Influence of a supplement containing conjugated linoleic acid on dairy performance,milk fatty acid composition,and adipose tissue reactivity to lipolytic challenge in mid-lactation goats

The objective of this work was to evaluate the effect of the supplementation of conjugated linoleic acid (CLA; 4.5 g of cis-9,trans-11 C18:2 and 4.5 g of trans-10,cis-12 C18:2) on milk performance, milk fatty acid (FA) composition, and adipose tissue reactivity in dairy goats fed a high-concentrate diet based on corn silage. Twenty-four multiparous dairy goats in early to mid lactation were used in a 10-wk trial, with a 3-wk adaptation to the experimental total mixed ration that contained corn silage (35%, dry matter basis), beet pulp (20%), barley (15%), and a commercial concentrate (30%). Goats were randomly allocated to 2 experimental groups and they were fed 45 g/d of a lipid supplement (either CLA or Ca salts of palm oil added on top of the total mixed ration). Individual milk production and composition were recorded weekly, and milk FA composition was analyzed in wk 2, 5, and 6. In the last week of the trial, an isoproterenol challenge was performed for 12 goats before morning feeding. The CLA supplementation had no effect on dry matter intake (DMI), body weight (BW), milk yield, milk protein content, and lactose yield and content, but it significantly decreased milk fat yield and content by 18 and 15%, respectively. The decrease in milk fat yield was related to a lower secretion of FA synthesized de novo, of the medium-chain FA, and to a lesser extent of the long-chain FA that are taken up from the peripheral circulation. The CLA supplementation decreased the proportion of the sum of C16:0 and C16:1 and the sum of total cis C18:1, and it increased the proportions of the sum of long-chain (C >16) and the sum of iso FA without modification of the total trans C18:1 and the sum of FA synthesized de novo (C <16). During the first 25 min relative to isoproterenol injection, the maximal concentrations, the increases above basal concentration, the changes in area under the curve, and the total area under the curve for glucose and nonesterified FA were not affected by CLA treatment. In conclusion, CLA supplementation associated with a high-concentrate diet based on corn silage resulted in decreased milk fat yield, increased net energy balance, and it did not affect the sensitivity of the adipose tissue to lipolytic challenge in lactating goats.     

Effect of linoleic acid and dietary vitamin E supplementation on sustained conjugated linoleic acid production in milk fat from dairy cows

Conjugated linoleic acid (CLA; cis-9,trans-11 18:2), a bioactive fatty acid (FA) found in milk and dairy products, has potential human health benefits due to its anticarcinogenic and antiatherogenic properties. Conjugated linoleic acid concentrations in milk fat can be markedly increased by dietary manipulation; however, high levels of CLA are difficult to sustain as rumen biohydrogenation shifts and milk fat depression (MFD) is often induced. Our objective was to feed a typical Northeastern corn-based diet and investigate whether vitamin E and soybean oil supplementation would sustain an enhanced milk fat CLA content while avoiding MFD. Holstein cows (n = 48) were assigned to a completely randomized block design with repeated measures for 28 d and received 1 of 4 dietary treatments: (1) control (CON), (2) 10,000 IU of vitamin E/d (VE), (3) 2.5% soybean oil (SO), and (4) 2.5% soybean oil plus 10,000 IU of vitamin E/d (SO-VE). A 2-wk pretreatment control diet served as the covariate. Milk fat percentage was reduced by both high-oil diets (3.53, 3.56, 2.94, and 2.92% for CON, VE, SO, and SO-VE), whereas milk yield increased significantly for the SO-VE diet only, thus partially mitigating MFD by oil feeding. Milk protein percentage was higher for cows fed the SO diet (3.04, 3.05, 3.28, and 3.03% for CON, VE, SO, and SO-VE), implying that nutrient partitioning or ruminal supply of microbial protein was altered in response to the reduction in milk fat. Milk fat concentration of CLA more than doubled in cows fed the diets supplemented with soybean oil, with concurrent increases in trans-10 18:1 and trans-11 18:1 FA. Moreover, milk fat from cows fed the 2 soybean oil diets had 39.1% less de novo synthesized FA and 33.8% more long-chain preformed FA, and vitamin E had no effect on milk fat composition. Overall, dietary supplements of soybean oil caused a reduction in milk fat percentage and a shift in FA composition characteristic of MFD. Supplementing diets with vitamin E did not overcome the oil-induced reduction in milk fat percentage or changes in FA profile, but partially mitigated the reduction in fat yield by increasing milk yield.     

Influence of grass-based diets on milk fatty acid composition and milk lipolytic system in Tarentaise and Montbeliarde cow breeds

Two experiments were conducted to evaluate the effects of nature of forage on fatty acid composition and lipolytic system in cow milk to increase the nutritional quality of dairy products. Each experiment was divided into a 4-wk preexperimental and 6- or 8-wk experimental period. During the 2 preexperimental periods, 56 midlactating Montbéliarde or Tarentaise cows received a diet based on corn silage. Subsequently, in Experiment 1,40 cowswere allocatedinto 5groups (4Montbéliarde and 4 Tarentaise cows per group) and assigned to dietary treatments: corn silage (87% of dry matter intake), grass silage (86%), ryegrass hay (90%), mountain natural grassland hay (87%), or a diet rich in concentrate (CONC, 65/35% concentrate/hay). In Experiment 2, 16 cows divided into 2 groups were fed during 3 or 6 wk mountain natural pasture (100%) or mountain natural grassland hay (87%). Principal component analysis was applied to describe the relationships among dairy performances, milk fatty acids (FA), and lipolytic system. The milk 18:0, cis-9-18:1, trans-11-18:1, and cis-9, trans-11-18:2 percentages were closely associated with 3-wk mountain natural pasture diet, whereas short- and medium-chain (mostly saturated) FA were associated with the CONC diet. Tarentaise milk fat contained a lower proportion (−3 to 4 g/100 g) of 16:0 and higher proportions of stearic acid and fewer markedly polyunsaturated FA than Montbéliarde milk fat. Milk lipolysis was lowest for CONC and corn silage groups. Milk from Tarentaise cows presented lower initial free FA and postmilking lipolysis. Diets given to cows, especially young grass, modified the milk content of FA with a putative nutritional effect on human health.     

Effect of plant oils and camelina expeller on milk fatty acid composition in lactating cows fed diets based on red clover silage

Five multiparous Finnish Ayrshire cows fed red clover silage-based diets were used in a 5 × 5 Latin square with 21-d experimental periods to evaluate the effects of various plant oils or camelina expeller on animal performance and milk fatty acid composition. Treatments consisted of 5 concentrate supplements containing no additional lipid (control), or 29 g/kg of lipid from rapeseed oil (RO), sunflower-seed oil (SFO), camelina-seed oil (CO), or camelina expeller (CE). Cows were offered red clover silage ad libitum and 12 kg/d of experimental concentrates. Treatments had no effect on silage or total dry matter intake, whole-tract digestibility coefficients, milk yield, or milk composition. Plant oils in the diet decreased short- and medium-chain saturated fatty acid (6:0-16:0) concentrations, including odd- and branched-chain fatty acids and enhanced milk fat 18:0 and 18-carbon unsaturated fatty acid content. Increases in the relative proportions of cis 18:1, trans 18:1, nonconjugated 18:2, conjugated linoleic acid (CLA), and polyunsaturated fatty acids in milk fat were dependent on the fatty acid composition of oils in the diet. Rapeseed oil in the diet was associated with the enrichment of trans 18:1 (Δ4, 6, 7, 8, and 9), cis-9 18:1, and trans-7,cis-9 CLA, SFO resulted in the highest concentrations of trans-5, trans-10, and trans-11 18:1, Δ9,11 CLA, Δ10,12 CLA, and 18:2n-6, whereas CO enhanced trans-13-16 18:1, Δ11,15 18:2, Δ12,15 18:2, cis-9,trans-13 18:2, Δ11,13 CLA, Δ12,14 CLA, Δ13,15 CLA, Δ9,11,15 18:3, and 18:3n-3. Relative to CO, CE resulted in lower 18:0 and cis-9 18:1 concentrations and higher proportions of trans-10 18:1, trans-11 18:1, cis-9,trans-11 CLA, cis-9,trans-13 18:2, and trans-11,cis-15 18:2. Comparison of milk fat composition responses to CO and CE suggest that the biohydrogenation of unsaturated 18-carbon fatty acids to 18:0 in the rumen was less complete for camelina lipid supplied as an expeller than as free oil. In conclusion, moderate amounts of plant oils in diets based on red clover silage had no adverse effects on silage dry matter intake, nutrient digestion, or milk production, but altered milk fat composition, with changes characterized as a decrease in saturated fatty acids, an increase in trans fatty acids, and enrichment of specific unsaturated fatty acids depending on the fatty acid composition of lipid supplements.     

Effect of supplementation with fish oil or microalgae on fatty acid composition of milk from cows managed in confinement or pasture systems

The objective of this study was to examine the interaction between lipid supplement (LS) and management system (MS) on fatty acid (FA) composition of milk that could affect its healthfulness as a human food. Forty-eight prepartal Holstein cows were blocked by parity and predicted calving date and deployed across pasture (PAS; n = 23) or confinement (CONF; n = 25) systems. Cows within each system were assigned randomly to a control (no marine oil supplement) or to 1 of 2 isolipidic (200 g/d) marine oil supplements: fish oil (FO) or microalgae (MA) for 125 ± 5 d starting 30 d precalving. The experiment was conducted as a split-plot design, with MS being the whole-plot treatment and LS as the subplot treatment. Cows were housed in a tie-stall barn from −30 until 28 ± 10 d in milk (DIM) and were fed total mixed rations with similar formulations. The PAS group was then adapted to pasture and rotationally grazed on a perennial sward until the end of the experiment (95 ± 5 DIM). Milk samples were collected at 60 and 90 DIM for major components and FA analyses. Milk yield (kg/d) was lower in PAS (34.0) compared with CONF (40.1) cows. Milk fat percentage was reduced with MA compared with FO (3.00 vs. 3.40) and the control (3.56) cows. However, milk fat yield (kg/d) was not affected by lipid supplements. Compared with CONF, PAS cows produced milk fat with a lower content of 12:0 (−38%), 14:0 (−28%), and 16:0 (−17%), and more cis-9 18:1 (+32%), 18:3 n-3 (+30%), conjugated linoleic acid (CLA; +70%) and trans 18:1 (+34%). Both supplements, regardless of MS, reduced similarly the milk fat content of 16:0 (−12%) and increased CLA (+28%) and n-3 long-chain polyunsaturated FA (n-3 LC-PUFA; +150%). Milk fat content of trans 18:1 (trans-6 to trans-16) was increased with FO or MA, although the effect was greater with MA (+81%) than with FO (+42%). The interaction between MS and LS was significant only for trans-11 18:1 (vaccenic acid, VA) and cis-9,trans-11 CLA (rumenic acid). In contrast to CONF, feeding FO or MA to PAS cows did not increase milk fat content of VA and rumenic acid. We concluded that compared with CONF, milk from PAS cows had a more healthful FA composition. Feeding either FO or MA improved n-3 long-chain polyunsaturated FA and reduced levels of 16:0 in milk fat, regardless of MS, but concurrently increased the trans 18:1 isomers other than VA, at the expense of VA, particularly in grazing cows.     

Addition of potassium carbonate to continuous cultures of mixed ruminal bacteria shifts volatile fatty acids and daily production of biohydrogenation intermediates

A recent study reported a 0.4 percentage unit increase in milk fat of lactating dairy cattle when dietary K was increased from 1.2 to 2% with potassium carbonate. Because milk fat yield has been associated with ruminal production of certain conjugated linoleic acid (CLA) isomers, 2 studies were conducted to determine if increasing potassium carbonate in the rumen would alter patterns of fermentation and biohydrogenation. In experiment 1, 5 dual-flow continuous fermenters were injected just before each feeding with a 10% (wt/wt) stock potassium carbonate solution to provide the equivalent of 1.1 (K1), 2.2 (K2), and 3.3 (K3) % of diet dry matter (DM) as added K. One of the remaining fermenters received no K (K0) and the last fermenter (NaOH) was injected with adequate NaOH stock solution (10%, wt/wt) to match the pH observed for the K3 treatment. For experiment 2, 6 dual-flow continuous fermenters were used to evaluate 6 treatments arranged in a 2 × 3 factorial to examine 2 levels of soybean oil (0 and 3.64% of diet DM) and added K at 0, 1.6, and 3.3% of diet DM. In both experiments, fermenters were fed 55 to 57 g of DM/d of a typical dairy diet consisting of 1:1 forage (10% alfalfa hay and 90% corn silage) to concentrate mix in 2 equal portions at 0800 and 1630 h, and fed the respective diets for 10-d periods. Potassium carbonate addition increased pH in both experiments. Acetate:propionate ratio and pH in experiment 1 increased linearly for K0 to K3. Acetate:propionate ratio was lower for NaOH compared with K3 but the pH was the same. The trans-11 18:1 and cis-9,trans-11 CLA production rates (mg/d) increased linearly from K0 to K3, but K3 and NaOH did not differ. Production of trans-10 18:1 decreased and that of trans-10,cis-12 tended to decrease from K0 to K3, but production of trans-10,cis-12 CLA remained high for NaOH. Addition of K to the cultures in experiment 2 decreased propionate and increased acetate and acetate:propionate ratio for the 0% fat diet but not for the 3.64% fat diet. Addition of K increased stearic acid and cis-9,trans-11 CLA but decreased daily production of trans-10 C18:1 and trans-10,cis-12 CLA. The results indicate that increasing potassium carbonate in the diet shifts both fermentation and biohydrogenation pathways toward higher milk fat percentage in dairy cows, but the effects are only explained in part by elevation of pH.     

Effects of incremental amounts of extruded linseed on the milk fatty acid composition of dairy cows receiving hay or corn silage

The effect of supplementation of increasing amounts of extruded linseed in diets based on hay (H; experiment 1) or corn silage (CS; experiment 2) was investigated in regard to dairy performance and the milk fatty acid (FA) composition. In each experiment, 4 lactating multiparous Holstein cows were used in a 4 × 4 Latin square design (28-d periods). The cows were fed a diet (50:50 and 40:60 concentrate:forage ratio for experiments 1 and 2, respectively; dry matter basis) without supplementation (H0 or CS0) or supplemented with 5% (H5 or CS5), 10% (H10 or CS10), or 15% (H15 or CS15) of extruded linseed. Regardless of the forage type, diet supplementation with increasing amounts of extruded linseed had no effect on the dry matter intake, milk yield, or protein content or yield. In contrast, the milk fat content decreased progressively from H0 to H10 diets, and then decreased strongly with the H15 diet in response to increasing amounts of extruded linseed. For CS diets, the milk fat content initially decreased from CS0 to CS10, but then increased with the CS15 diet. For the H diets, the milk saturated FA decreased (−24.1 g/100 g of FA) linearly with increasing amounts of extruded linseed, whereas the milk monounsaturated FA (+19.0 g/100 g), polyunsaturated FA (+4.9 g/100 g), and total trans FA (+14.7 g/100 g) increased linearly. For the CS diets, the extent of the changes in the milk FA composition was generally lower than for the H diets. Milk 12:0 to 16:0 decreased in a similar manner in the 2 experiments with increasing amounts of extruded linseed intake, whereas 18:0 and cis-9 18:1 increased. The response of total trans 18:1 was slightly higher for the CS than H diets. The milk trans-10 18:1 content increased more with the CS than the H diets. The milk cis-9,trans-11 conjugated linoleic acid response to increasing amounts of extruded linseed intake was linear and curvilinear for the H diets, whereas it was only linear for the CS diets. The milk 18:3n-3 percentage increased in a similar logarithmic manner in the 2 experiments. It was concluded that the milk FA composition can be altered by extruded linseed supplementation with increasing concentrations of potentially health-beneficial FA (i.e., oleic acid, 18:3n-3, cis-9,trans-11 conjugated linoleic acid, and odd- and branched-chain FA) and decreasing concentrations of saturated FA. Extruded linseed supplementation increased the milk trans FA percentage.     

Effects of grass silage and soybean meal supplementation on milk production and milk fatty acid profiles of grazing dairy cows

The effects of supplementation with grass silage and replacement of some corn in the concentrate with soybean meal (SBM) on milk production, and milk fatty acid (FA) profiles were evaluated in a replicated 4 × 4 Latin square study using 16 dairy cows grazing pasture composed of ryegrass, Kentucky bluegrass, and white clover. Each experimental period lasted for 3 wk. The 4 dietary treatments were PC, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn-based concentrate mixture (96% corn; C); PCSB, 20 h of access to grazing pasture, supplemented with 6 kg/d of corn- and SBM-based concentrate mixture (78% corn and 18% SBM; CSB); SC, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of C concentrate; and SCSB, 7 h of access to grazing pasture during the day and 13 h of ad libitum access to grass silage at night, supplemented with 6 kg/d of CSB concentrate. The concentrate mixtures were offered twice each day in the milking parlor and were consumed completely. Grass silage supplementation reduced dietary crude protein and concentration of total sugars, and dietary SBM inclusion increased dietary crude protein concentration and decreased dietary starch concentration. Milk yield and energy-corrected milk were increased by SBM supplementation of cows with access to grass silage. Milk protein concentration was lower in cows offered grass silage, regardless of whether SBM was fed. Dietary SBM inclusion tended to increase milk fat concentration. Plasma urea N was reduced by silage feeding and increased by SBM supplementation. Supplementation with grass silage overnight could represent a useful strategy for periods of lower pasture availability. Dietary inclusion of SBM in solely grazing cows had no effects on milk production and composition, exacerbated the inefficient capture of dietary N, and increased diet cost. Grass silage supplementation affected milk FA profiles, increasing both the FA derived from de novo synthesis and those derived from rumen microbial biomass, and decreasing the sum of C18 FA (mostly derived from diet or from mobilization of adipose tissue reserves). Milk fat concentrations of conjugated linoleic acid cis-9, trans-11, vaccenic acid (18:1 trans-11), and linolenic acid (18:3n-3) were unaffected by grass silage supplementation, suggesting that partial replacement of pasture by unwilted grass silage does not compromise the dietary quality of milk fat for humans.     

Effect of unsaturated fatty acids and triglycerides from soybeans on milk fat synthesis and biohydrogenation intermediates in dairy cattle

Increased rumen unsaturated fatty acid (FA) load is a risk factor for milk fat depression. This study evaluated if increasing the amount of unsaturated FA in the diet as triglycerides or free FA affected feed intake, yield of milk and milk components, and feed efficiency. Eighteen Holstein cows (132 ± 75 d in milk) were used in a replicated 3 × 3 Latin square design. Treatments were a control (CON) diet, or 1 of 2 unsaturated FA (UFA) treatments supplemented with either soybean oil (FA present as triglycerides; TAG treatment) or soybean FA distillate (FA present as free FA; FFA treatment). The soybean oil contained a higher concentration of cis-9 C18:1 (26.0 vs. 11.8 g/100 g of FA) and lower concentrations of C16:0 (9.6 vs. 15.0 g/100 g of FA) and cis-9,cis-12 C18:2 (50.5 vs. 59.1 g/100 g of FA) than the soybean FA distillate. The soybean oil and soybean FA distillate were included in the diet at 2% dry matter (DM) to replace soyhulls in the CON diet. Treatment periods were 21 d, with the final 4 d used for sample and data collection. The corn silage- and alfalfa silage-based diets contained 23% forage neutral detergent fiber and 17% crude protein. Total dietary FA were 2.6, 4.2, and 4.3% of diet DM for CON, FFA, and TAG treatments, respectively. Total FA intake was increased 57% for UFA treatments and was similar between FFA and TAG. The intakes of individual FA were similar, with the exception of a 24 g/d lower intake of C16:0 and a 64 g/d greater intake of cis-9 C18:1 for the TAG compared with the FFA treatment. Compared with CON, the UFA treatments decreased DM intake (1.0 kg/d) but increased milk yield (2.2 kg/d) and milk lactose concentration and yield. The UFA treatments reduced milk fat concentration, averaging 3.30, 3.18, and 3.11% for CON, FFA, and TAG treatments, respectively. Yield of milk fat, milk protein, and 3.5% fat-corrected milk remained unchanged when comparing CON with the UFA treatments. No differences existed in the yield of milk or milk components between the FFA and TAG treatments. The UFA treatments increased feed efficiency (energy-corrected milk/DM intake), averaging 1.42, 1.53, and 1.48 for CON, FFA, and TAG treatments, respectively. Although milk fat yield was not affected, the UFA treatments decreased the yield of de novo (<16-carbon) synthesized FA (40 g/d) and increased the yield of preformed (>16-carbon) FA (134 g/d). Yield of FA from both sources (16-carbon FA) was reduced by the UFA treatments but to a different extent for FFA versus TAG (72 vs. 100 g/d). An increase was detected in the concentration of trans-10 C18:1 and a trend for an increase in trans-10,cis-12 C18:2 and trans-9,cis-11 C18:2 for the UFA treatments compared with CON. Under the dietary conditions tested, UFA treatments supplemented at 2% diet DM as either soybean FA distillate or soybean oil increased milk yield but did not effectively cause a reduction in milk fat yield, with preformed FA replacing de novo synthesized FA in milk fat. Further research is required to determine if the response to changes in dietary free and esterified FA concentrations is different in diets that differ in their risk for milk fat depression.     

Effects of monensin and dietary soybean oil on milk fat percentage and milk fatty acid profile in lactating dairy cows

The objective of this study was to investigate the effect of monensin (MN) and dietary soybean oil (SBO) on milk fat percentage and milk fatty acid (FA) profile. The study was conducted as a randomized complete block design with a 2 × 3 factorial treatment arrangement using 72 lactating multiparous Holstein dairy cows (138 ± 24 d in milk). Treatments were [dry matter (DM) basis] as follows: 1) control total mixed ration (TMR, no MN) with no supplemental SBO; 2) MN-treated TMR (22 g of MN/kg of DM) with no supplemental SBO; 3) control TMR including 1.7% SBO; 4) MN-treated TMR including 1.7% SBO; 5) control TMR including 3.4% SBO; and 6) MN-treated TMR including 3.4% SBO. The TMR (% of DM; corn silage, 31.6%; haylage, 21.2%; hay, 4.2%; high-moisture corn, 18.8%; soy hulls, 3.3%; and protein supplement, 20.9%) was offered ad libitum. The experiment consisted of a 2-wk baseline, a 3-wk adaptation, and a 2-wk collection period. Monensin, SBO, and their interaction linearly reduced milk fat percentage. Cows receiving SBO with no added MN (treatments 3 and 5) had 4.5 and 14.2% decreases in milk fat percentage, respectively. Cows receiving SBO with added MN (treatments 4 and 6) had 16.5 and 35.1% decreases in milk fat percentage, respectively. However, the interaction effect of MN and SBO on fat yield was not significant. Monensin reduced milk fat yield by 6.6%. Soybean oil linearly reduced milk fat yield and protein percentage and linearly increased milk yield and milk protein yield. Monensin and SBO reduced 4% fat-corrected milk and had no effect on DM intake. Monensin interacted with SBO to linearly increase milk fat concentration (g/100 g of FA) of total trans-18:1 in milk fat including trans-6 to 8, trans-9, trans-10, trans-11, trans-12 18:1 and the concentration of total conjugated linoleic acid isomers including cis-9, trans-11 18:2; trans-9, cis-11 18:2; and trans-10, cis-12 18:2. Also, the interaction increased milk concentration of polyunsaturated fatty acids. Monensin and SBO linearly reduced, with no significant interaction, milk concentration (g/100 g of FA) of short- and medium-chain fatty acids (<C16). Soybean oil reduced total saturated FA and increased total monounsaturated FA. These results suggest that monensin reduces milk fat percentage and this effect is accentuated when SBO is added to the ration.     

Effects of different forage:concentrate ratios in dairy ewe diets supplemented with sunflower oil on animal performance and milk fatty acid profile

The aim of this study was to evaluate the effect of different forage:concentrate (FC) ratios in dairy ewe diets supplemented with sunflower oil (SO) on animal performance and milk fatty acid (FA) profile, particularly focusing on trans C18:1 FA and conjugated linoleic acid (CLA). Sixty lactating Assaf ewes were randomly assigned to 6 treatments in a 3 × 2 factorial arrangement: 3 FC ratios (30:70, 50:50, and 70:30) and 2 levels of SO addition (0 and 20 g/kg of dry matter). Both the diet FC ratio and SO supplementation affected milk yield, but differences between treatments were small. Although the proportion of concentrate induced limited changes in milk FA profile, dietary SO significantly decreased saturated FA and enhanced total CLA. Furthermore, the incorporation of SO in ewe diets decreased the atherogenicity index value by about 25% and doubled the contents of potentially healthy FA such as trans-11 C18:1 and cis-9,trans-11 CLA. However, the inclusion of SO in a high-concentrate diet (30:70) could switch linoleic acid biohydrogenation pathways, resulting in a significant increase in trans-10 C18:1, trans-9,cis-11 C18:2, and trans-10,cis-12 C18:2 milk fat percentages.     

Effects of dietary sources of vegetable oils on performance of high-yielding lactating cows and conjugated linoleic acids in milk

This study was conducted to examine the effects of dietary supplementation with vegetable oils on performance of high-yielding lactating cows and conjugated linoleic acid (CLA) content in milk fat. Twelve lactating Holstein cows in early lactation (30 to 45 d postpartum) were used in a triple 4 × 4 Latin square design. In each period, the cows in each group were fed the same basal diet and received one of the following treatments: 1) control (without oil), 2) 500 g of cottonseed oil, 3) 500 g of soybean oil, and 4) 500 g of corn oil. Each experimental period lasted for 3 wk, with the first 2 wk used for adaptation to the diet. Supplementation with vegetable oils tended to increase milk yield, with the highest milk yield in the cottonseed oil group (35.0 kg/d), compared with the control (34.4 kg/d). Milk fat percentage was decreased, but there were few effects on percentage and yield of milk protein as well as milk fat yield. The cows fed added soybean oil produced milk with the highest content of trans-11 C_18:1 (23.8 mg/g of fat), which was twice that of the control (12.6 mg/g of fat). Content of cis-9, trans-11 CLA in milk fat increased from 3.5 mg/g in the control to 6.0, 7.1, and 10.3 mg/g for the cows fed oils from cottonseed, corn, and soybean, respectively. A significant linear relationship existed between trans-11 C_18:1 and cis-9, trans-11 CLA. Supplementation with oils doubled the content of total fatty acids in blood plasma, with little difference between different vegetable oil sources. Octadecenoic acid content was significantly higher in blood plasma of animals fed added oils from cottonseed and soybean than those fed with corn oil and control. The plasma trans-11 C_18:1 content was significantly higher in the oil-added animals than in control. Supplementation of vegetable oils tended to improve milk production of lactating cows, and the CLA content in milk fat was significantly increased. Soybean oil seemed to be the optimal source to increase CLA production.     

The effect of rumen digesta inoculation on the time course of recovery from classical diet-induced milk fat depression in dairy cows

Ten ruminally cannulated cows were used in a crossover design that investigated the effect of rumen digesta inoculation from non-milk fat-depressed cows on recovery from classical diet-induced milk fat depression (MFD) characterized by reduced fat yield, reduced de novo milk fat synthesis, and increased alternate trans isomers. Two additional cows fed a high-fiber and low-polyunsaturated fatty acid (FA) diet (31.8% neutral detergent fiber, 4.2% FA, and 1.2% C18:2) were used as rumen digesta donors. Milk fat depression was induced during the first 10 d of each period by feeding a low-fiber and high-polyunsaturated FA diet (induction; 26.1% neutral detergent fiber, 5.8% FA, and 1.9% C18:2), resulting in a 30% decrease in milk fat yield. A recovery phase followed where all cows were switched to the high-forage, low-polyunsaturated FA diet and were allocated to (1) control (no inoculation) or (2) ruminal inoculation with donor cow digesta (8 kg/d for 6 d). Milk yield and composition were measured every 3 d. Milk yield progressively decreased during recovery. Milk fat concentration increased progressively during the recovery phase and no effect of treatment existed at any time point. Also, no treatment effect of milk fat yield was detected. The concentration of milk de novo FA increased progressively during recovery for both treatments and was higher for inoculated compared with control cows on d 6. In agreement, milk fat concentration of trans-10,cis-12 conjugated linoleic acid decreased progressively in both treatments and was lower in inoculated cows on d 3 and 6. Ruminal inoculation from non-milk fat-depressed cows did not change milk fat yield, but slightly accelerated the rate of recovery of de novo FA synthesis and normal ruminal FA biohydrogenation, demonstrating a possible opportunity for other interventions that improve the ruminal environment to accelerate recovery from this condition.     

Effects of conjugated linoleic acid supplementation and feeding level on dairy performance,milk fatty acid composition,and body fat changes in mid-lactation goats

The objective of this trial was to study the interaction between the supplementation of lipid-encapsulated conjugated linoleic acid (CLA; 4.5 g of cis-9,trans-11 C18:2 and 4.5 g of trans-10,cis-12 C18:2) and feeding level to test if milk performance or milk fatty acid (FA) profile are affected by the interaction between CLA and feeding level. Twenty-four dairy goats were used in an 8-wk trial with a 3-wk adaptation to the experimental ration that contained corn silage, beet pulp, barley, and a commercial concentrate. During the third week, goats were assigned into blocks of 2 goats according to their dry matter intake (DMI), raw milk yield, and fat yield. Each block was randomly allocated to control (45 g of Ca salt of palm oil/d) or CLA treatment. Within each block, one goat was fed to cover 100% (FL100) of the calculated energy requirements and the other was fed 85% of the DMI of the first goat (FL85). Individual milk production and composition were recorded weekly, and milk FA composition was analyzed in wk 3, 5, and 7. Conjugated linoleic acid supplementation reduced milk fat content and fat yield by 17 and 19%, respectively, independent of the feeding level. It reduced both the secretion of milk FA synthesized de novo, and those taken up from the blood. No interaction between CLA and feeding level was observed on milk secretion of any group of FA. The CLA supplementation had no effect on DMI, milk yield, protein, and lactose yields but it improved calculated net energy for lactation balance. Goats fed the FL100 × CLA diet tended to have the highest DMI and protein yield. The interaction between CLA and feeding level was not significant for any other variables. Compared with the goats fed FL100, those fed FL85 had lower DMI, lower net energy for lactation balance, and lower digestible protein in the intestine balance. The body weight; milk yield; milk fat, protein, and lactose yields; and fat, protein, lactose, and urea contents in milk were not affected by feeding level. In conclusion, reduction in energy spared via fat yield reduction after CLA supplementation was not partitioned toward milk lactose or protein in goats at a low feeding level, possibly because of a simultaneous shortage of energy and amino acids. In goats on the high feeding level, energy spared tended to be partitioned toward milk protein yield, and at the same time to the prevention of excessive lipid mobilization.     

Milk from cows fed clover-rich silage compared with cows fed grass silage is higher in n-3 fatty acids

The present study investigated the effect of a high proportion of different forage species in the diet, parity, milking time, and days in milk (DIM) on milk fatty acid (FA) profile, and transfer efficiency of C18:2n-6, C18:3n-3, n-6, and n-3 in dairy cows. Swards with perennial ryegrass [early maturity stage (EPR) and late maturity stage (LPR)], festulolium, tall fescue (TF), red clover (RC), and white clover (WC) were cut in the primary growth, wilted, and ensiled without additives. Thirty-six Danish Holstein cows in an incomplete Latin square design were fed ad libitum with total mixed rations containing a high forage proportion (70% on dry matter basis). The total mixed rations differed only in forage source, which was either 1 of the 6 pure silages or a mixture of LPR silage with either RC or WC silage (50:50 on dry matter basis). Proportion of C18:2n-6 in milk FA was affected by diet, and RC and WC diets resulted in the highest proportion of C18:2n-6 in milk FA (21.6 and 21.8 g/kg of FA, respectively). The highest and lowest milk C18:3n-3 proportion was observed in WC and LPR, respectively. In addition, WC diet resulted in highest transfer efficiency of C18:3n-3 from feed to milk (12.2%) followed by RC diet (10.7%), whereas EPR diet resulted in the lowest transfer efficiency of C18:3n-3 (3.45%). The highest milk proportion of cis-9,trans-11 conjugated linoleic acid (CLA) was observed in cows fed TF (3.20 g/kg of FA), which was 23 to 64% higher than the proportion observed in the cows fed the other diets. The highest α-tocopherol concentration (µg/mL) in milk was observed in EPR (1.15), LPR (1.10), and festulolium (1.06). Primiparous cows showed higher proportion of cis-9,trans-11 CLA (2.63 g/kg of FA) than multiparous cows (2.21 g/kg of FA). Cows early in lactation had a higher proportion of long-chain FA in milk than cows later in lactation, as long-chain FA decreased with 0.184 g/kg of FA per DIM, whereas medium-chain FA increased with 0.181 g/kg of FA per DIM. Proportion of C18:2n-6 in milk from evening milking was higher than in milk from morning milking (16.7 vs. 15.8 g/kg of FA). In conclusion, the results showed that milk FA profile of cows was affected by forage source in the diet, and RC and WC increased the health-promoting FA components, particularly n-3, whereas the TF diet increased proportion of CLA isomers in milk. Proportion of CLA isomers in milk FA from primiparous cows was higher than in milk from multiparous cows. In addition, evening milk contained more FA originating from diets compared with morning milk.     

Effect of dietary antioxidant and increasing corn oil inclusion on milk fat yield and fatty acid composition in dairy cattle

The objective of this study was to examine the effect of a dietary synthetic antioxidant on feed intake, yields of milk and milk components and milk fatty acids (FA), in combination with increasing concentrations of dietary corn oil to provide increasing rumen unsaturated fatty acid load (RUFAL) challenges. Twenty-six Holstein cows (177 ± 57 d in milk; mean ± standard deviation) were assigned to treatment in a randomized complete block design. Treatments were a control diet (CON; n = 13 cows) or the same diet supplemented with a synthetic antioxidant (AOX; 6.1 g/d; dry blend of ethoxyquin and propyl gallate, Novus International Inc., St. Charles, MO; n = 13 cows). In period 1 (21 d), no supplemental corn oil was fed; in periods 2, 3, and 4 (14 d each), corn oil was supplemented at 0.7, 1.4, and 2.8% of the diet [dry matter (DM) basis] to incrementally increase RUFAL. For all variables measured, no significant interactions were detected between treatment and period, indicating no differences between the CON and AOX treatments at all levels of oil inclusion. Intake of DM was lower for AOX compared with CON but AOX had no effect on milk yield or milk fat concentration and yield. Milk protein yield and feed efficiency (energy-corrected milk/DM intake) tended to be greater for AOX compared with CON. Increasing dietary corn oil concentration (RUFAL) decreased DM intake, milk yield, milk fat concentration and yield, and feed efficiency. The AOX treatment increased the concentration and yield of 16-carbon milk FA, with no effect on de novo (<16 carbon) or preformed (>16 carbon) milk FA. Milk FA concentration of trans-10 C18:1, trans-10,cis-12 C18:2, and trans-9,cis-11 C18:2 were unaffected by AOX but increased with increasing RUFAL. In conclusion, supplementation with AOX did not overcome the dietary-induced milk fat depression caused by increased RUFAL.     

Effects of corn silage particle length and forage:concentrate ratio on milk fatty acid composition in dairy cows fed supplemental flaxseed

This study aimed to evaluate the effects of length of chop of corn silage and forage:concentrate ratio (F:C) on performance and milk fatty acid profiles in dairy cows supplemented with flaxseed. Our hypothesis was that decreasing forage particle length and F:C ratio would increase unsaturated fatty acid flow to the small intestine and subsequent transfer of these unsaturated fatty acids into milk. Eight Holstein cows (648.1 ± 71.5 kg body weight; 109.6 ± 43.6 days in milk) were used in a replicated 4 × 4 Latin square design with 21-d periods and a 2 × 2 factorial arrangement of dietary treatments. Dietary factors were: 1) F:C ratios (dry matter basis) of 55:45 and 45:55; and 2) corn silage particle lengths of 9.52 and 19.05 mm. All experimental cows received 1 kg of flaxseed to substitute for 1 kg of a rolled barley grain-based concentrate daily. Diets were fed twice daily as a total mixed ration. Corn silage particle length and F:C ratio had no effect on dry matter intake, milk yield, and milk composition; however, feeding short cut corn silage depressed milk protein yield. Significant particle size × F:C ratio interactions were observed for milk fat proportions of C_16:0, C_18:1cis-9, and C_18:2cis-9, trans-11 (a conjugated linoleic acid isomer). At short corn silage particle size, decreasing F:C ratio depressed milk fat proportion of C_16:0. Conversely, feeding short corn silage at high F:C ratio increased the proportion of C_18:1cis-9 and C_18:2cis-9, trans-11 in milk fat. The milk fat proportion of C_18:2trans-10, cis-12, a conjugated linoleic acid isomer that is associated with milk fat depression, was not affected by dietary treatment. Our results show that corn silage particle length and F:C ratio influence milk fatty acid profiles in dairy cows fed supplemental flaxseed as a source of polyunsaturated fatty acids.     

Evaluation of corn germ from ethanol production as an alternative fat source in dairy cow diets

Sixteen multiparous cows (12 Holstein and 4 Brown Swiss, 132 ± 20 d in milk) were used in a replicated 4 × 4 Latin square design with 4-wk periods to determine the effects of feeding corn germ on dairy cow performance. Diets were formulated with increasing concentrations of corn germ (Dakota Germ, Poet Nutrition, Sioux Falls, SD) at 0, 7, 14, and 21% of the diet dry matter (DM). All diets had a 55:45 forage to concentrate ratio, where forage was 55% corn silage and 45% alfalfa hay. Dietary fat increased from 4.8% in the control diet to 8.2% at the greatest inclusion level of corn germ. The addition of corn germ resulted in a quadratic response in DM intake with numerically greater intake at 14% of diet DM. Feeding corn germ at 7 and 14% of diet DM increased milk yield and energy-corrected milk as well as fat percentage and yield. Milk protein yield tended to decrease as the concentration of corn germ increased in the diet. Dietary treatments had no effect on feed efficiency, which averaged 1.40 kg of energy-corrected milk/kg of DMI. Increasing the dietary concentration of corn germ resulted in a linear increase in milk fat concentrations of monounsaturated and polyunsaturated fatty acids at the expense of saturated fatty acids. Milk fat concentration and yield of cis-9, trans-11 and trans-10, cis-12 conjugated linoleic acid were increased with increased dietary concentrations of corn germ. Although milk fat concentrations of both total trans-18:1 and cis-18:1 fatty acids increased linearly, a marked numeric increase in the concentration of trans-10 C18:1 was observed in milk from cows fed the 21% corn germ diet. A similar response was observed in plasma concentration of trans-10 C18:1. Feeding increasing concentrations of corn germ had no effect on plasma concentrations of glucose, triglyceride, or β-hydroxybutyrate; however, the concentration of nonesterified fatty acids increased linearly, with plasma cholesterol concentration demonstrating a similar trend. Germ removed from corn grain before ethanol production provides an alternative source of fat for energy in lactating dairy cows when fed at 7 and 14% of diet DM. Our results suggest that fat from corn germ may be relatively protected with no adverse effect on DM intake, milk production, and milk composition when fed up to 14% of diet DM.     

Milk fatty acids in dairy cows fed whole crude linseed, extruded linseed, or linseed oil, and their relationship with methane output

This experiment studied the effect of 3 different physical forms of linseed fatty acids (FA) on cow dairy performance, milk FA secretion and composition, and their relationship with methane output. Eight multiparous, lactating Holstein cows were assigned to 1 of 4 dietary treatments in a replicated 4 × 4 Latin square design: a control diet (C) based on corn silage (59%) and concentrate (35%), and the same diet supplemented with whole crude linseed (CLS), extruded linseed (ELS), or linseed oil (LSO) at the same FA level (5% of dietary dry matter). Each experimental period lasted 4 wk. Dry matter intake was not modified with CLS but was lowered with both ELS and LSO (−3.1 and −5.1 kg/d, respectively) compared with C. Milk yield and milk fat content were similar for LSO and ELS but lower than for C and CLS (19.9 vs. 22.3 kg/d and 33.8 vs. 43.2 g/kg, on average, respectively). Compared with diet C, CLS changed the concentrations of a small number of FA; the main effects were decreases in 8:0 to 16:0 and increases in 18:0 and cis-9 18:1. Compared with diet C (and CLS in most cases), LSO appreciably changed the concentrations of almost all the FA measured; the main effects were decreases in FA from 4:0 to 16:0 and increases in 18:0, trans-11 16:1, all cis and trans 18:1 (except trans-11 18:1), and nonconjugated trans 18:2 isomers. The effect of ELS was either intermediate between those of CLS and LSO or similar to LSO with a few significant exceptions: increases in 17:0 iso; 18:3n-3; trans-11 18:1; cis-9, trans-11 conjugated linoleic acid; and trans-11, trans-13 conjugated linoleic acid and a smaller increase in cis-9 18:1. The most positive correlations (r = 0.87 to 0.91) between milk FA concentrations and methane output were observed for saturated FA from 6:0 to 16:0 and for 10:1, and the most negative correlations (r = −0.86 to −0.90) were observed for trans-16+cis-14 18:1; cis-9, trans-13 18:2; trans-11 16:1; and trans-12 18:1. Thus, milk FA profile can be considered a potential indicator of in vivo methane output in ruminants.