Saturated Fatty Acids In Milk Research Articles

Post‐Prandial Changes in Bone Turnover after High Saturated Fat Challenge Meals

Biomarkers of bone turnover fluctuate over the course of a day; these fluctuations are exaggerated with food intake. The effect of foods with differing fatty acid profiles on this phenomenon is unknown. We compared bovine milk saturated fatty acids (SFA) to plant‐based SFA on post‐prandial bone metabolism in overweight/obese subjects. Adult subjects (n=20) participated in a randomized controlled trial, consuming 2 isocaloric high fat meals (dairy cheese sandwich vs. vegan sandwich plus palm oil) separated by a 1‐2 week washout period. Blood samples were collected at baseline, 1, 3, and 6 hrs post‐prandial. Bone resorption marker C‐terminal telopeptide of type 1 collagen (CTx) and bone formation marker cross‐linked C‐telopeptide of type 1 collagen (C1CP) were measured by ELISA. Spearman's Correlation analyses showed that C1CP and CTx were significantly correlated at baseline for both treatments (dairy: rs=0.585, p=0.007; palm oil: rs=0.630, p=0.003). These correlations remained significant at all time points for palm oil, but not dairy, suggesting a potentially more potent effect of dairy SFA. However, ANOVA revealed no significant effects of time or treatment on C1CP. CTx significantly decreased from baseline to 3 hrs after both dairy (p<0.0001) and palm oil (p<0.01), but there was no significant treatment effect. Differences in SFA composition between dairy and palm oil did not affect the postprandial response of CTx and C1CP in this study.Funding:National Dairy Council

Maternal adiponectin controls milk composition to prevent neonatal inflammation.

Adiponectin is an important adipokine. Increasing evidence suggests that altered adiponectin levels are linked with metabolic and inflammatory disorders. Here we report an important yet previously unrecognized function of adiponectin in lactation by which maternal adiponectin determines the inflammatory status in the nursing neonates. Surprisingly, both maternal adiponectin overexpression in the transgenic mice and maternal adiponectin deletion in the knockout mice lead to systemic inflammation in the pups, manifested as transient hair loss. However, distinct mechanisms are involved. Adiponectin deficiency triggers leukocyte infiltration and production of inflammatory cytokines in the lactating mammary gland. In contrast, adiponectin overabundance increases lipid accumulation in the lactating mammary gland, resulting in excessive long-chain saturated fatty acids in milk. Interestingly, in both cases, the inflammation and alopecia in the pups can be rescued by Toll-like receptor (TLR)-2/4 deletion because TLR2/4 double-knockout pups are resistant. Mechanistically, long-chain saturated fatty acid activation of inflammatory genes is TLR2/4 dependent and can be potentiated by proinflammatory cytokines, indicating that the inflammatory stimuli in both scenarios functionally converge by activating the TLR2/4 signaling. Therefore, our findings reveal adiponectin as a dosage-dependent regulator of lactation homeostasis and milk quality that critically controls inflammation in the nursing neonates. Furthermore, these results suggest that inflammatory infantile disorders may result from maternal adiponectin dysregulation that can be treated by TLR2/4 inhibition.

Fatty acid composition of milk fat in milk of Tzigay sheep and their F2 cross-breeds with Chios

The study was conducted on aggregate milk samples, which were taken every month during the milking period from Tzigay sheep and their F2 cross-breeds of Chios, raised in the conditions of the Central Balkan Mountain. The fat extraction of milk samples was done by the Rose-Gottlieb method. Fatty acid composition was determined on a gas chromatograph with flame ionization detector and capillary column. The aim of the study was to follow the changes in the composition of fatty acids in the milk fat of milk of Tzigay sheep and their F2 cross-breeds. The saturated fatty acids in milk of the two groups had high values during both consecutive years, as they varied from 67.05% in milk of Tzigay sheep in the second lactation up to 70.87% at their F2 cross-breeds. The content of myristic acid was correspondingly 8.22-8.88% at Tzigay sheep and 8.45-8.74% at their F2 cross-breeds. The total amount of polyunsaturated fatty acids in the examined milk for the two types of sheep was comparatively low with near concentrations (4.39-5.20%) in the period of the two years. The milk of the two groups had high values of the correlation SFA/PUSFA (15.71 and 13.17) and low values of PUSFA/SFA (0.06-0.08). Mon?unsaturated fatty acids, represented mainly by the oleic acid (C18:1) varied during both periods from 21.92% to 25.32% and appeared as a substratum in the synthesis of CLA. The short-chain fatty acids (C4:0-C11:0) had higher values in Tzigay sheep in comparison with F2 cross-breeds of Chios. The long-chain fatty acids (C17iso-C25:0) maintained close concentration in the milk of Tzigay breed, while their content in the milk of F2 cross-breeds was increased.

Relationships of fatty acid group contents in milk and reproductiveperformance in Holstein cows

The aim of this study was to evaluate the relationships between milk fatty acid group contents and subsequent reproductive performance in Holstein cows. A total of 27 cows in the 1st to 4th lactations were included in the evaluation. Cows were divided into primiparous and multiparous groups. Daily milk yields increased in the first 8 weeks of lactation. Body condition score decreased until the third month of lactation. As the cows gradually recovered from the negative energy balance, the contents of saturated fatty acids (SFAs) increased, whereas the contents of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) decreased. The contents of SFAs and MUFAs were significantly (P < 0.01-0.05) correlated (r = -0.279 to r = 0.275) with all the reproductive traits evaluated (calving to first insemination interval, days open, and insemination index). PUFA was only correlated (P < 0.01) with calving to first insemination interval (r = -0.141). High milk SFA contents were associated with improved values of days open and insemination index, whereas opposite tendencies were observed for MUFA. It was concluded that the relationship was confirmed between the changes of different milk fatty acid group contents in early lactation, used as negative energy balance indicators, and subsequent reproduction results.

Polymorphisms in lipogenic genes and milk fatty acid composition in Holstein dairy cattle

Changing bovine milk fatty acid (FA) composition through selection can decrease saturated FA (SFA) consumption, improve human health and provide a means for manipulating processing properties of milk. Our study determined associations between milk FA composition and genes from triacylglycerol (TAG) biosynthesis pathway. The GC dinucleotide allele of diacylglycerol O-acyltransferase 1:g.10433-10434AA >GC was associated with lower palmitic acid (16:0) concentration but higher oleic (18:1 cis-9), linoleic (18:2 cis-9, cis-12) acid concentrations, and elongation index. Accordingly, the GC dinucleotide allele was associated with lower milk fat percentage and SFA concentrations but higher monounsaturated FA and polyunsaturated FA (PUFA) concentrations. The glycerol-3-phosphate acyltransferase, mitochondrial haplotypes were associated with higher myristoleic acid (14:1 cis-9) concentration and C14 desaturation index. The 1-acylglycerol-3-phosphate acyltransferase 1 haplotypes were associated with higher PUFA and linoleic acid concentrations. The results of this study provide information for developing genetic tools to modify milk FA composition in dairy cattle.

Effects of extruded linseed or alfalfa protein concentrate in interaction with two levels of concentrates on milk production and composition in dairy cows

Improving ω3 fatty acid (FA) transfer from feed to milk and decreasing milk saturated FA (SFA) without increasing trans mono-unsaturated FA are desirable goals. Our objective was to study the effects of supplying two α-linolenic acid (ALA)-rich feedstuffs in interaction with proportion of concentrate in the diet on milk FA composition. The two ALA sources were extruded linseed (LIN, 700g/d) and alfalfa protein concentrate (APC, 2kg/d), supplying 115 and 49g/d ALA, respectively, per cow per day. Two groups of 12 cows paired according to milk yield, milk fat and milk protein contents, lactation rank (primiparous or multiparous), lactation stage, DMI, milk proportions of saturated and polyunsaturated FA were fed a corn silage-based diet with 30% (C30) or 65% (C65) cereal-based concentrate and received the 2 ALA sources in a reversal design during 5-wk periods. The cows averaged 117±14 DIM at the beginning of the experiment. Data were analyzed according to a split-plot design using the Proc mixed procedure. There was no significant interaction between the concentrate level and ALA source for most measured parameters. Treatment C65 decreased milk fat content (−1.15%), milk fat yield (−301g/d), and proportion of SFA, especially C16:0, C18:0, C4:0, C6:0 and C8:0, and increased trans-C18:1, especially t9, t10 and t12. Treatment C65 significantly increased milk yield (+3.7kg), milk protein content (+0.16%) and milk protein yield (+141g/d), decreased casein-to-protein ratio (−2.6 percentage units). Compared to LIN, APC increased milk fat content (0.33%), milk fat yield (76g/d), proportion of SFA, especially C4 to C12, C14:0 and C16:0, and decreased cis and all trans C18:1 isomers. APC tended to decrease milk yield (0.9kg/d, P=0.061) although DMI was not affected, and did not affect protein yield. APC increased both total protein and total casein contents without impact on casein-to-protein ratio and milk protein yield. The transfer rate of C18:3 from feed to milk was much higher in APC treatment than in LIN treatment (15.3% vs 4.7%). This trial shows that adding ALA-rich feedstuffs to the diet to enrich milk can have very marked effects on milk FA composition but also on milk protein composition. These effects are stronger with high concentrate diets, resulting in acidogenic risk. The rate of transfer of ALA from feed to milk also varies according to lipid source. Higher transfer rates lead to lower modifications of milk composition.

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 (−24.1g/100g of FA) linearly with increasing amounts of extruded linseed, whereas the milk monounsaturated FA (+19.0g/100g), polyunsaturated FA (+4.9g/100g), and total trans FA (+14.7g/100g) 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.

Incremental effect of a calcium salt of cis-monounsaturated fatty acids supplement on milk fatty acid composition in cows fed maize silage-based diets

In most Western countries, saturated fatty acid (SFA) intake exceeds recommended levels, which is considered a risk factor for cardiovascular disease (CVD). As milk and dairy products are major contributors to SFA intake in many countries, recent research has focused on sustainable methods of producing milk with a lower saturated fat concentration by altering dairy cow diets. Human intervention studies have shown that CVD risk can be reduced by consuming dairy products with reduced SFA and increased cis-monounsaturated fatty acid (MUFA) concentrations. This milk fatty acid profile can be achieved by supplementing dairy cow diets with cis-MUFA-rich unsaturated oils. However, rumen exposure of unsaturated oils also leads to enhanced milk trans fatty acid (TFA) concentrations. Because of concerns about the effects of TFA consumption on CVD, feeding strategies that increase MUFA concentrations in milk without concomitant increases in TFA concentration are preferred by milk processors. In an attempt to limit TFA production and increase the replacement of SFA by cis-MUFA, a preparation of rumen-protected unsaturated oils was developed using saponification with calcium salts. Four multiparous Holstein-Friesian cows in mid-late lactation were used in a 4×4 Latin square design with 21-d periods to investigate the effect of incremental dietary inclusion of a calcium salt of cis-MUFA product (Ca-MUFA; 20, 40, and 60g/kg of dry matter of a maize silage-based diet), on milk production, composition, and fatty acid concentration. Increasing Ca-MUFA inclusion reduced dry matter intake linearly, but no change was observed in estimated ME intake. No change in milk yield was noted, but milk fat and protein concentrations were linearly reduced. Supplementation with Ca-MUFA resulted in a linear reduction in total SFA (from 71 to 52g/100g of fatty acids for control and 60g/kg of dry matter diets, respectively). In addition, concentrations of both cis- and trans-MUFA were increased with Ca-MUFA inclusion, and increases in other biohydrogenation intermediates in milk fat were also observed. The Ca-MUFA supplement was very effective at reducing milk SFA concentration and increasing cis-MUFA concentrations without incurring any negative effects on milk and milk component yields. However, reduced milk fat and protein concentrations, together with increases in milk TFA concentrations, suggest partial dissociation of the calcium salts in the rumen.

The comparison of lactation performance and milk fatty acid composition of Sarabi indigenous and Holstein cows

The objective of this study was to specify fatty acid content of milk from Sarabi indigenous cows and compare it with milk fatty acid profile of Holstein cows. Ten Holstein and twelve Sarabi confinement cows that have been fed on total mixed ration with corn silage, alfalfa hay and dairy concentrate were used in a completely randomized design. Holstein cows had greater milk production (P<.0001), whereas Sarabi cows on average had higher milk content of fat (P=0.0540), protein (P=0.0340) and lactose (P=0.1794). Milk from Sarabi and Holstein cows had similar content of the cis-9 trans-11 conjugated linoleic acid (0.28 and 0.30%, respectively) and short and medium chain fatty acids (18.58 and 18.62%, respectively) Sarabi cows numerically produced higher concentrations of saturated fatty acids (60.51 and 59.29%, respectively), and long chain fatty acids (43.32 and 41.26%, respectively), as well as lower concentrations of mono unsaturated fatty acids (20.75 and 21.65% respectively) than Holstein. The percentage of C16:0 main saturated fatty acid in milk fat was not different between the groups. Concentrations of C14:0 and C18:0, second and third prominent milk saturated fatty acids were respectively 9.98 and 9.93% in Sarabi and 10.10% and 9.60% in Holsteins. In summary, despite the slight differences between fatty acid content of milk from Sarabi and Holstein cows, we did not find any statistical significance. Key words: Breed, Sarabi cow, milk fatty acid, conjugated linoleic acid.

Effect of replacing calcium salts of palm oil distillate with incremental amounts of conventional or high oleic acid milled rapeseed on milk fatty acid composition in cows fed maize silage-based diets

Based on potential benefits to human health, there is increasing interest in altering the composition of ruminant-derived foods. Including rapeseeds in the dairy cow diet is an effective strategy for replacing medium-chain saturated fatty acids (SFA) with cis-monounsaturated fatty acids (MUFA) in bovine milk, but there is limited information on the optimum level of supplementation. Decreases in SFA due to plant oils are also accompanied by increases in milk trans fatty acid (FA) content and it is possible that high oleic acid rapeseeds may result in a higher enrichment of cis-9 18:1 and lower increases in trans FAs in milk compared with conventional varieties. Seven multiparous lactating Holstein–Friesian cows were allocated to one of seven treatments in an incomplete Latin square design with five 28-day experimental periods, to evaluate the effect of replacing calcium salts of palm oil distillate (CPO; 41 g/kg diet dry matter, DM) with 128, 168 or 207 g/kg diet DM of conventional (COR) or a high oleic acid (HOR) rapeseed fed as a supplement milled with wheat. Rapeseed variety and inclusion level had no effect (P > 0.05) on DM intake, milk yield and composition. Both rapeseed varieties decreased linearly (P < 0.001) milk fat SFA content, which was partially compensated for by a linear increase (P < 0.001) in cis-9 18:1 concentration. Reductions in milk SFA were also associated with increases (P < 0.05) in trans 18:1 and total trans FA content, with no difference (P > 0.05) between rapeseed varieties. Replacing CPO in the diet with milled rapeseeds had no effect (P > 0.05) on total milk conjugated linoleic acid (CLA) concentration. Relative to a COR, inclusion of a high oleic acid variant in the diet increased (P = 0.01) the ratio of trans-MUFA : trans-polyunsaturated fatty acids in milk that may have implications with respect to cardiovascular disease risk in humans. In conclusion, data indicated that replacing CPO with milled rapeseeds at levels up to 1150 g oil/day could be used as a nutritional strategy to lower milk SFA content without inducing adverse effects on DM intake and milk production. HOR reduced milk fat SFA content to a greater extent than a conventional variety, but did not minimise associated increases in trans FA concentrations. However, the high oleic acid variant did alter the relative abundance of specific trans 18:1, CLA and trans 18:2 isomers compared with conventional rapeseeds.

Short communication: Heritability of milk fatty acid composition and stearoyl-CoA desaturase indices in dairy cows

Activity of stearoyl-CoA desaturase (SCD) in the mammary gland is important for determining the relative proportions of saturated and monounsaturated fatty acids in milk and the concentration of the conjugated linoleic acid isomer rumenic acid (RA; cis-9,trans-11 18:2). Previous studies identified a large degree of between-cow variation in SCD activity, which was consistent across diets and suggests a genetic influence. The objectives of this study were to quantify genetic and phenotypic variations in fatty acid concentrations and SCD indices in milk fat and to estimate their heritabilities in a population of United Kingdom dairy cows. Milk samples were collected from 2,408 daughters of 597 Holstein-Friesian sires on 325 commercial farms for determination of fatty acid profiles. Indices of SCD activity were calculated by expressing each SCD product (cis-9 14:1, cis-9 16:1, cis-9 18:1, and RA) as a proportion of the precursor plus product [e.g., SCDI14=cis-9 14:1/(14:0+cis-9 14:1)]. For individual fatty acids, phenotypic variance was considerably greater than additive genetic variance, resulting in small and nonsignificant heritability estimates (± standard error) for all except 6:0 (h2=0.27±0.10), 8:0 (h2=0.27±0.09), 12:0 (h2=0.13±0.07), cis-9 14:1 (h2=0.28±0.10), and cis-9 18:1 (h2=0.12±0.07). Heritability estimates of desaturase indices were significant for SCDI14 (h2=0.38±0.11), SCDI18 (h2=0.19±0.09), and SCDIRA (h2=0.21±0.09), but not for SCDI16 (h2=0.05±0.06). This study provides evidence that additive effects are responsible for a significant proportion of the phenotypic variation in SCD activity in dairy cows. It is concluded that because heritability of desaturase indices is moderate and significant in many cases, these indices could be investigated further for use in future breeding programs to increase concentrations of monounsaturated fatty acids and RA while decreasing concentrations of saturated fatty acids in milk fat.

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

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

Effects of normal and high oleic acid rapeseed in the dairy cow diet on milk fatty acid composition

Milk and dairy products are the major source of saturated fatty acids (SFA) in the European diet and there is evidence that replacing SFA with cis-monounsaturated fatty acids (MUFA) will improve risk factors for cardiovascular disease. Rapeseed in dairy cow diets simultaneously reduces milk SFA and increases cis-MUFA, but also increases milk trans MUFA. A new variety of rapeseed with higher oleic acid content (therefore less potential for increasing milk trans-MUFA) was compared with a normal oleic acid rapeseed, and both compared with a control diet.

Effect of replacing calcium salts of palm oil distillate with rapeseed oil, milled or whole rapeseeds on milk fatty-acid composition in cows fed maize silage-based diets

Inclusion of rapeseed feeds in dairy cow diets has the potential to reduce milk fat saturated fatty acid (SFA) and increase cis-monounsaturated fatty acid (cis-MUFA) content, but effectiveness may depend on the form in which the rapeseed is presented. Four mid-lactation Holstein dairy cows were allocated to four maize silage-based dietary treatments according to a 4 × 4 Latin Square design, with 28-day experimental periods. Treatments consisted of a control diet (C) containing 49 g/kg dry matter (DM) of calcium salts of palm oil distillate (CPO), or 49 g/kg DM of oil supplied as whole rapeseeds (WR), rapeseeds milled with wheat (MR) or rapeseed oil (RO). Replacing CPO with rapeseed feeds had no effect (P > 0.05) on milk fat and protein content, while milk yields were higher (P < 0.05) for RO and MR compared with WR (37.1, 38.1 and 34.3 kg/day, respectively). Substituting CPO with RO or MR reduced (P < 0.05) milk fat total SFA content (69.6, 55.6, 71.7 and 61.5 g/100 g fatty acids for C, RO, WR and MR, respectively) and enhanced (P < 0.05) milk cis-9 18:1 MUFA concentrations (corresponding values 18.6, 24.3, 17.0 and 23.0 g/100 g fatty acids) compared with C and WR. Treatments RO and MR also increased (P < 0.05) milk trans-MUFA content (4.4, 6.8, 10.5 g/100 g fatty acids, C, MR and RO, respectively). A lack of significant changes in milk fat composition when replacing CPO with WR suggests limited bioavailability of fatty acids in intact rapeseeds. In conclusion, replacing a commercial palm oil-based fat supplement in the diet with milled rapeseeds or rapeseed oil represented an effective strategy to alter milk fatty acid composition with the potential to improve human health. Inclusion of processed rapeseeds offered a good compromise for reducing milk SFA and increasing cis-MUFA, whilst minimising milk trans-MUFA and negative effects on animal performance.

Performance of lactating dairy cows fed varying levels of total mixed ration and pasture

Two, 8-week experiments, each using 30 lactating Holstein cows, were conducted to examine performance of animals offered combinations of total mixed ration (TMR) and high-quality pasture. Experiment 1 was initiated in mid October 2004 and Experiment 2 was initiated in late March 2005. Cows were assigned to either a 100% TMR diet (100:00, no access to pasture) or one of the following three formulated partial mixed rations (PMR) targeted at (1) 85% TMR and 15% pasture, (2) 70% TMR and 30% pasture and (3) 55% TMR and 45% pasture. Based on actual TMR and pasture intake, the dietary TMR and pasture proportions of the three PMR in Experiment 1 were 79% TMR and 21% pasture (79:21), 68% TMR and 32% pasture (68:32), and 59% TMR and 41% pasture (59:41), respectively. Corresponding proportions in Experiment 2 were 89% TMR and 11% pasture (89:11), 79% TMR and 21% pasture (79:21) and 65% TMR and 35% pasture (65:35), respectively. Reducing the proportion of TMR in the diets increased pasture consumption of cows on all PMR, but reduced total dry matter intake compared with cows on 100:00. An increase in forage from pasture increased the concentration of conjugated linoleic acids and decreased the concentration of saturated fatty acids in milk. Although milk and milk protein yields from cows grazing spring pastures (Experiment 2) increased with increasing intakes of TMR, a partial mixed ration that was composed of 41% pasture grazed in the fall (Experiment 1) resulted in a similar overall lactation performance with increased feed efficiency compared to an all-TMR ration.

Matières grasses : un autre regard

The recent history of public recommendations for dietary intakes of macronutrients have targeted total fat, cholesterol and saturated fat intake as the principle means to improve human health. Such recommendations have been translated into a long term agricultural objective of eliminating these components from human foods. Agricultural change requires changes at many points over many years to eliminate these components. Once accomplished, such changes would be equally difficult to reverse. Furthermore, such recommendations fall disproportionately on a few commodities most notably dairy fats. Dramatic alterations in dairy consumption carry much more impact on dietary intakes than simply total fat, saturated fat and cholesterol. While it is becoming possible to alter the basic production of milk and dairy products and to envision a dramatically different milk fat composition, such steps will be difficult and expensive. Hence, it is appropriate to ask whether the data in support of this conclusion are complete and if indeed a finite intake of milk fats are beneficial to overall health. Mammalian milks, including human milk contain 50% of their total fatty acids as saturated fatty acids. Adding a single double bond is a relatively straightforward process already active within the mammary gland. Darwinian selective pressure therefore chose to maintain a significant content of saturated fatty acids in milk. Is it possible evolution found benefits to saturated fatty acids that current recommendations do not consider? Furthermore, milk does not contain simply saturated triglycerides as a bulk fat, but rather a conspicuous range of different fatty acids varying in chain length and unsaturation. Milk is present as highly complex globules with structural properties distinct from other biological sources of fats. In particular, there are complex phospholipids making up a highly glycosylated and protein embedded plasma membrane around each milk fat globule. Milkfat is thus a source of bioactive lipids provided as highly absorbable ensembles also serving as an important delivery medium for nutrients, including the fat-soluble vitamins. While very few studies have examined the nutritional consequences of these structures and compositions, their emergence through evolution implies that they provide distinct benefits to individuals consuming them.

Examination of the persistency of milk fatty acid composition responses to plant oils in cows given different basal diets, with particular emphasis ontrans-C18:1fatty acids and isomers of conjugated linoleic acid

AbstractIt is well established that plant oils reduce milk saturated fatty acid content and enhance concentrations of conjugated linoleic acid (CLA) and trans C18:1in milk fat, but there is increasing evidence to suggest that milk fat CLA responses are often transient and decline over time. It is probable that time dependent adaptations in ruminal biohydrogenation and changes in milk fatty acid composition to lipid supplements are, at least in part, related to the composition of the basal diet. To test this hypothesis, 18 Holstein cows were used in a continuous randomized block design to examine changes in milk fatty acid composition over time in response to plant oils included in diets of variable composition. Cows were randomly allocated to one of three basal diets containing (g/kg dry matter (DM)) maize silage (267) and concentrates (733) (diet C); maize silage (332), grass hay (148) and concentrates (520) (diet M), or grass hay (642) and concentrates (358) (diet H). Basal rations were offered for 21 days, after which diets were supplemented with 50 g sunflower per kg DM (diets C-S and M-S) or 50 g linseed oil per kg DM (diet H-L). Oils were included in all rations incrementally over a five day period (days 0–4), and responses to 50 g/kg DM of the respective oils were evaluated for 17 days (days 4 to 20). Milk fatty acid composition was intensively monitored from days −2 to 20. In contrast to the H-L diet, both C-S and M-S treatments decreased (P&lt;0·05) DM intake, milk fat content and yield, while the C-S diet also reduced (P&lt;0·05) milk yield. Milk fatcis-9,trans-11 CLA andtrans-11 C18:1contents were enhanced on the C-S and M-S treatments but the increases were transient reaching the highest concentrations between days 4 and 6 (cis-9,trans-11 CLA: 1·94 and 2·18 g per 100 g total fatty acids;trans-11 C18:1: 4·88 and 6·23 g per 100 g total fatty acids, respectively) but declined thereafter. In marked contrast, concentrations ofcis-9,trans-11 CLA andtrans-11 C18:1in milk from the H-L diet increased gradually over time, responses that were maintained until the end of the experiment (2·89 and 7·49 g per 100 g total fatty acids, respectively).Decreases in milk fatcis-9,trans-11 CLA andtrans-11 C18:1after day 6 on the M-S and C-S diets were associated with concomitant increases in milk fattrans-10 C18:1content reaching 7·22 and 18·62 g per 100 g total fatty acids on day 18, respectively, whereas concentrations oftrans-10 C18:1in milk on the H-L diet remained low throughout the experiment (0·70 g per 100 g total fatty acids on day 18). Furthermore, milk fattrans-11,cis-13 CLA,trans-11,trans-13 CLA andtrans-12,trans-14 CLA contents were all enhanced on the H-L diet, while the M-S and C-S diets increasedtrans-8,cis-10 CLA,trans-10,cis-12 CLA andtrans-9,cis-11 CLA concentrations. Across all diets, decreases in milk fat content were associated with increases in milktrans-10 C18:1,trans-10,cis-12 andtrans-9,cis-11 CLA concentrations (r2=0·93, 0·88 and 0·89, respectively). In conclusion, the relative abundance oftransC18:1and CLA isomers in milk fat were dependent on the composition of the basal diet, type of plant oil and duration of lipid supplementation, highlighting the challenges in developing nutritional strategies for the production of milk highly enriched with CLA over an extended period of time.

Fatty acid composition of ewe milk as affected by solar radiation and high ambient temperature.

Forty lactating Comisana ewes were either exposed to or protected from solar radiation and fed either in the morning or afternoon during summer in a Mediterranean climate. Individual milk samples were taken on days 7, 21 and 42 of the study period to determine fatty acid composition by gas chromatography. Exposure to solar radiation resulted in higher proportions of short-chain and saturated fatty acids in milk, primarily because of increased contents of caproic, capric, lauric, myristic and stearic acids (by 3-18%), and decreased contents of oleic, linoleic and linolenic acids (by 2-9%). As a consequence, the long to short chain and the unsaturated to saturated fatty acid ratios were significantly higher by 4 and 13% respectively in the milk of the protected ewes compared with that of the exposed animals. Provision of shade also led to an increase in the 18:0+18:1 to 16:0 ratio, and to a decrease in the 12:0 + 14:0 + 16:0 fatty acid group, which are regarded as reliable indexes of the nutritional property of dietary fat in reducing cholesterol levels in human plasma. Feeding time had little impact on milk fat. Our findings suggest that high ambient temperature may markedly modify the lipid composition of ewe milk and that provision of shade, but not feeding management, can improve the milk fatty acid profile in dairy sheep raised in hot climates.

Effect of Afterstimulation on Milk Yield and Fat Composition in Beef Cattle: A Form of Honest Begging?

Nine suckling calves were allowed to afterstimulate their dams at three levels, ad libitum , for 3 min or none, at each suckling meal twice daily in a repeated 3 2 3 Latin square experimental design. Each experimental unit consisted of one cow-calf pair for 6 days. Milk yield was recorded and samples were taken at the morning meal on day 7 by hand-milking one quarter while the calf suckled the other three. Samples were analysed for fat content and 19 fatty acids (FA), summarized in five groups: locally synthesized FA, FA deriving mainly from blood serum (BSFA), saturated FA (SFA), unsaturated FA (USFA) and essential FA (ESFA). Variables were expressed as g g -1 fat, kJ g -1 fat, g kg -1 milk delivered at the recorded suckling meal and kJ kg -1 delivered milk. The only factors affected were milk yield, and BSFA, SFA, USFA and ESFA when related to the delivered milk. The relationship between levels of AS and milk yield was a second-degree polynomial.

Milk Fat Composition and Nutritional Value

The perception of milk has changed over the past 25 years from one of being the ideal food to one of being detrimental nutritionally, mainly due to the fatty acid composition of its fat component. Now however, it has been discovered that milk contains a number of compounds, which may have positive nutritional benefits. It also appears that the association between saturated fatty acids in milk and effects on cholesterol may have been an oversimplification. It is accepted that the hypercholesterolaemic saturated fatty acids in milk fat are confined to lauric (C12:0), myristic (C14:0) and palmitic acid (C16:0) with the shorter chain saturated fatty acids and stearic acid having no cholesterol raising effect. Indeed bovine milk fat contains two fatty acids which may have important beneficial effects on human health, namely conjugated linoleic acid (cis-9,trans-11 linoleic acids – C18:2, CLA) and butyric acid (C4:0). Also monounsaturated fatty acids have been shown to be beneficial in altering the proportions of LDL and HDL cholesterol and it is possible to increase the concentration in milk of the principal monounsaturated fatty acid, oleic acid (C18:1), by optimising the diet of the cow. This paper will discuss nutritional strategies to optimise milk fat composition with particular reference to work from my own Research Centre in relation to oleic acid and CLA.