed dry-rolled or high-moisture typical or high-oil corn diets. J. Anim. Sci. 79(Suppl. 2):98 (Abstr.).

Chin, S. F, W. Lui, J. M. Storkson, Y. L. Ha and M. W. Pariza. 1992. Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens. J. Food Comp. Anal. 5:185–197.

Clary, E. M., R. T. Brandt, Jr., D. L. Harmon, and T. G. Nagaraja. 1993. Supplemental fat and ionophores in finishing diets: Feedlot performance and ruminal digesta kinetics in steers. J. Anim. Sci. 71:3115–3123.[Abstract]

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