Effect of lipids in milk replacers on calf performance and lipids in blood plasma, liver, and perirenal fat

Various fats (20% of dry matter) were fed in milk replacer to calves, from 3 to 31 d of age, to compare their effect on calf performance, feed efficiency, and lipids in blood plasma, liver, and perirenal fat. Dietary fats tested were tallow (control), canola oil, canola soapstocks, corn oil, reclaimed restaurant cooking fat, and a high phospholipid waste product. Corn oil plus tallow (1:1) diet promoted scours and poor calf gains, but canola oil diet, despite a high content of unsaturated fatty acids, gave excellent calf performance and feed utilization and no scours. Canola soapstocks plus tallow (1:1) and restaurant waste cooking fat lowered gains by 25 and 15% and reduced diet intake. Calves effectively utilized high phospholipid (23%) in dietary lipids. Main lipid classes in blood plasma were cholesterol esters and phosphatidylcholine, and in liver phosphatidylethanolamine and phosphatidylcholine. Fatty acid composition of the major blood plasma and liver lipids, and of perirenal fat, tended to reflect dietary fatty acid concentrations.     

Factors affecting poor performance and scours in preruminant calves fed corn oil

A 4-wk study with 12 3-d-old calves compared the effect of feeding tallow, corn oil, or corn oil plus aspirin on calf performance, feed utilization, incidence of scours, and composition of blood plasma lipids. Aspirin treatment was to inhibit a possible role of prostaglandins in promoting scours. Calves given both corn oil treatments had lower average daily gain, feed efficiency, and higher incidence of scours than those fed tallow. Unexpectedly, corn oil produced appreciably less scours in calves than encountered in previous studies. This appeared to be related to the fat dispersion method used here, which produced much smaller fat globules (less than 1 micron vs. 10 to 20 microns). Over-production of prostaglandins from corn oil was not a causative factor in scours development. Arachidonic acid and other linoleic acid prostaglandin precursors in blood plasma cholesteryl esters and phosphatidylcholine were reduced by dietary corn oil. Aspirin, a potent inhibitor of prostaglandin biosynthesis, was ineffective in reducing scours.     

Influence of low linoleic and linolenic acids in milk replacer on calf performance and lipids in blood plasma, heart, and liver

In a 6-wk study with 3-d-old calves (n = 32), we compared effects of low or adequate essential fatty acids in milk replacers on calf performance, feed utilization, and fatty acids in blood plasma, heart, and liver lipids. Four dietary treatments were hydrogenated coconut oil, as low-essential fatty acid basal; basal plus linoleic acid; basal plus linoleic plus linolenic acids; tallow control. None of the calves fed low essential fatty acid diet developed any external deficiency signs seen in monogastric animals. Supplementation of basal diet with essential fatty acids had no influence on weight gains, feed efficiency, or digestibility of lipids, nitrogen, and dry matter. Effects of low essential fatty acid intake were decreased resistance of erythrocytes to lysis, and in tissue lipids, marked reduction of linoleic acid and elevation of trienoic acid, palmitoleic acid, and ratio of trienoic acid to arachidonic acid, all indicative of low essential fatty acid status. Essential fatty acid intake in milk replacer may be more important than indicated here for longer term vealer calves, and where stresses, such as infectious diseases and high environmental temperature, are present.     

EFFECT OF DIETARY FATS ON THE FATTY ACID CONTENTS OF CHICKEN ADIPOSE TISSUE

SUMMARY— 150 broiler-type chicks were reared from hatching to 4 wk of age on a low-fat ration before being fed diets containing 10% of either corn oil, lard, beef tallow or hydrogenated coconut oil. Analyses of treatment effects were made at 2 wk intervals until the chicks were 10 wk old. The fatty acid content of extracted total lipids were characteristic of the dietary fats and dietary fatty acid patterns were incorporated into the adipose tissue within 2 wk after the experimental diets were fed. The total lipids when separated into solid fats and liquid oils at room temperature also reflected the fatty acid pattern of the experimental diets. Neutral triglycerides from the adipose tissue contained less linoleic acid and more palmitic and oleic acids than the total lipid fraction. High amounts of palmitic and oleic acids were observed in all of the fractions analyzed. No significant differences were found in total cooking loss, drip loss, taste preference, or TBA values of skin or adipose tissue among the 10 wk old chickens fed different experimental diets.     

Effects of dietary corn oil and fish oil concentrate on lipid composition of calf tissues

Lipid composition of calf blood plasma, liver platelets, muscle, heart, and brain was measured, as affected by high dietary intake of linoleic acid from corn oil or of polyunsaturated fatty acids from fish oil concentrate. Plasma total lipids, phosphatidylcholine, and cholesteryl esters were reduced by corn oil and fish oil concentrate. Dietary fatty acid composition had no influence on percentage distribution of the major phospholipid components of liver, heart, muscle, and brain, but did alter the polyunsaturated fatty acid composition of major phospholipids in plasma, liver, platelets, muscle, and heart. In general, high linoleic acid intake increased linoleic acid and decreased oleic, arachidonic, and linolenic acids in tissue phospholipids, and fish oil concentrate high in eicosapentaenoic and docosahexaenoic acids increased phospholipid concentrations of these fatty acids. The fatty acid composition of brain phosphatidylcholine and phosphatidyl-ethanolamine was relatively resistant to dietary lipid alterations. The fatty acid changes in tissue phospholipids that resulted from dietary lipid alterations may have important implications in eicosanoid metabolism, and in the structure and function of cell membranes.     

Evaluation of Heated Frying Oils Containing Added Fatty Acids

Frying oils (corn, lightly and highly hydrogenated soybean and tallow) were heated 24 hr at 200°C and acid value and percentage polar compounds measured. Fatty acids (stearic, oleic and linoleic) were added to the oils at 1 and 5% levels to determine their effect on oil quality. Corn oil formed acidic and polar compounds at faster rates than the other oils. With 5% fatty acids added, acid value decreased because acidic compounds evaporated faster than they were formed. Polar compound formation generally increased with fatty acid addition in corn oil and lightly hydrogenated soybean oil and decreased in highly hydrogenated soybean oil and tallow.     

The effects of sources of supplemental fat on performance,egg quality,and fatty acid composition of egg yolk in laying hens

BACKGROUND: The objective of this study was to determine the effects of sources of supplemental fat on laying performance, egg quality, and fatty acid composition of egg yolk. RESULTS: Two hundreds Isa Brown layers were assigned randomly to be fed ad libitum a standard commercial layer feed (BD), basal diet plus 2% tallow (T), basal diet plus a mixture of 1% tallow and 1% flaxseed oil (MTFO), basal diet plus 2% sunflower oil (SO), or basal diet plus 2% flaxseed oil (FO), which were offered for 8 weeks. Each diet was given to five groups, each containing 10 hens. The feed efficiency and egg production were 2.78 and 53.51% for BD; 2.30 and 63.47% for T; 2.45 and 60.14% for MTFO; 2.29 and 64.30% for SO, and 2.62 and 61.18% for FO groups, respectively. Dietary fat supplementation affected the laying performance but had no significant effects on egg quality parameters. The fatty acid composition of egg yolk lipids were significantly affected by dietary fatty acid composition. The supplemental tallow increased palmitic fatty acid. The proportions of linoleic and arachidonic fatty acids in egg yolks for layers fed the SO diet were higher than in the BD group and those on diets containing other fats. Concentrations of oleic and omega‐3 fatty acids were the highest in layers fed the FO diet during the laying period. CONCLUSION: The results indicated that dietary animal and plant fats changed the fatty acid composition of egg yolk. Copyright © 2008 Society of Chemical Industry     

植物油在婴儿配方乳粉中的应用探讨

从婴儿配方乳粉在用的7种植物油(大豆油、玉米油、核桃油、葵花籽油、高油酸葵花籽油、棕榈油和椰子油)入手,通过检测植物油的脂肪酸含量,对亚油酸、亚麻酸和油酸等几个主要指标进行了分析,进而与3种新型植物油(双低菜籽油、米糠油和红花籽油)的脂肪酸组成进行了比较,对新型植物油在婴儿配方乳粉中的应用进行了探讨。     

Conjugated linoleic acid content of milk from cows fed different diets.

Conjugated linoleic acid in milk was determined from cows fed different diets. In Experiment 1, cows were fed either normal or high oil corn and corn silage. Conjugated linoleic acid was 3.8 and 3.9 mg/g of milk fatty acids in normal and high oil treatments, respectively. In Experiment 2, cows consumed one-third, two-thirds, or their entire feed from a permanent pasture. Alfalfa hay and concentrates supplied the balance of feed for the one-third and two-third pasture treatments. Conjugated linoleic acid was 8.9, 14.3, and 22.1 mg/g of milk fatty acids in the one-third, two-third, and all pasture treatments, respectively. Cows grazing pasture and receiving no supplemental feed had 500% more conjugated linoleic acid in milk fat than cows fed typical dairy diets (Experiment 1). In Experiment 3, cows were fed either a control diet containing 55% alfalfa silage and 45% grain, or similar diets supplemented with 3% fish meal, or 250 g of monensin/cow/per day, or fish meal and monensin together. Conjugated linoleic acid was 5.3, 8.6, 6.8, and 8.9 mg/g of milk fatty acids in the control, fish meal, monensin, and fish meal plus monensin treatments, respectively. In Experiment 4, cows were fed either finely chopped alfalfa hay (Treatment 1), or coarsely chopped alfalfa hay (Treatment 2) in a 50% forage and 50% grain diet, or 66.6% grass hay and 33.4% grain (Treatment 3), or 98.2% grass hay (Treatment 4). Conjugated linoleic acid was 7.3, 8.3, 9.0, and 7.9 mg/g of milk fatty acids in treatments 1 through 4, respectively.     

Tropical oils: nutritional and scientific issues.

Individually and in combination with other oils, the tropical oils impart into manufactured foods functional properties that appeal to consumers. The use of and/or labeling in the ingredient lists give the impression that these oils are used extensively in commercially processed foods. The estimated daily intake of tropical oils by adult males is slightly more than one fourth of a tablespoon (3.8 g), 75% of which consists of saturated fatty acids. Dietary fats containing saturated fatty acids at the beta-position tend to raise plasma total and LDL-cholesterol, which, of course, contribute to atherosclerosis and coronary heart disease. Health professionals express concern that consumers who choose foods containing tropical oils unknowingly increase their intake of saturated fatty acids. The saturated fatty acid-rich tropical oils, coconut oil, hydrogenated coconut oil, and palm kernel oil, raise cholesterol levels; studies demonstrating this effect are often confounded by a developing essential fatty acid deficiency. Palm oil, an essential fatty acid-sufficient tropical oil, raises plasma cholesterol only when an excess of cholesterol is presented in the diet. The failure of palm oil to elevate blood cholesterol as predicted by the regression equations developed by Keys et al. and Hegsted et al. might be due to the dominant alpha-position location of its constituent saturated fatty acids. If so, the substitution of interesterified artificial fats for palm oil in food formulations, a recommendation of some health professionals, has the potential of raising cholesterol levels. A second rationale addresses prospective roles minor constituents of palm oil might play in health maintenance. This rationale is founded on the following observations. Dietary palm oil does not raise plasma cholesterol. Single fat studies suggests that oils richer in polyunsaturated fatty acid content tend to decrease thrombus formation. Anomalously, palm oil differs from other of the more saturated fats in tending to decrease thrombus formation. Finally, in studies comparing palm oil with other fats and oils, experimental carcinogenesis is enhanced both by vegetable oils richer in linoleic acid content and by more highly saturated animal fats. The carotenoid constituents of red palm oil are potent dietary anticarcinogens. A second group of antioxidants, the tocotrienols, are present in both palm olein and red palm oil. These vitamin E-active constituents are potent suppressors of cholesterol biosynthesis; emerging data point to their anticarcinogenic and antithrombotic activities. This review does not support claims that foods containing palm oil have no place in a prudent diet.     

Milk production and composition from cows fed high oil or conventional corn at two forage concentrations

Twelve multiparous Holstein cows (63 +/- 24 d in milk) were used in a replicated 4 x 4 Latin square with 28-d periods to evaluate conventional and high oil corn grains when fed at two different forage-to-concentrate ratios. Dietary treatments consisted of conventional or high oil corn supplementing a diet with a 25:25:50 mixture of corn silage: alfalfa: concentrate mix, or a high forage diet with a 30:30:40 mixture of corn silage: alfalfa: concentrate mix. Dry matter intake (28.1, 28.7, 26.9, and 26.2 kg/d for normal diets with conventional and high oil corn, and high forage diets with conventional and high oil corn, respectively) and milk yields (36.8, 37.2, 35.5, and 35.2 kg/d) were similar for conventional and high oil corn diets and were lower with the high forage diet, regardless of corn source. Milk fat concentrations were greater when cows were fed diets containing 60% forage (4.03 vs. 3.88%, for the 60 and 50% forages, respectively), but milk protein concentrations were not affected by forage content. Corn source did not affect milk fat or protein concentrations. Long-chain fatty acid concentrations, unsaturated fatty acid concentrations, and total 18:1 fatty acid concentrations were greater when cows were fed high oil corn but were unaffected by forage content of the diet. Concentrations of transvaccenic acid (0.58, 0.81, 0.62, and 0.69 g/100 g of fatty acids) and cis-9, trans-11 conjugated linoleic acid (0.28, 0.39, 0.32, and 0.33 g/100 g of fatty acids) were greater when cows were fed high oil compared with conventional corn when fed 50% forage but were similar for both corn sources at 60% forage. Total n-3 fatty acids were not affected by corn source or forage content. High forage diets decreased milk production and increased milk fat concentration. Feeding high oil corn increased concentrations of long-chain, unsaturated, transvaccenic, and conjugated linoleic fatty acids in milk; however, production of transvaccenic and conjugated linoleic acids were attenuated by high forage diet.     

The influence of chemical modification on the hydrolysis of fats by pancreatic lipase and pregastric esterase with reference to fat digestion in the pre-ruminant calf

The hydrolysis of various dietary fats and pure triglycerides by pregastric esterase and pancreatic lipase was studied in vitro in conjunction with a series of digestibility trials to examine the effect of various chemical modifications to beef tallow on its digestibility in milk replacers for pre-ruminant calves. Using pure triglycerides, it was shown that pregastric esterase preferentially hydrolyses triglycerides containing short chain fatty acids; the rate was highest with glyceryl tributyrate and decreased markedly with increase in chain length. Using butterfat, tallow and various modified forms of tallow, it was shown that the inclusion of butyric acid in tallow by interesterification, which markedly improved its digestibility, substantially increased its rate of hydrolysis by pregastric esterase. The initial rate of hydrolysis of tallow by pancreatic lipase was substantially less than that of butterfat. Little improvement in the rate of hydrolysis and solubilisation was obtained when the tallow sample was interesterified or when it was supplemented with the long chain fatty acids, myristic and oleic, or with the short chain fatty acid, butyric. A considerable increase in the initial rate of hydrolysis and solubilisation did occur with tallow samples with a reduced content of stearic acid. The results suggest that hydrolysis by pregastric esterase is a major site of discrimination between different fats in the pre-ruminant calf and an important factor in determining overall digestibility.     

Effects of tallow in diets based on corn silage or alfalfa silage on digestion and nutrient use by lactating dairy cows

Six multiparous Holstein cows (average 31 days in milk; 36.3 kg/d of milk) fitted with ruminal cannulas were used in a 6 x 6 Latin square with 21-d periods to investigate the effects of diets that varied in forage source and amount of supplemental tallow. Isonitrogenous diets in a 2 x 3 factorial arrangement were based on either high corn silage (40:10 corn silage to alfalfa silage, % of dry matter) or high alfalfa silage (10:40 corn silage to alfalfa silage, % of dry matter) and contained 0, 2, or 4% tallow. Intakes of dry matter and total fatty acids were lower when cows were fed the high corn silage diet. Tallow supplementation linearly decreased dry matter intake. Milk yield was unaffected by diet; yields of milk fat and 3.5% fat-corrected milk were higher for the high alfalfa silage diet but were unaffected by tallow. Milk fat percentage was higher for the high alfalfa silage and tended to decrease when tallow was added to the high corn silage diet. Contents of trans-C18:1 isomers in milk fat were increased by high corn silage and tallow, and tended to be increased more when tallow was fed in the high corn silage diet. Ruminal pH and acetate:propionate were lower when high corn silage was fed. Ruminal acetate:propionate decreased linearly as tallow increased; the molar proportion of acetate was decreased more when tallow was added to the high corn silage diet. Ruminal liquid dilution rates were higher for the alfalfa silage diet; ruminal volume and solid passage rates were similar among diets. Total tract apparent digestibilities of dry matter, organic matter, crude protein, starch, energy, and total fatty acids were unaffected by diet. Digestibilities of neutral detergent fiber, acid detergent fiber, hemicellulose, and cellulose were lower when high corn silage was fed. The high alfalfa silage diet increased intakes of metabolizable energy and N, and increased milk energy and productive N. Tallow decreased the amount of N absorbed but had few other effects on utilization of energy or N. Tallow linearly increased concentrations of nonesterified fatty acids and cholesterol in plasma; cholesterol was increased by high alfalfa silage. Overall, forage source had more pronounced effects on production and metabolism than did tallow supplementation. Few interactions between forage source and tallow supplementation were detected except that ruminal fermentation and milk fat content were affected more negatively when tallow was fed in the high corn silage diet.     

Comparison of full-fat corn germ, whole cottonseed, and tallow as fat sources for lactating dairy cattle

Twenty-four multiparous Holstein cows (124 ± 39 d in milk; 682 ± 72 kg of body weight) were used in 6 simultaneous 4 × 4 Latin squares to evaluate full-fat corn germ as a fat source for lactating dairy cows. Experimental diets were a control (containing 28% ground corn, 23% alfalfa hay, 19% wet corn gluten feed, and 10% corn silage, dry matter basis), and 3 diets with either whole cottonseed (WCS), tallow (TAL), or full-fat corn germ (FFCG) added to provide 1.6% supplemental fat. Cows were fed twice daily for ad libitum intake. Dry matter intake, milk yield, and energy-corrected milk did not differ among diets. Efficiency of milk production (energy-corrected milk/dry matter intake) was greater for cows fed WCS than for cows fed the control, TAL, or FFCG. Milk fat percentage from cows fed FFCG was less than that of cows fed WCS or the control, but was similar to that of cows fed TAL. Milk protein percentage was less for cows fed FFCG than for those fed the control. Total saturated fatty acids were less in milk from cows fed fat sources, and cows fed WCS and TAL had greater saturated fatty acids in milk than did cows fed FFCG. Unsaturated fatty acids were greater in milk from cows fed FFCG than in milk from cows fed the control, WCS, or TAL. The cis-9, trans-11 conjugated linoleic acid content was greater in milk from cows fed WCS, TAL, and FFCG than from cows fed the control, and it was greater in milk from cows fed FFCG than in milk from cows fed WCS or TAL. These results indicate that FFCG can be used effectively as a fat source in diets for lactating dairy cattle.     

Effects of feeding lactating dairy cows diets containing whole soybeans and tallow.

Four multiparous Holstein cows averaging 133 d postpartum and fitted with ruminal cannulas were utilized in a 4 x 4 Latin square design to investigate the effects of feeding diets containing whole soybeans and tallow. Treatments were 1) control, no added fat; 2) control and 10% whole raw soybeans; 3) control, 10% whole raw soybeans, and 2.5% tallow; and 4) control, 10% whole raw soybeans, and 4.0% tallow. Cows were fed for ad libitum intake a diet of alfalfa haylage, corn silage, and concentrate (45:5:50, DM basis). Intakes of DM and production of milk, milk CP, milk SNF, and 4% FCM were not affected by feeding supplemental fat. Production of milk fat and weight percentages and yields of long-chain fatty acids in milk fat were increased, whereas weight percentages and yields of short- and medium-chain fatty acids were decreased by feeding supplemental fat. Digestibilities of DM, OM, energy, cellulose, and fatty acids were decreased slightly when fat was added to the diet, but utilization of energy and N for production of milk was not altered. Supplemental fats increased concentrations of NEFA and cholesterol in plasma. These data indicate that relatively large amounts of unprotected fat can be added to the diet of lactating dairy cows without deleterious effects on milk composition, ruminal fermentation, or nutrient digestibilities.     

Digestive lipolysis in the preruminant calf. The abomasal hydrolysis of butter oil, coconut oil, palm oil and tallow

The effect of intramolecular short-chain fatty acids on the abomasal hydrolysis of long chain acyl ester bonds has been examined using four different fats. An evaluation of abomasal infusion of feeds as a technique to avoid hydrolysis of fat by salivary lipase has been made. Only calves considered to be typically functional preruminants were used for the investigations. Five preruminant calves each received five experimental milk feeds consisting of skim milk plus 3% of either butter oil, coconut oil, palm oil or tallow. All feeds were given by mouth but the feed that contained butter oil was also introduced directly into the abomasum via a simple cannula. In all cases, digesta leaving the abomasum were continuously sampled for 12 h via a re-entrant cannula in the proximal duodenum, anterior to the entry of the bile and pancreatic ducts. Butter oil given by mouth was hydrolysed to a greater extent than the other fats. This was due not only to the ease of liberation of the short chain fatty acids, but also to an enhanced liberation of longer chain acids when short chain acids are present in the triglyceride. Butter oil introduced directly into the abomasum of truly preruminant calves was not hydrolysed, suggesting that by using this technique studies could be made in vivo of the hydrolysis of fat by pancreatic lipase alone.     

婴儿配方乳粉中必需脂肪酸调配的研究

通过对婴儿配方乳粉中必需脂肪酸调配的研究实验，引用正交实验，得出最佳结果：按棕榈油10％、玉米油0．4％、葵花籽油0．4%、椰子油0．4％(均为质量分数)的比例进行油脂复配时，可使婴儿配方乳粉中亚油酸含量为34．10mg／g，亚麻酸含量为3．30mg／g，亚油酸和亚麻酸的比例在10：1(质量比)的范围，使配方粉中必需脂肪酸的含量和比例接近母乳，产品的综合评定最佳。     

Use of fatty acid methyl esters and edible fats and oils to reduce soft scald of apples

The incidence of soft scald that developed on Jonathan apples during cool storage was reduced by post-harvest dipping of the fruit in solutions of a wide range of fatty acid methyl esters and glyceride-type fats and oils. Compounds which reduced the disorder were: methyl laurate, methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, methyl linolenate, palm oil, sunflower oil, safflower oil, coconut oil, lard and lecithin.     

Melting Characteristics and Hardness of Milkfat Blend Sucrose Polyesters

Sucrose polyesters (SPE) are noncaloric fat substitutes prepared from fatty acid methyl esters (FAME) and sucrose. Our objectives were to determine and compare the effects of supplementing FAME from hydrolyzed milkfat with 25% FAME derived from beef tallow, coconut oil, or myristic acid on melting characteristics, hardness, and fatty acid profiles of SPE. DSC thermograms revealed different melting profiles among the SPE and anhydrous milkfat. Milkfat:tallow, milkfat:coconut, and milkfat SPE differed (p<0.05) in hardness from milkfat at 12.5, 22, and 27.5°C. Fatty acid compositions of the SPE were also different. Adjustments of melting characteristics, hardness, and fatty acid substituents of SPE are essential when substituting milkfat SPE for selected natural fats in foods.     

Plant oil supplements reduce methane emissions and improve milk fatty acid composition in dairy cows fed grass silage-based diets without affecting milk yield

Four lipid supplements varying in chain length or degree of unsaturation were examined for their effects on milk yield and composition, ruminal CH₄ emissions, rumen fermentation, nutrient utilization, and microbial ecology in lactating dairy cows. Five Nordic Red cows fitted with rumen cannulas were used in a 5 × 5 Latin square with five 28-d periods. Treatments comprised total mixed rations based on grass silage with a forage-to-concentrate ratio of 60:40 supplemented with no lipid (CO) or 50 g/kg of diet dry matter (DM) of myristic acid (MA), rapeseed oil (RO), safflower oil (SO), or linseed oil (LO). Feeding MA resulted in the lowest DM intake, and feeding RO reduced DM intake compared with CO. Feeding MA reduced the yields of milk, milk constituents, and energy-corrected milk. Plant oils did not influence yields of milk and milk constituents, but reduced milk protein content compared with CO. Treatments had no effect on rumen fermentation characteristics, other than an increase in ammonia-N concentration due to feeding MA, RO, and SO compared with CO. Lipid supplements reduced daily ruminal CH₄ emission; however, the response was to some extent a result of lower feed intake. Lipids modified microbial community structure without affecting total counts of bacteria, archaea, and ciliate protozoa. Dietary treatments had no effect on the apparent total tract digestibility of organic matter, fiber, and gross energy. Treatments did not affect either energy secreted in milk as a proportion of energy intake or efficiency of dietary N utilization. All lipids lowered de novo fatty acid synthesis in the mammary gland. Plant oils increased proportions of milk fat 18:0, cis 18:1, trans and monounsaturated fatty acids, and decreased saturated fatty acids compared with CO and MA. Both SO and LO increased the proportion of total polyunsaturated fatty acids, total conjugated linolenic acid, and cis-9,trans-11 conjugated linoleic acid. Feeding MA clearly increased the Δ⁹ desaturation of fatty acids. Our results provide compelling evidence that plant oils supplemented to a grass silage-based diet reduce ruminal CH₄ emission and milk saturated fatty acids, and increase the proportion of unsaturated fatty acids and total conjugated linoleic acid while not interfering with digestibility, rumen fermentation, rumen microbial quantities, or milk production.