Effects of supplemental rumen-protected conjugated linoleic acid or corn oil on fatty acid composition of adipose tissues in beef cattle

Thirty-six Angus x Hereford heifers (365 +/- 60 kg) were used to determine the effects of supplemental dietary lipid sources on fatty acid composition of i.m., perianal (p.a.), and s.c. lipid depots. Lipid was supplied to diets as either corn oil or a rumen-protected conjugated linoleic acid (CLA) salt for two specific treatment periods of either the final 32 or 60 d on feed. Following an initial 56-d feeding period, heifers were fed one of three dietary treatments (DM basis): 1) basal diet containing 88% concentrate and 12% grass hay (CON), 2) basal diet plus 4% corn oil (OIL), or 3) basal diet plus 2% rumen-protected CLA salt (RPCLA) containing 31% CLA. The trans-10, cis-12 CLA concentration was greatest (P < 0.05) for heifers fed RPCLA and OIL diets and least (P < 0.05) for CON, regardless of time on dietary treatment. Heifers fed supplemental RPCLA had greater (P < 0.05) total CLA content than either CON- or OIL-fed heifers. Adipose tissue concentration of trans-11 vaccenic acid (TVA) was less (P < 0.05) for CON than OIL or RPCLA, which did not differ (P > 0.05). Percentages of C18:1 trans-10 were least (P < 0.05) in i.m. lipid compared with p.a. and s.c., which did not differ (P > 0.05). Following 60 d of lipid supplementation, heifers fed OIL and RPCLA had lower (P < 0.05) concentrations of oleic acid and total monounsaturated fatty acids (MUFA) compared with CON. The ratio of cis-9, trans-11 CLA:TVA was higher (P < 0.05) for heifers fed 60 vs. 32 d, but did not differ (P > 0.05) between adipose depots. Feeding OIL increased (P < 0.05) adipose concentration of C18:2 fatty acid, whereas feeding RPCLA increased (P < 0.05) total CLA isomers by 22%. Intramuscular lipid contained the lowest (P < 0.05) percentage of cis-9, trans-11 CLA, total CLA, C18:1 cis-9, C18:1 trans-10, and TVA. Total CLA and cis-9, trans-11 CLA isomers were increased (P < 0.05) in p.a. and s.c. adipose depots, whereas i.m. adipose tissue contained increased (P < 0.05) amounts of total PUFA. Results from this study indicate that short-term lipid supplementation to feedlot cattle can increase adipose tissue CLA concentrations, but only marginally (8.3 to 17.5%). Moreover, observed decreases in oleic acid and total MUFA concentrations of adipose tissues from heifers fed rumen-protected CLA or corn oil suggest that lipid supplementation may decrease delta9 desaturase activity in adipose tissues, which in turn would lower the conversion of TVA to cis-9, trans-11 CLA isomer.     

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

Conjugated linoleic acid (CLA), a mixture of isomers of linoleic acid, has many beneficial effects, including decreased tumor growth in animal cancer models. The cis-9, trans-11 isomer of CLA (CLA9,11) can be formed in the rumen as an intermediate in biohydrogenation of linoleic acid. Recent data, however, indicate that tissue desaturation of trans-fatty acids is an important source of CLA9,11 in milk. Our objective was to determine whether supplementing a high-corn diet with soybean oil (SBO; a source of linoleic acid) would increase concentrations of CLA in ruminal contents and tissue lipids. Four ruminally cannulated steers were utilized in a Latin square design with 28-d periods. A control diet (80% cracked corn, 2.0% corn steep liquor, 8.0% ground corn cobs, and 10% supplement [soybean meal, ground shelled corn, minerals, and vitamins]) was supplemented with 2.5, 5.0, or 7.5% (DM basis) SBO. Supplemental SBO did not affect ruminal pH or concentrations of the major VFA. The proportion and amount (mg FA/g DM ruminal contents) of CLA9,11 were not increased by increasing dietary SBO. However, the proportion and amount of the trans-10, cis-12 CLA isomer (CLA10,12) in ruminal contents increased linearly (P < 0.006) as dietary SBO increased. Trans-18:1 isomers in ruminal contents increased linearly (P < 0.02) as dietary SBO increased. The proportion of CLA10,12 was correlated positively (P < 0.001) with proportions of trans-C 18:1 isomers in ruminal contents. Conversely, CLA9,11 was correlated negatively (P < 0.05) with the proportions of trans-18:1 in ruminal contents. The same high-corn diet, supplemented with 0 or 5% SBO, was fed to 20 Angus-Wagyu heifers for 102 d in a randomized complete block design to determine the effect of added SBO on tissue deposition of CLA. Supplemental SBO did not affect feed intake, gain:feed, or carcass quality. Tissue samples were obtained from the hindquarter, loin, forequarter, liver, large and small intestine, and subcutaneous, mesenteric, and perirenal adipose depots. The concentration of CLA9,11 was greatest in subcutaneous adipose tissue but was not affected in any tissue by SBO. Supplementing high-corn diets with SBO does not increase CLA9,11 concentrations in tissues of fattening heifers. Research is needed to identify regulatory factors for pathways of biohydrogenation that lead to increased concentrations of CLA10,12 in ruminal contents when high-oil, high-concentrate diets are fed.     

Effects of forage and sunflower oil levels on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets

Six Hereford steers (295 kg) cannulated in the proximal duodenum were used to evaluate the effects of forage and sunflower oil level on ruminal biohydrogenation (BH) and conjugated linoleic acid (CLA) outflow. Steers were fed one of six treatment diets in a 3 x 2 factorial arrangement of treatments (grass hay level: 12, 24, or 36% of DM; and sunflower oil level: 2 or 4% of DM) in a 6 x 6 Latin square design. The remainder of the diet was made up of steam rolled corn and protein/mineral supplement. Duodenal samples were collected for 4 d following 10-d diet adaptation periods. Data were analyzed with animal, period, forage level, sunflower oil level, and two-way interaction between forage and sunflower oil level in the model. Dry matter intake showed a quadratic response (P < 0.04), with an increase in DMI as forage level increased from 12 to 24% followed by a decrease in DMI when 36% forage was fed. Flow of fatty acids at the duodenum was higher (P < 0.03) for 4 vs. 2% sunflower oil diets, and similar among forage levels. Apparent ruminal digestibility of NDF increased in a linear manner (P < 0.04) as dietary forage level increased. Ruminal BH of dietary unsaturated 18-C fatty acids, oleic acid, and linoleic acid increased linearly (P < 0.05) as dietary forage level increased. Linoleic acid BH tended (P < 0.07) to be greater for 4 than 2% sunflower oil level. Duodenal flow of pentadecyclic, stearic, linolenic, and arachidic acids increased linearly (P < 0.05) as dietary forage level increased from 12 to 36%. Duodenal flow of linoleic acid decreased in a linear manner (P < 0.03) with increasing dietary forage level. Flow of trans-10 octadecenoate decreased linearly (P < 0.03) as dietary forage level increased, whereas trans-11 vaccenic acid flow to the duodenum increased (P < 0.01) linearly with increased dietary forage. Dietary forage or sunflower oil levels did not alter the outflow of cis-9, trans-11 CLA. Flows of cis-11, trans-13, and cis-9, cis-11 CLA increased linearly (P < 0.05) with increased dietary forage. Flows of cis-11, cis-13, and trans-11, trans-13 CLA decreased linearly (P < 0.05) with increased dietary forage. Increasing dietary forage levels from 12 to 36% in beef cattle finishing diets increased BH of unsaturated 18-C fatty acid and outflow of trans-11 vaccenic acid to duodenum without altering cis-9, trans-11 CLA outflow.     

Effects of supplemental rumen-protected conjugated linoleic acid or corn oil on lipid content and palatability in beef cattle

Thirty-six Angus x Hereford heifers were used in a 3 x 2 factorial (3 dietary treatments; 2 supplementation times) to examine the effect of dietary lipid supplementation on lipid oxidation, lipid composition, and palatability of ribeye steaks and ground beef. Lipid was supplied in the diets as corn oil or a partially rumen-protected CLA salt for 2 specific treatment periods of the final 32 or 60 d on feed, corresponding to a total time on feed of 89 or 118 d. After an initial 56-d feeding period (basal diet), the heifers were fed 1 of 3 dietary treatments (DM basis): 1) a basal diet containing 88% concentrate and 12% grass hay (CON), 2) the basal diet plus 4% corn oil (OIL), or 3) the basal diet plus 2% partially rumen-protected CLA (RPCLA) containing 31% CLA. Heifers were randomly allotted to dietary treatments at the initiation of the study and fed individually. At 48 h postmortem, the right forequarter of each carcass was fabricated into retail cuts. Steaks (2.54-cm thick) were obtained from the posterior end of the ribeye roll (NAMP 112), and beef trim was ground for all subsequent analyses. Dietary treatment did not affect (P > 0.05) lipid oxidation in ground beef or ribeye steaks. Total trans-octadecenoate fat and trans-10 octadecenoic acid content in ribeye steaks increased (P < 0.05) with RPCLA compared with CON. Total CLA and the cis-9 trans-11 isomer of CLA contents in ribeye steaks were unchanged (P > 0.05) by lipid supplementation. In ground beef, RPCLA supplementation increased (P < 0.05) the amount of trans fat and trans-10 octadecenoic acid compared with CON or OIL; supplementation of RPCLA increased (P < 0.05) the amount of CLA cis-9 trans-11 isomer and total CLA. Lipid supplementation did not alter (P > 0.05) off-flavor ratings in ground beef or ribeye steaks. Supplementation of corn oil increased (P < 0.05) total PUFA content of ribeye steaks compared with CON and RPCLA. Dietary RPCLA supplementation increased the amount of trans fat per serving (85.5 g, broiled) by 110 and 88% in ribeye steak and ground beef, respectively, and CLA cis-9 trans-11 by 58% in ground beef compared with CON. Supplementing OIL or RPCLA resulted in minimal changes in lipid oxidation and sensory attributes of steaks and ground beef.     

Effect of forage:concentrate ratio on ruminal digestion and duodenal flow of fatty acids in ewes

The objective of this study was to determine the forage:concentrate ratio that would provide the greatest duodenal flow of unsaturated fatty acids in ewes supplemented with soybean oil and to determine how diets differing in forage content affect flow of conjugated linoleic acid (CLA) and trans-vaccenic acid (18:1(trans-11)). Five mature ewes (66.5 +/- 12.8 kg) fitted with ruminal and duodenal cannulas were used in a 5 x 5 Latin square experiment. Diets were isonitrogenous and included bromegrass hay, cracked corn, corn gluten meal, urea, and limestone. Dietary fat was adjusted to 6% with soybean oil. Five ratios of forage:concentrate (18.4:81.6, 32.2:67.8, 45.8:54.2, 59.4:40.6, and 72.9:27.1) were fed at 1.3% of BW daily in equal allotments at 0630 and 1830. After 14 d, Cr2O3 (2.5 g) was dosed at each feeding for 7 d and ruminal, duodenal, and fecal collections were taken for the next 3 d. Duodenal flow of 18:0 increased linearly (P < 0.01) with dietary forage. Duodenal flow of 18:1(cis-9) and 18:2(cis-9,12) decreased (P < 0.001) but duodenal flow of 18:3(cis-9,12,15) increased (P < 0.01) with increased dietary forage. Biohydrogenation of dietary unsaturated fatty acids increased (P < 0.001) as dietary forage increased, which was concomitant with increased ruminal pH. Duodenal flow of 18:2(cis-9,trans-11) increased linearly (P < 0.01) with increased dietary forage but increased abruptly when forage was fed at 45.8%. Duodenal flow of the trans-10, cis-12 and cis-10, cis-12 CLA isomers decreased as dietary forage increased, but flow tended to increase on the highest-forage diet, resulting in both linear (P < 0.01) and quadratic (P < 0.01) effects. Duodenal flow of 18:1(trans-11) decreased from 8.28 g/d on the 18.4% forage diet to 5.47 g/d on the 59.4% forage diet then increased to 7.29 g/d on the highest-forage diet (quadratic, P < 0.1). Duodenal flow of 18:1(trans-11) was 27- to 69-fold greater than flow of CLA. We conclude that when ewes were fed a 6% crude fat diet duodenal flows of dietary fatty acids changed incrementally as dietary forage was increased, whereas changes in flows of CLA isomers seemed to be more abrupt. Biohydrogenation changes were gradual with diet, suggesting a gradual shift in ruminal microbial populations with increasing forage. Finally, the highest-concentrate diet supported the greatest duodenal flows of dietary unsaturated fatty acids, as well as the highest flow of 18:1(trans-11).     

Effect of feeding high-temperature, microtime-treated diets with different lipid sources on conjugated linoleic acid formation in finishing Hanwoo steers

The present study was conducted to examine the effects of different plant oils or plant oil mixtures and high-temperature, microtime processing (HTMT) on the CLA content in Hanwoo steers. Experiment 1, consisting of 3 in vitro trials, was conducted to determine how the biohydrogenation of C18 fatty acids and CLA production were affected by fat sources (tallow, soybean oil, linseed oil, or mixtures of soybean oil and linseed oil) or HTMT treatment in the rumen fluid. The results showed that HTMT was capable of protecting unsaturated fatty acids from biohydrogenation by ruminal bacteria. The HTMT-treated diet containing 4% linseed oil (LU) and a supplement containing 2% linseed oil and 1% soybean oil treated with HTMT + 1% soybean oil (L(2)S(1)U+S(1)) produced an increased quantity of trans-11 C18:1 and cis-9, trans-11 CLA, and a reduced quantity of trans-10, cis-12 CLA. Based on these results, in vivo studies (Exp. 2) were conducted with LU and L(2)S(1)U+S(1). These 2 treatments increased the content of cis-9, trans-11 CLA in LM compared with the control diet. The content of trans-10, cis-12 CLA in subcutaneous fat was also increased in the L(2)S(1)U+S(1) treatment compared with other treatments. The subcutaneous fat thickness in the LU treatment was decreased compared with the L(2)S(1)U+S(1) treatment. The LU treatment significantly decreased fatty acid synthase expression but simultaneously increased leptin expression. In this report, we showed that diets containing LU and L(2)S(1)U+S(1) were capable of increasing CLA in the intramuscular fat of beef.     

Corn oil supplementation to steers grazing endophyte-free tall fescue. II. Effects on longissimus muscle and subcutaneous adipose fatty acid composition and stearoyl-CoA desaturase activity and expression

Eighteen steers were used to evaluate the effect of supplemental corn oil level to steers grazing endophyte-free tall fescue on fatty acid composition of LM, stearoyl CoA desaturase (SCD) activity and expression as well as cellularity in s.c. adipose. Corn oil was supplemented (g/kg of BW) at 0 (none), 0.75 (medium), and 1.5 (high). Cottonseed hulls were used as a carrier for the corn oil and were supplemented according to pasture availability (0.7 to 1% of BW). Steers were finished on a rotationally grazed, tall fescue pasture for 116 d. Fatty acid composition of LM, s.c. adipose, and diet was determined by GLC. Total linoleic acid intake increased linearly (P < 0.01) with corn oil supplementation (90.7, 265.1, and 406.7 g in none, medium, and high, respectively). Oil supplementation linearly reduced (P < 0.05) myristic, palmitic, and linolenic acid percentage in LM and s.c. adipose. Vaccenic acid (C18:1 t11; VA) percentage was 46 and 32% greater (linear, P = 0.02; quadratic, P = 0.01) for medium and high, respectively, than none, regardless of tissue. Effect of oil supplementation on CLA cis-9, trans-11 was affected by type of adipose tissue (P < 0.01). In the LM, CLA cis-9, trans-11 isomer was 25% greater for medium than for none and intermediate for high, whereas CLA cis-9, trans-11 CLA isomer was 48 and 33% greater in s.c. adipose tissue for medium and high than for none, respectively. Corn oil linearly increased (P 0.05) the percentage of total SFA, MUFA, or PUFA but linearly increased (P = 0.03) n-6:n-3 ratio from 2.4 to 2.9 in none and high, respectively. Among tissues, total SFA and MUFA were greater in s.c. adipose than LM, whereas total PUFA, n-6, and n-3 fatty acids and the n-6:n-3 ratio were lower. Trans-10 octadecenoic acid, VA, and CLA trans-10, cis-12 were greater (P < 0.01) in s.c. adipose than in LM. Oil supplementation did not alter (P > 0.05) stearoyl CoA desaturase activity or mRNA expression. Corn oil supplementation to grazing steers reduced the percentages of highly atherogenic fatty acids (myristic and palmitic acids) and increased the percentages of antiatherogenic and anticarcinogenic fatty acids (VA and cis-9, trans-11 CLA).     

Effects of feeding high-oil corn to beef steers on carcass characteristics and meat quality

To assess the effects of feeding high-oil corn on carcass characteristics and meat quality, 60 yearling steers were fed high concentrate diets containing either control corn (82% of diet), high-oil corn (82% of diet), or high-oil corn at a concentration that was isocaloric with the control diet (74% of diet). After being fed for 84 d, steers were slaughtered. At 72 h postmortem, carcass data were collected and rib sections from five steers grading U.S. Choice and five steers grading U.S. Select from each treatment were collected, vacuum packaged, and aged for 14 d. Three steaks (2.54 cm thick) were removed from each rib for Warner-Bratzler shear force measurement, sensory appraisal, and fatty acid composition analyses. Data were analyzed with treatment as the main effect for the carcass data and treatment, quality grade, and two-way interaction in the model for the longissimus data. The two-way interaction was nonsignificant (P > 0.05) for all variables tested. No differences were detected (P > 0.05) in carcass measurements except for marbling scores and quality grades, both of which were greater (P < 0.05) for carcasses from steers fed the high-oil corn. Overall, 78% of steers fed the high-oil corn graded U.S. Choice compared with 47% for the control and 67% for isocaloric group. Shear force and sensory properties of the longissimus were not different (P > 0.05) among treatments. Steaks from U.S. Choice carcasses rated higher (P < 0.05) for tenderness and tended to rate higher (P < 0.10) for juiciness. Feeding the isocaloric and high-oil diets increased (P < 0.05) linoleic acid, arachidonic acid, and the total PUFA content of lipid extracted from the longissimus. Saturated fatty acid percentage was lowest (P < 0.05) for high-oil corn and highest (P < 0.05) for control, with isocaloric being intermediate. Feeding high-oil corn increased (P < 0.05) pentadecyclic acid, margaric acid, and total odd-chain fatty acid content. Feeding high-oil corn in finishing beef cattle diets enhanced intramuscular lipid deposition and increased unsaturation of fatty acids of the longissimus.     

Dietary conjugated linoleic acid changes belly and bacon quality from pigs fed varied lipid sources

The objective of this experiment was to determine the effects of dietary lipid source with or without the addition of CLA on bacon composition and quality. Forty-eight barrows at a beginning BW of 55 kg +/- 2.2 were fed 1 of 6 diets for 56 d. These diets consisted of: 1) normal corn (NC), 2) NC + 1.25% CLA-60 oil (NC + CLA), 3) high-oil corn (HOC), 4) HOC + 1.25% CLA-60 oil (HOC-CLA), 5) NC + choice white grease (CWG; NC + CWG), and 6) NC + CWG + 1.25% CLA-60 oil (NC + CWG + CLA). The CLA-60 contains 60% CLA isomers in the oil, and therefore, 1.25% oil was needed to achieve 0.75% CLA in the diet. Soy oil replaced CLA in control diets. Choice white grease and high-oil corn were selected as fat sources for this study because of their utility in energy density for growing-finishing pigs, especially in hot weather. Pigs were slaughtered at an average BW of 113 kg +/- 4.1, and carcasses were fabricated at 24 h postmortem. Statistical analysis was performed using the mixed model procedure of SAS, and the main effects tested were dietary lipid source, CLA, and 2-way interaction. The addition of CLA to each basal diet improved (P < 0.05) belly firmness measured either lean side down or fat side down from the belly bar firmness test [4.39 cm vs. 7.01 cm (lean down) and 5.75 cm vs. 10.54 cm (fat down)] for 0 and 0.75% dietary CLA, respectively. The compression test used on bacon slabs showed that bacon from CLA-supplemented pigs was approximately 20% firmer than that from controls. Pigs fed the HOC diets had softer bellies compared (P < 0.05) with pigs fed the NC diet as measured by the belly bar test [6.94 cm vs. 9.26 cm (fat down)], respectively. Conjugated linoleic acid did not, however, improve bacon sliceability. No differences were observed for moisture, protein, or lipid percentages between any treatments. Overall, there was a CLA effect (P < 0.04) for lipid oxidation, in which the addition of CLA decreased bacon oxidation (0.1498 CLA vs. 0.1638 no CLA). Dietary CLA increased the percentage of SFA in tissues from pigs supplemented with CLA. Dietary inclusion of CLA increased the concentration of all measured isomers of CLA in bacon. Sensory scores of bacon showed no differences for any of the sensory attributes measured between any of the treatments. Our results indicate that inclusion of dietary CLA will improve belly firmness, extend the shelf life stability of bacon, and increase the degree of fat saturation.     

Effect of linseed oil and fish oil alone or as an equal mixture on ruminal fatty acid metabolism in growing steers fed maize silage-based diets

Because of the potential benefits to human health, there is interest in increasing 18:3n-3, 20:5n-3, 22:6n-6, and cis-9,trans-11 CLA in ruminant foods. Four Aberdeen Angus steers (406 ± 8.2 kg of BW) fitted with ruminal and duodenal cannulas were used in a 4 × 4 Latin square experiment with 21-d periods to examine the potential of fish oil (FO) and linseed oil (LO) in the diet to increase ruminal outflow of trans-11 18:1 and total n-3 PUFA in growing cattle. Treatments consisted of a control diet (60:40; forage:concentrate ratio, on a DM basis, respectively) based on maize silage, or the same basal ration containing 30 g/kg of DM of FO, LO, or a mixture (1:1, wt/wt) of FO and LO (LFO). Diets were offered as total mixed rations and fed at a rate of 85 g of DM/(kg of BW(0.75)/d). Oils had no effect (P = 0.52) on DMI. Linseed oil had no effect (P > 0.05) on ruminal pH or VFA concentrations, whereas FO shifted rumen fermentation toward propionate at the expense of acetate. Compared with the control, LO increased (P < 0.05) 18:0, cis 18:1 (Δ9, 12-15), trans 18:1 (Δ4-9, 11-16), trans 18:2, geometric isomers of 9,11, 11,13, and 13,15 CLA, trans-8,cis-10 CLA, trans-10,trans-12 CLA, trans-12,trans-14 CLA, and 18:3n-3 flow at the duodenum. Inclusion of FO in the diet resulted in greater (P < 0.05) flows of cis-9 16:1, trans 16:1 (Δ6-13), cis 18:1 (Δ9, 11, and 13), trans 18:1 (Δ6-15), trans 18:2, 20:5n-3, 22:5n-3, and 22:6n-3, and decreased (P < 0.001) 18:0 at the duodenum relative to the control. For most fatty acids at the duodenum, responses to LFO were intermediate of FO and LO. However, LFO resulted in greater (P = 0.04) flows of total trans 18:1 than LO and increased (P < 0.01) trans-6 16:1 and trans-12 18:1 at the duodenum compared with FO or LO. Biohydrogenation of cis-9 18:1 and 18:2n-6 in the rumen was independent of treatment, but both FO and LO increased (P < 0.001) the extent of 18:3n-3 biohydrogenation compared with the control. Ruminal 18:3n-3 biohydrogenation was greater (P < 0.001) for LO and LFO than FO, whereas biohydrogenation of 20:5n-3 and 22:6n-3 in the rumen was marginally less (P = 0.05) for LFO than FO. In conclusion, LO and FO at 30 g/kg of DM altered the biohydrogenation of unsaturated fatty acids in the rumen, causing an increase in the flow of specific intermediates at the duodenum, but the potential of these oils fed alone or as a mixture to increase n-3 PUFA at the duodenum in cattle appears limited.     

日粮精料水平对绵羊瘤胃内容物亚油酸及其氢化产物组成的影响

选用4只装有永久性瘤胃瘘管的杂交一代(小尾寒羊×无角陶赛特)羯羊(平均体重45.0kg),采用4×4拉丁方设计,研究日粮精料水平对绵羊瘤胃内容物中亚油酸及其氢化产物组成的影响。在日粮中添加大豆油,调整粗脂肪和亚油酸含量分别至(7.3±0.1)%和(25.4±0.9)mg/g(干物质基础),日粮精料水平分别为30.2,39.3,48.8和57.7%(干物质基础)。试验结果表明,57.7%精料日粮组瘤胃内容物中亚油酸的含量(mg/gDM)及其在总18C脂肪酸中的比例最高(P<0.01),反11C18∶1、顺9,反11CLA的含量及二者在总18C脂肪酸中的比例最低(P<0.01);各组瘤胃内容物中C18∶0的含量及其在总18C脂肪酸中的比例没有显著差异(P>0.05)。瘤胃内容物中亚油酸、顺9,反11CLA和反11C18∶1的含量与日粮NDF水平呈极显著线性相关(P<0.01)。亚油酸的氢化效率随日粮精料水平的提高而显著降低(P<0.05)。     

Supplemental algal meal alters the ruminal trans-18:1 fatty acid and conjugated linoleic acid composition in cattle

The effects of dietary algal supplementation, a source of docosahexaenoic acid, on the fatty acid profile of rumen lipids in cattle were evaluated, with special emphasis on CLA and trans fatty acids produced by rumen microbes. A diet based on corn silage was fed with supplements containing the following: 1) no algal meal and fed at 2.1 kg of DM/d (control), 2) algal meal and fed at 1.1 kg of DM/d (low algal meal), 3) algal meal and fed at 2.1 kg of DM/d (medium algal meal), and 4) algal meal and fed at 4.2 kg of DM/d (high algal meal). A modified lipid extraction procedure was developed to analyze the lipid changes in rumen fluid. The percentage of stearic acid (18:0) in rumen fluid was decreased by algal meal supplementation (P < 0.001) compared with control and was linearly dependent on the level of algal meal supplementation (P = 0.005). Total trans-18:1 in rumen fluid of cattle fed the control diet was 19% of total fatty acids. Addition of algal meal increased (P < 0.001) total trans-18:1 up to 43%, mostly due to 18:1 trans-10 that increased (P = 0.002) to 29.5% of total rumen fatty acids. This increase in 18:1 trans-10 seems to suggest a change in the rumen microbial population. Vaccenic acid (18:1 trans-11) increased quadratically (P = 0.005) with increasing level of algal meal supplementation in the diets. The total CLA content was low in the control (<0.9%) and increased with dietary algal meal addition, although not significantly; the greatest level was 1.5% with the medium algal meal diet. The increase of rumenic acid (cis-9, trans-11 CLA) was quadratic (P = 0.05) with algal meal supplementation, whereas trans-10, cis-12 CLA increased linearly with increased level of algal meal from 0.08 to 0.13% (P = 0.03). The ratio of trans-11 (cis-9, trans-11 CLA + 18:1 trans-11) to trans-10 (trans-10, cis-12 CLA + 18:1 trans-10) decreased from 2.45 to 0.77, 0.87, and 0.21 for the control, low algal meal, medium algal meal, and high algal meal diets, respectively. The content of docosahexaenoic acid in rumen fluid increased (P = 0.002) from 0.3 to 1.4% of total fatty acids with increasing level of algal meal supplementation in the diets. Our results suggest that algal meal inhibits the reduction of trans-18:1 to 18:0, giving rise to the high trans-18:1 content. In conclusion, algal meal could be used to increase the concentration in rumen contents of trans-18:1 isomers that serve as precursors for CLA biosynthesis in the tissues of ruminants.     

Effect of extruded full-fat soybeans on conjugated linoleic acid content of intramuscular,intermuscular, and subcutaneous fat in beef steers

Crossbred Angus steers (n = 30) were used to determine whether the conjugated linoleic acid (CLA) content of beef fat could be increased by feeding varying levels of extruded full-fat soybeans as a source of polyunsaturated fatty acids for rumen biohydrogenation. Diets were as follows: 1) control, 2) 12.7% extruded full-fat soybeans (LESB), and 3) 25.6% extruded full-fat soybeans (HE SB). Steers were individually housed and fed the diets for 111 d during the finishing period. Over the experimental period, treatment groups were similar in ADG (1.7 +/- 0.1 kg/d) and had a similar slaughter weight (603 +/- 11.6 kg). Dressing percentage averaged 61.6% and carcass composition averaged 14.3% protein, 30.9% lipid, and 54.8% water. At slaughter, the intramuscular, intermuscular, and subcutaneous fat depots were sampled from the rib longissimus, eye of round, and chuck tender muscles. Across all fat depots, the CLA content differed (P < 0.05), averaging 6.6, 6.7, and 7.7 mg/g of fatty acids for the control, LESB, and HESB diets, respectively. There were significant differences in CLA content between fat depots within a cut, but differences were relatively small and the hierarchy in fat depots was not consistent among cuts. The cis-9, trans-11 isomer was the predominant CLA isomer and its content in fat was related to trans-11 C18:1 content (r = 0.53; P < 0.001). There was substantial individual variation in CLA content and this varied from 2.6 to 17.0 mg/g fatty acids across all treatments and fat depots. Overall, results demonstrated that including extruded full-fat soybeans in the diet of finishing steers increased the CLA content of beef fat. Differences were relatively small and the relationship of this to rumen fermentation and endogenous synthesis of CLA is considered.     

Effects of feeding pigs increasing levels of C 18:1 trans fatty acids on fatty acid composition of backfat and intramuscular fat as well as backfat firmness.

Forty Large White pigs were fed from 30 kg to 103 kg body mass on diets supplemented with 6% of pure high-oleic sunflower oil (HO) or HO plus increasing amounts of partially hydrogenated rape seed oil (HR; 1.85%, 3.70%, 5.55%), containing high levels of delta 6 to delta 11 C 18:1 trans fatty acid isomers. Increasing dietary C 18: trans fatty acids resulted in a linear increase in C 18:1 trans fatty acids and conjugated linoleic acid (cis-9, trans-11 CLA) in backfat (BF) as well as in neutral lipids (NL) and phospholipids (PL) of M. long. dorsi. Thus, the rate of bioconversion of trans vaccenic acid (TVA) into CLA and incorporation of C 18:1 trans and CLA into pig adipose tissue was not limited up to 25 g total C 18:1 trans fatty acids including 3.3 g of TVA per kg feed. BF was higher in C 18:1 trans fatty acids and CLA than M. long. dorsi NL and PL. In BF and NL the sum of saturated fatty acids (SFA) increased with increasing dietary amounts of HR, while in PL SFA were reduced. Thus, according to their physical properties, C 18:1 trans fatty acids partly replaced SFA in PL. Firmness of backfat was also significantly increased (P < 0.05) with increasing amounts of HR in feed.     

Fatty acid compositions of mixed ruminal microbes isolated from sheep supplemented with soybean oil

Two experiments were conducted to examine the changes in the fatty acid (FA) composition of mixed ruminal microbes (MRM) from sheep fed various levels of dietary forage and soybean oil (SBO). In Experiment 1, diets included five ratios of forage to concentrate. Increased dietary forage did not change MRM concentrations of 18:1(trans-11) and 18:2 (P>0.10), but increased 18:3 (P<0.01) and cis-9, trans-11 conjugated linoleic acid (CLA) (P<0.01). In Experiment 2, SBO was added to the diets at 0%, 3.2%, 6.3%, or 9.4% of dietary DM. Increasing dietary SBO resulted in linear increases (P<0.01) in 18:1(trans-11)and 18:1(cis-9), but linear decreases (P<0.01) in 18:2 of MRM. It was concluded that FA composition of MRM was affected by diet. Additionally, MRM of sheep fed the diet containing 18.4% forage and 9.4% SBO contained the greatest individual and total FA concentrations.     

Feeding flaxseed in grass hay and barley silage diets to beef cows increases alpha-linolenic acid and its biohydrogenation intermediates in subcutaneous fat

The objective of the study was to determine temporal fat deposition and fatty acid profiles in beef cows fed hay- or barley silage-based diets, with or without flaxseed. Crossbred cull beef cows (n = 64, >30 mo of age, 620 ± 5 kg) were removed from grassland pastures, randomly assigned to 16 pens, and given ad libitum access to 50:50 (wt/wt, DM basis) forage:concentrate diets containing 0 or 15% ground flaxseed (DM basis, 5.2% added fat). Diets consisted of hay control (HC), hay+flaxseed (HF), barley silage control (SC), and silage+flaxseed (SF). Backfat biopsies were obtained from each cow at 0, 6, and 12 wk, and at slaughter (~20 wk) to assess fatty acid composition. With the exception of feed efficiency, flaxseed × forage interactions were not significant for backfat accumulation or performance parameters. Flaxseed improved (P < 0.01) feed conversion when supplemented to hay-based diet and increased ADG (P = 0.03), resulting in a heavier (P = 0.02) BW. Compared with hay, barley silage increased (P < 0.01) DMI, ADG, and feed efficiency. Subcutaneous fat contained 0.68% n-3 fatty acids at wk 0, and reached 0.68, 0.81, and 0.94% in HF cows after 6, 12, and 20 wk, respectively (Y(n-3) = 0.0133X + 0.6491, r = 0.87). It was 0.67% at wk 0, and reached 0.65, 0.77, and 0.90% in SF cows after 6, 12, and 20 wk, respectively (Y(n-3) = 0.0121X + 0.6349, r = 0.75). In contrast, weight percentage of n-3 fatty acids decreased in HC cows from 0.63, 0.50, and 0.47, to 0.43%, and in SC cows from 0.63, 0.40, and 0.36, to 0.33% over the 20 wk. A forage × flaxseed interaction (P < 0.05) occurred for many of the α-linolenic acid (ALA) biohydrogenation intermediates, including vaccenic acid (C18:1 trans-11) and CLA (combined C18:2 trans-7,cis-9 and cis-9,trans-11) in plasma, and in subcutaneous fat this also included non-CLA dienes. Concentrations of most α-linolenic acid biohydrogenation intermediates were greater when feeding flaxseed with hay. In conclusion, forage source altered plasma concentrations and rate of accumulation of ALA biohydrogenation products in subcutaneous fat from beef cows fed flaxseed. Factors responsible for this response are yet to be defined, but may include forage-mediated changes in ruminal biohydrogenation of ALA, as well as alterations in fatty acid metabolism and deposition.     

Impact of beef cattle diets containing corn or sorghum distillers grains on beef color, fatty acid profiles, and sensory attributes

Strip loins from 236 carcasses from crossbred yearling steers were collected on each of 2 slaughter dates (slaughter 1 or 2) to determine the effects of feeding corn or sorghum distillers grains (DG) on beef color, fatty acid profiles, lipid oxidation, tenderness, and sensory attributes. Dietary treatments consisted of a steam-flaked corn (SFC) diet without (control) or with 15% (DM basis) corn dry or wet DG (CDDG and CWDG) or sorghum dry or wet DG (SDDG and SWDG) and alfalfa hay (R). Additional treatments included SDDG or SWDG with no alfalfa hay (NR). In slaughter 2, steaks from steers fed SFC had lesser L*, but greater a* (P < 0.05) values than those from steers fed DG. When comparing sorghum and corn DG steaks, the same color differences were detected. Steaks from steers fed sorghum DG had lower L*, but greater a* (P < 0.05) values than those from steers fed corn DG. Also, L* values in steaks from steers fed SWDG with R were greater (P < 0.05) than those from steers fed SWDG with NR. In slaughter 1, feeding DG increased (P < 0.05) steak n-6 fatty acid concentrations compared with SFC. In both slaughter groups, feeding dry DG increased (P < 0.05) steak linoleic acid concentrations compared with wet DG. In slaughter 2, feeding corn DG diets increased (P < 0.05) linoleic acid concentrations of steaks compared with sorghum DG diets. In addition, increased (P < 0.05) concentrations of alpha-linolenic acid in steaks resulted from feeding SDDG or SWDG with R compared with those sorghum treatments with NR. In each slaughter group, feeding DG increased (P < 0.05) the n-6:n-3 ratio of steaks compared with SFC, and feeding corn DG increased (P < 0.05) this ratio compared with sorghum DG. Furthermore, steaks from steers fed corn DG had greater (P < 0.05) concentrations of trans-vaccenic acid than those from steers fed sorghum DG. In slaughter 1, the CLA isomer 18:2, trans-10, cis-12 was greater (P < 0.05) in steaks from DG diets. On d 1 of retail display, steaks from steers fed SDDG with R in slaughter 2 had greater (P < 0.05) thiobarbituric acid reactive substances values than those from steers fed SDDG with NR. Feeding DG at 15% of the dietary DM did not affect sensory attributes or Warner-Bratzler shear force values of steaks. Feeding DG from either corn or sorghum as either a wet or dry by-product had no effect on beef sensory attributes.     

Conjugated linoleic acid depresses the delta9 desaturase index and stearoyl coenzyme A desaturase enzyme activity in porcine subcutaneous adipose tissue

Conjugated linoleic acid (CLA) has been shown to have an effect on subcutaneous fatty acid composition and has been reported to decrease stearoyl coenzyme A desaturase (SCD) activity by decreasing mRNA expression and(or) catalytic activity in rodents and rodent cell lines. This investigation was designed to study the effects of CLA, corn oil, or beef tallow supplementation on s.c. adipose tissue fatty acid composition, adiposity, SCD enzyme activity, and the delta9 desaturase index in piglets. Eighteen crossbred barrows 16 to 18 d of age were adapted to diet for 1 wk and then assigned randomly to one of three treatments: 1.5% added CLA, 1.5% added corn oil, or 1.5% added beef tallow. Barrows were penned individually and fed the supplemental oils for 35 d (to 25.6 +/- 0.6 kg BW). Subcutaneous adipose tissue samples were obtained after slaughter. Fatty acid composition of the s.c. adipose tissue differed for each fatty acid measured due to diet with the exception of 18:3. The concentrations of CLA trans-10, cis-12 and cis-9, trans-11 were elevated from nondetectable to 1.62 and 2.52 g/100 g lipid, respectively (P < 0.001 for both isomers). Conjugated linoleic acid decreased the delta9 desaturase index (P < 0.01) and SCD enzyme activity, expressed as nanomoles of palmitate converted to palmitoleate/(7 min x g of tissue) (P = 0.075) and nanomoles of palmitate converted to palmitoleate/(7 min 105 cells) (P= 0.056). Tallow-fed pigs had a greater proportion of large adipocytes (> 700 pL) and the greatest SCD activity. These data provide the first direct evidence that dietary CLA depresses SCD enzyme activity in porcine adipose tissue, which may in part be responsible for the depression of adiposity by CLA observed by others in market weight pigs.     

Effectiveness of short-term feeding strategies for altering conjugated linoleic acid content of beef

A steer finishing trial was performed to determine the effect of short-term dietary regimens on conjugated linoleic acid (CLA) content of muscle tissues. The experimental design was an incomplete 3 x 2 factorial, with three levels of soybean oil (SBO; 0, 4, and 8% of diet DM) and two levels of forage (20 vs. 40% of diet DM). Forty Angus x Hereford steers averaging 504 +/- 29.0 kg were allotted randomly to one of four treatments for the last 6 wk of the finishing period. Treatments were: 80:20 concentrate:forage control diet (C); 80:20 concentrate:forage + 4% SBO (C4); 60:40 concentrate:forage + 4% SBO (F4); and 60:40 concentrate:forage + 8% SBO (F8). After 42 d on the experimental diets, steers were sacrificed and samples were collected from the chuck, loin, and round muscle groups. Fatty acid (FA; mg/100 mg of FA) composition was determined by gas-liquid chromatography. Data were statistically analyzed with mixed models procedures. The performance and carcass quality model included the effects of SBO and forage. The model for FA composition included the effects of SBO, forage, muscle group, and interactions. Orthogonal contrasts were used to determine linear effects of SBO. There were no differences in growth performance among treatments (P > 0.05). Increasing dietary SBO linearly decreased dressing percent (P = 0.04), and tended to linearly decrease marbling score (P = 0.12) and quality grade (P = 0.08). The only CLA isomer detected in tissue samples was cis-9,trans-11. Addition of SBO to diets linearly increased linoleic acid (18:2n-6; P = 0.04) and tended to linearly increase linolenic acid (18:3n-3; P = 0.10) in muscle tissues. The CLA in lean tissues was decreased (P = 0.005) with SBO-containing diets. These findings suggest that increased PUFA may limit ruminal production of CLA and trans-vaccenic acid (VA) and/or may depress stearoyl-CoA desaturase expression or activity in lean tissues, which in turn limits CLA formation and accretion in tissues. Increasing dietary forage tended to increase 18:0, 18:2n-6, CLA, and 18:3n-3 (P < 0.15), suggesting that increased forage may mitigate toxic effects of PUFA on ruminal biohydrogenation, thereby increasing the pool of CLA and VA available for CLA formation and accretion in tissues. Short-term feeding of elevated SBO and forage levels can alter FA profiles in muscle tissues.