Efficacy of a novel whey protein gel complex to increase the unsaturated fatty acid composition of bovine milk fat

A novel whey protein emulsion gel (WPEG) complex was developed to protect dietary unsaturated fatty acids from rumen biohydrogenation with the goal of modifying the fatty acid composition of milk fat. Three experiments were conducted with WPEG complexes made from either whey protein concentrate containing 80% crude protein, whey protein isolate, or whey protein concentrate high-gel capacity. Each experiment lasted 3 wk. All cows received a basal total mixed ration (TMR). During wk 1 and 3, all cows received only the TMR. During wk 2, 3 control cows received 330 g/d of soybean oil added to the TMR, and the other 3 cows received 330 g/d of soybean oil in one of the WPEG complexes. During wk 2, C18:2 increased from 3.29 to 5.88 g/100 g of fat in Experiment 1, 2.91 to 7.42 g/100 g of fat in Experiment 2, and 3.57 to 6.56 g/100 g of fat in Experiment 3 for WPEG cows. Fatty acid C18:3 increased from 0.51 to 0.84, 0.52 to 1.15, and 0.51 to 0.97 g/100 g of fat for Experiments 1, 2, and 3, respectively, for WPEG cows. Higher proportions of C18:1 trans-9 in milk fat of control cows compared with WPEG cows were seen in all experiments. The proportion of C18:1 trans-11 was also higher in control cows in Experiments 1 and 2, but not in Experiment 3. The WPEG complexes successfully protected unsaturated fatty acids from rumen biohydrogenation and resulted in an increase in the unsaturated fatty acid composition of milk fat produced by Holstein cows without increasing the trans 18-carbon monoenes.     

Effect of Dietary Starch or Micro Algae Supplementation on Rumen Fermentation and Milk Fatty Acid Composition of Dairy Cows

Two experiments with rumen-fistulated dairy cows were conducted to evaluate the effects of feeding docosahexaenoic acid (DHA; C22:6 n-3)-enriched diets or diets provoking a decreased rumen pH on milk fatty acid composition. In the first experiment, dietary treatments were tested during 21-d experimental periods in a 4 × 4 Latin square design. Diets included a control diet, a starch-rich diet, a bicarbonate-buffered starch-rich diet, and a diet supplemented with DHA-enriched micro algae [Schizochytrium sp., 43.0 g/kg of dry matter intake (DMI)]. Algae were supplemented directly through the rumen fistula. The total mixed ration consisted of grass silage, corn silage, soybean meal, and a standard or glucogenic concentrate. The glucogenic and buffered glucogenic diet had no effect on rumen fermentation and milk fatty acid composition because, unexpectedly, no reduced rumen pH was detected. The algae diet had no effect on rumen pH but provoked decreased butyrate and increased isovalerate molar proportions in the rumen. In addition, algae supplementation affected rumen biohydrogenation of linoleic and linolenic acid as reflected in the modified milk fatty acid composition toward increased conjugated linoleic acid (CLA) cis-9 trans-11, CLA trans-9 cis-11, C18:1 trans-10, C18:1 trans-11, and C22:6 n-3 concentrations. Concomitantly, on average, a 45% decrease in DMI and milk yield was observed. Based on these drastic and impractical results, a second animal experiment was performed for 20 d in which 9.35 g/kg of total DMI of algae were incorporated in the concentrate and supplemented to 3 rumen-fistulated cows. Algae concentrate feeding increased rumen pH, which was associated with decreased rumen short-chain fatty acid concentrations. Moreover, a different shift in rumen short-chain fatty acid proportions was observed compared with the first experiment because molar proportions of butyrate, isobutyrate, and isovalerate increased, whereas acetate molar proportion decreased. The milk fatty acid profile changed as in experiment 1. However, the decrease in DMI and milk yield was less pronounced (on average 10%) at this algae supplementation level, whereas milk fat percentage decreased from 47.9 to 22.0 g/kg of milk after algae treatment. In conclusion, an algae supplementation level of about 10 g/kg of DMI proved effective to reduce the milk fat content and to modify the milk fatty acid composition toward increased CLA cis-9 trans-11, C18:1 trans, and DHA concentrations.     

Effect of level of oil inclusion in the diet of dairy cows at pasture on animal performance and milk composition and properties

The effect of including additional oil, incorporated as whole rapeseeds, in the diet of 64 Holstein–Friesian dairy cows (32 mid‐ and 32 late‐lactation) at pasture on animal performance and milk fat composition and properties was followed over a continuous trial of 20 weeks duration. Within two stages of lactation (mid, 130 ± 16.2 days, or late, 231 ± 58.9 days), cows were allocated to concentrate treatments representing four levels of rapeseed oil inclusion, 0 (control), 200, 400 and 600 g oil day^?1. Oil inclusion had little effect on milk yield but decreased milk fat content significantly (P < 0.01), with a mean depression of 0.40% at the highest level of oil inclusion. The content of milk protein also decreased with increasing addition of oil, but the decrease was smaller than the milk fat depression and was not statistically significant. Increasing the level of rapeseed oil in the diet to 600 g oil day^?1 resulted in linear changes in milk fat and protein concentrations which were described by regression equations. For each 100 g of rapeseed oil added to the diet, milk fat content decreased by 0.068% in mid‐lactation cows and 0.061% in late‐lactation cows, while protein content decreased by 0.026% in mid‐lactation cows and 0.028% in late‐lactation cows. Total unsaturated fatty acid content of milk fat also increased in a linear fashion with increased level of oil addition, from 345.7 g kg^?1 total fatty acids in control milk fat to 459.3 g kg^?1 total fatty acids at 600 g oil day^?1, while total saturated fatty acids decreased in the same milk fats from 640.7 to 522.2 g kg^?1 total fatty acids. These changes were reflected in lower solid fat contents (SFC) in the milk fat at the lower temperatures of measurement, eg 41% SFC at 5 °C at the highest level of oil inclusion compared with 52% in the control milk fat. However, SFC at 20 °C showed little difference with increasing level of dietary oil addition, an important factor in maintaining product integrity at room temperatures. The relatively high content of the monounsaturated fatty acid C18:1 (345.5 g kg^?1 total fatty acids at 600 g oil day^?1) and low content of polyunsaturated fatty acids (total C18:2 and C18:3 <40 g kg^?1 total fatty acids at 600 g oil day^?1) ensured that the oxidative stability of the treatment and control milk fats did not differ significantly. Stage of lactation had an unexplained effect of consistent magnitude on milk fat composition throughout the trial period, with late‐lactation animals producing milk fats containing a significantly (P < 0.001) higher proportion of unsaturated fatty acids than the mid‐lactation animals. Changes in the proportions of unsaturated fatty acids in milk fat, as reflected by changes in iodine value, were established within 2 weeks of the trial commencing and persisted over the 20 weeks of the trial duration. No adverse effect on animal health from this type of dietary manipulation was identified. Copyright © 2004 Society of Chemical Industry     

Susceptibility of dairy cows to subacute ruminal acidosis is reflected in milk fatty acid proportions,with C18:1 trans-10 as primary and C15:0 and C18:1 trans-11 as secondary indicators

The current study was carried out to assess 2 hypotheses: (1) cows differ in susceptibility to a subacute ruminal acidosis (SARA) challenge, and (2) the milk fatty acid (FA) pattern can be used to differentiate susceptible from nonsusceptible cows. For this, 2 consecutive experiments were performed. During experiment 1, the milk FA pattern was determined on 125 cows fed an increasing amount of concentrate during the first 4 wk in milk (WIM). The coefficient of variation of several SARA indicative milk FA (i.e., C15:0, C18:1 trans-10, C18:2 cis-9,trans-11, and C18:1 trans-10 to C18:1 trans-11 ratio) increased, indicating that cows reacted differently upon the concentrate build-up. A first grouping was based on the milk fat C18:1 trans-10 proportion in the third WIM. Fifteen cows with the highest proportion of the latter FA (HT10) and their counterparts with low C18:1 trans-10 and equal parity distribution (LT10) were compared, which revealed that milk fat content and milk fat to protein ratio were lower for the HT10 group. From each of the HT10 and LT10 groups, 5 animals were selected for experiment 2. The subselection of the HT10 group, referred to as HT10s, showed a high proportion of C18:1 trans-10 at 3 WIM (>0.31 g/100 g of FA), a high level of C15:0 (on average ≥1.18 g/100 g of FA over the 4 WIM), and a sharp decrease of C18:1 trans-11 (Δ ≥ 0.25 g/100 g of FA during the 4 WIM). Their counterparts (LT10s) had a low milk fat C18:1 trans-10 proportion at 3 WIM (<0.23 g/100 g of FA), an average C15:0 proportion of 0.99 g/100 g of FA or lower, and a rather stable C18:1 trans-11 proportion. The HT10s group was hypothesized to be more susceptible to a SARA challenge, achieved by increasing amounts of rapidly fermentable carbohydrates in experiment 2. The HT10s cows had a lower nadir, mean, and maximum reticulo-ruminal pH; longer period of reticulo-ruminal pH below 6.0; and higher daily reticulo-ruminal pH variation compared with LT10s cows. Throughout experiment 2, HT10s and LT10s cows differed in levels of SARA indicative milk FA. Five animals, including one LT10s and 4 HT10s cows, experienced SARA, defined as reticulo-ruminal pH <6.0 for more than 360 min/d. These results indicate that it is possible to distinguish cows with different susceptibility to a SARA challenge within a herd by monitoring the milk FA composition when cows receive the same diet.     

Flaxseed supplementation improves fatty acid profile of cow milk

The objective of the study was to determine the effects of adding flaxseed or fish oil to the diet on the milk fatty acid profile of cows. The experiment was conducted in the summer of 2006 and involved 24 Friesian cows that were divided into 3 groups of 8 animals according to different type of fat supplementation: a traditional diet with no fat supplementation, a diet supplemented with whole flaxseed, and a diet supplemented with fish oil. Results suggested that whole flaxseed supplementation positively affects the milk fatty acid profile during summer. In particular, milk from cows receiving flaxseed supplementation showed a decrease in saturated fatty acid, an increase in monounsaturated fatty acid, and, together with the milk from fish oil-supplemented cows, an increase in polyunsaturated fatty acid content compared with milk from control cows. As expected, both fish oil and flaxseed supplementation increased the content of n-3 polyunsaturated fatty acids in milk fat. The increased dietary intake of C18:3 in flaxseed-supplemented cows resulted in increased levels of milk C18:1 trans-11 and increased conjugated linoleic acid C18:2 cis-9,trans-11 by Δ⁹-desaturase activity. Milk from flaxseed-supplemented cows together with the high conjugated linoleic acid content was characterized by low atherogenic and thrombogenic indices, suggesting that its use has less detrimental effects concerning the atherosclerosis and coronary thrombosis risk associated with the consumption of milk and dairy products. In conclusion, flaxseed supplementation improves composition and nutritional properties of milk from cows milked during times of high ambient temperature.     

Chemical, physical, and sensory properties of dairy products enriched with conjugated linoleic acid

Recent studies have illustrated the effects of cis-9,trans-11 conjugated linoleic acid (CLA) on human health. Ruminant-derived meat, milk and dairy products are the predominant sources of cis-9,trans-11 CLA in the human diet. This study evaluated the processing properties, texture, storage characteristics, and organoleptic properties of UHT milk, Caerphilly cheese, and butter produced from a milk enriched to a level of cis-9,trans-11 CLA that has been shown to have biological effects in humans. Forty-nine early-lactation Holstein-British Friesian cows were fed total mixed rations containing 0 (control) or 45 g/kg (on dry matter basis) of a mixture (1:2 wt/wt) of fish oil and sunflower oil during two consecutive 7-d periods to produce a control and CLA-enhanced milk, respectively. Milk produced from cows fed the control and fish and sunflower oil diets contained 0.54 and 4.68 g of total CLA/100 g of fatty acids, respectively. Enrichment of CLA in raw milk from the fish and sunflower oil diet was also accompanied by substantial increases in trans C18:1 levels, lowered C18:0, cis-C18:1, and total saturated fatty acid concentrations, and small increases in n-3 polyunsatu-rated fatty acid content. The CLA-enriched milk was used for the manufacture of UHT milk, butter, and cheese. Both the CLA-enhanced butter and cheese were less firm than control products. Although the sensory profiles of the CLA-enriched milk, butter, and cheese differed from those of the control products with respect to some attributes, the overall impression and flavor did not differ. In conclusion, it is feasible to produce CLA-enriched dairy products with acceptable storage and sensory characteristics.     

Milk production, conjugated linoleic acid content, and in vitro ruminal fermentation in response to high levels of soybean oil in dairy ewe diet

Feeding vegetable oils rich in linoleic acid has been demonstrated to be an effective strategy to enrich milk with conjugated linoleic acid (CLA). However, high amounts of vegetable oil in the diet in free form could adversely affect animal performance, mainly in sheep. The aim of this work was to improve the ewe milk fatty acid profile by increasing potentially healthy acids such as CLA without any detrimental effects on milk production and ruminal fermentation with soybean oil (SBO) diet supplementation. Twenty-four ewes were assigned to 2 treatments and fed 2 diets (control or supplemented with 6% of SBO; 2 lots of 6 animals per treatment) and fed ad libitum for 4 wk. The forage:concentrate ratio was 20:80. Batch cultures of rumen microorganisms were used to study in vitro rumen fermentation. Changes in fatty acid profile were characterized as a reduction in C6:0 to C16:0 at the expense of an increase in C18:0, C18:1 isomers, and CLA concentrations. Proportions of milk CLA and trans-11 C18:1 (vaccenic acid) went from 1.04 to 3.44 and 2.08 to 6.20 g/100 g of total fatty acids, respectively. However, the SBO diet also increased trans-10 C18:1 and other trans C18:1 content. No significant decreases were found in the treatments for dry matter intake and milk production. The notable increases in trans-10, cis-12 and trans-9, cis-11 were not accompanied by fat level decreases in ewe milk. Concerning in vitro ruminal fermentation, no significant differences were found in the extent and rate of gas production, effective degradability, in vitro true digestibility, and volatile fatty acid production. The results demonstrate that dairy sheep milk CLA content can be substantially increased (more than 3-fold) by adding high levels of SBO in the diet as free oil, without any negative effects on animal performance.     

Comparative potential of white and red clover to modify the milk fatty acid profile of cows fed ryegrass‐based diets from zero‐grazing and silage systems

BACKGROUND: Two experiments were conducted to compare the effects of white and red clover on the fatty acid composition of milk fat from cows fed ryegrass‐based diets. In experiment 1, fresh ryegrass was mixed with white or red clover (60/40, on a dry matter (DM) basis). Experiment 2 involved similar mixed diets in ensiled form, and one ryegrass‐silage diet without the addition of clover. RESULTS: Total DM intake, milk yield and milk fat content were not affected by dietary treatments. Feeding freshly cut white versus red clover supplemented diets resulted in a higher proportion of n‐3 fatty acids, especially α‐linolenic acid, in milk fat. Addition of any clover silage to ryegrass silage increased the proportions of n‐3 fatty acids in milk fat, and reduced the proportions of conjugated linoleic acids (CLA), including C18:2 c9t11, and C18:1cis isomers. The n‐6/n‐3 ratio was elevated compared to the diet not supplemented with clover. CONCLUSION: White clover seemed to be slightly superior to red clover supplementation, but the effects of clover supplementation as such were generally larger than that of clover type. However, a higher concentration of n‐3 fatty acids with clover supplementation coincided with a lower concentration of CLA in the milk fat. Copyright © 2007 Society of Chemical Industry     

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.     

Short communication: The effect of substituting fish oil in dairy cow diets with docosahexaenoic acid-micro algae on milk composition and fatty acids profile

The effects of substituting fish oil (FO) with docosahexaenoic acid (DHA)-micro algae on milk chemical and fatty acid composition were examined in this study. Twenty-four Holstein cows in mid lactation grazing on an alfalfa-grass based pasture were divided into 4 treatment groups (6 cows/treatment) and supplemented with 7 kg/d grain mix plus 350 g of soybean oil and one of the following: 1) 150 g of FO, 2) 100 g of FO plus 50 g of algae, 3) 50 g of FO plus 100 g of algae, or 4) 150 g of algae. Cows were fed treatment diets for 3 wk, and milk samples were collected from each cow during the last 3 d of the study. Milk production (17.96, 17.56, 17.55, and 19.26 kg/d for treatment diets 1 to 4, respectively), milk fat percentages (3.17, 3.49, 3.74, and 3.43%), and milk protein percentages (3.35, 3.50, 3.71, and 3.42%) were similar between treatment diets. Concentrations (g/100 g of fatty acids) of milk cis-9 trans-11 (c9t11) conjugated linoleic acid (CLA; 3.41, 3.69, 4.47, and 4.21 for treatment diets 1 to 4, respectively) and vaccenic acid (11.80, 12.83, 13.87, and 13.53) were similar between treatment diets. Results of this study suggest that DHA-micro algae can partially or fully substitute FO in a cow's diet without any adverse effects on milk production, milk composition, or milk c9t11 CLA content. The DHA-micro algae may be used as a viable alternative for FO in cow's diet to modify rumen biohydrogenation to increase milk c9t11 CLA content.     

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.     

Diets supplemented with starch and corn oil,marine algae,or hydrogenated palm oil differentially modulate milk fat secretion and composition in cows and goats: A comparative study

A direct comparative study of dairy cows and goats was performed to characterize the animal performance and milk fatty acid (FA) responses to 2 types of diets that induce milk fat depression in cows as well as a diet that increases milk fat content in cows but for which the effects in goats are either absent or unknown. Twelve Holstein cows and 12 Alpine goats, all multiparous, nonpregnant, and at 86 ± 24.9 and 61 ± 1.8 DIM, respectively, were allocated to 1 of 4 groups and fed diets containing no additional lipid (CTL) or diets supplemented with corn oil [5% dry matter intake (DMI)] and wheat starch (COS), marine algae powder (MAP; 1.5% DMI), or hydrogenated palm oil (HPO; 3% DMI), according to a 4 × 4 Latin square design with 28-d experimental periods. Dietary treatments had no significant effects on milk yield and DMI in both species, except for COS in cows, which decreased DMI by 17%. In cows, milk fat content was lowered by COS (?45%) and MAP (?22%) and increased by HPO (13%) compared with CTL, and in goats only MAP had an effect compared with CTL by decreasing milk fat content by 15%. In both species, COS and MAP lowered the yields (mmol/d per kg of BW) of <C16 and C16 FA. With COS, this decrease was compensated by an increase of >C16 FA in goats, but not in cows, and the >C16 FA yield decreased with MAP in both species. HPO supplementation increased the milk yield of C16 FA in cows. Compared with CTL, COS induced an increase of trans-10,cis-12 conjugated linoleic acid by 18 fold in cows and 7 fold in goats and of trans-10 18:1 by 13 fold in cows and 3 fold in goats. Moreover, other conjugated linoleic acid isomers, such as trans-10,trans-12 and trans-7,cis-9, were increased to a greater extent in cows (8 and 4 fold, respectively) compared with goats (4 and 2 fold, respectively) on the COS treatment. In both species, the responses to MAP were characterized by a decrease in the milk concentration of 18:0 (3 fold, on average) and cis-9 18:1 (2 fold, on average) combined with a 3-fold increase in the total trans 18:1, with an increase in trans-10 18:1 only observed in cows. Compared with CTL, the response to HPO was distinguished by an increase in 16:0 (10%) in cows. This comparative study clearly demonstrated that each ruminant species responds differently to COS and HPO treatments, whereas MAP caused similar effects, and that goats are less sensitive than cows to diets that induce a shift from the trans-11 toward the trans-10 ruminal pathways.     

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.     

Seasonal changes of CLA isomers and other fatty acids of milk fat from grazing dairy herds in the Azores

BACKGROUND: Season of the year associated with dietary changes has been recognized as a factor implicated in milk fat fatty acid (FA) profile in dairy cows. However, a lack of information exists concerning cows grazing all year round as is practiced in the Azores, where cows are supplemented in winter with maize silage plus concentrates, while in spring the higher grass allowance only requires supplementation with concentrate. The main objective of this study was to detect any seasonal variation of FA profile of milk fat from milk sampled in bulk tanks of 12 Azorean dairy herds. RESULTS Compared to winter milk, milk fat from spring presented a higher proportion of CLA cis‐9,trans‐11 (14.3 versus 9.6 g kg^?1 FA), C18:1 trans‐11 (32 versus 22 g kg^?1 FA), C18:2 trans‐11,cis‐15 (3.7 versus 2.2 g kg^?1 FA), CLA trans‐11,cis‐13 (0.34 versus 0.23 g kg^?1 FA) and C18:3 n‐3 (5.7 versus 5.4 g kg^?1 FA). The C18:2 n‐6/C18:3 n‐3 ratio was lower (P < 0.05) in spring. Branched‐chain FA, except the anteiso‐C15:0, were higher in spring, while odd‐chain FA (C15:0) were higher in winter. CONCLUSION: Dairy herd management in the Azores presents a seasonal variation of milk fat FA composition, where the spring milk may present increased potential benefits for human consumers. Copyright © 2008 Society of Chemical Industry     

Conjugated linoleic acid increases in milk from cows fed condensed corn distillers solubles and fish oil

Twelve lactating Holstein cows were randomly assigned to 1 of 4 experimental diets in a replicated 4 × 4 Latin square design with 4-wk periods to ascertain the lactational response to feeding fish oil (FO), condensed corn distillers solubles (CDS) as a source of extra linoleic acid, or both. Diets contained either no FO or 0.5% FO and either no CDS or 10% CDS in a 2 × 2 factorial arrangement of treatments. Diets were fed as total mixed rations for ad libitum consumption. The forage to concentrate ratio was 55:45 on a dry matter basis for all diets and the diets contained 16.2% crude protein. The ether extract concentrations were 2.86, 3.22, 4.77, and 5.02% for control, FO, CDS, and FOCDS diets, respectively. Inclusion of FO or CDS or both had no effect on dry matter intake, feed efficiency, body weight, and body condition scores compared with diets without FO and CDS, respectively. Yields of milk (33.3 kg/d), energy-corrected milk, protein, lactose, and milk urea N were similar for all diets. Feeding FO and CDS decreased milk fat percentages (3.85, 3.39, 3.33, and 3.12%) and yields compared with diets without FO and CDS. Proportions of trans-11 C18:1 (vaccenic acid), cis-9 trans-11 conjugated linoleic acid (CLA; 0.52, 0.90, 1.11, and 1.52 g/100 g of fatty acids), and trans-10 cis-12 CLA (0.07, 0.14, 0.13, and 0.16 g/100 g of fatty acids) in milk fat were increased by FO and CDS. No interactions were observed between FO and CDS on cis-9 trans-11 CLA although vaccenic acid tended to be higher with the interaction. The addition of CDS to diets increased trans-10 C18:1. Greater ratios of vaccenic acid to cis-9 trans-11 CLA in plasma than in milk fat indicate tissue synthesis of cis-9 trans-11 CLA in the mammary gland from vaccenic acid in cows fed FO or CDS. Feeding fish oil at 0.5% of diet dry matter with a C18:2 n-6 rich source such as CDS increased the milk CLA content but decreased milk fat percentages.     

Effectiveness of oils rich in linoleic and linolenic acids to enhance conjugated linoleic acid in milk from dairy cows

Forty Holstein dairy cows were used to determine the effectiveness of linoleic or linolenic-rich oils to enhance C_18:2cis-9, trans-11 conjugated linoleic acid (CLA) and C_18:1trans-11 (vaccenic acid; VA) in milk. The experimental design was a complete randomized design for 9 wk with measurements made during the last 6 wk. Cows were fed a basal diet containing 59% forage (control) or a basal diet supplemented with either 4% soybean oil (SO), 4% flaxseed oil (FO), or 2% soybean oil plus 2% flaxseed oil (SFO) on a dry matter basis. Total fatty acids in the diet were 3.27, 7.47, 7.61, and 7.50 g/100 g in control, SO, FO, and SFO diets, respectively. Feed intake, energy-corrected milk (ECM) yield, and ECM produced/kg of feed intake were similar among treatments. The proportions of VA were increased by 318, 105, and 206% in milk fat from cows in the SO, FO, and SFO groups compared with cows in the control group. Similar increases in C_18:2cis-9, trans-11 CLA were 273, 150, and 183% in SO, FO, and SFO treatments, respectively. Under similar feeding conditions, oils rich in linoleic acid (soybean oil) were more effective in enhancing VA and C_18:2cis-9, trans-11 CLA in milk fat than oils containing linolenic acid (flaxseed oil) in dairy cows fed high-forage diets (59% forage). The effects of mixing linoleic and linolenic acids (50:50) on enhancing VA and C_18:2cis-9, trans-11 CLA were additive, but not greater than when fed separately. Increasing the proportion of healthy fatty acids (VA and CLA) by feeding soybean or flaxseed oil would result in milk with higher nutritive and therapeutic value.     

Responses to increasing amounts of high-oleic sunflower fatty acids infused into the abomasum of lactating dairy cows

Increasing the oleic acid (18:1 cis-9) content of milk fat might be desirable to meet consumer concerns about dietary healthfulness and for certain manufacturing applications. The extent to which milk fat could be enriched with oleic acid is not known. Increasing the intestinal supply of polyunsaturated fatty acids decreases dry matter intake (DMI) in cows, but the effects of oleic acid have not been quantified. In a crossover design, 4 multiparous Holstein cows were abomasally infused with increasing amounts (0, 250, 500, 750, or 1,000 g/d) of free fatty acids from high-oleic sunflower oil (HOSFA) or with carrier alone. Continuous infusions (20 to 22 h/d) were for 7 d at each amount. Infusions were homogenates of HOSFA with 240 g/d of meat solubles and 11.2 g/d of Tween 80; controls received carrier only. The HOSFA contained (by wt) 2.4% 16:0, 1.8% 18:0, 91.4% 18:1 cis-9, and 2.4% 18:2. The DMI decreased linearly (range 22.0 to 5.8 kg/d) as the infused amount of HOSFA increased. Apparent total tract digestibilities of dry matter, organic matter, neutral detergent fiber, and energy decreased as the infusion increased to 750 g/d and then increased when 1,000 g/d was infused. Digestibility of total fatty acids increased linearly as infused fatty acids increased. Yields of milk, fat, true protein, casein, and total solids decreased quadratically as infused amounts increased; decreases were greatest when 750 or 1,000 g/d of HOSFA were infused. Concentrations of fat and total solids increased at the higher amounts of HOSFA. The volume mean diameter of milk fat droplets and the diameter below which 90% of the volume of milk fat is contained both increased as HOSFA infusion increased. Concentrations of short-chain fatty acids, 12:0, 14:0, and 16:0 in milk fat decreased linearly as HOSFA increased. The concentration of 18:1 cis-9 (19.4 to 57.4% of total fatty acids) increased linearly as HOSFA infusion increased. Concentrations of 18:1 cis-9 in blood triglyceride-rich lipoproteins increased linearly as infusion increased, whereas contents of 14:0, 16:0, 18:0, total 18:1 trans, and 18:2n-6 decreased linearly. The composition and physical characteristics of milk fat can be altered markedly by an increased intestinal supply of 18:1 cis-9, which could influence processing characteristics and the healthfulness of milk fat. However, an increased supply of free 18:1 cis-9 to the intestine decreased DMI and milk production.     

The effect of dietary fiber level on milk fat concentration and fatty acid profile of cows fed diets containing low levels of polyunsaturated fatty acids

The objective of this study was to investigate the effect of dietary fiber level on milk fat concentration, yield, and fatty acid (FA) profile of cows fed diets low in polyunsaturated fatty acid (PUFA). Six rumen-fistulated Holstein dairy cows (639 ± 51 kg of body weight) were used in the study. Cows were randomly assigned to 1 of 2 dietary treatments, a high fiber (HF; % of dry matter, 40% corn silage, 27% alfalfa silage, 7% alfalfa hay, 18% protein supplement, 4% ground corn, and 4% wheat bran) or a low fiber (LF; % of dry matter, 31% corn silage, 20% alfalfa silage, 5% alfalfa hay, 15% protein supplement, 19% ground wheat, and 10% ground barley) total mixed ration. The diets contained similar levels of PUFA. The experiment was conducted over a period of 4 wk. Ruminal pH was continuously recorded and milk samples were collected 3 times a week. Milk yield and dry matter intake were recorded daily. The rumen fluid in cows receiving the LF diet was below pH 5.6 for a longer duration than in cows receiving the HF diet (357 vs. 103 min/d). Neither diet nor diet by week interaction had an effect on milk yield (kg/d), milk fat concentration and yield, or milk protein concentration and yield. During wk 4, milk fat concentration and milk fat yield were high and not different between treatments (4.30% and 1.36 kg/d for the HF treatment and 4.31% and 1.33 kg/d for the LF treatment, respectively). Cows receiving the LF diet had greater milk concentrations (g/100 g of FA) of 7:0; 9:0; 10:0; 11:0; 12:0; 12:1; 13:0; 15:0; linoleic acid; FA <C16; and PUFA; and lower concentrations of iso 15:0; 18:0; trans-9 18:1; cis-9, trans-11 conjugated linoleic acid (CLA); trans-9, cis-12 18:2; 20:0; and cis-9 20:1 compared with cows receiving the HF diet. Milk concentrations (g/100 g of FA) of total trans 18:1; trans-10 18:1; trans-11 18:1; trans-10, cis-12 CLA, and trans-9, cis-11 CLA were not different between treatments. The study demonstrated that cows fed a diet low in fiber and low in PUFA may exhibit subacute ruminal acidosis and moderate changes to milk fatty acid profile but without concomitant milk fat depression. The changes in FA profile may be useful for the diagnosis of SARA even in the absence of milk fat depression.     

Diet supplementation with fish oil and sunflower oil to increase conjugated linoleic acid levels in milk fat of partially grazing dairy cows

The objective of this study was to determine the long-term effect on milk conjugated linoleic acid (cis-9, trans-11 CLA) of adding fish oil (FO) and sunflower oil (SFO) to the diets of partially grazing dairy cows. Fourteen Holstein cows were divided into 2 groups (7 cows/treatment) and fed either a control or oil-supplemented diet for 8 wk while partially grazing pasture. Cows in group 1 were fed a grain mix diet (8.0 kg/d, DM basis) containing 400 g of saturated animal fat (control). Cows in the second group were fed the same grain mix diet except the saturated animal fat was replaced with 100 g of FO and 300 g of SFO. Cows were milked twice a day and milk samples were collected weekly throughout the trial. Both groups grazed together on alfalfa-based pasture ad libitum and were fed their treatment diets after the morning and afternoon milking. Milk production (30.0 and 31.2 kg/d), milk fat percentages (3.64 and 3.50), milk fat yield (1.08 and 1.09 kg/d), milk protein percentages (2.97 and 2.88), and milk protein yield (0.99 and 0.91 kg/d) for diets 1 and 2, respectively, were not affected by the treatment diets. The concentrations of cis-9, trans-11 CLA (1.64 vs. 0.84 g/100 g of fatty acids) and vaccenic acid (5.11 vs. 2.20 g/100 g of fatty acids) in milk fat were higher for cows fed the oil-supplemented diet over the 8 wk of oil supplementation. The concentration of cis-9, trans-11 CLA in milk fat reached a maximum (1.0 and 1.64 g/100 g of fatty acids for diets 1 and 2, respectively) in wk 1 for both diets and remained relatively constant thereafter. The concentration of vaccenic acid in milk fat followed the same temporal pattern as cis-9, trans-11 CLA. In conclusion, supplementing the diet of partially grazing cows with FO and SFO increased the milk cis-9, trans-11 CLA content, and that increase remained relatively constant after 1 wk of oil supplementation.     

Milk conjugated linoleic acid response to fish oil and sunflower oil supplementation to dairy cows managed under two feeding systems

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