Examination of the persistency of milk fatty acid composition responses to fish oil and sunflower oil in the diet of dairy cows

Based on the potential benefits of cis-9, trans-11 conjugated linoleic acid (CLA) for human health, there is a need to develop effective strategies for enhancing milk fat CLA concentrations. Levels of cis-9, trans-11 CLA in milk can be increased by supplements of fish oil (FO) and sunflower oil (SO), but there is considerable variation in the response. Part of this variance may reflect time-dependent ruminal adaptations to high levels of lipid in the diet, which lead to alterations in the formation of specific biohydrogenation intermediates. To test this hypothesis, 16 late lactation Holstein-British Friesian cows were used in a repeated measures randomized block design to examine milk fatty acid composition responses to FO and SO in the diet over a 28-d period. Cows were allocated at random to corn silage-based rations (8 per treatment) containing 0 (control) or 45 g of oil supplement/kg of dry matter consisting (1:2; wt/wt) of FO and SO (FSO), and milk composition was determined on alternate days from d 1. Compared with the control, the FSO diet decreased mean dry matter intake (21.1 vs. 17.9 kg/d), milk fat (47.7 vs. 32.6 g/kg), and protein content (36.1 vs. 33.3 g/kg), but had no effect on milk yield (27.1 vs. 26.4 kg/d). Reductions in milk fat content relative to the FSO diet were associated with increases in milk trans-10 18:1, trans-10, cis-12 CLA, and trans-9, cis-11 CLA concentrations (r² = 0.74, 0.57, and 0.80, respectively). Compared with the control, the FSO diet reduced milk 4:0 to 18:0 and cis 18:1 content and increased trans 18:1, trans 18:2, cis-9, trans-11 CLA, 20:5 n-3, and 22:6 n-3 concentrations. The FSO diet caused a rapid elevation in milk cis-9, trans-11 CLA content, reaching a maximum of 5.37 g/100 g of fatty acids on d 5, but these increases were transient, declining to 2.35 g/100 g of fatty acids by d 15. They remained relatively constant thereafter. Even though concentrations of trans-11 18:1 followed the same pattern of temporal changes as cis-9, trans-11 CLA, the total trans 18:1 content of FSO milk was unchanged because of the concomitant increases in the concentration of other isomers (Δ^4-10 and Δ^12-15), predominantely trans-10 18:1. In conclusion, supplementing diets with FSO enhances milk fat cis-9, trans-11 CLA content, but the high level of enrichment declines because of changes in ruminal biohydrogenation that result in trans-10 replacing trans-11 as the major 18:1 biohydrogenation intermediate formed in the rumen.     

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.     

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.     

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.     

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.     

Effect of fish oil and sunflower oil on rumen fermentation characteristics and fatty acid composition of digesta in ewes fed a high concentrate diet

Studies in ruminants have shown that supplementing the diet with a mixture of fish oil (FO) and sunflower oil (SO) enhances the concentration of cis-9, trans-11 conjugated linoleic acid (CLA), 20:5 n-3, and 22:6 n-3 in milk because of alterations in ruminal biohydrogenation, but the intermediates formed under these conditions are not well characterized. Five ewes fitted with rumen cannula and fed a high concentrate diet were used to examine the effect of a mixture (30 g/kg of DM) of FO and SO (1:2, wt/wt) on temporal changes in rumen fermentation characteristics and the relative abundance of biohydrogenation intermediates in ruminal digesta collected after 0, 3, and 10 d on diet. Appearance and identification of biohydrogenation intermediates was determined based on complementary gas-liquid chromatography and Ag+-HPLC analysis of fatty acid methyl esters and gas chromatography-mass spectrometry analysis of corresponding 4,4-dimethyloxazoline derivatives. Inclusion of FO and SO in the diet had no effect on rumen pH, volatile fatty acid concentrations, or nutrient digestion, but altered the fatty acid composition of ruminal digesta, changes that were characterized by time-dependent decreases in 18:0 and 18:2 n-6 and the accumulation of trans 16:1, trans 18:1, 10-O-18:0, and trans 18:2. Lipid supplements enhanced the proportion of 20:5 n-3 and 22:6 n-3 in digesta and resulted in numerical increases in cis-9, trans-11 conjugated linoleic acid concentrations, but decreased the relative abundance of trans-10, cis-12 conjugated linoleic acid. Furthermore, detailed analysis revealed the appearance of several unique 20:1, 20:2, 22:1, 22:3, and 22:4 products in ruminal digesta that accumulated over time, providing the first indications of 20 and 22 carbon fatty acid intermediates formed during the biohydrogenation of long-chain unsaturated fatty acids in sheep. In conclusion, FO and SO in a high concentrate diet caused a time-dependent inhibition of the complete biohydrogenation of 16 and 18 carbon unsaturated fatty acids, and resulted in the accumulation of trans 16:1, trans 18:1, and trans 18:2, 20, and 22 carbon metabolites in ruminal digesta of sheep, with no evidence of a shift in ruminal biohydrogenation pathways toward trans-10 18:1 formation.     

High-concentrate diets and polyunsaturated oils alter trans and conjugated isomers in bovine rumen, blood, and milk

Three Holstein cows were fed a high-concentrate diet (65:35 concentrate to forage) supplemented with either 5% sunflower oil (SO), 5% linseed oil (LO), or 2.5% fish oil (FO) to examine effects on biohydrogenation and fatty acid profiles in rumen, blood plasma, and milk. Diets were fed in a 3 × 3 Latin square with 4-wk periods with grass hay as the forage. Milk yield, dry matter intake, and percentages of milk fat (2.64) and protein (3.22) did not differ. All diets resulted in incomplete hydrogenation of unsaturated fatty acids as indicated by the profiles of 18:1 isomers, conjugated 18:2 isomers, nonconjugated 18:2 isomers, and 18:0 in ruminal fluid. Percentages of 8:0-14:0 and 16:0 in milk fat were greater with FO. Percentage and yield of trans10,cis12-18:2 were small and greater in cows fed SO (0.14%, 0.57 g/d) than FO (0.03%, 0.15 g/d) or LO (0.04%, 0.12 g/d). Percentage and yield of trans10-18:1, however, increased with FO (6.16%) and SO (6.47%) compared with LO (1.65%). Dietary FO doubled percentage of cis11-18:1 in rumen, plasma, and milk fat. Despite a lack of difference in ruminal percentage of trans11-18:1 (10.5%), cows fed FO had greater plasma trans11-18:1 (116 vs. 61.5 μg/mL) but this response did not result in greater trans11-18:1 percentage in milk fat, which averaged 5.41% across diets. Percentage (2.2%) and yield (14.3 g/d) of cis9,trans11-18:2 in milk fat did not differ due to oils. Unique responses to feeding LO included greater than 2-fold increases in percentages of trans13+14-18:1, trans15-18:1, trans16-18:1, cis15-18:1, cis9,trans12-18:2 and trans11,cis15 -18:2 in umen, plasma, and milk, and cis9,trans13-18:2 in plasma and milk. Ruminal 18:0 percentage had the highest positive correlation with milk fat content (r = 0.82) across all diets. When compared with previous data with cows fed high-concentrate diets without oil supplementation, results suggest that greater production of trans10-18:1, cis11-18:1, and trans11,cis15-18:2 coupled with low production of 18:0 in the rumen may be associated with low milk fat content when feeding high-concentrate diets and fish oil. In contrast, SO or LO could lead to low milk fat content by increasing ruminal trans10-18:1 (SO) or trans11,cis15-18:2 and trans9,trans12-18:2 (LO) along with a reduction in mammary synthesis of 8:0-16:0. Simultaneous increases in ruminal trans11-18:1 with fish oil, at a fraction of sunflower oil supplementation, may represent an effective strategy to maintain cis9,trans11-18:2 synthesis in mammary while reducing milk fat output and sparing energy.     

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.     

Milk fatty acid profile and dairy sheep performance in response to diet supplementation with sunflower oil plus incremental levels of marine algae

In an attempt to develop strategies for enhancing the nutritional value of sheep milk fat, dairy ewe diet was supplemented with 3 incremental levels of marine algae (MA), in combination with sunflower oil, to evaluate the effects of these marine lipids on milk fatty acid (FA) profile and animal performance. Fifty Assaf ewes in mid lactation were distributed in 10 lots of 5 animals each and allocated to 5 treatments (2 lots per treatment): no lipid supplementation (control) or supplementation with 25 g of sunflower oil/kg of DM plus 0 (SO), 8 (SOMA₁), 16 (SOMA₂), or 24 (SOMA₃) g of MA (56.7% ether extract)/kg of DM. Milk production and composition, including FA profile, were analyzed on d 0, 3, 7, 14, 21, and 28 of treatment. Neither intake nor milk yield were significantly affected by lipid addition, but all MA supplements decreased milk fat content from d 14 onward, reaching a 30% reduction after 28 d on SOMA₃. This milk fat depression might be related not only to the joint action of some putative fat synthesis inhibitors, such as trans-9,cis-11 C18:2 and probably trans-10 C18:1, but also to the limited ability of the mammary gland to maintain a desirable milk fat fluidity, that would have been caused by the noticeable increase in trans-C18:1 together with the lowered availability of stearic acid for oleic acid synthesis through Δ⁹-desaturase. Furthermore, all lipid supplements, and mainly MA, reduced the secretion of de novo FA (C6:0-C14:0) without increasing the yield of preformed FA (>C16). Supplementation with sunflower oil plus MA resulted in larger increases in cis-9,trans-11 C18:2 than those observed with sunflower oil alone, achieving a mean content as high as 3.22% of total FA and representing a more than 7-fold increase compared with the control. Vaccenic acid (trans-11 C18:1) was also significantly enhanced (on average +794% in SOMA treatments), as was C22:6 n-3 (DHA) content, although the transfer efficiency of the latter, from the diets to the milk, was very low (5%). However, the highest levels of MA inclusion (SOMA₂ and SOMA₃) reduced the milk n-6:n-3 ratio, but MA supplements caused an important increase in trans-10 C18:1, which would rule out the possibility that this milk has a healthier fat profile before determining the specific role of each individual FA and ensuring that this trans-FA is at least innocuous in relation to cardiovascular disease risk.     

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.     

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.     

A conjugated linoleic acid supplement containing trans-10, cis-12 reduces milk fat synthesis in lactating sheep

The efficacy of conjugated linoleic acid (CLA) supplements containing trans-10, cis-12 for reducing milk fat synthesis has been well documented in dairy cows, but studies with other ruminant species are less convincing, and there have been no investigations of this in sheep. Therefore, the current study was designed to determine whether trans-10, cis-12 CLA would inhibit milk fat synthesis in sheep. Twenty multiparous ewes in early lactation were paired and randomly allocated to 2 treatments: grass hay plus concentrate either unsupplemented (control) or supplemented with lipid-encapsulated CLA to provide 2.4 g/d of trans-10, cis-12 CLA. The CLA dose was based on published responses of dairy cows extrapolated to ewes on a metabolic body weight basis. The experimental design was a 2-period crossover with 10-d treatment periods separated by a 10-d interval. Compared with the control, CLA supplementation reduced milk fat content from 6.4 to 4.9% and reduced fat yield from 95 to 80 g/d. The CLA treatment also increased milk yield from 1,471 to 1,611 g/d and increased protein yield from 68 to 73 g/d. Milk protein content and DMI were unaffected by treatment. The reduction in milk fat yield was due to decreases in both de novo fatty acid synthesis and uptake of preformed fatty acids. Milk fat content of trans-10, cis-12 CLA was < 0.01 and 0.12 g/100 g of fatty acids for the control and CLA treatments, respectively. The transfer efficiency of trans-10, cis-12 CLA from the dietary supplement into milk fat was 3.8%. Results of the present study demonstrate that a CLA supplement containing trans-10, cis-12 CLA reduces milk fat synthesis in lactating sheep in a manner similar to dairy cows when fed at an equivalent dose (metabolic body weight basis). Furthermore, the nutrients spared by the reduction in milk fat coincided with an increase in milk and milk protein yield.     

Pregnancy, bovine somatotropin, and dietary n-3 fatty acids in lactating dairy cows: III. Fatty acid distribution

Our objective was to examine effects of exogenous bovine somatotropin (bST), pregnancy, and dietary fatty acids on fatty acid distribution in various tissues of lactating dairy cows. Two diets were fed, starting about 17 d in milk (DIM), in which oil of whole cottonseed (control diet) was compared with a calcium salt of fish oil-enriched lipid (FO; 1.9% of dietary DM). Starting at 44 ± 5 DIM, ovulation was synchronized with a presynchronization plus Ovsynch protocol (d 0 = time of synchronized ovulation). Some cows were inseminated (77 ± 12 DIM) to create a pregnant group. On d 0 and 11, cows received bST (500 mg) or no bST, and were killed on d 17 (94 ± 12 DIM). Number of cows in control group was 5 bST-treated cyclic (bST-C), 5 non-bST-treated cyclic (no bST-C), 4 bST-treated pregnant (bST-P), and 5 non-bST-treated pregnant (no bST-P) cows; and for the FO diet: 4 bST-treated (bST-FO-C) and 5 non-bST-treated cyclic (no bST-FO-C) cows. At slaughter, samples of endometrium, liver, muscle, s.c. adipose, internal adipose, and mammary gland were collected. Milk was collected at 75 ± 5 DIM. Gas chromatography was used to determine fatty acid percentages in tissues and milk fat. Endometrium from the cows fed FO had increased proportions of C20:5 and C22:6, whereas C20:4 was decreased. Injections of bST reduced both C18:2 and the n-6:n-3 ratio, but increased C22:6 in endometrium of cyclic control-fed, but not pregnant cows. In addition, FO decreased the n-6:n-3 ratio in all tissues and milk fat except for s.c. and internal adipose tissue. Cows fed FO also had increased C18:3, C20:5, and C22:6 in the liver and mammary tissue, and C18:3 and C22:6 were increased in the milk fat. The FO diet decreased the Δ⁹-desaturase index [(product of Δ⁹-desaturase]/(product of Δ⁹-desaturase + substrate of Δ⁹-desaturase]; DIX) in muscle and s.c. tissues, accompanied by an increase in saturated fatty acid (SFA) percentage. In addition, FO diet decreased DIX in the endometrium. In mammary and internal adipose tissues, bST increased DIX in cyclic control-fed cows, whereas bST decreased DIX in FO-fed cows, with no difference in the concentration of SFA and UNSFA. Cis-9, trans-11 conjugated linoleic acid was increased in milk fat, but decreased in the muscle and s.c. adipose tissue of FO-fed cows. The FO-enriched lipid, bST treatment, and early pregnancy can alter fatty acid percentages and distributions that may alter tissue functionality and functional nutrients of consumer products.     

Milk and cheese from cows fed calcium salts of palm and fish oil alone or in combination with soybean products

Twenty cows were used in a randomized block design experiment for 6 wk to determine the influence of feeding partial ruminally inert Ca salts of palm and fish oil (Ca-PFO), alone or in combination with extruded full-fat soybeans or soybean oil, on milk fatty acid (FA) methyl esters composition and consumer acceptability of milk and Cheddar cheese. Cows were fed either a diet containing 44% forage and 56% concentrate (control) or a diet supplemented with 2.7% Ca-PFO (FO), 5% extruded full-fat soybeans + 2.7% Ca-PFO (FOESM), or 0.75% soybean oil + 2.7% Ca-PFO (FOSO). Total dietary FA content in the control, FO, FOESM, and FOSO diets were 4.61, 6.28, 6.77, and 6.62 g/100 g, respectively. There was no difference in nutrient intake, milk yield, or milk composition among treatments. Conjugated linoleic acid (CLA) C_18:2cis-9, trans-11 isomer, C_18:1trans-11 (VA), and total n-3 FA in milk from cows on the control, FO, FOESM, and FOSO treatments were 0.56, 1.20, 1.36, and 1.74; 3.29, 4.66, 6.34, and 7.81; 0.62, 0.69, 0.69, and 0.67 g/100 g of FA, respectively. Concentrations of CLA, VA, and total n-3 FA in cheese were similar to milk. A trained sensory panel detected no difference in flavors of milk and cheese, except for acid flavor below a slightly perceptible level in cheese from all treatments. Results suggest that feeding Ca-PFO alone or in combination with extruded full-fat soybeans or soybean oil enhanced the CLA, VA, total unsaturated and n-3 FA in milk and cheese without negatively affecting cow performance and consumer acceptability characteristics of milk and cheese.     

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 the supplementation of dairy sheep diet with incremental amounts of sunflower oil on animal performance and milk fatty acid profile

The aim of this study was to investigate a suitable amount of sunflower oil (SO) inclusion in dairy sheep diet, in order to enhance the milk content of some potentially healthy fatty acids (FA; such as cis-9 trans-11 C18:2 –RA- and trans-11 C18:1 –VA-) without increasing other potentially unhealthy FA (such as trans-10 C18:1) or detrimentally affecting animal performance. Eighty dairy ewes were allocated to 4 treatments: no lipid supplementation (control), supplementation with 17 (SO1), 34 (SO2), or 51 (SO3) g of SO per kg of dry matter, for 28 days. Incremental amounts of dietary SO did not affect milk production nor the milk’s fat, protein and lactose contents. However, the FA profile was substantially modified. Treatment SO3 caused the highest enrichment in VA and RA and decreases in saturated FA, but it also enhanced the accumulation of trans-10 C18:1, which might jeopardise potentially the health-promoting properties of the ewe milk fat.     

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.     

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.     

Short communication: Effects of milk fat depression induced by a dietary supplement containing trans-10, cis-12 conjugated linoleic acid on properties of semi-hard goat cheese

Dietary supplements of conjugated linoleic acid (CLA) containing trans-10, cis-12 CLA reduce milk fat synthesis in lactating goats. This study investigated effects of milk fat depression induced by dietary CLA supplements on the properties of semi-hard goat cheese. Thirty Alpine does were randomly assigned to 1 of 3 groups and fed diets with lipid-encapsulated CLA that provided trans-10, cis-12 CLA at 0 (control), 3 (CLA-1), and 6 g/d (CLA-2). The experiment was a 3 × 3 Latin square design. Periods were 2 wk in length, each separated by 2-wk periods without CLA supplements. Bulk milk was collected on d 3 and 13 of each of 3 periods for cheese manufacture. The largest decrease (23.2%) in milk fat content, induced by the high dosage (6 g/d per doe) of trans-10, cis-12 CLA supplementation at d 13 of treatment, resulted in decreases of cheese yield and moisture of 10.2 and 10.0%, respectively. Although CLA supplementation increased the hardness, springiness, and chewiness, and decreased the cohesiveness and adhesiveness of cheeses, no obvious defects were detected and no significant differences were found in sensory scores among cheeses. In conclusion, milk fat depression induced by a dietary CLA supplement containing trans-10, cis-12 CLA resulted in changes of fat-to-protein ratio in cheese milk and consequently affected properties of semi-hard goat cheese.     

Combined effects of trans-10,cis-12 conjugated linoleic acid, propionate, and acetate on milk fat yield and composition in dairy cows

Diets inducing milk fat depression (MFD) are known to alter ruminal lipid metabolism, leading to the formation of specific isomers [such as trans-10,cis-12 conjugated linoleic acid (CLA)] that inhibit milk fat synthesis in lactating dairy cows. However, ruminal outflow of these isomers does not fully account for the decreases in milk fat synthesis observed during diet-induced MFD. The high-concentrate diets inducing MFD also induce a greater production of propionate, suggesting a possible inhibition of milk fat by propionate associated with trans-10,cis-12-CLA during MFD. The present experiment aimed to study the combined effects of propionate and trans-10,cis-12-CLA (both inhibitors of milk fat synthesis) on milk fat secretion and the effects of the combination of 2 nutrients with opposite effects (acetate and propionate). Six Holstein cows were used in a 6 × 6 Latin square design with 21-d periods (14 d of nutrient infusion). The treatments were control; ruminal infusion of 1,500 g/d of acetate (A); ruminal infusion of 800 g/d of propionate (P); duodenal infusion of 1.60 g/d of trans-10,cis-12-CLA (CLA); ruminal infusion of 750 g/d of acetate + 400 g/d of propionate (A+P); and duodenal infusion of 1.60 g/d of trans-10,cis-12-CLA + ruminal infusion of 800 g/d of propionate (CLA+P). The amounts of nutrients infused were chosen to induce a similar variation in milk fat content. Treatments A and P decreased dry matter intake. Compared with the control, P and CLA treatments decreased milk fat content and yield by 9% and 15% on average. Treatment A increased milk fat content by 6.5% but did not modify milk fat yield (because of a decrease in milk yield). The effects of A and P, and CLA and P on milk fat and fatty acid percentages and yield were additive (A+P and CLA+P treatments). With a same dose of trans-10,cis-12-CLA, the additional supply of propionate induced a decrease in milk fat 40% higher than that induced by trans-10,cis-12-CLA alone. The milk fatty acid profile obtained with CLA+P was similar to those observed with high-concentrate diets inducing MFD. In conclusion, under our experimental conditions, the effects of the 3 nutrients were additive on mammary lipogenesis, regardless of their separate effects. We also show that propionate could contribute to the milk fat reductions unaccounted for by trans-10,cis-12-CLA during MFD induced by high-concentrate diets.