Ruminal Biohydrogenation Of Fatty Acids Research Articles

Enhanced oxidative stability of meat by including tannin-rich leaves of woody plants in goat diet.

ObjectiveThe aim of this study was to evaluate the effect of dietary incorporation of tannin-rich woody species on meat oxidative stability, carcass traits and meat quality in goats.MethodsTwo tannin-rich species were tested using a three-treatments feeding trial, where treatments consisted of: Larrea divaricata and Acacia aroma both at 12.5% in dry matter basis of the diet and a control diet (alfalfa hay). All feeding diets were iso-protein and iso-energy. Carcass conformation, carcass compactness, carcass fatness and subcutaneous fat deposition were evaluated. Intake, liveweigh, Longissimus thoracis et lumborum muscles of goats were analyzed in order to evaluate quality parameters such as pH value, instrumental color evaluation, water holding capacity, total phenolic content, antioxidant activity, meat oxidative stability and fatty acid profiles in meat.ResultsFeed intake, liveweight gain, carcass, and meat traits did not differ among treatments. Changes in meat lipid profile among treatments were observed for oleic and elaidic acid contents. Meat total phenolic content and antioxidant activity did not differ among treatments; although, meat oxidative status after storage at room temperature, as well as under refrigerated and frozen conditions were different between control and both supplemented groups.ConclusionThe inclusion of Acacia aroma and Larrea divaricata leaves in goat diet enhanced meat oxidative stability. Modulation of the ruminal biohydrogenation of fatty acids produced by condensed tannins of these plant species need to be further investigated.

Evaluation of a Rumen Protected Omega 3 Supplement for Reproduction in Dairy Cows as Determined in Three Large Herd Field Trials

Omega 3 fatty acids have been shown to support reproductive performance in dairy cows, but large amounts are needed due to ruminal biohydrogenation of fatty acids. Three long-term large herd feeding trials, two with heifers and one with mature cows, were conducted to evaluate the effects of adding a rumen protected fish oil supplement on reproduction. In all trials, there were over 1000 animals eligible to be bred/treatment. Cows received a ration with 40 g of a rumen protected fish oil supplement (Salmate® the Ballard Group, Cincinnati Ohio) during the test periods, while controls received no supplementation. The additive was provided to the test cows from the onset of lactation until 90 ± 5 days in milk. Cows entering the pen on or after the first day of the study were included in the dataset. Individual cow records were compiled by Dairy Herd Improvement Association (National DHIA, Verona WI USA) were compared to records from the same time period the year prior. Results were compared using ANOVA for single mean variables and Fisher’s exact test for proportional data. In trials 1 and 2 involving heifers, pregnancy rates were improved (22.4% vs 14.8% in trial 1 and 22.0 vs 17.8% in trial 2, (p P P P > 0.05). However, early embryonic abortion rates were 16.8 during the control period, as compared to 4.7% during the test feeding period. The rumen protected omega 3 fatty acid supplement was found to be of benefit to reproductive performance in dairy cows. The supplement may improve the percentage of cattle bred that become pregnant in herds where this metric is low. Early term abortions may be lowered, particularly in herds where this is high.

Garlic oil reduces ruminal fatty acid biohydrogenation in vitro

Nutritional policies recommend that animal products should be made to contain more polyunsaturated FA, especially n‐3 FA. This means finding ways to limit ruminal lipolysis and/or biohydrogenation. In pursuit of this goal, we performed an in vitro study to test the ability of four feed additives, typically used for other purposes, to reduce ruminal biohydrogenation of a linolenic acid‐rich substrate. The four additives tested were cinnamon essential oil, brown algae (Ascophyllum nodosum), synthetic vitamin E, and garlic essential oil. The first three additives had no effect on ruminal fermentation and biohydrogenation. Garlic essential oil led to a decrease in methane production (P < 0.001), an increase in propionate (P = 0.002) and butyrate (P < 0.001) production at the expense of acetate (P < 0.001), and a decrease in biohydrogenation evaluated by the disappearance of linolenic acid (P = 0.083) and linoleic acid (P = 0.008). Stearic acid proportion in FA decreased, while biohydrogenation intermediates such as C18:2t11c15 and vaccenic acid proportion increased (P < 0.001).Practical applications: Garlic essential oil emerges as a promising additive for decreasing biohydrogenation, but its efficiency needs to be confirmed in vivo in different dietary conditions, and possible side effects of the incorporation of garlic oil in diets will have to be evaluated.When garlic oil is added to a control substrate in an incubator containing rumen contents, biohydrogenation of linolenic acid (18:3c9c12c15) is reduced, and proportion of different unsaturated FA increases at the expense of stearic acid (18:0) which decreases from 71.8 to 62.2%. If this is confirmed in vivo, this may contribute to reduce saturated FA in milk and meat from ruminants.

Effects of Feeding Garlic and Juniper Berry Essential Oils on Milk Fatty Acid Composition of Dairy Cows.

Essential oils (EOs) from plant extracts have been reported to have an antibacterial activity against gram-negative and gram-positive bacteria. Several of the gram-positive bacteria are involved in ruminal biohydrogenation of fatty acids (FAs), thus suggesting that feeding EOs could lower biohydrogenation of FA because of a decrease in the number of bacteria involved in that process. As a result, milk FA profiles are expected to be modified. In addition, monensin was approved as an antibiotic to be fed in dairy cattle, and it was reported that dairy cows supplemented with monensin produced milk containing higher concentration of 18:1 t10 and 18:1 t11. The objective of this study was to evaluate the effects of two EOs (garlic and juniper berry oils) and monensin on FA profiles of milk fat. Four ruminally fistulated Holstein dairy cows were used in a 4 × 4 Latin square experiment. Cows were fed for ad libitum intake a total mixed ration without supplementation (control), or supplemented with monensin (330 mg/head per day), garlic oil (5 g/head per day), or juniper berry oil (2 g/head per day). The FA composition of saturated, monounsaturated, or polyunsaturated was not affected by supplementation of EO and monensin. However, proportion of conjugated linoleic acid trans 10, cis 12 (CLA t10, c12) was higher (P < 0.05) for cows fed EO or monensin than for control cows. Supplementation of monensin increased (P < 0.05) the proportion of total trans FA compared with the control. These results indicate that supplementation of the dairy cow diet with garlic or juniper berry EO or monensin had the potential to increase the proportion of CLA t10, c12 in milk fat with minimal overall effects on FA of milk fat. The results also confirm the increase of 18:1 t10 in milk fat by feeding monensin to dairy cows.

Effects of sucrose and sunflower oil addition to diet of Saanen dairy goats on performance and milk fatty acid profile

The current study was conducted to examine the effect of dietary sucrose with or without sunflower oil on dairy goat performance, ruminal fermentation and milk fatty acid (FA) profile. Sixteen Saanen goats were assigned to the experimental diets control (basal diet without added oil and sucrose (CON), the basal diet supplemented with sunflower oil (SO, 3.7% of diet DM), sucrose (SU, 5.2% of diet DM) and sunflower oil plus sucrose (SO+SU, 3.7% and 5.2% of diet DM, respectively). Sucrose and sunflower oil replaced barley grain in the diets. Milk production and composition were analyzed on days 18, 36 and 54 on treatments, and ruminal fermentation parameters and milk FA profile on days 18 and 54. Dry matter intake, milk fat, protein and lactose concentrations were not affected by treatments. The SU increased (P<0.1) milk yield compared with CON whereas the SU and SO led to higher (P<0.01) 4% fat-corrected milk yield. The SO and SU diets increased (P<0.1) the milk lactose yield more than the CON diet. We observed a higher (P<0.01) content of ruminal acetate in the CON diet, and also higher (P<0.05) valerate content with the SU and SO+SU diets compared with the CON diet. Feeding SU and SO+SU tended to decrease (P<0.05) ruminal pH, yet goats fed SU had the highest (P<0.01) ruminal propionate concentration. There was no effect of diet on ruminal butyrate, isovalerate and ammonia-N concentrations. The acetate:propionate ratio substantially decreased (P<0.05) with the SU compared with the CON and SO+SU, and did not change with SO diet. Feeding sunflower oil increased (P<0.01) plasma triglyceride and cholesterol concentrations compared with feeding the CON and SU diets. The majority of fatty acids measured were not affected by inclusion of sucrose compared with the CON diet. The SO and SO+SU diets increased the proportion of total trans-C18:1, total CLA, and C18 family in milk fat compared to CON or SU diets. The current study implies that replacing barley grain with sucrose may improve milk yield and modify ruminal fermentation pattern in dairy goats. Moreover, sucrose did no alter ruminal fatty acid biohydrogenation pathways and following milk fatty acid composition when goats were fed with a combination of unsaturated fat and sugar.

Liver x receptors stimulate lipogenesis in bovine mammary epithelial cell culture but do not appear to be involved in diet-induced milk fat depression in cows.

Milk fat synthesis of ruminants can be inhibited by intermediates of ruminal fatty acid biohydrogenation including trans‐10, cis‐12 conjugated linoleic acid (CLA). These biohydrogenation intermediates signal a coordinated downregulation of genes involved in mammary FA synthesis, transport, and esterification. We have previously reported decreased mammary expression of sterol response element‐binding protein 1 (SREBP1), SREBP1‐activating proteins, and thyroid hormone‐responsive spot 14 (S14) in the cow during diet‐induced milk fat depression (MFD), and treatment with trans‐10, cis‐12 CLA. Liver x receptors (LXR) and retinoid x receptors (RXR) regulate lipogenesis and are known to bind polyunsaturated FA and LXR agonist increases lipid synthesis in mammary epithelial cell culture. The current studies investigated if biohydrogenation products of rumen origin inhibit mammary lipogenesis through LXR and/or RXR. Expression of LXRs was not different in lactating compared to nonlactating bovine mammary tissue, and expression of LXRs, RXRα, and selected LXR and RXR target genes was not changed in mammary tissue during diet‐induced or CLA‐induced MFD in the cow. In bovine mammary epithelial cell culture, LXR agonist stimulated lipogenesis and expression of LXRß, ATP‐binding cassette 1 (ABCA1), SREBP1c, and S14, but LXR activation did not overcome CLA inhibition of lipogenesis and downregulation of LXRß, SREBP1c, and S14 expression. Lastly, expression of the LXR‐regulated carbohydrate‐responsive element‐binding protein (ChREBP) was higher in lactating than nonlactating tissue and was decreased during CLA‐induced MFD. We conclude that changes in mammary LXR expression in dairy cows are not involved in MFD and that trans‐10, cis‐12 CLA inhibition of lipogenesis and diet‐induced MFD appears independent of direct LXR signaling.

Garlic derived compounds modify ruminal fatty acid biohydrogenation and induce shifts in the Butyrivibrio community in continuous-culture fermenters

Garlic essential oil contains a variety of fat soluble organosulfur compounds with antibacterial activity. Nevertheless, only recent studies have evaluated garlic oil and its constituents as modulators of ruminal processes. The present study was undertaken to evaluate the potential of diallyl disulfide (DDS) and propyl propane thiosulfinate (PTS) to modulate rumen biohydrogenation in vitro. Six continuous-culture fermenters, inoculated with rumen fluid from goats, were used in two replicated incubation runs of 12 days each. Two fermenters per run received either a control diet (without additive) or the same diet with 80μl/L of DDS or 200μl/L of PTS daily. At the end of each incubation run, samples of fermenter contents were taken for fatty acid analysis. The DDS addition resulted in lower (P=0.012) total saturated fatty acids (SFA) and higher monounsaturated fatty acids (MUFA; P=0.001) and polyunsaturated fatty acids (PUFA; P=0.018) contents as compared to the control. Increases in trans-10, cis-12 CLA (P=0.065), trans-10 18:1 (P<0.001) and vaccenic acid (VA; trans-11-18:1) (P=0.009) were also observed. Similar results were found for PTS addition, although significant differences with the control group were detected only for PUFA and trans-10 18:1 amounts. Additionally, 1mL of the fermenter contents was incubated in vitro with 0.167g/L of linoleic acid (cis-9, cis-12 18:2; LA) for 0, 1, 3, 6, 9 and 24h. Vaccenic acid and trans-10 18:1 accumulated to higher concentrations (P=0.054 at 9h and P=0.021 at 3h, respectively) when LA was incubated with the fermenter contents treated with DDS and PTS. Garlic derived compounds did not affect the amount of total bacteria (P=0.936) or abundances of Butyrivibrio proteoclasticus (P=0.693); although PTS increased the abundance of Butyrivibrio fibrisolvens (P=0.001), in comparison to the control and DDS treatments. Differences in the Butyrivibrio group structure were observed from the cluster analysis, which showed segregation for fermenters with garlic derived compounds from those without additives. It was concluded that adding DDS and PTS to the diet of fermenters modified the fatty acid of rumen contents, with potential health benefits of ruminant products. These changes in biohydrogenation appeared to be related to shifts within the Butyrivibrio bacterial community. In vivo studies are now required to confirm the potential of these compounds.

In vitro study of dietary factors affecting the biohydrogenation shift from trans-11 to trans-10 fatty acids in the rumen of dairy cows

On the basis of the isomer-specific effects of trans fatty acids (FA) on human health, and the detrimental effect of t10,c12-conjugated linoleic acid (CLA) on cows’ milk fat production, there is a need to identify factors that affect the shift from trans-11 to trans-10 pathway during ruminal biohydrogenation of FA. This experiment was conducted in vitro and aimed at separating the effects of the diet of the donor cows from those of the fermentative substrate, which is necessary to prevent this shift. A total of four dry Holstein dairy cows were used in a 4 × 4 Latin square design. They received 12 kg of dry matter per day of four diets based on maize silage during four successive periods: the control diet (22% starch, <3% fat); the high-starch diet, supplemented with wheat plus barley (35% starch, <3% crude fat); the sunflower oil diet, supplemented with 5% of sunflower oil (20% starch, 7.6% crude fat); and the high-starch plus oil diet (33% starch, 7.3% crude fat). Ruminal fluid of each donor cow was incubated for 5 h with four substrates having similar chemical composition to the diets, replacing sunflower oil by pure linoleic acid (LA). The efficiency of isomerisation of LA to CLA was the highest when rumen fluids from cows receiving dietary oil were incubated with added LA. The shift from trans-11 to trans-10 isomers was induced in vitro by high-starch diets and the addition of LA. Oil supplementation to the diet of the donor cows increased this shift. Conversely, the trans-10 isomer balance was always low when no LA was added to incubation cultures. These results showed that a large accumulation of trans-10 FA was only observed with an adapted microflora, as well as an addition of non-esterified LA to the incubation substrate.

Dietary molasses increases ruminal pH and enhances ruminal biohydrogenation during milk fat depression

Feeding high-concentrate diets has the potential to cause milk fat depression, but several studies have suggested that dietary sugar can increase milk fat yield. Two experiments were conducted to evaluate the ability of dietary molasses to prevent milk fat depression in the presence of a 65% concentrate diet. In trial 1, molasses replaced corn grain at 0, 2.5, or 5% of diet dry matter in diets fed to 12 second-lactation Holstein cows (134±37 d in milk) in a 3×3 Latin square design. Trial 1 demonstrated that replacing up to 5% of dietary dry matter from corn with molasses had positive effects on de novo fatty acid synthesis, increasing the yield of short- and medium-chain fatty acids during diet-induced milk fat depression. Increasing inclusion rate of molasses increased milk fat concentration, but decreased milk yield and milk protein yield. Trial 2 used 7 ruminally cannulated, multiparous, late-lactation Holstein cows (220±18 d in milk) to evaluate effects of dietary molasses on ruminal parameters and milk composition, and also to assess whether increased metabolizable protein supply would alter these responses. Cows were randomly assigned to a dietary treatment sequence in a crossover split plot design with 0 and 5% molasses diets. Dietary treatments were fed for 28 d, with 16 d for diet adaptation, and the final 12 d for 2 abomasal infusion periods in a crossover arrangement. Abomasal infusions of water or AA (5g of l-Met/d+15g of l-Lys-HCl/d+5g of l-His-HCl-H2O/d) were administered 3 times daily for 5 d, with 2 d between infusion periods. Administration of AA had no effect on concentration or yield of any milk components. Addition of molasses increased milk fat concentration (2.71 vs. 2.94±0.21%), but had no effect on yields of milk fat or protein. Dietary molasses decreased total volatile fatty acid concentration (141 vs. 133±4.6mM), decreased the molar proportion of propionate, and increased the molar proportion of butyrate in ruminal fluid. Molasses also increased ruminal pH (5.73 vs. 5.87±0.06), decreased the yield of trans-10 C18:1, and increased the yield of trans-11 C18:1 in milk fat. These data provide evidence that molasses may promote mammary de novo fatty acid synthesis in cows fed high-energy rations by moderating ruminal pH and altering ruminal fatty acid biohydrogenation pathways.

Influence of alpine forage either employed as donor cow's feed or as incubation substrate on in vitro ruminal fatty acid biohydrogenation

The effects of alpine grazing on ruminal fatty acid biohydrogenation were studied in vitro in comparison to different lowland controls, by (i) adapting a fistulated ruminal fluid donor cow to alpine pasture and (ii) by incubating alpine forages with the resulting ruminal fluid. The cow first received a grass–maize silage based diet in the lowlands. Subsequently, the cow grazed for 10weeks a species-rich alpine pasture at about 2000m elevation. This was followed by another lowland period on the mixed silage diet. Ruminal fluid was collected during the initial lowland period, after 2, 6, and 10weeks of alpine sojourn, and 2 and 6weeks after returning to the lowlands. Always 3.5h after collection, 24-h in vitro incubations with batch cultures were started. Incubations were done in triplicate with either alpine pasture hay, lowland ryegrass hay or a grass–maize silage mixture. Non-incubated rumen fluid and all incubation liquid samples were analysed for fatty acid composition. Contents of total phenols were about twice as high in forage of alpine compared to lowland forage. Incubations with ruminal fluid of alpine origin compared to lowland origin increased the apparent net production and the proportion in total fatty acids of vaccenic acid (18:1 trans-11) by more than 1.5 times (P<0.05).This happened across all incubated forages and indicated that alpine pasture may have an inhibitory effect on the last step of ruminal fatty acid biohydrogenation. Linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3) proportions of total fatty acids remained unaffected like also apparent stearic acid production. No clear influence of the type of forage incubated was observed, except for a higher 18:2n-6 disappearance rate during incubation with the mixed silage compared to the two hay types. Incubating the alpine hay resulted in a trend towards a lower 18:3n-3 disappearance rate during incubation. These results indicate that adapting the ruminal fluid donor cow for several weeks to different diets was more decisive for ruminal fatty acid biohydrogenation in vitro than the immediate effects of the different incubated forages. The present results provided no clear evidence which would help to explain the repeatedly described elevation of 18:3n-3 concentration in alpine milk fat. Different from that, indications explaining the extra conjugated linoleic acid were obtained.

Significance of phenolic compounds in tropical forages for the ruminal bypass of polyunsaturated fatty acids and the appearance of biohydrogenation intermediates as examined in vitro

The purpose of the present study was to assess the influence of phenol-rich tropical ruminant feeds on the extent of ruminal biohydrogenation (BH) of polyunsaturated fatty acids (PUFA). Samples of 27 tropical forages (mainly tree and shrub leaves), characterised by different phenolic profiles, were incubated in vitro (n = 4 replicates) with buffered rumen fluid for 24 h using the Hohenheim gas test method. Linseed oil was added as a rich source of PUFA. In the plants, total extractable phenols (TEP), non-tannin phenols, condensed tannins, and fatty acids were determined. After terminating incubation, the fatty acid profile present in fermentation fluid (total syringe content) was analysed by gas chromatography. The relationship between TEP and the disappearance of α-linolenic acid from the incubation fluid was negative (R2 = 0.48, P &lt; 0.001), indicating that TEP reduced the ruminal BH of this PUFA. Similarly, TEP were negatively related with the disappearances of linoleic acid (R2 = 0.52, P &lt; 0.001) and oleic acid (R2 = 0.58, P &lt; 0.001). The appearance of rumenic acid, an important conjugated linoleic acid isomer, was positively correlated with TEP (R2 = 0.30, P &lt; 0.01), while the opposite result was seen with stearic acid (R2 = 0.22, P &lt; 0.05). Leaves of avocado (Persea americana) were particularly interesting, because they changed the BH pattern at a moderate TEP content of 73 g/kg DM. It is concluded that, in the tropical feedstuffs investigated, TEP have an impact on ruminal fatty acid BH and are associated with an increased bypass of PUFA and the generation of conjugated linoleic acid.

Methods of Emulsifying Linoleic Acid in Biohydrogenation Studies In Vitro May Bias the Resulting Fatty Acid Profiles

The effects of three emulsifying methods on ruminal fatty acid biohydrogenation (BH) in vitro were compared. Using a static in-vitro gas test system, four replicates of each treatment were incubated in buffered ruminal fluid. Hemicellulose (300 mg dry matter) was supplemented either with or without linoleic acid (9c12c-18:2, 5% in diet dry matter) and incubated for 4 and 24 h. Three methods of emulsifying 9c12c-18:2 were tested: (1) ethanol, (2) Tween 80, and (3) sonication. The products were then compared to non-emulsified 9c12c-18:2. Out of the three emulsifying methods tested, ethanol and sonication resulted in stable 9c12c-18:2 emulsions, indicating good 9c12c-18:2 distribution, while the Tween 80 emulsion was less stable. BH was strongly inhibited by treating 9c12c-18:2 with ethanol and sonication at different steps of the BH-pathway, resulting in changed concentrations of certain BH intermediates. The fatty acid profile generated from the major BH-pathways of 9c12c-18:2 with Tween 80 was comparable to that without emulsification after 24 h of incubation. We conclude that it is not recommended to emulsify lipids before incubating them in vitro when investigating fatty acid BH. If emulsification of 9c12c-18:2 is necessary, Tween 80 seems to be the method that interferes least with BH.

Effects of oil source and fish oil addition on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets

Four Hereford steers (500 +/- 4.5 kg of BW) cannulated in the proximal duodenum were used to evaluate the effects of vegetable oil source or fish oil quantity on ruminal biohydrogenation (BH) and CLA outflow. Steers were fed 1 of 4 treatment diets in a 2 x 2 factorial arrangement of treatments (oil source: canola vs. corn oil; fish oil quantity: 0 or 1%) in a 4 x 4 Latin square design. The remainder of the diet included chopped bermudagrass hay, dry-rolled corn, and protein/mineral supplement. Duodenal samples were collected for 4 d after 11-d diet adaptation periods. Data were analyzed with animal, period, oil source, fish oil, and 2-way interaction among oil source and fish oil quantity in the model. All interactions among oil source and fish oil inclusion were nonsignificant with the exception of trans-11 vaccenic acid (TVA) and trans-9 octadecenoic acid. Intake and duodenal flow of total long-chain fatty acids did not differ between treatments. Apparent ruminal DM digestibility was not altered by oil source or fish oil inclusion. Apparent ruminal digestion of fatty acids did not differ among oil sources but was increased (P = 0.03) with fish oil supplementation. Ruminal BH of oleic and linolenic acids was increased (P = 0.01) for diets containing supplemental canola oil compared with corn oil. Ruminal BH of linoleic acid was greater (P = 0.01) for diets containing supplemental corn oil compared with canola oil. Fish oil addition reduced (P = 0.01) oleic acid BH but did not alter (P > 0.26) linoleic or linolenic acid BH. Duodenal flow of palmitic acid was greater (P = 0.05) for steers supplemented with corn oil compared with canola oil. Fish oil inclusion in the diet increased (P = 0.01) flow of n-3 fatty acids (eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid), trans-10 octadecenoic acid, trans-12 octadecenoic acid, and cis-9, trans-11 CLA. Trans-9 octadecenoic acid and TVA flows to the duodenum were increased (P = 0.01) when fish oil was included in the canola oil-supplemented diet; however, no changes were observed when fish oil was included in the corn oil-supplemented diet (P of interaction = 0.06 and 0.08). Fish oil inclusion increased the outflow of n-3 fatty acids, trans-10 octadecenoic acid, and the majority of CLA isomers including cis-9, trans-11. These results suggest that fish oil addition alters ruminal formation of BH intermediates that is dependent on oil source supplemented in the diet.

Effects of supplemental fat source on nutrient digestion and ruminal fermentation in steers1

Five Holstein steers (235 kg of BW) fitted with ruminal, duodenal, and ileal cannulas were used in a 5 x 5 Latin square design experiment to determine the effects of supplemental fat source on site and extent of nutrient digestion and ruminal fermentation. Treatments were diets based on steam-flaked corn containing no supplemental fat (control) or 4% (DM basis) supplemental fat as tallow, dried full-fat corn germ (corn germ), corn oil, or flax oil. Fat supplementation decreased (P < 0.08) ruminal starch digestion but increased (P < 0.03) small intestinal starch digestion as a percentage of intake. Feeding corn germ decreased (P < 0.09) ruminal starch digestion and increased (P < 0.03) large intestinal starch digestion compared with steers fed corn oil. Large intestinal starch digestion was less (P < 0.04), and ruminal NDF digestion was greater (P < 0.09) for steers fed tallow compared with steers fed other fat sources. Small intestinal (P < 0.08) and total tract NDF digestibilities were greater (P < 0.02) for steers fed corn germ than for those fed corn oil. Feeding tallow increased total ruminal VFA (P < 0.03) and NH(3) (P < 0.07) concentrations compared with steers fed the other fat sources. Feeding corn germ led to a greater (P < 0.02) rate of ruminal liquid outflow compared with corn oil. A diet x hour interaction (P < 0.04) occurred for ruminal pH, with steers fed corn oil having the greatest ruminal pH 18 h after feeding, without differences at other time points. Fat supplementation increased (P < 0.09) ruminal concentrations of Fusobacterium necrophorum. Duodenal flow of C18:3n-3 was greater (P < 0.01) for steers fed flax oil compared with those fed corn oil. Feeding corn germ led to less (P < 0.01) ruminal biohydrogenation of fatty acids compared with corn oil. Steers fed tallow had greater small intestinal digestibility of C14:0 (P < 0.02) and C16:1 (P < 0.04) than steers fed the other fat sources. Fat supplementation decreased (P < 0.06) small intestinal digestibility of C18:0. Feeding corn germ decreased (P < 0.10) small intestinal digestibility of C18:1 compared with corn oil. It appears that source of supplemental fat can affect the site and extent of fatty acid and nutrient digestion in steers fed diets based on steam-flaked corn.

Australian plants with potential to inhibit bacteria and processes involved in ruminal biohydrogenation of fatty acids

Conjugated linoleic acids (CLA) are health-promoting fatty acids found in foods derived from ruminant products that are formed in the rumen during bacterial biohydrogenation of linoleic acid (LA). Although selective antimicrobials might increase CLA production by manipulation of ruminal microflora, feeding of antibiotic growth promoters to livestock is declining due to fears of development of antibiotic resistance in human pathogens. This has initiated a search for alternatives, including plants containing bioactive compounds, which can have similar positive effects on ruminal microflora, but without negative impact on animal and human health. In this study we investigated effects of natural compounds in Australian plants on the bacteria and processes involved in ruminal biohydrogenation. Ethanolic extracts and essential oils were obtained from 91 Australian plants collected during 2004/2005 in Western Australia. Minimal Inhibitory Concentrations for the main bacterial species involved in rumen biohydrogenation were established using an agar dilution method, and effects of selected candidates on LA biohydrogenation was examined using an in vitro system with a mixed rumen bacterial population. A wide range of the plant extracts had selective inhibitory effect towards Clostridium proteoclasticum (which forms stearate from LA) without affecting Butyrivibrio fibrisolvens (which forms CLA and vaccenic acid, but not stearate). However, only a few plants, including Acacia iteaphylla and Kennedia eximia, inhibited LA metabolism or stearate formation in the mixed bacterial community in vitro. Further experiments are needed to investigate effects of selected candidates on CLA production in vivo.

Effects of preconditioning and extrusion of linseed on the ruminal biohydrogenation of fatty acids. 2. In vitro and in situ studies

The extent and/or intermediates of ruminal biohydrogenation (BH) of fatty acids (FA) were investigated in vitro and in situ using a raw, pre-conditioned or extruded blend of linseed and wheat bran (70:30). The duration of in vitro incubations were 2, 4, 8, 16 and 24 h, with 5 replicates. In situ studies used 3 dry ruminally fistulated Holstein cows in a 3 × 3 Latin square design, with 3 weeks adaptation to the linseed form. The diet contained 20% (DM basis) of the linseed based blend. The duration of in situ incubations were 2, 4, 8, 16, 24 and 48 h. BH was much slower in situ than in vitro, resulting in a much lower effective disappearance of C18:2 and C18:3. Moreover, the in situ technique suggested that the technological pre-treatment of linseed did not affect C18:2 and C18:3 rate of BH, whereas reduced rates were observed in vitro. After 8 h of in vitro incubation and onwards, proportions of cis-9,trans-11C18:2 were the highest with extruded linseed. The BH of FA from linseed resulted in the appearance of great proportions of trans-10+11 to trans-16C18:1 intermediates. Extrusion increased the proportions oftrans-10+11C18:1 both in vitro and in situ and proportions or trans-C18:1 were higher in situ than in vitro. Compared to previous in vivo results with the same material, the in situ method provided poor estimates of BH rates and intermediates. biohydrogenation / linseed / preconditioning / extrusion / in vitro / in situ

Effects of preconditioning and extrusion of linseed on the ruminal biohydrogenation of fatty acids. 1. In vivo studies

The extent and intermediates of ruminal biohydrogenation (BH) of fatty acids (FA) from a blend of linseed and wheat bran (70:30) were investigated in the rumen fluid, rumen particle phase and duodenal flow. The blend was ground through a 3 mm screen and used raw or extruded, or was ground through a 6 mm screen and preconditioned. Three dry Holstein cows fitted with ruminal and duodenal cannulas were used in a 3 × 3 Latin square design, with 18 days adaptation. The diet contained 20% (DM basis) of the linseed based blend. Twelve samples taken over 3 days were composited for analysis of rumen fluid, rumen particle phase and duodenal flow. The BH of FA from linseed resulted in the appearance of a great number of C18:1 intermediates, among which trans-10+11 to trans-16C18:1 were the most abundant. The proportion of cis-9,trans-11C18:2 was low. Preconditioning coarsely ground linseed resulted in a lower extent of C18:2 and C18:3 BH, and lower proportions of trans-12 to trans-16C18:1 intermediates than extrusion or a lack of processing of finely ground linseed. On the contrary, extrusion did not affect the extent of BH and had no significant effect on the proportions of trans-C18:1 intermediates, but increased the proportion of cis-9,trans-11C18:2 in both rumen phases. Different digesta types resulted in different estimates of BH. The extent of BH and the proportions of trans-C18:1 intermediates were lower in the rumen particle phase and higher in the rumen fluid than in the duodenum. Moreover, interactions between digesta type and treatment of linseed were observed.

Fat Supplements Affect Fractional Rates of Ruminal Fatty Acid Biohydrogenation and Passage in Dairy Cows

Rates of fatty acid biohydrogenation and passage were determined for fat supplements varying in saturation using lactating dairy cows. First-order fractional passage rates were determined by dividing the duodenal flux of fatty acids by their respective ruminal pool sizes. The determination of rates of biohydrogenation required the development of a model to account for the transfer of fatty acids among pools. Ruminally and duodenally cannulated multiparous Holstein cows (n = 8) were used in a replicated 4 x 4 Latin square design with 21-d periods. Treatments were control and a linear substitution of 25 g/kg supplemented fatty acids varying in saturation as follows: saturated (prilled hydrogenated free fatty acids), intermediate mix of saturated and unsaturated (calcium soaps of long-chain fatty acids), and partially unsaturated fatty acids. Passage rates of 16:0, 18:0, and total 18-carbon fatty acids were linearly decreased with increasing unsaturated fatty acids and the trans-18:1 fractional passage rate was quadratically affected with a maximum for the intermediate treatment. Increasing unsaturated fatty acids increased the extent of 18:2 and 18:3 biohydrogenation and decreased the extent of 18:1 and trans-18:1 biohydrogenation. Calcium salts did not protect PUFA from ruminal biohydrogenation despite a mean ruminal pH of 6.0, and unsaturated fatty acids decreased ruminal biohydrogenation of trans-18:1, resulting in increased duodenal flow of these fatty acids. The model allows a mechanistic description of ruminal biohydrogenation and determination of the extent of 18:1 biohydrogenation.

In situ ruminal biohydrogenation of fatty acids from extruded soybeans: effects of dietary adaptation and of mixing with lecithin or wheat straw

Kinetics and intermediates of biohydrogenation of fatty acids were investigated in situ using extruded soybeans, a blend of extruded soybeans and lecithin (99:1), or a blend of extruded soybeans plus wheat straw (66:34). Two dry dairy cows received successively a diet with added palmitic acid and a diet with added extruded soybeans, and assays were completed after a 3-week adaptation to each diet. Adaptation of the cows to dietary polyunsaturated fatty acids suppressed the lag time before the beginning of biohydrogenation. Adaptation of cows, and mixing straw with soybeans, increased the rate of biohydrogenation of C18:2 and C18:3, resulting in less C18:2 and C18:3, and more trans C18:1 and C18:0 in the in situ bags. Lecithin did not affect the kinetics of biohydrogenation or the profile of fatty acids in the in situ bags. Differences in the rate of biohydrogenation, and profile of residual fatty acids in the bags were observed between the two cows. Even with a mixture of soybeans and straw in cows receiving dietary polyunsaturated fatty acids, biohydrogenation was slower and resulted in higher proportions of trans-C18:1 than expected from results of literature in vivo. Results show that the biohydrogenation in situ is slow, highly dependent on experimental conditions, and that the use of several cows, adapted to the test fat source before the assay is initiated, is necessary in order to obtain a reliable estimate of kinetics parameters.

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.