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PubMed1996

Fatty acid digestion in lactating dairy cows fed fats varying in degree of saturation and different fiber sources.

Six cannulated cows were assigned to six treatments in a 6 x 6 Latin square design to evaluate the effects of fat saturation and amount and source of effective fiber on fatty acid metabolism. Cows were fed a control diet with no added fat or diets with 5% added fat from saturated tallow, tallow, or animal-vegetable fat; the diets with animal-vegetable fat had three percentages of effective fiber: 40% forage, 40% forage plus 20% soyhulls, or 60% forage. Cows fed diets supplemented with fat tended to have more disappearance of total fatty acids in the rumen than did those fed the control diet. Disappearance of fatty acids from the rumen, especially C16 and C18, was higher for cows fed the low fiber diet. The apparent digestibility of fatty acids in the small intestine was higher for cows fed the control diet than for those fed supplemental fat. Apparent digestibility also was reduced as fat saturation increased, primarily because of saturated tallow. Digestibility of C18:1 in saturated tallow was reduced, apparently in association with other saturated fatty acids. Fiber source had no effects on apparent intestinal digestibility of fatty acids. Concentrations of C18:0 and C18:1 in milk fat increased as the degree of fat saturation decreased, reflecting higher unsaturated C18 intake and ruminal biohydrogenation of polyunsaturated C18 fatty acids.

Animal Feed↗

PubMed1996

Butylsoyamide increases unsaturation of fatty acids in plasma and milk of lactating dairy cows.

This study was designed to determine whether dietary butylsoyamide increased unsaturation of fatty acids in milk of lactating dairy cows. Nine Holstein cows were fed three diets in a 3 x 3 Latin square design, replicated three times. One diet was a control with no added fat, and the other two diets were supplemented (3.5% of the DM) with either soybean oil or butylsoyamide. Milk yields and DMI were similar for the three diets. Milk fat percentage and FCM were reduced by soybean oil, but not by butylsoyamide. Milk protein yield was reduced when butylsoyamide was fed, and milk fat yield was reduced when soybean oil was fed. The soybean oil supplement disrupted ruminal fermentation, causing total VFA and acetate concentrations to decline; the butylsoyamide supplement had no effect on ruminal VFA. The proportion of linoleic acid in plasma fatty acids was similar with the control (54.3%) and soybean oil (52.0%) diets but was higher with butylsoyamide (59.0%). Linoleic acid concentration in milk fat averaged 3.60, 4.77, and 6.28% for the control, soybean oil, and butylsoyamide diets, respectively. Conversion of soybean oil to butylsoyamide protected unsaturated fatty acids from ruminal biohydrogenation, causing linoleic acid to increase in the plasma and milk of dairy cows.

Acetates↗

PubMed1997

Effects of heat treatment and physical processing of cottonseed on nutrient digestibility and production performance by lactating cows.

Four primiparous Holstein cows were used in an experiment with a 5 x 4 Youden square design. The effects of heat processing and particle size of cottonseed used in the diets of dairy cows were investigated. Dietary treatments were control (3.6% tallow, 4.5% casein), whole cottonseed, ground cottonseed, roasted whole cottonseed, and roasted ground cottonseed. Diets consisted of 55% corn silage, 1.54% urea, and cottonseed at 18.1% or dry matter. Cottonseeds were roasted at 149 degrees C and steeped for 30 min. Roasting increased the amount of ruminally undegradable protein measured in vivo, the ratio of ruminal acetate to propionate, pH, and milk protein percentage. Ruminal digestibilities of organic matter (OM) and neutral detergent fiber and biohydrogenation of fatty acids were reduced by roasting. The grinding of cottonseed increased the total tract digestibility of OM and N and tended to increase ruminally undegradable protein of cottonseed in vivo. Interactions between heat treatment and particle size of cottonseed revealed that roasted ground cottonseed resulted in the highest total tract digestibility of OM, N, and neutral detergent fiber. Utilization of cottonseed may be improved by heat or mechanical processing as was indicated by this study.

Ammonia↗

PubMed1997

Effect of dietary forage concentration and buffer addition on duodenal flow of trans-C18:1 fatty acids and milk fat production in dairy cows.

Milk fat depression in cows fed high grain diets has been shown to be related to increased trans-C18:1 fatty acids in milk. Trans-C18:1 fatty acids are produced as a result of incomplete biohydrogenation of dietary polyunsaturated fatty acids in the rumen. The objective of this study was to determine the effects of varying amounts of dietary concentrate and buffer addition on duodenal flow, apparent absorption, and incorporation of trans-C18:1 fatty acids into milk fat. Four ruminally and duodenally cannulated multiparous Holstein cows in midlactation were fed diets consisting of 60% (high) or 25% (low) forage with or without buffer (1.5% NaHCO3 and 0.5% MgO). Treatments were arranged in a 2 x 2 factorial within a 4 x 4 Latin square design. The diet containing low forage and no buffer increased the flow of trans-C18:1 fatty acids to the duodenum compared with the effects of other diets (120 vs. 57 to 66 g/d). Ruminal pH was lower for cows fed the low forage diets. The addition of buffer increased ruminal pH by 0.19 and 0.02 units for cows fed the low forage and high forage diets, respectively. Cows fed the diet containing low forage and no buffer produced milk with a lower fat percentage. The addition of buffer to the low forage diet partially corrected milk fat depression. Milk trans-C18:1 fatty acids were higher for cows fed the low forage diet without buffer than for cows fed the other diets (5.8% vs. 3.0%). Altered ruminal function resulting from low ruminal pH for cows fed the low forage diet and no buffer may play a role in the increased production of trans-C18:1 fatty acids in the rumen.

Animal Feed↗

PubMed1997

Effect of fat source on duodenal flow of trans-C18:1 fatty acids and milk fat production in dairy cows.

The objective of the study was to determine the effects of dietary fat source on duodenal flow, apparent absorption, and milk fat incorporation of trans-C18:1 fatty acids. Four ruminally and duodenally cannulated multiparous Holsteins cows in mid to late lactation were fed a basal diet containing 36% corn silage, 24% alfalfa haylage, and 40% concentrate (dry matter basis). Diets contained 0% supplemental fat (control diet), 3.7% high oleic sunflower oil, 3.7% high linoleic sunflower oil, or 3.7% partially hydrogenated vegetable shortening; treatments were administered in a 4 x 4 Latin square design with 3-wk experimental periods. The flow of trans-C18:1 to the duodenum was higher for cows fed diets supplemented with fat than for cows fed the control diet (283 vs. 64 g/d). Incomplete biohydrogenation accounted for the increased flow of trans-C18:1 to the duodenum in cows fed diets containing high oleic and high linoleic sunflower oil. Increased flow of trans-C18:1 in cows fed the diet containing partially hydrogenated vegetable shortening most likely originated from the trans-C18:1 in the diet. Milk fat percentages were 3.48, 3.07, 3.18, and 3.38% for cows fed the control diet and diets containing high oleic sunflower oil, high linoleic sunflower oil, and vegetable shortening, respectively. Milk trans-C18:1 increased from 2.9 to 11.2% of the total fatty acids for cows fed the control diet and the diets supplemented with fat, respectively. Milk trans-C18:1 were equal across all diets supplemented with fat. Ruminal and total tract digestion of organic matter, neutral detergent fiber, and N did not change with fat supplementation. Results showed that trans-C18:1 is increased in the milk of cows with reduced milk fat; however, excessive amounts of trans-C18:1 in milk do not necessarily correspond directly to milk fat depression.

Animal Nutritional Physiological Phenomena↗

PubMed1998

Fatty acid composition of milk from Holstein cows fed oleamide or canola oil.

Based on previous in vitro results that showed reduced biohydrogenation of oleamide by ruminal microbes, this study was conducted to determine whether the addition of oleamide to the diets of dairy cows would enhance the C18:1 concentration in milk. Nine first lactation Holstein cows were fed three diets in a 3 x 3 Latin square replicated three times. Each period lasted 3 wk. The total mixed diets consisted of 42% corn silage and 58% concentrate (dry matter basis) with either no added fat (control), 3.5% high oleic canola oil, or 3.5% oleamide. Dry matter intake was reduced when oleamide was added to the diet but not when canola oil was added. Milk yields were the same for cows fed all three diets. Canola oil reduced fat-corrected milk yield and milk fat concentration, but these were not affected by oleamide. Milk protein concentration was lower for cows fed oleamide than for cows fed canola oil. Milk C18:1 averaged 23.16% of total fatty acids for cows fed the control diet and increased to 35.13% when canola oil was fed. Oleamide further increased C18:1 to 48.16% of total fatty acids in milk. All fatty acids with > or = 16 carbon chain length were reduced by oleamide. Oleamide was more effective than was canola oil in this study at increasing the oleic acid content of bovine milk. Oleamide reduced dietary intake when added at 3.5% of the dietary dry matter but still had no effect on milk yield or milk composition.

Animals↗

PubMed1998

Fatty acid flow to the duodenum and in milk from cows fed diets that contained fat and nicotinic acid.

Four cows fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square design; treatments were arranged in a 2 x 2 factorial. Treatments were 1) low fat diet, no nicotinic acid; 2) low fat diet, 12 g/d of nicotinic acid; 3) high fat diet, no nicotinic acid; and 4) high fat diet, 12 g/d of nicotinic acid. Cows were fed for ad libitum intake diets consisting of 35% alfalfa silage, 15% corn silage, and either 50% low fat concentrate or 40% high fat concentrate (tallow supplied 6.25% of concentrate) and 10% whole raw soybeans (dry matter basis). Intake of gross energy (104 Mcal/d) was not different among treatments. Ruminal and postruminal digestibility of energy was not altered by fat or nicotinic acid. Fatty acid intake and flow to the duodenum were increased by fat but were not affected by nicotinic acid. For all diets, flows to the duodenum of C16:0, C18:0, total C18, and total fatty acids increased, and flows of C16:1, C18:1, C18:2, and C18:3 decreased, compared with their intakes. Biohydrogenation of unsaturated C18 was decreased by fat but was not affected by nicotinic acid. Digestibilities of C18:0, C18:1, C18:2, C18:3, and total fatty acids that flowed to the duodenum were decreased by fat but were not affected by nicotinic acid. The yield of C18:0 in milk was increased, and yields of C6:0 to C16:0 fatty acids were decreased, by fat, but yields were not affected by nicotinic acid.

Animals↗

PubMed2003

Might analysis, synthesis and metabolism of CLA contribute to explain the biological effects of CLA?

Conjugated Linoleic Acids (CLA) are of great interest for analysts since techniques have been developed to determine the dietary occurrence of CLA with a good accuracy. CLA is found in animal products from ruminant sources as the result of biohydrogenation of polyunsaturated fatty acids in the rumen and as the consequence of the delta-9 desaturation of vaccenic acid in animal tissues. CLA can also be obtained in the laboratory by isomerisation of linoleic acid or by total chemical synthesis. While the "natural" isomer is rumenic acid (9c,11t-18:2), synthetic mixtures contain mainly two isomers: the 9c,11t- and the 10t,12c-18:2. Although CLA have been shown to be metabolized into desaturated and chain elongated products, it remains unclear whether these so-formed conjugated metabolites may be involved in the effects of CLA on fatty acid metabolism. Experiments carried out on animal models with CLA have shown different health benefits: anticarcinogenic, antiatherosclerotic effects, modulation of body composition , the "natural" CLA (9c,11t-18:2) being closely related to the protection against cancer and the 10t,12c-18:2 to the reduction of the fat mass. Nevertheless, recent findings have suggested adverse effects in mice. Most of the studies carried out on humans concern the influence of CLA on body composition and its possible inverse association with cancer. Since the results are still controversial and since very few data dealing with the safety of using CLA in long term feeding studies have so far been published, further works are warranted to consider the benefits of CLA for humans.

Animals↗

PubMed2003

Influence of trans fatty acids on infant and fetus development.

Trans isomers are formed from cis unsaturated fatty acids during biohydrogenation by rumen microorganisms and by commercial partial hydrogenation during the processing of vegetable and fish oils. Recent estimates indicate that consumers in Western countries may receive from 0.5-2.1% to 2.5% of total energy intake as trans fatty acids. In recent years special attention has been given to the potential impairment of essential fatty acids metabolism to their long-chain metabolites by trans isomers in humans. These long-chain polyunsaturates metabolities are of great physiological importance during prenatal and postnatal development, as essential membrane components and precursors for synthesis of prostaglandins and other eicosanoids. Humans do not synthesise trans isomers of fatty acids so their presence in human milk is based on the maternal diet. Trans fatty acids content in human milk varied between countries from 0.35% in Africa to 7.2% of total fatty acids in Canada as a result of variation in dietary exposure to trans isomers. Although the negative effect of the human milk trans fatty acids on breast-fed infants is not yet well documented, ingested levels of trans fatty acids by infants may reflect current breastfeeding mothers diet and also the early consumed diet during pregnancy.

Breast Feeding↗

PubMed2005

[Recent advances on the structure and catalytic mechanism of hydrogenase].

Hydrogenases are enzymes that catalyse the oxidation of hydrogen and the reduction of protons. It plays an important role in the process of biohydrogen production. According to the metal atoms within hydrogenase, it can be classified as NiFe-hydrogenase, Fe-hydrogenase and metal-free hydrogenase. The overwhelming majority of hydrogenases are metalloenzymes. The metal atoms are involved in the forming of active site and [Fe-S] clusters. The active site directly catalyzes the reduction of protons and the oxidation of hydrogen. The [Fe-S] clusters are involved in the transport of electrons between the H2-activating site and the redox partners of hydrogenase. Presently, the crystal structures of NiFe-hydrogenase and Fe-hydrogenase from a few kinds of microorganism have been revealed. The metal-free hydrogenase, characterized by the absence of [Fe-S] cluster and the presence of an iron-containing cofactor, shows a great diversity comparing with those of NiFe-hydrogenases and Fe-hydrogenases. Recent progress have also indicated the mechanisms of activation.

Catalysis↗

PubMed1995

Dietary trans fatty acids and their impact on plasma lipoproteins.

Foods contain isomers of unsaturated fatty acids that have double bonds in unusual configurations (trans instead of cis) or unusual positions, or both. Such fatty acids arise through biohydrogenation in the rumen of cows and sheep or catalytic hydrogenation in industrial hardening of oils. The effects of transmonounsaturates on lipoproteins in man are opposite to those of their cis-isomer, oleic acid: trans fatty acids raise low density lipoprotein (LDL) cholesterol and lipoprotein Lp(a) and lower high density lipoprotein (HDL) cholesterol, all in a dose-dependent fashion. Trans fatty acids raised serum cholesteryl ester transfer activity in 52 of 55 volunteers (mean change 18%, P < 0.02), and lowered the ratio of cholesteryl esters to triglycerides in HDL. Lecithin cholesterol acyl transferase was unchanged. The effects of trans fatty acids on HDL and LDL may thus be mediated through cholesterol ester transfer protein.

Carrier Proteins↗

PubMed1997

Trans fatty acids, lipoproteins, and coronary risk.

Most dietary fatty acids contain at least one double bond, which is usually in the cis configuration. However, biohydrogenation in the rumen of cows and sheep, or catalytic hydrogenation of vegetable oils in the food industries, will convert some of the cis double bonds to the trans configuration. Trans fatty acid intake in western Europe and North America probably ranges from 5 to 15 g/day. Major dietary sources are frying fats used in industrial food preparation, margarines, and other spreads. In the past, margarines contained up to 50% trans fatty acids; however, these are now being phased out. Trans fatty acids raise serum low density lipoprotein (LDL) cholesterol and lower high density lipoprotein (HDL) cholesterol in humans when substituted for cis unsaturated fatty acids in the diet. These effects may be mediated by the cholesteryl ester transfer protein. Trans fatty acids also increase lipoprotein (a) levels relative to other fatty acids. The effects of trans fatty acids on the risk profile for coronary heart disease are thus unfavorable, and labels of food products should state the trans fatty acid content.

Cholesterol, HDL↗