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ANIMAL NUTRITION |
Department of Animal and Veterinary Science, University of Idaho, Moscow 83844-2330
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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Key Words: Cattle • Conjugated Linoleic Acid • Performance • Protozoa • Safflower Oil
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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) could improve the healthful characteristics of the fat produced by ruminants. Conjugated linoleic acids, present in meat and milk from ruminant animals, have potential health benefits (Belury, 2002) and are formed through isomerization of linoleic acid by ruminal bacteria (Harfoot and Hazlewood, 1997) and via desaturation by body tissues of another product of biohydrogenation, trans-vaccenic acid (t11 18:1, VA; Griinari et al., 2000). Thus, it may be possible to increase the content of CLA in fat and muscle from beef animals through increased dietary availability of the substrate, linoleic acid. Linoleic acid also may increase CLA concentrations by altering ruminal protozoa (Sutton et al., 1983; Hristov et al., 2004), either directly through increased lipolysis, or indirectly by affecting the bacterial population, including Group A bacteria that are thought to be primarily responsible for the biohydrogenation of dietary linoleic acid (Harfoot and Hazlewood, 1997). Oleic acid, on the other hand, produces no CLA and very little VA during its biohydrogenation (Mosley et al., 2002), and thus should not lead to enhanced CLA concentrations in body tissues. Therefore, oleic acid provides a good comparison with linoleic acid, as it also is an unsaturated fatty acid that undergoes biohydrogenation in the rumen, but it will lead to very minor CLA formation in tissues. The objectives of this study were to 1) decrease protozoal counts in the rumen; and 2) increase concentration of CLA in beef through supplementation of the diet of finishing cattle with linoleic acid-rich safflower oil. We hypothesized that feeding of a linoleic acid-rich oil would enhance the concentration of CLA in beef tissues compared with an oleic acid-rich oil.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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). Each period consisted of two subperiods, covariate and experimental. The covariate subperiod was 14 d long and the experimental subperiod was 21 d long. During the experimental subperiods, the basal diet was supplemented with high-oleic acid safflower oil (76.5% oleic acid) or high-linoleic acid safflower oil (76.5% linoleic acid) at 5% of dietary DM replacing 5% barley grain. Both oils were from Adams Vegetable Oils, Inc., in Arbuckle, CA (Table 2). Oils were not fed during the covariate subperiods. Diets were fed as total mixed rations (Data Ranger, American Calan Inc., Northwood, NH) twice daily (0800 and 1700) at 90% of ad libitum intake, established before initiation of the trial. Samples were taken twice within a period: during the last 4 d of the covariate and of the experimental subperiods. Data from the covariate subperiod were used as a covariate or a baseline in the statistical analysis of the data. To ensure minimum carryover effect from the previous treatment, on d 1 (beginning of the covariate subperiod) and d 15 (d 1 of the experimental subperiod) of each period, the animals were inoculated with approximately 10 kg/animal of whole ruminal contents (replacing a similar amount of ruminal contents) obtained from three ruminally cannulated donor dairy cows fed a diet containing 60% barley grain and 40% forage (wheat silage/alfalfa hay) on a DM basis.
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) as an internal digestibility marker. Nutrient digestibility was calculated as described by Schneider and Flatt (1975). Flow of DM and nutrients to the duodenum was determined using the double-marker method of Faichney (1975). Lithium/Co-EDTA and indigestible NDF were used as fluid and particulate phase markers, respectively. Lithium/Co-EDTA (Uden et al., 1980) was applied to the diets at a daily dose equivalent to 3.5 g of Co/steer for the duration of the trial. Microbial protein flow to the duodenum was determined with purines as a microbial marker, assuming all purines present in duodenal digesta were of microbial origin. True digestibilities of DM, OM, and nonammonia N (NAN) in the rumen were calculated as duodenal flows of DM, OM, or NAN corrected for microbial flow of DM, OM, or NAN. Digestibility of dietary starch was not corrected for microbial starch flow.
Chromium-EDTA (Uden et al., 1980) was used as a ruminal fluid passage rate marker and was pulse-dosed (equivalent of 2.5 g of Cr/steer) into the rumen of the steers at 0900 on d 13 and 34 (d 20 of the experimental subperiod) of each period.
Samples and Analyses.
Diets and individual feed samples were dried at 70°C to constant weight in a forced-air oven and analyzed for ash (AOAC, 1999), total N (Hristov et al., 2001), NDF, ADF (Ankom 200 fiber analyzer, Ankom Technology), and starch. Starch was analyzed with a kit from Megazyme Int. Ireland, Ltd. (Wicklow, Ireland; McCleary et al., 1994). A heat-stable amylase (
-amylase, EC No. 232-560-9; Sigma Chemical Co., St. Louis, MO) was used in the NDF analysis (Van Soest et al., 1991); sodium sulfite was not used in the analysis. Indigestible NDF content of the diet and duodenal digesta samples was determined according to Rinne et al. (2002).
Samples of ruminal contents were taken before (0 h) and 2, 4, and 6 h after the morning feeding on d 13 and 14 (covariate subperiod) and d 34 and 35 (experimental subperiod) of each period. Samples were taken from three locations in the reticulorumen: the ventral sac, reticulum, and dorsal sac (approximately 250 g each). The three samples were composited and squeezed through two layers of cheesecloth. The filtrate was immediately analyzed for pH and processed for analyses of ammonia, VFA, and total protozoal counts (Hristov et al., 2000). Entodinium spp. were identified according to Dehority (1993). Bacterial samples were isolated through differential centrifugations (an initial centrifugation at 500 xg for 5 min and a subsequent centrifugation of the low-speed supernatant fraction at 20,000 xg for 15 min at 4°C), freeze-dried, and analyzed for OM, NAN (Firkins et al., 1992), and purines. Purines were analyzed according to the procedures of Zinn and Owens (1986), using the modified washing solution of Aharoni and Tagari (1991) and 0.6 M HClO4 (Makkar and Becker, 1999). Ruminal filtrate samples plus two additional samples (d 14 and 34 only), taken at 10 and 14 h after the morning feeding, were centrifuged at 20,000 xg for 15 min at 4°C and the supernatant fractions were analyzed for Cr concentration (Iris ICP atomic emission spectrophotometer, Thermo Jarrell Ash Corp., Franklin, MA). Fractional outflow rate of the ruminal fluid phase was determined as slope of the lntransformed Cr concentrations vs. time. Polysaccharide-degrading activities (carboxymethylcellulase, xylanase, and amylase) in ruminal fluid samples were determined according to the procedures of Hristov et al. (1999).
Duodenal samples (300 mL per sampling) were taken at 0900, 1500, and 2100 (d 11 and 32 of each subperiod), and at 0300, 0600, 1200, 1800 (d 12 and 33), and 0000 (d 13 and 34). Samples were stored frozen at –40°C. After thawing, digesta samples were composited on a wet weight basis (per steer and subperiod). The composited samples were separated into fluid and solid phases by filtering through a 100-µm fabric (Sefar America Inc., Depew, NY). Both phases were freeze-dried, ground to pass a 1-mm sieve, and analyzed for ash/OM, Co (Iris ICP atomic emission spectrophotometer), indigestible NDF, NAN, purines, NDF, ADF, and starch. Purine:N ratio in ruminal bacterial samples was used to determine the flow of microbial N to the duodenum.
Rectal samples (200 g per sampling) were collected at the same sampling times used for duodenal digesta. Samples were composited per steer and subperiod, oven-dried at 70°C to constant weight, ground to pass a 1-mm sieve, and analyzed for OM, N, acid-insoluble ash, NDF, ADF, and starch.
Finishing Trial
Eight Angus crossbred steers and eight heifers (423 ± 7.4 kg average initial BW) were ranked by BW and assigned to two treatment groups to achieve similar average BW and an equal number of males and females in each group. One group was fed a diet with 5% (DM basis) added high-oleic acid safflower oil and the other group was fed a diet with 5% (DM basis) added high-linoleic acid safflower oil. The basal diet was identical to the diet fed during the experimental subperiods in the metabolism trial (Table 1
). Cattle were gradually adapted to the diet over a 21-d period and fed individually using electronic feeding gates (American Calan, Inc., Northwood, NH) for 116 d. Oils were fed during the last 86 d of the experiment. The cattle were cared for according to the guidelines of the University of Idaho Animal Care and Use Committee.
Feeds and oils were mixed in a Data Ranger (American Calan, Inc.) and fed daily as a total mixed ration. Initial and final animal BW were calculated as the average of weights recorded on two consecutive mornings (0700) following an overnight stand without feed and water. Intermediate weights were obtained every 2 wk, and feed intake and refusals were recorded on a weekly basis during the last 90 d before slaughter. At slaughter, backfat thickness and LM area were measured, and muscle and adipose tissues were sampled and analyzed for fatty acids, including CLA content. Approximately 5 g of muscle (longissimus, semitendinosus, and semi-membranosus) and fat (s.c. over loin and kidney-pelvic fat) were obtained for analysis of fatty acid content. Tissues were freeze-dried and then ground in a blender with frozen CO2 present. Lipids were extracted using a modified Folch procedure (Clark et al., 1982). Methyl esters were formed using a methanolic sodium methoxide solution (Christie, 1982). Analysis of the methyl esters was performed on a gas-liquid chromatograph (Hewlett-Packard 6890 series with auto injector; Agilent Technologies, Inc., Palo Alto, CA) fitted with a flame ionization detector. Fatty acid profile was determined by split injection (20:1) onto a CP-Sil 88 fused-silica capillary column (100 m x 0.25 mm, Chrompack, Raritan, NJ) using a programmed temperature gradient method. The H2 carrier gas pressure was constant, and the injector and detector temperatures were 255°C. Initial oven temperature was 70°C. After injection of sample, oven temperature was increased at 4°C/min to 175°C and held for 3 min. Oven temperature was then raised at 1°C/min to 185°C and held for 20 min. Oven temperature was then increased 3°C/min to 215°C, followed by an increase of 10°C/min, and then held for 5 min, after which oven temperature was returned to 70°C. The majority of fatty acids were identified by comparison of retention times to those of pure standards (Matreya, Inc., Pleasant Gap, PA). Specific trans 18:1 isomer peaks were confirmed by gas-liquid chromatograph-mass spectrometer analysis (Mosley et al., 2002). A response correction factor for FAME was used to convert peak area percent to weight percent based on analysis of a butter oil with a known fatty acid profile and certified values (CRM 164, European Community Bureau of Reference, Brussels, Belgium). Data on HCW, LM area, and backfat thickness also were collected.
Statistical Analyses
To determine the effect of linoleic acid-rich oil vs. oleic acid-rich oil, ruminal fermentation data (averaged per animal and period), duodenal nutrient flows, and digestibility data (metabolism trial) were analyzed using analysis of covariance for a crossover design with the subperiod of no oil feeding used as a covariate using the following model:
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where µ is the overall mean; G, P, A, T and cov are group, period, animal, treatment, and covariate measurement, respectively; and e is an error term.
Statistical analysis of total protozoal counts was performed on log10-transformed data. Ruminal pH, ammonia, VFA, and protozoal counts data also were analyzed as a split-plot using the following model:
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where H is time of sampling. Treatment (Tk) was tested with animal within group + period + treatment [A(GP-T)ijkl]. Time of sampling and the time of sampling x treatment interaction were tested with the residual error (eijklm).
The finishing trial data were analyzed using analysis of covariance for a completely random design with initial BW of the experimental animals as a covariate using the following model:
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where S is the gender of the animals and cov is initial BW. All terms were tested with the residual error. Long-chain fatty acid data were analyzed within sample location.
Statistical difference was declared at P 
0.05, with trends declared at P = 0.06 to 0.10. All data were analyzed using SAS software (SAS Inst., Inc., Cary, NC).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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Ruminal pH and ammonia concentration were not affected (P = 0.84 and P = 0.43) by type of oil (Table 3). Concentrations of total and individual VFA, acetate-to-propionate ratio, polysaccharide-degrading activities of ruminal fluid, and ruminal fluid passage rate also did not differ (P = 0.18 to 0.96) between oleic acid- and linoleic acid-rich oils, except that concentrations of iso-butyrate and valerate tended to be, or were greater (by 12 and 5%; P = 0.07 and 0.05, respectively) for oleic acid-rich oil than linoleic acid-rich oil. Total protozoal and Entodinium spp. counts or microbial N flow and efficiency did not differ (P = 0.57, 0.84, and 0.92, respectively) between the two oils. Treatment x time interactions for pH, ammonia and VFA concentrations, and protozoal counts were not significant (P = 0.22 to 0.78).
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). Type of oil did not affect apparent or true digestibility of nutrients in the rumen, except NDF digestibility, which was greater (P = 0.05) with oleic acid-rich oil than with linoleic acid-rich oil.
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). Carcass characteristics also did not differ (P = 0.44 to 0.84) between cattle fed either diet. The effect of gender and gender x type of oil interactions were not significant (P = 0.24 to 0.94 and P = 0.13 to 0.88, respectively) for these variables.
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and 7). For the major fatty acids, adipose tissue from cattle fed oleic acid-rich oil had greater proportions of 14:0 (P = 0.03; kidney-pelvic fat [KPF] only) and 18:0 (P = 0.02 and P = 0.03 for KPF and s.c. fat, respectively; Table 6). Proportions of 18:1c9 did not differ between treatments in s.c. fat, whereas 18:1c9 was less (P = 0.02) in KPF from cattle fed oleic acid-rich oil. Proportions of CLA isomers were greater (c9t11; P = 0.01) or tended to be greater (c11t13; P = 0.07 and P = 0.08 for s.c. fat and KPF, respectively) in adipose tissue from cattle fed linoleic acid-rich oil compared with oleic acid-rich oil (Table 6). Other fatty acids that were altered in adipose tissue included greater 18:0 (P = 0.02 and P = 0.03 in s.c. fat and KPF, respectively), but lower 18:1t10 (trend at P = 0.08) in KPF from cattle fed oleic acid-rich oil. There were fewer consistent responses in muscle. Consumption of linoleic acid-rich oil led to greater (trend at P = 0.06) C18:2n-6 proportions in semimembranosus muscle (Table 7). The only CLA altered in muscle was a trend for an increase (P = 0.09) in t10c12 in semimembranosus muscle from cattle fed linoleic acid-rich oil (Table 7). Proportions of fatty acids in adipose and muscle tissues were not affected by gender (P = 0.11 to 0.98), with the following exceptions: compared with steers, heifers had greater proportions of 18:1t11 (0.96 vs. 0.63%; P = 0.01), 19:0 (0.12 vs. 0.10%; P = 0.01), and CLA c9t11 (0.23 vs. 0.16%; P < 0.01) in their KPF, and greater proportions of CLA c9t11 (0.38 vs. 0.27%; P = 0.01) and c11t13 (0.08 vs. 0.07%; P = 0.04) in semitendinosus muscle. Gender x type of oil interactions were not significant (P = 0.08 to 0.99) for fatty acid proportions in any tissue.
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). The relative proportion of MUFA and the difference between MUFA and trans 18:1 monoenes were less (P = 0.001 and P = 0.01, respectively) in KPF with the oleic acid-rich oil diet than with the linoleic acid-rich oil diet (Table 6). The proportion of CLA isomers was greater (P = 0.03) in cattle fed the linoleic acid-rich oil diet than the oleic acid-rich oil diet. The relative proportion of SFA was greater (P = 0.01), and that of MUFA and CLA isomers lower (P = 0.01 and 0.02, respectively), with the oleic acid-rich oil diet compared with the linoleic acid-rich oil diet in the s.c. fat (Table 6). Treatments did not differ (P = 0.23 and 0.34 for s.c. fat and KPF, respectively) in adipose tissue proportion of PUFA. Proportion of SFA in semitendinosus muscle was lower (P = 0.03) with the linoleic acid-rich oil diet compared with oleic acid-rich oil diet (Table 7). There were no other differences in fatty acid composition of this muscle between treatments. The relative proportion of SFA in semimembranosus muscle tended to be greater (P = 0.06) and that of PUFA tended to be lower (P = 0.06) with the oleic acid-rich oil diet than with the linoleic acid-rich oil diet. No differences in fatty acids composition of LM were observed between treatments (P = 0.14 to 0.91), except that the proportion of SFA tended (P = 0.08) to be greater with oleic acid-rich oil diet than with the linoleic acid-rich oil diet (Table 7). Proportions of SFA, MUFA, PUFA, and trans monoenes in adipose and muscle tissues were not affected by gender (P = 0.06 to 0.80), except that the relative proportions of CLA isomers were greater in KPF (0.31 vs. 0.22%; P = 0.02) and semitendinosus muscle (0.51 vs. 0.36%; P = 0.01) from heifers compared with steers. Gender x type of oil interactions were not significant (P = 0.23 to 0.95) for fatty acid proportions in any tissue. |
Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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; Hristov et al., 2004) and in vitro (Newbold and Chamberlain, 1988) with linoleic acid application. Our in vitro data indicated 48, 88, and 100% eradication of ruminal protozoa with inclusion of 0.25, 0.5, and 1% linoleic acid in the incubation media, respectively; oleic acid decreased protozoal counts by 26, 45, and 78%, respectively, at the same concentrations (Hristov et al., 2004). It seems the magnitude of the antiprotozoal properties of feed oils depends on the degree of unsaturation of their fatty acids; oleic acid has one unsaturated double bond compared with two double bonds for linoleic acid. Oils containing high concentrations of C18 unsaturated fatty acids, such as linseed oil, have consistently decreased protozoal counts in cattle or sheep (Doreau and Ferlay, 1995). Oldick and Firkins (2000) observed a linear decrease in ruminal protozoa with increasing degree of unsaturation of dietary fats. Our present data, however, showed no difference in the defaunating properties of the two oils in vivo, although protozoal counts were decreased compared with the covariate period. Decreased protozoal populations in the rumen are usually associated with lowered ammonia concentrations (Williams and Coleman, 1992), primarily as a result of a decrease in proteolysis of bacterial protein by ruminal protozoa (Broderick et al., 1991). In the present trial, both oils had a similar effect on ammonia concentration, which was decreased compared with the covariate period. In accordance with the similar effect on ruminal protozoa, ruminal VFA concentration and composition did not differ between the two oils, although propionate was increased and butyrate concentration was decreased with oil addition to the diet compared with the covariate period, effects commonly associated with decreased ruminal fauna (Sutton et al., 1983; Williams and Coleman, 1992). The decreased concentrations of iso-butyrate and valerate may be indicative of decreased proteolysis (Wolin et al., 1997), although protozoal counts were only numerically decreased with the linoleic acid compared with the oleic acid diet.
The type of oil did not alter total-tract apparent digestibility of nutrients in the present trial, although ruminal NDF digestibility was decreased with the linoleic acid-rich oil diet. This effect is difficult to interpret because the two oils had similar effects on ruminal protozoa and overall fermentation. Decreased fiber digestion in the rumen and partial compensatory digestion in the intestine are commonly observed in defaunated animals vs. those with normal ruminal fauna (Williams and Coleman, 1992). Compared with the covariate period, the oleic acid-rich oil apparently decreased ruminal DM and OM digestibility in the present trial.
Jouany (1996) reviewed 16 studies with sheep or cattle and found significant performance responses from defaunation in only three of them; in one study, defaunation significantly decreased performance by lambs. Performance expectations are usually based on the hypothesis that decreased or eradicated fauna in the rumen will result in increased microbial protein flow to the intestine (Williams and Coleman, 1992). Growth characteristics and feed efficiency of the cattle in the finishing trial were not different between the two oils.
Altering the PUFA concentrations of beef tissues is rarely directly related to the fatty acids composition of the diet. Enhancing the linoleic acid content of the diet for finishing cattle through either oils or oilseeds failed to enrich muscle or adipose tissue with linoleic acid due to the extensive biohydrogenation that occurs in the rumen (Beaulieu et al., 2002; Mir et al., 2003), but it increased linoleic acid concentrations in other studies (Andrae et al., 2001; Madron et al., 2002; Mir et al., 2002). Griswold et al. (2003) demonstrated that the response to added soybean oil depended on the forage-to-concentrate ratio in the diet, with increased linoleic acid content of muscle tissues when greater forage was present in the diet. However, Andrae et al. (2001) did not observe any added benefit with more moderate increases in the forage content of the diet. The lack of response detected in the current study may be due to a low forage content of the diet. Feeding of a rumen-protected source of linoleic acid enriched muscle and adipose tissue with linoleic acid (Scollan et al., 2003). Felton and Kerley (2004) found increased oleic acid in perinephric fat and LM external fat-free lean samples, but not in s.c. fat from steers fed high-oleic soybeans compared with normal soybeans. Oleic acid concentration was not increased in adipose or muscle tissue from lambs fed high-oleic safflower seeds compared with diets without safflower seeds (Bolte et al., 2002). Those authors also fed high-linoleate safflower seeds and found decreased oleic acid concentrations in muscle and adipose tissue compared with either the control or high-oleate safflower-fed lambs. This finding suggests an effect of linoleic acid on the presence of oleic acid. Yang et al. (1999) demonstrated that a rumen-protected cottonseed oil decreased the activity of the 
9 desaturase enzyme, leading to lower oleic acid concentrations. Therefore, effects of specific fatty acids can lead to unique biohydrogenation products, as well as tissue effects related to the 9 desaturase enzyme.
Efforts to enhance the CLA content of beef have focused on improving the output of c9t11 CLA from ruminal biohydrogenation; however, studies demonstrate clearly that little CLA flows out of the rumen (Duckett et al., 2002; Sackmann et al., 2003), although it is the first intermediate in the biohydrogenation of linoleic acid (Harfoot and Hazlewood, 1997). Flow of VA to the duodenum was more than 20 times greater than CLA in steers fed typical finishing diets (Duckett et al., 2002; Sackmann et al., 2003). The key to increasing the CLA content of beef tissues is to produce CLA using the 9 desaturase enzyme shown to be important for c9t11 CLA in milk (Griinari et al., 2000). The greatest activity of the 9 desaturase enzyme was found in adipose tissue, with some activity in the LM and intestinal mucosa of growing steers (Chang et al., 1992). The lack of increase in c9t11 CLA in muscle tissues with the linoleic acid-rich oil in the current study could have been due to the low production of VA in the rumen and/or decreased activity of stearoyl CoA desaturase. Oleic acid, on the other hand, produces no CLA and little VA during its biohydrogenation (Mosley et al., 2002), and thus should not lead to enhanced CLA concentrations in body tissues. It is apparent from duodenal outflow data that CLA and t18:1 are only a minor proportion (5 to 25%) of the linoleic acid intake (Duckett et al., 2002; Sackmann et al., 2003). Sackmann et al. (2003) showed that duodenal output of t18:1 fatty acids was predominately t10 18:1 in diets with low forage concentrations. In the current study, concentrations of t10 18:1 were four to six times greater than VA in adipose and muscle tissues, supporting the notion that the animal absorbed little VA. Some experiments with oils or oilseeds rich in linoleic acid indicated an increased tissue concentration of c9t11 CLA in sheep and cattle (Bolte et al., 2002; Madron et al., 2002; Mir et al., 2002), whereas others have failed to detect any change in CLA in muscle or adipose tissue (Beaulieu et al., 2002; Griswold et al., 2003).
The greater deposition of t10 18:1 vs. t11 18:1 VA suggests that a substantial shift in the biohydrogenation pathway has occurred (Bauman and Griinari, 2003). Concentrations of t10c12 CLA were much lower than c9t11 CLA in all tissues examined, suggesting that, considering the amount of t10 18:1 present, a significant amount of linoleic acid in the diet was biohydrogenated by the t10, not the t11, pathway. This has strong implications for the ability to enhance the c9t11 CLA concentrations in tissues as it seems that conversion of t11 18:1 VA to c9t11 CLA by the 9 desaturase enzyme is critical. French et al. (2000) demonstrated the greatest c9t11 CLA concentrations in tissues from steers that grazed grass. Sackmann et al. (2003) supported the idea that forage can alter CLA production by showing that a diet with greater forage content decreased the t10 and enhanced the t11 pathway of biohydrogenation. Kim et al. (2002) identified a strain of Megasphaera elsdenii (YJ-4) capable of producing t10c12 CLA. The growth of this bacterium is promoted during high-grain feeding (Counotte et al., 1981), supporting the concept of the forage:concentrate ratio having an effect on the specific pathway of biohydrogenation.
In conclusion, ruminal fermentation, protozoal counts, microbial protein flow to the duodenum, and apparent nutrient digestibility did not differ in cattle when highlinoleic or high-oleic acid safflower oils were included at 5% of the DM in a high-barley grain finishing diet. Apparently, differences in level of unsaturation between the two oils were not sufficient to affect ruminal microbial composition, fermentation, or nutrient digestion. Type of oil did not affect cattle performance in an associated finishing trial. Overall, the difference in dietary fatty acids provided to the cattle produced few changes in tissue fatty acids. Weight percentages of c9t11 CLA in muscle tissues were unaltered by the addition of linoleic acid to the diet compared with oleic acid, probably as a result of low production of VA in the rumen because the pathway of biohydrogenation was apparently primarily through the t10 pathway.
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Footnotes |
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2 Correspondence: P.O. Box 442330 (phone: 208-885-7204; fax: 208-885-6420; e-mail: ahristov{at}uidaho.edu).
Received for publication August 20, 2004. Accepted for publication March 9, 2005.
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionLiterature Cited |
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9-desaturase. J. Nutr. 2000 130:2285–2291.9 desaturase activity in bovine subcutaneous adipose tissue of different fatty acid composition. Lipids 34:971–978.[Medline]
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