Conjugated Linoleic Acid Content In Milk Research Articles

Lithium Chloride Promotes Endogenous Synthesis of CLA in Bovine Mammary Epithelial Cells.

Although conjugated linoleic acid (CLA) can promote human health, its content in milk is insufficient to have a significant impact. The majority of the CLA in milk is produced endogenously by the mammary gland. However, research on improving its content through nutrient-induced endogenous synthesis is relatively scarce. Previous research found that the key enzyme, stearoyl-CoA desaturase (SCD) for the synthesis of CLA, can be expressed more actively in bovine mammary epithelial cells (MAC-T) when lithium chloride (LiCl) is present. This study investigated whether LiCl can encourage CLA synthesis in MAC-T cells. The results showed that LiCl effectively increased SCD and proteasome α5 subunit (PSMA5) protein expression in MAC-T cells as well as the content of CLA and its endogenous synthesis index. LiCl enhanced the expression of proliferator-activated receptor-γ (PPARγ), sterol regulatory element-binding protein 1 (SREBP1), and its downstream enzymes acetyl CoA carboxylase (ACC), fatty acid synthase (FASN), lipoprotein lipase (LPL), and Perilipin 2 (PLIN2). The addition of LiCl significantly enhanced p-GSK-3β, β-catenin, p-β-catenin protein expression, hypoxia-inducible factor-1α (HIF-1α), and downregulation factor genes for mRNA expression (P < 0.05). These findings highlight that LiCl can increase the expression of SCD and PSMA5 by activating the transcription of HIF-1α, Wnt/β-catenin, and the SREBP1 signaling pathways to promote the conversion of trans-vaccenic acid (TVA) to the endogenous synthesis of CLA. This data suggests that the exogenous addition of nutrients can increase CLA content in milk through pertinent signaling pathways.

CONJUGATED LINOLEIC ACID-ENRICHED DAIRY PRODUCTS: A REVIEW

Conjugated linoleic acid (CLA) is a family of more than 28 isomers of linoleic acid wherein the isomers cis-9, trans-11 (rumenic acid) and trans-10, cis-12 are the most abundant. It is associated with a number of potential health benefits for human organism. Many foods are a good source of it but it is mosty found in meat and dairy products, derived from ruminants. Dairy products contain CLA in different amounts. The enrichment of these products with CLA is appropriate given the lower CLA content in these products in comparison with the recommended health intake. Modification of CLA concentration can be done by specific animal feeding and diet modification, by direct CLA supplementation in the form of oils or by addition of specific starter culture. The influence of technological treatments on the stability of the final product during storage and maturation is still not completely elucidated. There is a need for further studies on the physiological effects of CLA isomers on humans. The purpose of this review is to summarize the possibilities for increasing CLA content in milk and dairy products and to determine the possible effects of this enrichment on product stability – sensory, chemical, microbiological profile, shelf life and potential health effects of the obtained products.

Effect of alternating total mixed ration and pasture feeding on the fatty acid content and health indices of Jersey and Fleckvieh x Jersey milk

Certain fatty acids (FAs), such as omega-3 and conjugated linoleic acid (CLA) are considered essential FAs with beneficial health effects for humans. Milk is considered a relatively inexpensive and readily available source of these FAs and is part of a recommended healthy daily diet. The aim of the study was to determine the effect of diet changes on the FA composition of Jersey (J) and Fleckvieh x Jersey (FxJ) milk. Cows were alternately put on kikuyu-ryegrass pasture, followed by a feedlot system, then returned to kikuyu-ryegrass pasture for four weeks each. The same concentrate mixture was fed to cows regardless of feeding system. The feedlot system consisted of a partial total mixed ration (pTMR). Milk samples were collected two and four weeks after diet changes and stored at −20 °C until laboratory analysis by gas chromatography. The FA concentration of milk was not affected by breed, although it was affected significantly by diet changes. Most notably, the total omega-3 and -6 FAs decreased when cows were fed pTMR while increasing when the diet was changed back to pasture feeding. The CLA content of milk was similarly affected. That is, concentrations decreased significantly when the cows were on the pTMR diet and increased when cows were put back on the pasture-based diet. The results suggested that the health benefits of milk fat are affected negatively when cows are fed pTMR compared with being fed in a pasture-based system. The health benefits of milk are reduced owing to decreased levels of the CLA content of milk fat. Therefore, feeding additional hay in a pasture-based production system should be reconsidered when aiming to produce milk that provides health beneficial qualities. Keywords: breed, diet, n-3 fatty acid, n-6 fatty acid, pasture, Fleckvieh

Obtención de leche bovina reducida en grasa saturada y naturalmente enriquecida en ácido linoleico conjugado

Te aim of the work was to reduce the presence of the potentially atherogenic fatty acids (FA) of milk (C12: 0,C14: 0 and C16: 0) and increase the presence of conjugated linoleic acid (CLA) in confned dairy cows fed a total mixed ration (TMR) supplemented with polyunsaturated fatty acids (PUFA). Two batches of 70 multiparous cows in the frst third of lactation were used. Afer six experimental weeks and for fve consecutive days, milk samples (5) were obtained from the collector tank of non-supplemented cows (LE) and of CLA milk (LCLA) from the tank of PUFA supplemented cows. Fat content (g/100g) in LE (3,84) was higher (p<0,001) than LCLA (2.84) explained by a signifcant reduction (17,21%) in the concentration of the potentially atherogenic FA of milk. The milk atherogenic index was higher (p<0,001) in LE (4,07) compared to LCLA (2.58). Milk CLA content increased (p<0,001) by 122% in LCLA (0,77 g/100 g FA) compared to LE (0,34 g/100 g FA). Oleic acid concentration (g/100 g FA) resulted higher (p<0,001) in LCLA (23,37) compared to LE (18,78). Supplementation with PUFA in confned dairy cows increased the healthy value of the milk produced maintaining an adequate omega-6/omega-3 ratio (6,59) and confrmed the plasticity in milk fatty acid composition.

A metaanalysis of feeding strategies to increase the content of conjugated linoleic acid (CLA) in dairy cattle milk and the impact on daily human consumption

Interest in functional foods has increased in recent years, being the enrichment of milk with conjugated linoleic acid (CLA) one of the targeted products. The objectives of this research were: (a) To identify the source of current human daily recommendations for CLA (literature search); (b) To determine the effect of feeding strategies on CLA concentration in milk (meta-analysis); and (c) To determine current average human intake of CLA and the expected improvement if milk and milk products were consumed in a CLA enriched form (literature search). The most commonly reported intake recommendation for humans is 0.8g/d (from 0.6 to 3.0g/d). However, these recommendations have been extrapolated from animal models and the few human studies reported contradictory results. We selected published papers (n=69) where dairy cows were fed different fats and the milk fat content and fatty acid (FA) profile, including CLA isomers, were reported. Treatments were categorized by source (vegetable fats, fish oils or the combination) and method of processing (raw, processed or extruded seeds, and oils). Data were analyzed using meta-analysis techniques. The combination of fish and vegetable fats resulted in the greatest increase (0.61 vs. 1.34g of CLA/100g of FA), but milk fat content decreased (36.1 vs. 31.2g/kg). Linseed increased CLA proportion (0.61 vs. 0.90g of CLA/100g of FA) without affecting milk fat content. The best processing method to enrich milk with CLA were extrusion of oilseeds (0.57 vs. 1.11g of CLA/100g of FA) and oils (0.57 vs. 1.10g of CLA/100g of FA), but extruded seeds decreased milk yield (30.4 vs. 28.9kg/d) and oils decreased milk fat content (36.1 vs. 33.1g/kg). Considering the changes in CLA and milk fat content, supplementation with fish oils together with vegetable fats would be the best strategy (395mg of cis-9, trans-11CLA/l vs. 188mg of cis-9, trans-11CLA/l; increase of 2.1 times). The estimated current average human consumption in Europe, US and Canada is 0.21g/d, ranging from 0.06g/d in Portugal to 0.40g/d in Germany, well below the recommendationss. If we assume a 2.1 times increase in CLA in milk and milk products, average human consumption would increase from 0.21 to 0.44g/day. Although there is sufficient data on feeding strategies to increase CLA content in milk, human requirements have not been well established and, based on current recommendations, they are unattainable even if all milk and milk products were consumed as CLA enriched products.

Safety and efficacy of methylester of conjugated linoleic acid (t10,c12 isomer) for pigs for fattening, sows and cows

A mixture of methylated (ME) conjugated linoleic acid (CLA) isomers (t10,c12 and c9,t11) in equal proportions was not genotoxic and caused no reproductive toxicity. In a sub-acute study in dogs, a sub-chronic toxicity study in rats and a chronic study in dogs, no adverse effects were seen up to the highest levels tested. The maximum recommended feed concentration (5 g CLA (t10,c12)-ME from Lutalin®/kg feed for piglets, pigs for fattening and sows) or dose (30 g CLA (t10,c12)-ME from Lutrell® Pure/cow per day) is considered safe for target species. The CLA content of milk from cows treated with the highest recommended dose did not exceed background values (in milk of untreated cows) for both CLA isomers. An estimate of consumer exposure to both CLA isomers from food from pigs receiving 3 g of both CLA isomers/kg feed is ≤ 320 mg CLA isomers/person and day. This quantity corresponds to about 9% of the quantity considered safe for 6 months and is considered unlikely to raise concerns for consumer safety. Exposure of users by inhalation of the additive is likely to be minimal. Neither of the products under application, the liquid or the solid product, was tested as such for skin and eye irritation and skin sensitisation. The use of the additive in animal nutrition would not pose a risk to the environment. In pigs for fattening, CLA (t10,c12)-ME has a potential for improving feed to gain ratio. More consistent effects are a reduction in subcutaneous fat, an increase in intramuscular fat and fat firmness. No essential effects were found in sows. Administration of CLA to dairy cows reduces in a dose-dependent manner the fat content of milk, and milk fat yield. Energy balance in early lactation is improved by CLA (t10,c12)-ME; however, reproductive parameters were not influenced.

The effects of probiotics and prebiotics on the fatty acid profile and conjugated linoleic acid content of fermented cow milk

The ability of probiotic bacteria (Lactobacillus acidophilus La5 and Bifidobacterium animalis Bb12), to produce conjugated linoleic acid (CLA) in association with Streptococcus thermophilus and Lb. bulgaricus during milk fermentation has been evaluated in this study. Pasteurized cow milk and infant formula were used. Infant formula was selected for its high linoleic acid content, for being a source of CLA and for its prebiotic compounds, e.g. galacto-oligosaccharides. The microorganisms were not able to increase the CLA content of the fermented products under the given experimental conditions. No statistically significant differences (p > 0.05) occurred between the CLA content in milk and the fermented samples. The CLA contents of 10 commercial fermented milk products were determined. The highest CLA content was observed in fermented milk containing only Str. thermophilus and Lb. bulgaricus.

Variation of Fatty Acid Content in Zamorano-Type Ovine Cheese According to the Milk Conjugated Linoleic Acid Content

A total of 30 Zamorano-type cheeses were manufactured in order to study the effects of milk conjugated linoleic acid (CLA) content, ripening time, and interactions between both effects on fatty acid (FA) profile. Cheeses elaborated from milk with a high CLA content showed higher contents of vaccenic, oleic, alpha-linolenic (ALA), CLA, monounsaturated (MUFA) and polyunsaturated (PUFA) FA, and lower contents of capric, lauric, myristic, palmitic, estearic, linoleic, and saturated (SFA) FA than cheese from milk with a low CLA content. Content of unsaturated C18 FA along with MUFA and PUFA groups increased throughout the ripening, while SFA content decreased. The interactions between milk CLA content and ripening time were significant for palmitic, linoleic, CLA, SFA, and omega-6/omega-3 ratio in Zamorano-type cheese. Decreases in cheese omega-6/omega-3 ratio were obtained from milk with a high CLA content; this ratio worsened over ripening in cheeses from low-CLA milk. In conclusion, these results emphasize the importance of the initial CLA content in milk with regard to improve the lipid profile in cheese for consumption.

Cheddar Cheese from Cow Milk with Elevated Conjugated Linoleic Acid Levels

The aim of the study was to evaluate the effect of feed management on conjugated linoleic acid (CLA) level in milk and subsequently on fatty acid profile of cheese. Twenty cows were divided into 2 groups, fed on grass silage and pasture feed with sunflower supplementation for 14 days. Milk samples were collected and analyzed for composition and fatty acid profile using gas chromatograph. Cheddar cheese was manufactured from both milk types and ripened for 120 days. During ripening, it was analyzed for composition and fatty acid quantification. The supplemented diet significantly increased the CLA content in milk. Similarly the cis-9, trans-11 CLA content in Cheddar cheese were more than twofold in case of supplemented diet as compared to grass silage. During ripening, CLA concentration remained stable. The sunflower supplementation showed no effect on cheese composition. Hence, supplemented pasture resulted in elevated CLA content in milk compared to grass silage.

Starter cultures and cattle feed manipulation enhance conjugated linoleic acid concentrations in Cheddar cheese

Conjugated linoleic acid (CLA) is a fatty acid (FA) that provides several health benefits to humans. The feeding of fish oil-supplemented diets to dairy cows has been extensively studied as a means to improve the CLA content in milk. Several studies have also been conducted on the ability of many microorganisms to produce CLA by utilizing substrates containing linoleic acid. In the present study, the dietary manipulated milk was used in combination with the CLA-producing culture to manufacture Cheddar cheese. The two diets fed to cattle were control and treatment diets to obtain control and treatment milk, respectively. The treatment diet containing fish oil (0.75% of dry matter) was fed to 32 dairy cows grouped in a pen for 18 d to increase the total CLA content in milk. Treatment milk had a CLA content of 1.60g/100g of FA compared with 0.58g/100g of FA in control milk obtained by feeding the control diet. A 2 × 2 factorial design with 3 replicates was used to test the combined effect of the CLA-producing starter culture of Lactococcus lactis (CI4b) versus a commercial CLA nonproducing cheese starter as the control culture, and type of milk (control vs. treatment milk) on CLA content in Cheddar cheese. Chemical composition (moisture, salt, fat, and protein) was not affected by the type of culture used. However, the age of the cheese affected the sensory properties and microbiological counts in the different treatments. Ripening with the CI4b culture was found to be effective in further enhancing the CLA content. The CI4b cheeses made from control milk and treatment milk contained 1.09 and 2.41 (±0.18) g of total CLA/100g of FA after 1 mo of ripening, which increased to 1.44 and 2.61 (±0.18) g of total CLA/100g of FA after 6 mo of ripening, respectively. The use of treatment milk resulted in an increase in the CLA isomers (trans-7,cis-9+cis-9,trans-11, trans-9,cis-11+cis-10,trans-12, trans-10,cis-12, cis-9,cis-11, trans-11,cis-13, cis-11,cis-13, trans-11,trans-13, and trans-9,trans-11). The CI4b culture specifically increased cis-11,cis-13 and trans-10,cis-12 isomers in cheese. The total CLA content in cheese was significantly higher when the CI4b culture was used compared with CLA nonproducing culture cheeses made from control milk and treatment milk after 1 mo [1.09 and 2.14 (±0.18) g of total CLA/100g of FA] and 6 mo [0.99 and 2.05 (±0.18) g of total CLA/100g of FA] of ripening, respectively. The results indicated that the combination of a CLA-producing starter culture and milk from cattle fed fish oil-supplemented diets (0.99g of CLA/100g of FA) could enhance levels of total CLA in Cheddar cheese by up to 2.6 times compared with cheese made from control milk with CLA nonproducing starter culture (2.61g of CLA/100g of FA) after 6 mo.

Effect of pressure-assisted thermal sterilization on conjugated linoleic acid (CLA) content in CLA-enriched milk

Conjugated linoleic acid (CLA) has been recently studied for its health-promoting and disease-preventing properties. The objective of this study was to evaluate the effect of pressure (100–600 MPa), temperature (60–120 °C) and treatment time (0–14 min) on CLA content in milk and anhydrous milk fat (AMF) rich in CLA. In milk treated up to 14 min at 100 MPa, CLA was stable (> 80% of retention), regardless of the temperature. In contrast, only 3.4 ± 2% of CLA was retained at 600 MPa and 120 °C. For AMF, CLA retention was considerably higher (40.2 ± 2%) than that obtained for milk. The presence of free metal ions in milk might catalyze CLA degradation. When the antioxidant catechin (1 g/kg) was used, CLA retention increased significantly (> 90%) in milk and AMF, regardless of the experimental conditions. Previous research led by Dr. John Kennelly resulted in CLA-enriched milk by manipulating the diet of dairy cattle. CLA in milk suffers significant losses in terms of its biological activity during processing at high temperatures like UHT. High consumption of CLA products has been associated with many health benefits. This study provided new data on CLA retention with and without an antioxidant at pressure-assisted thermal sterilization (PATS) conditions and confirmed the role of catechin in reducing oxidative damage by PATS treatments. Milk rich in CLA can be treated with PATS to deliver shelf-stable milk while CLA activity is preserved.

Contenido de ácido linoleico conjugado (CLA) en leche de ganado lechero Holstein estabulado en el noroeste de México

Experimental animal studies suggest that conjugated linoleic acid (CLA) has beneficial health properties. Ruminant-derived products such as meat and milk are the principal natural sources of CLA. Milk CLA content is influenced by several factors, including diet and production system. An evaluation was done of CLA content in milk from confined Holstein cows at a farm in Hermosillo municipality, Sonora State, Mexico, during the summer months, when daytime temperatures surpass 40 °C. Milk samples were collected from 120 cows. Quality parameters such as fat, lactose, protein and total solids percentages were measured using AOAC methods. The fatty acid and CLA profile was generated by gas chromatography. Average milk production was 15.8 ± 0.5 kg/day, fat content was 1.91 ± 0.06 %, lactose content was 4.30 ± 0.2 %, protein content was 3.34 ± 0.03 and total solids content was 10.4 ± 0.09 %. Unsaturated fatty acids content was higher (P<0.05) in August than during June and July. Average cis-9, trans-11 CLA concentration was 9.36 mg/g fat (10.78 ± 0.41 in June, 8.50 ± 0.37 in July, and 10.16 ± 0.39 in August), which is high compared to concentrations reported in countries with a temperate climate. The relatively high CLA content observed in the present study was probably caused by the 58.8 % alfalfa content in the summer diet, since this legume is rich in CLA fatty acids precursors (linoleic and linolenic acid).

Milk production and fatty acid profile of dairy cows supplemented with flaxseed oil, soybean oil, or extruded soybeans

The objective of the study was to investigate the effects of oil sources in the diet on milk yield, milk composition, and fatty acid (FA) profiles in mid-lactating dairy cows. Forty-eight Chinese Holstein dairy cows averaging 150 days in milk (DIM) at the start of the experiment (body weight = 596±19 kg; milk yield = 29.7±3.00 kg/d) were used in a completely randomized block design. The animals were assigned into four dietary treatments according to DIM and milk yield, and supplemented with no oil (control), 2% flaxseed oil (FSO), 2% soybean oil (SBO), and 2% oil from extruded soybeans (ESB). The experiment lasted nine weeks including the first week for adaptation. Milk yields, milk compositions (fat, protein, and lactose), and milk FA profiles were measured. Daily milk yield from cows fed with FSO, SBO, and ESB were higher than milk yield of the control cows (27.0, 27.0, and 26.5 vs. 25.4 kg/d). Milk fat percentage of the control cows was greater than those cows fed with oil-supplemented diets. However, increasing dietary fat content resulted with no change in fat-corrected milk yield. The FA profile of milk was changed by fat supplementation. Feeding oil reduced the proportion of both short-chain (C8:0 to C12:0) and medium-chain (C14:0 to C16:1) FAs, and increased the proportion of long-chain (≥C18:0) FAs in milk fat. Cis-9, trans-11 conjugated linoleic acid (CLA) in milk fat was increased from 0.38% for the control to 0.79, 1.51, and 1.56% of fat for the cows supplemented with FSO, SBO, and ESB, respectively. Feeding oils rich in linoleic acid (SBO and ESB) was more effective in enhancing cis-9, trans-11 CLA in milk fat than oils containing linolenic acid (FSO). There was a linear relationship between transvaccenic acid and cis-9, trans-11 CLA content in milk. Overall, feeding the FSO, SBO, and ESB diets increased monounsaturated and polyunsaturated fatty acids and decreased the saturated fatty acid in milk fat.

The effect of steam-flaked and extruded full-fat soybeans on the concentration of conjugated linoleic acid in the milk fat of dairy cows

Conjugated linoleic acid (CLA) is naturally produced in ruminants and exerts many beneficial health effects to humans. Feeding dairy cows with extruded soybeans has been reported to boost the CLA concentration in milk. However, the impact of steam-flaking soybeans on milk CLA content remains unknown. To study the potential of feeding steam-flaked soybeans on enhancing the CLA concentration in milk, a total of 27 Holstein lactating cows were fed with either conventional corn-soybean meal-based (control, CON) diet, steam-flaked full-fat soybean-based (SFS) diet or extruded full-fat soybean-based (ES) diet (nine cows per treatment) in an eight-week trial. Milk yield and other milk components were largely unaffected by dietary treatment. As compared with the CON diet, feeding SFS and ES diets resulted in an increase (p < 0.05) in the concentration of cis-9, trans-11 CLA from 0.76–1.00 and 0.98 g/100 g fatty acids in milk fat, respectively. Similarly, the concentration of trans-11 C18:1 in milk fat also increased (p < 0.01) with feeding the SFS and ES diets. No statistical difference in either cis-9, trans-11 CLA or trans-11 C18:1 concentration was observed between the SFS and ES diets. Collectively, our results suggest that, similar to extrusion, steam-flaking of full fat soybeans can increase milk CLA.

Variations in Conjugated Linoleic Acid (CLA) Content of Processed Cheese by Lactation Time, Feeding Regimen, and Ripening

Dairy products are major sources of conjugated linoleic acid (CLA); thus, an increase in CLA content can improve the quality value of dairy products. The objective of this work was to determine the effects of lactation time, feeding regimen, and ripening period on the level of CLA in processed cheese. CLA content in milk varied with the period of lactation; high in spring (April and May, about 6.8 mg CLA/g fat) and relatively low in mid summer and winter (about 4.3 mg CLA/g fat). The effects of dietary regimen and ripening period were determined in milk, which was obtained from March to May. After aging for 4 months, the cheese made from milk obtained from cows fed on pasture contained relatively higher levels of CLA compared to cheese made from milk obtained from cows fed indoors (8.12 mg CLA/g fat vs 6.76 mg CLA/g fat), but there was no difference in 7 month-aged cheeses. In both pasture and indoor feeding, 7 month-aged cheeses showed higher CLA content than 4 month-aged cheeses. The contents of stearic acid (C18:0) and linolenic acid (C18:3) were significantly higher in cheese from pasture fed cows compared to those in cows fed indoors. These findings should be helpful for the efficient production of functional dairy products with high CLA contents.

Conjugated linoleic acid producing potential of lactobacilli isolated from the rumen of cattle

Lactobacilli isolated from the rumen of cattle were subjected to morphological and biochemical characterizations followed by PCR-based identification. Among isolates, Lactobacillus brevis was found to be the most prevalent species in the rumen. For in vitro conjugated linoleic acid (CLA) production, the two isolates of L. brevis and one each of Lactobacillus viridescens and Lactobacillus lactis were selected. The sunflower oil (i.e., 0.25, 0.5 and 1.0%; a rich source of linoleic acid) was added to skim milk as a substrate for CLA production by isolates at 37 degrees C/12 h. L. brevis 02 was found to be the most potential CLA producer (10.53 mg CLA/g fat) at 0.25% concentration of sunflower oil followed by L. brevis 01 (8.27 mg CLA/g fat). However, at higher level of sunflower oil (i.e., 1.0%), L. lactis was the highest CLA producer (9.22 mg/g fat) when compared to L. brevis and L. viridescens. The results indicated that L. brevis and/or CLA production was inhibited with increasing concentration of sunflower oil in skim milk. In contrast, L. lactis and L. viridescens could tolerate the increasing concentrations of sunflower oil and produced higher CLA. Overall, L. brevis extends a possibility to be used as a direct-fed microbial for ruminants to increase the CLA content in milk, however, in vivo trials are needed for validation of results obtained.

Human breast milk enrichment in conjugated linoleic acid after consumption of a conjugated linoleic acid–rich food product: a pilot study

Human breast milk is a complex mixture of organic and inorganic compounds. Some compounds, such as conjugated linoleic acid (CLA), come partly from the mother's diet and are produced by the mother's body and secreted into the milk. Although several studies have examined the effect of chronic CLA supplementation on breast milk CLA appearance, little is known about the transfer of food CLA to breast milk over the short term. The objective of this study was to conduct a preliminary analysis of the kinetics of CLA appearance in breast milk over the short term. Seven women expressed breast milk at 4- to 6-hour intervals for 2 days after eating either CLA-enriched (1912 mg CLA) or control (231 mg CLA) cookies. Milk samples were freeze-dried, fatty acid methyl esters were prepared using methanolic-potassium hydroxide (KOH), and CLA isomers were quantified by gas chromatography. Analysis revealed the following: (1) CLA enrichment of total fatty acids in the breast milk for 48 hours post ingestion of the CLA-enriched cookies was 2.9-fold above control; (2) total breast milk CLA content for 48 hours post CLA-enriched cookies ingestion was 46% greater than post CLA-moderate cookies ingestion; (3) after ingestion of the CLA-enriched cookies, breast milk CLA enrichment plateaued between 8 to 28 hours. This preliminary study suggests that breast milk fatty acids are enriched in CLA compared to control within 28 hours after the ingestion of a CLA-rich food product and invites further research on the extent and timing with which breast milk composition reflects dietary CLA content.

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 4wk. 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/100g 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.

Supplementation of dairy cows with a fish oil containing supplement and sunflower oil to increase the CLA content of milk produced at pasture

It has been shown that the cis 9, trans 11 isomer of conjugated linoleic acid (CLA) can be increased in milk by supplementation with fish oil and vegetable oils. Feeding a high level of oil, however, can impact negatively on gross milk composition. The principal aim of this study was to determine if relatively low levels of fish oil or sunflower oil, either alone or in combination, offered to dairy cows on pasture would increase the C18:2 cis 9, trans 11 CLA concentration in milk. Forty autumn-calved cows on a diet of grazed grass were assigned to 4 supplementation treatments: (i) No supplement (P), (ii) 255 g/day of sunflower oil (SO), (iii) 255 g/day of sunflower oil + 52.5 g/day of fish oil (SOFO), and (iv) 105 g/day of fish oil (FO). The fish oil was supplied in a proprietary product called Omega-3 Supplement which is a mixture of marine oils and an extracted oilseed meal and contains 500 g/kg of oil. The oils were fed in a concentrate mixture, which was offered at a rate of 3.0 kg/cow per day. The production of the cows was measured for 54 days and the milk fatty acid composition was determined on day 0 (immediately before the supplements were introduced) and on days 14, 28 and 42 after the treatments were imposed. Supplementation increased the yield of milk ( P < 0.01), protein ( P < 0.05) and lactose ( P < 0.001), decreased milk fat ( P < 0.05) and protein ( P < 0.01) concentrations and increased ( P < 0.01) lactose concentration. Type of oil did not significantly affect any production variable. The concentration of C18:1 trans 9 + C18:1 trans 11 (mainly C18:1 trans 11) ( P < 0.001) and C18:2 cis 9, trans 11 CLA ( P < 0.01) were greater on supplemented treatments than on P and the concentration of both were greater ( P < 0.05) on FO than on SO. The results confirm that the concentration of C18:2 cis 9, trans 11 CLA can be increased further, from an already relatively high concentration in milk from pasture, by offering supplements containing a low level of fish oil either alone or in combination with sunflower oil.

Stearoyl CoA desaturase (SCD) gene polymorphisms in Italian cattle breeds

Stearoyl CoA desaturase (SCD) is the key enzyme involved in the endogenous synthesis of conjugated linoleic acid (CLA) in ruminants. Changes in the enzymatic activity as a result of SCD gene polymorphism and regulation have been hypothesized to cause diet-independent variations of CLA content in milk. Evidences for the direct influence of SCD polymorphism on fatty acid composition of milk and beef have also been reported. To evaluate genetic differences because of breed and/or selection goal, we investigated the polymorphism of three previously reported single nucleotide polymorphisms located in exon 5 of the SCD gene in 11 cattle breeds raised in Italy and selected for different production goals. Results obtained: (i) evidenced a high variability in the allele frequencies across breeds; (ii) detected three novel haplotypes, one of which is private to indigenous beef breeds, and (iii) showed a significant association between haplotypes and selective goal.