CLA In Milk Fat Research Articles

665 Production, composition, and fatty acid profile of goat milk supplemented with buriti oil

This study was conducted to test the hypothesis that buriti oil (Mauritia flexuosa L.) can replace ground corn in goats' diet, improving production, composition, and fatty acid profile of goat milk. This experiment was approved by the Ethics Committee for Experimentation with Animals. Four Anglo–Nubian multiparous goats with average 50 ± 4 d of lactation and weight of 38.4 ± 1.1 kg were treated for the control of internal and external parasites. The animals were randomly distributed in a double Latin square (4 × 4) comprising 4 periods and 4 buriti oil concentrations (0.00, 1.50, 3.00, and 4.50% of total DM) replacing ground corn. The animals were manually milked twice daily (at 6 and 16 h). The data were subjected to an ANOVA and regression analyses (linear and quadratic) using the GLM and REG procedures implemented in SAS statistical software (version 9.1.2; SAS Inst. Inc., Cary, NC). Goat milk production, corrected production4%fat, and chemical composition were not influenced by the concentration of buriti oil replacement; however, milk fat concentration (P = 0.04) and feed efficiency (P < 0.01) linearly increased with the amount of buriti oil in the diet. There was a linear reduction on hypercholesterolemic SFA, such as C12:0 (P < 0.01) and C14:0 (P < 0.01), as well as the atherogenic index (P < 0.01) with buriti oil inclusion in goat's diet. In contrast, the fatty acids C18:0 (P < 0.01) and C18:1 cis-9 (P < 0.01) linearly increased in the milk of goats that were fed with buriti oil. However, CLA (P < 0.01) quadratically varied; the maximum production of 0.62 g/100 g of fat was observed when using 1.50% buriti oil. The sensory characteristics of the milk were not changed (P > 0.05) by the replacement of corn with buriti oil in the goats' diet. It is recommended to replace corn with buriti oil in goat feed by up to 4.5% of total DM, resulting in improved milk fat without affecting production; this recommendation satisfies the minimum requirements of the industry and preserves the organoleptic characteristics of the milk and its acceptability for human consumption. In addition, buriti oil replacing ground corn by up to 4.5% DM in the diet of lactating goats decreased medium-chain SFA, which are hypercholesterolemic and increase the concentrations of the C18:1 cis-9, CLA, and DFA in goat milk fat, helping to protect against cardiovascular disease.

Production, composition, fatty acid profile and sensory analysis of goat milk in goats fed buriti oil

This study evaluated the effects of replacing ground corn with buriti oil (Mauritia flexuosa L.) on feed intake and digestibility and on the production, composition, fatty acid profile and sensory characteristics of goat milk. A double Latin square (4 × 4) was used; eight goats were distributed in a completely randomized design. The square comprised four periods and four buriti oil concentration (0.00; 1.50; 3.00 and 4.50% of total DM) replacing corn. Intakes of DM, CP, NDF, ADF, non-fibrous carboydrates (NFC) and TDN were not affected by the replacement of corn with oil in the diet. However, lipids intake was increased (P < 0.01) by 100% in the diet of goats with 4.50% oil inclusion, as total DM. DM and CP digestibility were similar between the buriti oil concentrations. However, lipid digestibility increased linearly (P = 0.01) and may have contributed to a quadratic reduction in NDF digestibility (P = 0.01) and a linear reduction of NFC (P = 0.04) with buriti oil content in the goat feed. Goat milk production, corrected production4%fat and chemical composition were not influenced by the concentration of buriti oil replacement; however, milk fat concentration (P = 0.04) and feed efficiency (P < 0.01) increased linearly with the amount of buriti oil in the diet. There was a linear reduction on hypercholesterolemic SFA such as C12:0 (P < 0.01) and C14:0 (P < 0.01) as well as the atherogenic index (AI; P < 0.01) with buriti oil inclusion in goat's diet. In contrast, the fatty acids C18:0 (P < 0.01) and C18:1 cis9 (P < 0.01) increased linearly in the milk of goats that were fed with buriti oil. However, CLA (P < 0.01) varied quadratically; the maximum production of 0.62 g/100 g of fat was observed when using 1.50% buriti oil. The sensory characteristics of the milk were not changed (P > 0.05) by the replacement of corn with buriti oil in the goats' diet. It is recommended to replace corn with buriti oil in goat feed by up to 4.5% of total DM, resulting in improved feed efficiency and milk fat without affecting production; this recommendation satisfies the minimum requirements of the industry and preserves the organoleptic characteristics of the milk and its acceptability for human consumption. In addition, buriti oil replacing ground corn by up to 4.5% DM in the diet of lactating goats decrease medium-chain SFA which are hypercholesterolemic and increase the concentrations of the C18:1cis9, CLA and DFA in goat milk fat, helping to protect against cardiovascular disease.

EFFECTS OF FLAX SEED SUPPLEMENTATION TO LACTATING GOATS ON MILK FATTY ACID CONTENT

Abstract Goat milk is very valuable and desired food for its high digestibility and unique composition, because contains only small amount of milk protein casein, thus is suitable for casein allergy. The aim of the study was to assess the quality of pastures located in lessfavoured areas of Czech Republic and to investigate the influence of that quality on the content of fatty acids in goat milk. Two groups of goats were fed ad libitum intake of meadow hay and concentrate supplements, for experimental group contained 0.1 kg of flaxseed. Results of experimental group shows reduced SFA and increased content of MUFA and PUFA. Flax seed supplementation has an positive effect on increasing CLA in milk fat

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) 10,000IU of vitamin E/d (VE), (3) 2.5% soybean oil (SO), and (4) 2.5% soybean oil plus 10,000IU 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.

Rapeseed or linseed in grass-based diets: Effects on conjugated linoleic and conjugated linolenic acid isomers in milk fat from Holstein cows over 2 consecutive lactations

Changes in the distribution of conjugated linoleic (CLA) and conjugated linolenic (CLnA) acid isomers in milk from Holstein cows in response to 4 different oilseed supplements rich in either cis-9 18:1 or 18:3n-3 were determined over 2 consecutive lactations in 58 and 35 cows during the first and second years, respectively. For the first 5wk of the first lactation, all cows were fed the same diet. Thereafter, cows received 1 of 5 treatments for 2 consecutive lactations, including the prepartum period. Treatments comprised the basal diet with no additional lipid, or supplements of extruded linseeds (EL), extruded rapeseeds (ER), cold-pressed fat-rich rapeseed meal, or whole unprocessed rapeseeds to provide 2.5 to 3.0% of additional oil in diet dry matter. During indoor periods, cows were housed and received a mixture (3:1, wt/wt) of grass silage and hay, whereas cows were at pasture during outdoor periods. Over the entire study, EL resulted in the enrichment of ∆11,13 CLA, ∆12,14 CLA, trans-9,trans-11 CLA, trans-13,trans-15 CLA, ∆9,11,15 CLnA, and cis-9,trans-11,trans-13 CLnA (identified for the first time in bovine milk fat) in milk fat, whereas ER and cold-pressed fat-rich rapeseed meal in particular, increased milk fat trans-7,cis-9 CLA concentration. With the exception of the first indoor period, whole unprocessed rapeseeds decreased cis-9,trans-11 CLA, trans-9,cis-11 CLA, and trans-10,trans-12 CLA abundance. During the second indoor period, EL increased milk trans-9,cis-11 CLA and trans-10,cis-12 CLA concentrations, but the increases in cis-9,trans-11 CLA, cis-12,trans-14 CLA, trans-11,cis-13 CLA, and cis-9,trans-11,cis-15 CLnA concentrations to EL and ER were lower for the second than first indoor period. In contrast to the indoor periods, EL and ER decreased milk cis-9,trans-11 CLA, trans-9,cis-11 CLA, and trans-10,cis-12 CLA concentrations at pasture. The extent of changes in the relative distribution and abundance of CLA and CLnA isomers in milk fat were related to the nature (rapeseed or linseed) and form of oilseed (extruded, cold-pressed fat-rich meal or whole unprocessed) supplement and their interactions with the composition of the basal diet (conserved grass or pasture and dietary starch content). Furthermore, milk fat CLA and CLnA responses to treatments were repeatable between both outdoor periods. Variations in milk fat content and yield measured during the entire study were significantly and inversely associated with milk trans-10 18:1, trans-10,cis-12 CLA, and in particular, trans-9,cis-11 CLA concentrations.

Genetic variation of C18:1 and C18:2 isomers in sheep milk fat

The aim of the present study was to evaluate the genetic variation of milk fat CLA, together with the variation of CLA precursors, including the individual PUFA that are potentially involved in the metabolic pathway of CLA. The allelic substitution effect, upon these FA, was estimated for a number of polymorphisms, that are located within 9 candidate genes known to influence milk FA partitioning. Sheep milk was chosen because it contains higher total fat percentage, and higher CLA levels per gram fat, than milk of other ruminants. Milk FAME analyses were performed on individual milk samples of sheep from three different breeds. Our results reflect the association of three genes (alpha-1-antichymotrypsin; diacylglycerol O-acyltransferase homolog-2; and zona pellucida glycoprotein-2) with the values of both linolenic FA and CLA; of three more genes (insulin-like growth factor I; lecithin-cholesterol acyltransferase and propionyl coenzyme A carboxylase, beta polypeptide) with the variability of linolenic FA; and of one gene, the fatty acid synthetase with the variability of CLA and stearic FA. The current study might contribute to the understanding of the metabolic pathway of PUFA in sheep milk, providing suggestions to modify milk fat composition through selection.

Milk performance of dairy cows supplemented with rape seed oil, peanut oil, and sunflower seed oil

The objective of the study was to investigate the effects of supplementing different plant oils to the basal diet on milk yield and milk composition in mid-lactating dairy cows. Forty Chinese Holstein dairy cows averaging 120 days in milk (DIM) at the start of the experiment (body weight = 580 &amp;plusmn; 18.2 kg; milk yield = 33.0 &amp;plusmn; 2.00 kg/day) were used in a completely randomized block design. The animals were assigned to four dietary treatments according to DIM and milk yield, and supplemented with no oil (control), 2% rapeseed oil (RSO), 2% peanut oil (PNO) and 2% sunflower seed oil (SFO). Milk yield and milk composition (fat, protein, and lactose) were measured. Dry matter intake was similar in all treatments. The supplementation of plant oil increased milk yield, with the highest milk yield in RSO group. Percentages of milk fat, lactose, solids-not-fat and SCC were not affected by treatments except for an increase in milk protein content in oil supplemented groups. The fatty acid (FA) profile of milk was altered by fat supplementation. Feeding plant oils reduced the proportion of both short-chain (C4:0 to C12:0) and medium-chain (C14:0 to C16:1) fatty acids, and increased the proportion of long-chain (&amp;ge; C18:0) fatty acids in milk fat. The inclusion of vegetable oils increased the concentration of cis-9, trans-11 CLA. The cis-9, trans-11 CLA content in milk fat was higher from RSO to PNO and SFO was higher than the control. The TVA concentration was higher in the SFO diet, followed by PNO, RSO, and control diets. The results of this study indicated that linoleic acid was more effective in enhancing contents of TVA and CLA in milk fat than oleic acid. No significant effects of week and treatment by week interaction were found out in this study. Overall, feeding plant oils increased monounsaturated and polyunsaturated fatty acids and decreased saturated fatty acids in milk fat. In conclusion, dietary supplementation of RSO increases milk yield the most, while SFO enhances the cis-9, trans-11 CLA content in milk fat more effectively.

Polyunsaturated fatty acids and choline in dairy goats nutrition: Production and health benefits

The potential to modify milk fatty acid composition and milk production by dietary administration of marine oils rich in n-3 PUFAs in goats diets is reviewed. Moreover animal and human health implications are considered. Role of nutrition in dairy goats for enhancing content of CLA in milk fat is also discussed. At last, rumen protected choline supplementation is evaluated to improve productive performance and metabolic health. While the effects of n-3 PUFAs administration on goat productive performance seem to depend on many factors, fish oil administration has been extensively shown to lower average concentration of C18:0 and saturated fatty acids, with a relative increase of C16:1, C18:3 n-3 and very long-chain n-3 PUFAs. Positive results have been evidenced in animals health following administration of EPA and DHA from fish oil, leading to increased phagocytic activity with no effects on extracellular ROS production in incubated goats cells. The nutritional and health properties of goat's milk could be further improved by increasing the content of CLA in milk fat. Provision of PUFAs from fresh pasture and plant lipids, mainly C18:2 n-6 and C18-3 n3 which serve as precursor for trans C18:1 formation in the rumen, have proved to enhance content of CLA in goat milk fat. Marine oils rich in n-3 PUFAs have been shown to be very effective at increasing CLA content in bovine milk, but very scarce data are available on dairy goats. Rumen protected choline has been show to increase productive performance, particularly milk production, fat percentage, and fat and protein yield without detrimental effects on methyl groups, thus reducing BHBA plasma content and hepatocellular lipid accumulation around transition. However the magnitude of the production response seems to be affected by the composition of the diet, and other factors as already reported for n-3 PUFAs administration.

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 (33.3kg/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 1.52g/100g of fatty acids), and trans-10 cis-12 CLA (0.07, 0.14, 0.13, and 0.16g/100g 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.

Conjugated linoleic acid content in adipose tissue of calves suckling beef cows on pasture and supplemented with raw or extruded soybeans1,2

The concentration of CLA in adipose tissue can be increased in ruminants by feeding pasture and extruded soybeans. The objective of this study was to evaluate maternal supplementation of raw (RS) or extruded (ES) soybeans on the concentrations of CLA in milk fat of cows and s.c. adipose tissue of suckling calves. Thirty-two spring-calving cows (BW 624 +/- 76 kg; BCS 3.5 +/- 0.4; mean +/- SD) and calves (BW 127 +/- 15 kg) were separated into 2 groups. Cows were distributed to have 8 calves of each sex in both groups. When animals were turned out to pasture, dams received 2 kg/d of either RS or ES. Dietary treatments had no effect on average milk intake (P = 0.22) and pasture forage intake (P = 0.13) for calves over the course of the grazing season. As a result, no effect of treatments was observed on ADG (P = 0.26). At weaning, milk fat content of CLA reached 15.4 and 24.2 mg/g of total fatty acids for cows fed RS and ES, respectively (P = 0.02). The CLA concentrations in adipose tissue were 16.9 and 25.0 mg/g of total fatty acids for calves suckling dams fed RS and ES, respectively (P < 0.001). Overall, results demonstrated supplementing grazing cows with ES increased CLA content in milk and adipose tissue of suckling calves.

Influence of feeding whole sunflower seed and extruded linseed on production of dairy cows, rumen and plasma constituents, and fatty acid composition of milk

Holstein cows were fed total mixed rations (TMR) supplemented with protected palm fat (PPF), whole sunflower seed (WSS) or extruded linseed (ELS) for 100 days. Percentage of dietary crude fat was 5.3, 5.1 and 5.1, respectively. Diet had no (p > 0.05) effect on feed intake, milk yield or milk protein content. Percentage of milk fat and yield of fat – corrected milk were significantly increased when diets were supplemented with WSS and ELS. Feeding PPF resulted in the lowest (p < 0.05) ruminal concentration of volatile fatty acids. No significant dietary effect on plasma characteristics was observed. Concentration of polyunsaturated fatty acids (PUFA) was higher (p < 0.05), and PUFA n-6/n-3 ratio lower (p < 0.05), in the milk fat from cows fed ELS compared to WSS. Supplementation of TMR with oilseeds compared to PPF increased the content of CLA in milk fat (p < 0.005) and decreased its atherogenicity, primarily due to a significant reduction of palmitic acid concentration. Both oilseeds significantly improved the spreadability index of manufactured butter. ELS, but not WSS, increased the susceptibility of milk fat to oxidation (p < 0.05). It can be concluded that feeding of oilseeds to dairy cows improved nutritional quality of milk fat, with supplementation with ELS producing an even more desirable milk fatty acid profile than WSS supplementation.

Effect of fish oil and sunflower oil supplementation on milk conjugated linoleic acid content for grazing dairy cows

The objective of this study was to determine the effect of adding fish oil (FO) and sunflower oil (SFO) to grazing dairy cows’ diets on the temporal changes in milk conjugated linoleic acid (c is-9, trans-11 CLA). Sixteen Holstein cows were divided into two diet regimen groups. One group (CONT) was fed a basal diet (7.6 kg DM basis) plus 400 g animal fat. The other group (FOSFO) were fed a basal diet plus 100 g of FO and 300 g of SFO (FOSFO). The cows were milked twice a day and milk samples were collected every 3-day for a period of 21 days. Both groups grazed together on pasture ad libitum and fed treatment diets after the morning and afternoon milking. Milk production, milk fat percentages, milk fat yield, milk protein percentages, and milk protein yield were not affected (P>0.05) by treatment diets. The concentrations of c is-9 trans-11 CLA and vaccenic acid (VA) in milk fat were higher (P<0.05) for cows fed the FOSFO over 3 week of lipid supplementation. The concentration of c is-9 trans-11 CLA in milk fat reached maximum on day 3 with both diets and remained relatively constant thereafter. The concentration of VA in milk fat followed the same pattern of temporal changes as c is-9 trans-11 CLA. In conclusion, milk cis-9, trans-11 CLA and VA concentrations increased with FO and SFO supplementation compared with the CONT diet and the increase reached a plateau on day 3 of supplementation and remained relatively constant throughout the remainder of the study.

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 (8.0kg/d, DM basis) containing 400g 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 100g of FO and 300g 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 31.2kg/d), milk fat percentages (3.64 and 3.50), milk fat yield (1.08 and 1.09kg/d), milk protein percentages (2.97 and 2.88), and milk protein yield (0.99 and 0.91kg/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. 0.84g/100g of fatty acids) and vaccenic acid (5.11 vs. 2.20g/100g 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 1.64g/100g 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.

The effect of breed, stage of lactation and parity on sheep milk fat CLA content under the same feeding practices

Abstract The cis-9, trans-11 C18:2 (CLA) content in milk fat of four pure sheep breeds (Awassi, Lacaune, Friesland and Chios) was examined. All sheep were kept indoors all year round under the same feeding practices, without any grazing at all. Sheep nutrition was based on alfalfa hay and concentrates. A total of 237 individual milk samples were collected at three sampling times (December, January and March) from sheep of different parity and different days in milk, for CLA determination. The results showed that: (a) there was a large variation in milk fat CLA content among individuals consuming the same diet, (b) the CLA content of milk fat was lower in Friesland breed, compared to the other three breeds but without any significant difference among the four sheep breeds, (c) the CLA content of milk fat was not affected by ewes parity or days in milk, (d) there was a negative but not significant correlation between milk fat and CLA concentration, (e) the CLA content of milk fat was not correlated with milk yield. In conclusion, no others factors, such as breed, parity, days in milk, etc., can affect CLA content in milk fat, which means that the dietary ones remain the sovereign factors explaining the highest proportion of CLA content variability in sheep milk fat.

The contents of trans fatty acids and cla in cow colostrum and milk fat in the early lactation period

The trans fatty acids as well as cis-9 trans-11 C18:2 (CLA) were determined in the colostrum and milk fat of individual cows during up to 82 days of lactation. The analyses were performed using gas chromatography (GLC) on a capillary column (CP Sil 88) combined with the method of argentation thin-layer chromatography (Ag-TLC). The results obtained in the study indicated that the milk fat of individual cows, kept under identical living and feeding conditions, was characterised by an extremely high variability of trans isomers concentration, especially of those of C18:1 acid. The differences referred not only to the total content of trans C18:1 isomers but also to the proportion of trans-10 and trans-11 isomers of C18:1. In some fat samples, a high concentration of trans C18:1 isomers was observed and trans-10 &lt;br /&gt;isomer of C18:1 was found to dominate. In the case of all the cows, the colostrum fat was characterised by a lower average content of the examined acids as compared to the milk fat. The average value of CLA in the colostrum fat of all the cows under study was 0.34%, and in the milk fat 0.42% of total fatty acids. &amp;nbsp;

Changes in the milk and cheese fat composition of ewes fed commercial supplements containing linseed with special reference to the CLA content and isomer composition

A study was carried out to increase the CLA contents in ewes' milk fat under field conditions by dietary means and to investigate the extent of the changes and consequences for milk processing and cheese quality. During a 3-mon period, ewes' bulk milk samples were collected every week from two different herds. For the first 4 wk the ewes were fed a conventional diet. Then the following 6 wk a supplement enriched in alpha-linolenate (whole linseed) was incorporated into the ovine diet. Finally, in the last 3 wk the feeding was the same as in the first 4 wk. The FA profile in milk fat was monitored by GC, and the distribution of CLA isomers was thoroughly tested by combining GC-MS of 4,4-dimethyloxazoline derivatives (DMOX) with silver ion-HPLC (Ag(+)-HPLC) of FAME. Reconstructed mass spectral profiles of CLA characteristic ions from DMOX were used to identify positional isomers, and Ag(+)-HPLC was used to quantify them. An increase in total CLA in milk fat was observed, and total CLA remained elevated during the weeks of enriched alpha-linolenate feeding. In our experimental conditions there was a linear relationship between trans-vaccenic acid (trans-11-octadecenoic acid; trans-11 18:1) and 9-cis,11-trans CLA in ewes' milk fat. Concerning the CLA isomer profile, increases in the 11,13- and 12,14-18:2 positional isomers were considerable when linseed was included in the diet. Organoleptic characteristics of cheeses made with CLA-enriched milk did not substantially differ from those made with nonsupplemented ewes' milk. CLA total content and isomer profile did not change during ripening.

Effect of Supplemental Conjugated Linoleic Acids on Heat-Stressed Brown Swiss and Holstein Cows

Heat-stressed dairy cattle are bioenergetically similar to early-lactation cows in that dietary energy may be inadequate to support maximum milk and milk component synthesis. Study objectives were to evaluate whether conjugated linoleic acids- (CLA-) induced milk fat depression (MFD) during heat stress would allow for increased milk and milk component synthesis. In addition, CLA effects on production variables and its ability to induce MFD were compared between Holstein and Brown Swiss cows. Multiparous cows (n = 8, Holstein; n = 5, Brown Swiss) averaging 97±17 d in milk were used in a crossover design during the summer (mean temperature-humidity index = 75.7). Treatment periods were 21 d with a 7-d adaptation period before and between periods. During adaptation periods, all cows received a supplement of palm fatty acid distillate (242g/d). Dietary treatment consisted of 250g/d of CLA supplement (78.9g/d of CLA) or 242g/d of palm fatty acid distillate to provide equal amounts of fatty acids. The CLA supplement contained a variety of CLA isomers (3.0% trans-8, cis-10; 3.4% cis-9, trans-11; 4.5% trans-10, cis-12; and 4.8% cis-11, trans-13 CLA). Treatments were applied 2 ×/d with half of the supplement top-dressed at 0600h and the remainder top-dressed at 1800h. There was no overall treatment effect on dry matter intake (23.9kg/d), milk yield (40.0kg/d), somatic cell count (305,000), protein (2.86%), or lactose content (4.51%) or yields of these milk components. Supplementation with CLA decreased overall milk fat content and yield by 26 and 30%, irrespective of breed. The reduction of milk fat content and yield was greatest on d 21 (28 and 37%, respectively). Energy availability predicted by energy balance was improved with CLA supplementation compared with controls (3.7 vs. 7.1 Mcal/d, respectively). Respiration rate (78 breaths/min) and skin temperature (35.4°C) during maximum heat load were not affected by treatment. The group receiving CLA had higher total milk fat CLA concentration (9.3 vs. 4.9mg/g). Supplementation with CLA induced MFD and altered milk fat composition similarly between breeds and improved calculated energy balance during heat stress, but had no effect on production measures under these conditions.

Modifying milk fat composition of dairy cows to enhance fatty acids beneficial to human health

There is increased consumer awareness that foods contain microcomponents that may have beneficial effects on health maintenance and disease prevention. In milk fat these functional food components include EPA, DHA, and CLA. The opportunity to enhance the content of these FA in milk has improved as a result of recent advances that have better defined the interrelationships between rumen fermentation, lipid metabolism, and milk fat synthesis. Dietary lipids undergo extensive hydrolysis and biohydrogenation in the rumen. Milk fat is predominantly TG, and de novo FA synthesis and the uptake of circulating FA contribute nearly equal amounts (molar basis) to the FA in milk fat. Transfer of dietary EPA and DHA to milk fat is very low (<4%); this is, to a large extent, related to their extensive biohydrogenation in the rumen, and also partly due to the fact that they are not transported in the plasma lipid fractions that serve as major mammary sources of FA uptake (TG and nonesterified FA). Milk contains over 20 isomers of CLA but the predominant one is cis-9,trans-11 (75-90% of total CLA). Biomedical studies with animal models have shown that this isomer has anticarcinogenic and anti-atherogenic activities. cis-9,trans-11-CLA is produced as an intermediate in the rumen biohydrogenation of linoleic acid but not of linolenic acid. However, it is only a transient intermediate, and the major source of milk fat CLA is from endogenous synthesis. Vaccenic acid, produced as a rumen biohydrogenation intermediate from both linoleic acid and linolenic acid, is the substrate, and delta9-desaturase in the mammary gland and other tissues catalyzes the reaction. Diet can markedly affect milk fat CLA content, and there are also substantial differences among individual cows. Thus, strategies to enhance milk fat CLA involve increasing rumen outflow of vaccenic acid and increasing delta9-desaturase activity, and through these, several-fold increases in the content of CLA in milk fat can be routinely achieved. Overall, concentrations of CLA, and to a lesser extent EPA and DHA, can be significantly enhanced through the use of diet formulation and nutritional management of dairy cows.

CLA isomers in milk fat from cows fed diets with high levels of unsaturated fatty acids.

The concentrations of CLA isomers were determined by Ag+ -HPLC in the milk fat of cows fed a control diet consisting of hay ad libitum and 15 kg of fodder beets or this diet supplemented with oilseeds containing either high levels of oleic acid (rapeseed), linoleic acid (sunflower seed), or alphalinolenic acid (linseed). Highly significant (P < or = 0.001) correlations were found between the daily intakes of oleic acid and the concentration of the CLA isomer trans-7,cis-9 in milk fat; of linoleic acid and the CLA isomers trans-10,trans-12, trans-9,trans-11, trans-8,trans-10, trans-7,trans-9, trans-10,cis-12, cis-9,trans-11, trans-8,cis-10, and trans-7,cis-9; and of alpha-linolenic acid and the CLA isomers trans-12,trans-14, trans-11 ,trans-13, cis,trans/trans,cis-12,14, trans-11 ,cis-13, and cis-11 ,trans-13. CLA concentrations were also determined in the milk fat of cows grazing in the lowlands (600-650 m), the mountains (900-1210 m), and the highlands (1275-2120 m). The concentrations of many isomers were highest in milk fat from the highlands, but only three CLA isomers (cis-9,trans-11, trans-11 ,cis-13, and trans-8,cis-10) showed a nearly linear increase with elevation. Therefore, these three CLA isomers, and particularly the CLA isomer trans- 11,cis-13, the second-most important CLA in milk fat from cows grazing at the three altitudes, could be useful indicators of milk products of Alpine origin.

Effect of cereal grain and fibre supplements on the fatty acid composition of milk fat of grazing dairy cows in early lactation.

Two experiments were undertaken to determine the effects of cereal grain and fibre (hay or straw) supplements on the fatty acid composition of milk fat of grazing dairy cows in early lactation. In both experiments, grain supplements significantly increased (P < 0.05) the proportion of the endogenously synthesized 10:0-16:0 fatty acids. Of the C18 acids, the proportion of 18:0 and 18:3 was significantly decreased (P < 0.05) by grain supplementation, while that of 18:2 was significantly increased (P < 0.05). Irrespective of diet, 18:1 trans-11 was the most dominant trans 18:1 isomer in milk fat. In the first experiment, the proportions of the 18:1 trans-11 isomer and conjugated linoleic acid (CLA, 18:2 cis-9, trans-11) were highest for the pasture-only diets, and significantly (P < 0.05) decreased with grain supplementation. The opposite result was observed in the second experiment, conducted in a different dairy region, suggesting that factors such as the quality of pasture on offer and the physiological state of the cow could affect the content of CLA and trans fatty acids in milk fat. In both experiments, there was a significant positive linear relationship between CLA and 18:1 trans-11. Fibre supplements had little effect on the fatty acid composition of the milk.