Trans-11 Conjugated Linoleic Acid Concentrations Research Articles

Effects of different vegetable oils on rumen fermentation and conjugated linoleic acid concentration in vitro.

Aim:The objective of this study was to investigate the effect of different vegetable oils on rumen fermentation and concentrations of beneficial cis-9 trans-11 C18:2 conjugated linoleic acid (CLA) and trans-11 C18:1 fatty acid (FA) in the rumen fluid in an in vitro condition.Materials and Methods:Six vegetable oils including sunflower, soybean, sesame, rice bran, groundnut, and mustard oils were used at three dose levels (0%, 3% and 4% of substrate dry matter [DM] basis) in three replicates for each treatment in a completely randomized design using 6 × 3 factorial arrangement. Rumen fluid for microbial culture was collected from four goats fed on a diet of concentrate mixture and berseem hay at a ratio of 60:40 on DM basis. The in vitro fermentation was performed in 100 ml conical flakes containing 50 ml of culture media and 0.5 g of substrates containing 0%, 3% and 4% vegetable oils.Results:Oils supplementation did not affect (p>0.05) in vitro DM digestibility, and concentrations of total volatile FAs and ammonia-N. Sunflower oil and soybean oil decreased (p<0.05) protozoal numbers with increasing levels of oils. Other oils had less pronounced effect (p>0.05) on protozoal numbers. Both trans-11 C18:1 FA and cis-9, trans-11 CLA concentrations were increased (p<0.05) by sunflower and soybean oil supplementation at 4% level with the highest concentration observed for sunflower oil. The addition of other oils did not significantly (p>0.05) increase the trans-11 C18:1 FA and cis-9, trans-11 CLA concentrations as compared to the control. The concentrations of stearic, oleic, linoleic, and linolenic acids were not altered (p>0.05) due to the addition of any vegetable oils.Conclusion:Supplementation of sunflower and soybean oils enhanced beneficial trans-11 C18:1 FA and cis-9, trans-11 CLA concentrations in rumen fluid, while sesame, rice bran, groundnut, and mustard oils were ineffective in this study.

Conjugated linoleic acid synthesis-related protein proteasome subunit α 5 (PSMA5) is increased by vaccenic acid treatment in goat mammary tissue

This study was conducted to identify proteins associated with the endogenous synthesis of conjugated linoleic acid (CLA) from trans-vaccenic acid (TVA; trans-11 C18:1, a precursor for CLA endogenous synthesis) in mammary tissues. Six lactating goats were divided into 2 groups. One group was given an intravenous bolus injection of TVA (150mg) twice daily over 4 d; the other group received saline injections. Treatment with TVA increased the concentration of cis-9,trans-11 CLA and TVA in goat milk. Additionally, TVA treatment increased the expression of stearoyl-CoA desaturase (SCD) in mammary tissue. Using 2-dimensional gel electrophoresis and electrospray ionization quadrupole time-of-flight mass spectrometry, 3 proteins affected by infusions of TVA were identified. Proteasome (prosome, macropain) subunit α type 5 (PSMA5) was upregulated, whereas peroxiredoxin-1 and translationally controlled tumor protein 1 were downregulated in TVA-treated animals compared with the vehicle-injected controls. Only the effect of TVA on PSMA5 could be confirmed by Western blot analysis. To further explore the regulation of PSMA5 in mammary epithelial cells when TVA is converted into CLA, we used a differentiated bovine mammary epithelial cell line treated with TVA for 6h. Changes in cis-9,trans-11 CLA concentrations and mRNA expression patterns of both SCD and PSMA5 were monitored. The concentration of cis-9,trans-11 CLA increased after TVA treatment. The mRNA expression level of PSMA5 was significantly elevated to 6h, but SCD mRNA expression only increased in 2h after TVA treatment. These results indicate that PSMA5 is highly expressed in goat mammary tissue and bovine mammary epithelial cells when TVA is converted into CLA. Our data suggest that PSMA5 protein is associated with CLA biosynthesis in mammary tissue.

Effect of amount and source of vegetable oils in a high fibrous cattle diet on in vitro rumen fermentation, nutrient degradability and rumen cis-9, trans-11 CLA concentration

Four diets with two vegetable oils at two different levels were evaluated for their in vitro rumen fermentation pattern, nutrient degradability and cis-9, trans-11 CLA production using a rumen simulation technique (RUSITEC). Control diet (C) was having roughage to concentrate in the ratio of 65:35. Treatment diets were formed by supplementing with sunflower oil (SF) and soya bean oil (SB) at 4.5 (SF4.5, SB4.5) and 6.0% (SF6, SB6) levels and incubated in RUSITEC fermenters. After seven days of adaptation period, fermentation parameters, nutrient degradability and rumen cis-9, trans-11 concentration were assessed for the next 3 days. Cis-9, trans-11 conjugated linoleic acid (CLA) content was higher in effluent from diets supplemented with 6% oil compared to that of control and 4.5% oil. SF6 and SF4.5 were more effective in increasing rumen cis-9, trans-11 CLA compared with corresponding levels of soya bean oil. However, the degradability of dry matter, acid detergent fibre, neutral detergent fibre and hemicellulose was significantly (P<0.05) reduced in SF6 and SB6 diets. Significantly (P<0.05) higher pH, lower proportion of acetate and butyrate and higher proportion of propionate were indicative of the aforementioned changes in the corresponding fermenters. Rumen fermentation pattern and nutrient degradability were not affected in SF4.5 and SB4.5 diets. The study indicated that vegetable oil supplementation at 6% level was deleterious for rumen fermentation and nutrient degradability despite an increase in cis-9, trans-11 CLA.

Contenido de ácido linoleico conjugado (CLA) en leche de ganado lechero Holstein estabulado en el noroeste de México

Experimental animal studies suggest that conjugated linoleic acid (CLA) has beneficial health properties. Ruminant-derived products such as meat and milk are the principal natural sources of CLA. Milk CLA content is influenced by several factors, including diet and production system. An evaluation was done of CLA content in milk from confined Holstein cows at a farm in Hermosillo municipality, Sonora State, Mexico, during the summer months, when daytime temperatures surpass 40 °C. Milk samples were collected from 120 cows. Quality parameters such as fat, lactose, protein and total solids percentages were measured using AOAC methods. The fatty acid and CLA profile was generated by gas chromatography. Average milk production was 15.8 ± 0.5 kg/day, fat content was 1.91 ± 0.06 %, lactose content was 4.30 ± 0.2 %, protein content was 3.34 ± 0.03 and total solids content was 10.4 ± 0.09 %. Unsaturated fatty acids content was higher (P<0.05) in August than during June and July. Average cis-9, trans-11 CLA concentration was 9.36 mg/g fat (10.78 ± 0.41 in June, 8.50 ± 0.37 in July, and 10.16 ± 0.39 in August), which is high compared to concentrations reported in countries with a temperate climate. The relatively high CLA content observed in the present study was probably caused by the 58.8 % alfalfa content in the summer diet, since this legume is rich in CLA fatty acids precursors (linoleic and linolenic acid).

Nutritive merits of whole Nutrasaff safflower seed when fed to Holstein dairy cows during midlactation

A lactation study was conducted to assess productive performance of dairy cows fed varying levels of whole Nutrasaff safflower seed (NSS), a new variety of safflower seed, and identify its impact on milk fat content and milk fatty acid (FA) composition. Fifteen Holstein dairy cows in midlactation (118 ± 38.5 days in milk) were assigned randomly to three balanced 5 × 5 Latin squares according to previous milk yield. Each period lasted 21 d with 14 d of treatment adaptation and 7 d of data collection. The cows were fed diets containing approximately 560 g/kg dry matter (DM) forage and 440 g/kg DM concentrate mixture. Within square, cows were randomly assigned to one of five dietary treatments being: whole linted-cottonseed without NSS (CS), 10 g/kg DM NSS (NSS10), 20 g/kg DM NSS, 30 g/kg DM NSS and 40 g/kg DM NSS. The NSS was added to the diets by replacing whole linted-cottonseed in the CS diet. Intake of DM, N and fiber decreased by the NSS10 diet compared to the CS diet. Increasing level of NSS inclusion linearly decreased N intake, but it linearly increased fiber intake. Digestibilities of DM and organic matter (OM) increased in the NSS10 diet compared to the CS diet, whereas they linearly decreased with increasing dietary level of NSS. Milk yield averaged 33.7 kg/d, and was similar among dietary treatments. Milk fat content linearly decreased with increasing NSS inclusion, while milk true protein and lactose contents did not differ among dietary treatments. Milk fat content was affected when NSS was included at 40 g/kg DM, with an 11% reduction. Efficiency of use of feed N to milk N increased, but milk urea N decreased by feeding the NSS10 diet compared to the CS diet, implying that NSS supplementation improved dietary N use for milk production. However, the N utilization efficiency tended to decrease ( P=0.08) with increasing NSS inclusion level, and milk urea N was not affected by level of NSS inclusion. Cis-9, trans-11 conjugated linoleic acid (CLA), and trans-10 18:1 FA linearly increased with increasing NSS inclusion level. This study demonstrates that supplementing NSS in dairy diets can be a promising means of fat supplementation to lactating dairy cows without negative impacts on lactational performance at up to 30 g/kg DM. The increased cis-9, trans-11 CLA concentration due to addition of NSS can enhance milk quality because of its potentially beneficial health effects. However, the beneficial effect of NSS was counterbalanced by an unfavorable increase of trans-10 18:1 FA.

Estimation of cis-9, trans-11 conjugated linoleic acid content in UK foods and assessment of dietary intake in a cohort of healthy adults

Dietary conjugated linoleic acid (CLA) from ruminant-derived foods may be potentially beneficial to health. The quantity of cis-9, trans-11 CLA and trans-10, cis-12 CLA in a range of UK foodstuffs (112 foods) was determined using triple-column silver ion HPLC. The cis-9, trans-11 CLA content ranged from 1.9 mg/g lipid (mild Cheddar) to 7.3 mg/g lipid (processed cheese) in cheeses, from 0.9 mg/g lipid (ice cream) to 3.7 mg/g lipid (double cream) in non-cheese dairy products, and from 2.9 mg/g lipid (Swedish meatballs) to 6.0 mg/g lipid (minced lamb) in meat products. cis-9, trans-11 CLA concentrations for chocolate and sweets ranged from 0.1 mg/g lipid (hot chocolate) to 4.8 mg/g lipid (buttermint). The trans-10, cis-12 CLA isomer was undetected or negligible in the food samples examined. To provide information about dietary cis-9, trans-11 CLA intakes in the UK, a study was performed to estimate the daily intake of CLA in a cohort of eighteen healthy volunteers (nine female and nine male; aged 21-60 years; mean BMI = 24.0 kg/m2 (sd 2.2)) with a 7-d weighed food record. This information combined with the CLA isomer contents of UK foodstuffs was used to estimate the daily intake of the cohort. The mean daily intake of cis-9, trans-11 CLA was estimated to be 97.5 (sd 73.3) mg/d. Due to its potential health benefits, it is important to determine the CLA content of food and dietary intake as these data will be useful in determining the role of CLA in health and disease.

Milk fatty acid composition of indigenous goat and ewe breeds from Sindh, Pakistan

The present study was undertaken to evaluate the breed influence on milk fatty acid (FA) composition, particularly on the concentration of conjugated linoleic acid (CLA) from two different indigenous breeds of goats (Pateri and Kamori; n = 30 for each breed) and ewes (Kachi and Kooka; n = 25 for each) from Sindh, Pakistan. All animals were managed together and received the same diet. Statistical significant differences ( P < 0.05) in the proportions of individual fatty acids were observed among goat and ewe breeds. Milk fat cis-9, trans-11 CLA concentration from Kamori goats and Kooka ewes were [17–28%] higher when compared to Pateri goats and Kachi ewes, with mean values of 0.48 g/100 g for goat breeds and 0.82 g/100 g for ewes. The greatest differences ( P < 0.01) were observed between the group of saturated fatty acids (SFA) in goat (Pateri and Kamori 64.37 vs. 59.07 g/100 g) and ewe breeds (Kachi and Kooka 66.96 vs. 59.00 g/100 g). The sum of the mono-unsaturated fatty acids (MUFAs) was lower in Pateri goat and Kooka breed ewe as compared to Kamori goats and Kachi ewes (27.60 vs. 31.04 g/100 g and 25.35 vs. 30.33 g/100 g). The proportion of polyunsaturated fatty acids (PUFAs) did not differ statistically ( P > 0.05) among goat and ewe breads, ranging from 2.45 to 3.60 for goats and 2.48 to 3.27 g/100 g for ewes. The present study reveals that the breed has a pronounced effect on FA composition of goat and ewes milk fat, and in the future genetic selection plans along with improved nutrition program of goats and ewes may result in optimum levels of various fatty acids in milk.

The effect of dietary linola oil on CLA and other fatty acids in bovine milk

To evaluate the effects of fat source on milk fat composition and milk conjugated linoleic acid (CLA) concentration, cows were fed diets that were high in either C18:2 or C18:0. Twenty-two Holstein cows were blocked by parity and milk production and randomly assigned within block to one of two dietary treatments containing either 3% pork fat (LARD) or 3% linola oil (OIL) on a dry matter (DM) basis. The diets were fed for 21 d. Feed intake and milk and milk component yields were unaffected by treatment, whereas milk fat percent was decreased with the linola oil treatment. The cis-9, trans-11 CLA concentration of milk from cows fed linola oil was significantly higher than from cows fed pork lard. Key words: CLA, fatty acids, linola oil, milk

Milk Conjugated Linoleic Acid Response to Fish Oil and Sunflower Oil Supplementation to Dairy Cows Managed Under Two Feeding Systems

Earlier research showed that conjugated linoleic acid (CLA) content in milk fat is highest when cows’ diets are supplemented with a blend of fish oil (FO) and linoleic acid-rich oils. The objective of this study was to compare the effect of FO and sunflower oil (SFO) supplementation on milk cis-9, trans-11 CLA when dairy cows managed on pasture or in confinement. Fourteen Holstein cows were assigned into 2 treatment groups: cows grazed on alfalfa-grass pasture (PAS) or were fed corn silage-alfalfa hay mix ad libitum (LOT). Both groups were supplemented with a 8.2 kg/d grain supplement containing 640g of FO and SFO (1:3 wt/wt). Grain supplement was fed in 2 equal portions after each milking, for a period of 3 wk. Milk samples were collected during the last 3 d of the experimental period. Milk yield was greater with the LOT diet (23.1 kg/d) compared with the PAS diet (19.4 kg/d). Milk fat percentages (2.51 and 2.95 for the LOT and PAS, respectively) and yields (0.57 and 0.51 kg/d) were similar for the 2 diets. Milk protein percentages were not affected by diets (3.34 and 3.35 for the LOT and PAS diets, respectively), but protein yields were lower for the PAS diet (0.61 kg/d) compared with the LOT diet (0.75 kg/d). Treatment diets had no effect on milk trans C18:1 concentrations [10.64 and 9.82 g/100g of total fatty acids (FA) for the LOT and PAS, respectively] or yields (60.65 and 64.01 g/d), but did affect isomers distributions. Concentration (g/100g of total FA) of vaccenic acid was lower with the LOT diet (2.15) compared with the PAS diet (4.52), whereas concentration of trans-10 C18:1 was greater with the LOT diet (4.99) compared with the PAS diet (1.69). Milk cis-9, trans-11 CLA concentration was greater with the PAS diet (1.52) compared with the LOT diet (0.84). In conclusion, the increase in milk cis-9, trans-11 CLA content was greater when pasture-based diets were supplemented with FO and SFO. The lower cis-9, trans-11 CLA concentration in milk from the confinement-fed cows resulted from trans-10 C18:1 replacing vaccenic acid as the predominant trans C18:1 isomer.

Transfer of Absorbed cis-9, trans-11 Conjugated Linoleic Acid into Milk Is Biologically More Efficient than Endogenous Synthesis from Absorbed Vaccenic Acid in Lactating Cows ,3

Cis-9, trans-11, the major isomer of conjugated linoleic acid (CLA) in bovine milk fat, is derived from ruminal biohydrogenation of 18:2 (n-6) and endogenous conversion of trans-11 18:1 (vaccenic acid; VA) in the mammary gland. Most evidence to date suggests that endogenous synthesis is the major source of cis-9, trans-11 CLA, but the extent of VA desaturation is less well defined. Four lactating cows were used in consecutive 4 × 4 Latin squares to examine changes in milk fatty acid composition and secretion in response to abomasal infusions of lipid supplements enriched with cis-9, trans-11 CLA (88.8%) or VA (29.4%). Treatments were infused over 4-d, followed by a 3-d washout, during 7 d experimental periods and administered to deliver 0, 3, 6, and 12 g cis-9, trans-11 CLA/d (Expt. 1) or 0, 7.5, 15 and 30 g VA/d (Expt. 2). Infusions of cis-9, trans-11 CLA increased linearly milk cis-9, trans-11 CLA concentrations from 0.68 to 1.46 g/100 g fatty acids. Abomasal infusions of VA increased linearly milk VA and cis-9, trans-11 CLA content from 1.22 to 2.72 and 0.61 to 1.24 g/100 g fatty acids, respectively. Changes in milk fatty acid secretion indicated that 28.9% of VA was converted to cis-9, trans-11 CLA. Results provide evidence that conversion by ∆9-desaturase to cis-9, trans-11 CLA in the lactating cow is independent of postruminal VA supply. In conclusion, endogenous synthesis via VA was equivalent to ∼21% of the response to increases in cis-9, trans-11 CLA available for absorption.

Meat quality and fatty acid composition of pasture-finished beef steers fed barley and soybeans

The effect of supplemention on the performance, carcass characteristics, meat quality, and fatty acid composition of pasture-finished cattle was studied. Thirty-two steers were assigned to four treatments in a randomized block design. Treatments were: totally mixed ration (TMR) [confinement-fed total mixed ration (60% grass silage, 40% rolled barley], pasture only (rotationally grazed temperate mixed pasture); pasture plus barley (the same pasture plus 4.5 kg DM hd-1 d-1 rolled barley) and pasture plus soybeans (the same pasture plus 1.8 kg DM hd-1 d-1 whole roasted soybeans). Steers were slaughtered after 105 d on test. Tissue samples were collected at slaughter for analysis of meat quality and fatty acid content. Dry matter (DM) intakes were greater for TMR-fed cattle (P &lt; 0.05). Among the pasture-fed cattle those fed barley (P &lt; 0.05) consumed more total DM than those given pasture alone. Rates of BW gain were higher for TMR-fed steers than those fed pasture only (P &lt; 0.05). Carcass weights and dressing percentage were similar across all treatments. Feeding barley or soybeans on pasture increased backfat thickness (P &lt; 0.05), but the pasture-only cattle had greater loin eye area (P &lt; 0.05). Pasture-only beef had more thaw drip loss (P &lt; 0.05) and less cooking drip loss (P &lt; 0.05) than TMR-fed beef. Evaporative cooking losses were greater in beef from unsupplemented pasture than from barley- or soybean-supplemented pasture (P &lt; 0.05). Pasture-only beef had 25% more polyunsaturated fatty acids and 37% greater cis-9, trans-11 conjugated linoleic acid (CLA) concentrations in longisimus thoracis (l. thoracis) tissue than TMR-fed beef (P &lt; 0.05). Among pasture-fed cattle, soybean supplementation increased C18:2 concentration by 34% (P &lt; 0.05), while barley reduced C18:3 concentration by 8% (P &lt; 0.05) in l. thoracis tissue. Soybean supplementation increased cis-9, trans-11 CLA concentration by 30% (P &lt; 0.05) in l. thoracis tissue over pasture only. Beef finished on pasture has higher levels of beneficial fatty acids than TMR-fed beef, with few differences in meat quality. Supplementation on pasture improves animal performance, but barley has some negative effects on beneficial fatty acids in meat. Key words: Pasture, steers, fatty acids, conjugated linoleic acid

Effect of forage type and proportion of concentrate in the diet on milk fatty acid composition in cows given sunflower oil and fish oil

AbstractBased on the potential benefits ofcis-9,trans-11 conjugated linoleic acid (CLA) for human health there is a need to develop effective strategies for enhancing milk fat CLA concentrations. In this experiment, the effect of forage type and level of concentrate in the diet on milk fatty acid composition was examined in cows given a mixture of fish oil and sunflower oil. Four late lactation Holstein-British Friesian cows were used in a 4 × 4 Latin-square experiment with a 2 × 2 factorial arrangement of treatments and 21-day experimental periods. Treatments consisted of grass (G) or maize (M) silage supplemented with low (L) or high (H) levels of concentrates (65 : 35 and 35 : 65; forage : concentrate ratio, on a dry matter (DM) basis, respectively) offered as a total mixed ration at a restricted level of intake (20 kg DM per day). Lipid supplements (30 g/kg DM) containing fish oil and sunflower oil (2 : 3 w/w) were offered during the last 14 days of each experimental period. Treatments had no effect on total DM intake, milk yield, milk constituent output or milk fat content, but milk protein concentrations were lower (P&lt; 0.05) for G than M diets (mean 43.0 and 47.3 g/kg, respectively). Compared with grass silage, milk fat contained higher (P&lt; 0.05) amounts of C12:0, C14:0, trans C18:1and long chain ≥ C20 (n-3) polyunsaturated fatty acids (PUFA) and lower (P&lt; 0.05) levels of C18:0and trans C18:2when maize silage was offered. Increases in the proportion of concentrate in the diet elevated (P&lt; 0.05) C18:2(n-6) and long chain ≥ C20 (n-3) PUFA content, but reduced (P&lt; 0.05) the amount of C18:3(n-3). Concentrations oftrans-11 C18:1in milk were independent of forage type, but tended (P&lt; 0.10) to be lower for high concentrate diets (mean 7.2 and 4.0 g/100 g fatty acids, for L and H respectively). Concentrations oftrans-10 C18:1were higher (P&lt; 0.05) in milk from maize compared with grass silage (mean 10.3 and 4.1 g/100 g fatty acids, respectively) and increased in response to high levels of concentrates in the diet (mean 4.1 and 10.3 g/100 g fatty acids, for L and H, respectively). Forage type had no effect (P&gt; 0.05) on total milk conjugated linoleic acid (CLA) (2.7 and 2.8 g/100 g fatty acids, for M and G, respectively) orcis-9,trans-11 CLA content (2.2 and 2.4 g/100 g fatty acids). Feeding high concentrate diets tended (P&lt; 0.10) to decrease total CLA (3.3 and 2.2 g/100 g fatty acids, for L and H, respectively) andcis-9,trans-11 CLA (2.9 and 1.7 g/100 g fatty acids) concentrations and increase milktrans-9,cis-11 CLA andtrans-10,cis-12 CLA content. In conclusion, the basal diet is an important determinant of milk fatty acid composition when a supplement of fish oil and sunflower oil is given.

Conjugated Linoleic Acid Increases in Milk When Cows Fed Fish Meal and Extruded Soybeans for an Extended Period of Time

The objective of this study was to determine the effect of feeding a conjugated linoleic acid (CLA) stimulating diet for an extended period of time on milk cis-9, trans-11 CLA and vaccenic acid (VA) concentrations. Twenty cows (16 Holstein and 4 Brown Swiss) were divided into 2 groups (n = 10 per treatment) for a 10-wk study. Cows in group 1 were fed a traditional corn-soybean-basal diet (control), while those in group 2 were fed a blend of 0.5% fish oil from fish meal and 2% soybean oil from extruded soybeans (FMESB) to achieve higher milk fat cis-9, trans-11 CLA and VA. Diets were formulated to contain 18% CP and were composed (dry matter basis) of 50% concentrate mix, 25% corn silage, and 25% alfalfa hay. Dry matter intake was not affected by diet. Milk production increased in cows fed the FMESB diet. Milk fat and milk protein percentages decreased with the FMESB diet; however, milk fat and protein yields were not affected by treatments. Milk fat cis-9, trans-11 CLA and VA concentration (g/100 of fatty acids) and yield (g/d) were 2.5-fold greater for cows fed the FMESB diet over the 10 wk of fat supplementation. For cows fed the FMESB diet, contents of milk fat cis-9, trans-11 CLA and VA gradually increased from the first week of fat supplementation, reached the highest concentrations in wk 3, then gradually decreased during wk 4 and 5 and then remained relatively constant until wk 10. The concentration of cis-9, trans-11 CLA and VA from the control diet was relatively constant over the 10 wk of fat supplementation. Concentrations of cis-9, trans-11 CLA and VA in milk fat can be increased within a week by feeding a blend of fish meal and extruded soybeans, and that increase remains relatively constant after wk 5 of fat supplementation.

Endogenous synthesis of cis-9, trans-11 conjugated linoleic acid in dairy cows fed fresh pasture.

New Zealand Holstein-Friesian cows (n = 4) were used to quantify the importance of endogenous synthesis of cis-9, trans-11 conjugated linoleic acid (CLA) via Delta(9)-desaturase in cows fed a fresh pasture diet. The experiment was a 4 x 4 Latin square design with treatments arranged in a 2 x 2 factorial. Treatments lasted 4 d and were pasture only, pasture plus sterculic oil, pasture plus sunflower oil, and pasture plus sunflower oil plus sterculic oil. Abomasal infusion of sterculic oil inhibited Delta(9)-desaturase and decreased the concentration of cis-9, trans-11 CLA in milk fat by 70%. Using the changes in cis-9 10:1, cis-9 12:1 and cis-9 14:1 to correct for incomplete inhibition of Delta(9)-desaturase, a minimum estimate of 91% of cis-9, trans-11 CLA in milk fat was produced endogenously in cows fed fresh pasture. Dietary supplementation of a pasture diet with sunflower oil increased the proportion of long chain fatty acids in milk fat; however, the increase in vaccenic acid concentration was small (18%) and there was no increase in cis-9, trans-11 CLA concentration. Overall, results show that endogenous synthesis is responsible for more than 91% of the cis-9, trans-11 CLA secreted in milk fat of cows fed fresh pasture. However, the failure of plant oil supplements to increase the concentration of cis-9, trans-11 CLA in milk fat from pasture-fed cows requires further investigation.

Factors affecting conjugated linoleic acid and trans-C18:1 fatty acid production by mixed ruminal bacteria.

The objective of this study was to identify environmental factors that influence conjugated linoleic acid (CLA) and trans-C18:1 fatty acid production by mixed ruminal bacteria. Ruminal contents were collected from a 600-kg ruminally fistulated Hereford steer maintained on pasture. Mixed ruminal bacteria were obtained by differential centrifugation under anaerobic conditions and added to a basal medium that contained a commercial emulsified preparation of soybean oil and a mixture of soluble carbohydrates (cellobiose, glucose, maltose, and xylose). Culture samples were collected from batch culture incubations at 0, 2, 4, 6, 8, 12, 24, 26, 28, 30, 32, and 48 h. Continuous culture incubations were conducted at dilution rates of 0.05 and 0.10 h(-1) with extracellular pH values of 5.5 and 6.5, and 0.5 and 1.0 g/L of mixed soluble carbohydrates. Culture samples were obtained from the culture vessel once steady-state conditions had been achieved. In batch culture, trans-C18:1 concentrations increased over time and reached a maximum at 48 h. Little CLA was produced during the first 8 h, but cis-9, trans-11 CLA concentrations remained high between 24 and 30 h. When mixed ruminal bacteria were maintained in continuous culture on 0.5 g/L of mixed soluble carbohydrates, concentrations of trans-C18:1 and cis-9, trans-11 CLA were reduced (P < 0.05) at a dilution rate of 0.05 h(-1) and an extracellular pH of 5.5. Similar effects were also observed when 1.0 g/L of mixed soluble carbohydrates was used. When extracellular pH was lowered to 5.0, neither trans-C18:1 or CLA isomers were detected. In conclusion, our results suggest that culture pH appears to have the most influence on the production of trans-C18:1 and CLA isomers by mixed ruminal bacteria.

Independent effects of dietary linoleic and linolenic fatty acids on the conjugated linoleic acid content of cows’ milk

AbstractIt may be desirable to increase the level of conjugated linoleic acid (CLA) in milk as a health benefit in human nutrition. The purpose of this work was to separate the effects of linoleic and linolenic acids on CLA production in dairy cows and to determine to what extent endogenous synthesis contributes to cis-9, trans-11 CLA concentration in milk fat. Eight lactating cows and four non-lactating duodenal fistulated cows were used in a 4 ✕ 4 Latin-square design. All cows received a basal diet of grass silage that was supplemented with one of four concentrates, which were designed to differ in their linoleic and linolenic acid contents. The oil components of the concentrates were produced from mixtures of olive, linseed, rape, soya and sunflower oils to produce the four treatments: low linoleic/ low linolenic acid (LL), low linoleic/high linolenic acid (LH), high linoleic/low linolenic acid (HL) and high linoleic/ high linolenic acid (HH). Milk cis-9, trans-11 CLA contents were 0·8, 0·9, 0·9 and 1·1 g/100 g fatty acid methyl esters (P &lt; 0·05) and yields were 5, 7, 7 and 8 g/day (P &lt; 0·05) for the LL, LH, HL and HH treatments, respectively. The yields of trans-C18:1fatty acids in milk were 19, 22, 21 and 23 g/day (P &lt; 0·05), respectively. Taking the data for the cis-9, trans-11 CLA content and flow of duodenal fluid from the fistulated cows and representing this in terms of dietary intake by the lactating animals, the amounts of cis-9, trans-11 CLA produced in the rumen were calculated to be 0·8, 0·9, 1·2 and 1·1 g/day (P &lt; 0·05) and for trans-C18:1fatty acids 58, 58, 66 and 69 g/day (P &lt; 0·05). Increasing linoleic and/or linolenic acids in the diet can increase the cis-9, trans-11 CLA content of cows’ milk. Only diets high in linoleic acid increased cis-9, trans-11 CLA production in the rumen. On all four diets, more than 80% of cis-9, trans-11 CLA in milk was produced endogenously by Δ9-desaturase from trans-11 C18:1in the mammary gland. Cows on the same diet have different milk fat cis-9, trans-11 CLA concentrations that may be partially explained by differences in Δ9-desaturase activity between cows. Increasing the activity of Δ9-desaturase in the mammary gland may offer greater potential for enhancing the cis-9, trans-11 CLA content of milk fat than increasing cis-9, trans-11 CLA production in the rumen.