Assessing and Enhancing Conjugated Linoleic Acid (CLA) Concentrations in Foods from Pastured Dairy and Beef Cattle

Final Report for LNC01-191

Project Type: Research and Education
Funds awarded in 2001: $81,144.00
Projected End Date: 12/31/2004
Region: North Central
State: Missouri
Project Coordinator:
Lora Friest
Resource Conservation and Development for Northeast Iowa, Inc
Expand All

Project Information

Summary:

This research assessed the concentration of conjugated linoleic acid (CLA) in milk and beef from farms that varied management systems. On-farm dairy- and beef-controlled studies compared the CLA concentration in milk and beef from cattle either pastured or fed with stored feeds and higher amount of concentrates. Intensively pastured cows produced milk with CLA concentrations that were about 3- to 4-fold greater than in milk from cows fed mostly stored feeds and concentrates.

Introduction:

Conjugated linoleic acid (CLA) is a collective term for a mixture of positional and geometric isomers of linoleic acid (C18:2). This fatty acid is produced as an intermediate during the biohydrogenation of linoleic acid to stearic acid by the bacterium Butyrivibrio fibrisolvens (Kepler et al., 1966), producing cis9 trans11 CLA, which is the primary isomer found in ruminant milk and meat. Vaccenic acid (C18:1, trans11) also is an intermediate product in the ruminal biohydrogenation process and is a precursor for endogenous formation of CLA via 9-desaturase activity. Endogenous synthesis is estimated to contribute about 64% of the CLA in milk fat (Griinari et al., 2000). The normal concentration of cis9 trans11 isomer in milk from cows fed a typical dairy ration is about 0.38 g/100 g of total fatty acids (Dhiman et al., 1999) and about 0.35% in beef lipids. However, this concentration can be elevated markedly by increasing the supply of precursors for CLA synthesis through nutritional manipulations. For example, inclusion of oils, extruded oil seeds, and raw oil seeds all increase CLA content in the milk. Fish oil is even more effective in increasing CLA in milk.

Pasture feeding has haspreviously been demonstrated to increase CLA concentration in milk (Dhiman et al., 1999) and beef (French et al., 2000). Pasture grasses are rich in linolenic acid, which can be converted to trans vaccenic acid during the biohydrogenation process in the rumen and then synthesized to CLA.

Although pasture feeding is a regular production protocol among organic dairy and beef producers, the intensity of grazing practice vary between farms in the U.S. We evaluated the CLA concentrations of milk and beef from a broad spectrum of largely pasture-based beef and dairy operations in northeast Iowa and southwest Wisconsin. Furthermore, we studied the effect of pasture grazing on milk and beef CLA concentrations.

Project Objectives:

Determine factors affecting and optimizing CLA concentrations in milk and meat across a broad spectrum of largely pasture-based dairy and beef operations throughout the year (dairy and beef comparison studies).

Describe seasonal CLA concentration changes in milk from cows moving from winter rations onto spring pasture, determine ability of feeding supplements to enhance presumed increases, and quantify costs involved in enhancing CLA concentrations above pasture levels (dairy controlled study).

Describe seasonal CLA concentration changes in meat from steers moving from fresh pasture onto winter feeding, determine winter feeding strategies that maintain the highest CLA concentrations, and quantify costs involved (beef controlled study).

Increase awareness and knowledge of factors affecting and maximizing CLA concentrations in meat and milk from grazing systems among researchers, producers, and marketers and stimulate the application of this knowledge in additional research, management changes by producers, and marketing efforts of individual producers and the Coulee Region of Organic Producers Pool (CROPP).

Research

Materials and methods:

Methodology

Comparison study of management–related, between herd CLA concentration variation in milk and beef

Twelve dairy producers from two regional locations, northeast Iowa and southwest Wisconsin, participated in this study. The participants from Iowa were Don Baker (A), Todd Bushman (B), Dennis Cline (C), Ken Kriener/Dann Kime (D), and Rick Langland (E). The Wisconsin producers included Don Austin (F), James Heisner (G), Dennis Knapp (H), Jay Richard (I), Ronald Runde (J), and Keith Wilson (K). Another farmer from Wisconsin with the name of Charles Timmerman started participating in May 2002 but discontinued his involvement in the research after the sale of his farm in December 2002. Iowa producer Ken Kriener participated in 2002, and, beginning in January 2003, management of the farm was switched to Dann Kime, who decided to have the farm remain involved in the project. Farms A and F are seasonal dairy operations; hence, sampling in a year always started in April.

Four beef producers were enrolled in the comparison study of management-related, between herd CLA concentration variation in meat. The beef cattle producers involved in the project included Dan Specht (L), Lachlan Gabel (M), William Larson (N), and Gary Welsh (O). Farm L had three groups of cattle that were fed with the following diets:

Group 1
Winter 2001-2002: Alfalfa silage, alfalfa hay, and high moisture corn.
Summer 2002: Orchardgrass, bromegrass, bluegrass, red clover, white clover, birdsfoot trefoil, timothy grass pasture + corn and barley.
Group 2
Winter 2001-2002: Alfalfa silage, alfalfa hay, and high moisture corn
Summer 2002: Orchardgrass, bromegrass, bluegrass, red clover, white clover, birdsfoot trefoil, timothy grass pasture + corn and barley.
Winter 2002-2003: Alfalfa hay + corn and barley with sodium bicarbonate.
Group 3
Summer 2002: Orchardgrass, bromegrass, bluegrass, red clover, white clover, birdsfoot trefoil, timothy grass pasture + corn and barley.
Winter 2002-2003: Alfalfa hay + corn and barley with sodium bicarbonate.

The cattle from the other three producers were finished with conserved forages such as alfalfa hay, grass hay, and corn silage; each farm supplemented the diets with different concentrate mixes.

In years 2002 and 2003, a monthly visit was undertaken to the different farms to collect a sample of every feed component of the cattles’ diet as well as milk samples from the bulk tank. Beef samples were collected after harvest of finished cattle. Milk, beef, and feed samples were analyzed for total fatty acids including CLA.

CLA Concentrations in Milk from Pastured Dairy Cows (Dairy Controlled Study)

This controlled study was conducted in summer 2002 on the family farm of Dan and Bonnie Beard who are members of CROPP. The design and detailed activities of the experiment were done with full participation of the cooperating farmers. The objective of the study was to compare the concentrations of CLA in the milk from cows subjected to two different feeding regimens. Sixteen second or greater parity purebred Jersey cows were divided into two groups. Group 1 cows were allowed to graze rotationally on a ryegrass, bluegrass, and white and red clover pasture and supplemented with the Beards’ standard ration (BR): 7 kg corn silage, 5.2 kg ground shelled corn, and 0.81 kg mineral mix daily. Group 2 cows were fed with the above-described pasture only. Prior to the experiment, all cows were fed a winter ration composed of corn silage, alfalfa-grass silage, alfalfa hay, ground shelled corn, soybean meal, and mineral mix. All cows were fed the Beards’ standard ration after the experiment.

Milk samples were collected at morning and evening milkings on April 20, May 5, May 18, and June 1, 2002. Feed samples were collected two days before each milk sampling date. Both milk and feed samples were frozen immediately for fatty acids including CLA analysis.

CLA Concentration of Beef from Cattle Finished Mostly on Pasture (Beef Controlled Study)

This study was conducted at the Rosmann Family Farms owned by Ron and Maria Rosmann of Harlan, IA, which was started on April 30, 2002. Thirty yearling steers and heifers were selected and fed to choice grade either on pasture or drylot. The cattle on the pasture treatment grazed forages consisting primarily of cool-season endophyte-free tall fescue with some orchardgrass and alfalfa. The drylot group of cattle was fed with ground alfalfa-orchardgrass hay as the forage source. Two mortalities from the pasture group were incurred on June 17, 2002 and were caused by acute acidosis resulting from accidental excessive availability of ground corn released from a grain bin installed in the pasture. In addition to the basal forages, both groups of cattle were fed a concentrate mixture composed of 86.60% ground yellow and white corn, 12.08% ground raw soybeans, and 1.32% minerals on a DM basis. Toward late summer (beginning in September), the percentage of soybeans in the concentrate mixture was increased to 14.51% (DM basis) but the proportion of minerals was maintained. Pasture-fed cattle were targeted to receive the concentrate mixture at about 0.5% of body weight in early summer, which then was increased to 1.0% of body weight beginning in July. The percentage of concentrates in the drylot system were increased gradually to about 2.0% of body weight and was maintained at this level for the last 90 to 120 days of the finishing period, which is the typical diet for finishing cattle in the Rosmann Family Farms. In addition to the concentrate mixture, all animals were allowed free access to salt and minerals.

When the cattle were ready for harvest, the animals were transported to two different packing plants. Nine cattle from the pasture group and eight from the drylot group were slaughtered and processed at Amend Packing, Des Moines, IA. The rest of the animals were slaughtered and processed at Lorentz Meats, Cannon Falls, MN. All carcasses were graded by a USDA federal beef grader.

Steaks from the 12th-13th rib, trim (85% lean to represent hamburger patties) and adipose tissues from the rump area of the carcasses of animals that were slaughtered and processed at Amend Packing were removed and transported to Iowa State University. The samples from each beef part were assayed for content of dry matter (DM) and total lipids and for fatty acid composition including CLA.

Dry matter content was determined by drying about 1 g of ground sample at 105 0C for 24 h. Total lipids were extracted by the modified Folch method using chloroform and methanol. The extracted lipids then were stored at –20 0C, and about 9 to 10 mg were butylated eventually with butanol and acetyl chloride. The butyl esters of fatty acids were separated by gas chromatography and identified by comparing their retention times with individual standard fatty acids. Concentration of each fatty acid including the major isomers of CLA was determined. Atherogenic index (AI), which is an index of healthfulness, was calculated for each beef part.

Research results and discussion:

Results

Comparison study of management-related, between herd CLA concentration variation in milk

The linoleic (C18:2) and linolenic (C18:3n-3) acid concentrations of feeds from the different farms in northeast Iowa and southwest Wisconsin are presented in Tables 1 and 2. Differences in concentrations of these two fatty acids were observed between feeds. Linolenic acid constitutes more than 50% of the total fatty acids in most of the grass-legume pasture forages, but the percentage is lower in predominantly legume pastures. On the other hand, more than 50% of the fatty acids in soybeans, corn silage, corn grain, and corn-based concentrate mixes is linoleic acid.

The fatty acid composition of milk that was collected every month from January 2002 to November 2003 is summarized in Tables 3a, 3b, 3c, 3d, and 3e for northeast Iowa and Tables 3f, 3g, 3h, 3i, 3j, and 3k for southwest Wisconsin. Each datum for a calendar month is an average of two years except for December, which is from year 2002 only. The major components of the milk fat are palmitic acid (C16:0), oleic acid (C18:1), and stearic acid (C18:0). Myristic acid (C14:0), which is four times more atherogenic than the other fatty acids, also constitutes a relatively large percentage of milk fat. Among the omega-3 fatty acids, linolenic acid (C18:3n-3) made up the greatest percentage of composition. Docosapentaenoic acid (C22:5n-3) was detectable more frequently than docosahexaenoic acid (C22:6n-3). Linoleic acid (C18:2n-6) comprised the greatest proportion of the omega-6 fatty acids. Higher percentage of C18:2 in milk fat is a desirable attribute for making softer butter. This fatty acid (C18:2) was observed to be highest in Farm B that feeds extruded soybeans consistently. The other omega-6 fatty acids that were detected included gamma linolenic acid (C18:3n-6), homo-gammal inolenic acid (C20:3n-6), and arachidonic acid (C20:4n-6). Also presented in the above-mentioned tables are the atherogenic index (AI) and ratio of omega-3 to omega-6 fatty acids. These parameters are measures of healthfulness of any lipid-containing food product. Atherogenic index ranged from 2.11 to 3.43 for milks from northeast Iowa farms and from 2.81 to 3.30 for milks from southwest Wisconsin farms. In both regional locations, the farms (Farms D and I) that had the highest myristic acid concentration also had the highest atherogenic indices. The average ratio of omega-3 to omega-6 fatty acids ranged from 0.22 to 0.76 for northeast Iowa farms and 0.43 to 0.57 for southwest Wisconsin farms. Omega-3 to omega-6 ratios were influenced more by the concentration of linoleic acid as this fatty acid was greater in percentage and more variable than the other fatty acids considered in the calculation.

The CLA concentration of milk from the different farms in northeast Iowa and southwest Wisconsin are shown in Figures 1 and 2, respectively. Each data point for a calendar month is an average of two years (2002 and 2003) except for December, which was obtained from year 2002 only. Presented in the graphs is the concentration of cis9 trans11, which accounts for more than 80% of all the CLA isomers measured and will be referred to as CLA in this section of the report. In all farms, CLA concentration was lowest at the first quarter and at the end of the year when cows were consuming hays, silages, and concentrates. The concentration of CLA begins to rise in April when grazing season begins. Peak CLA concentration was observed in the months of May and June for most farms; then, the concentration declined thereafter. Among the northeast Iowa farms, Farm A had CLA concentration of 1.42 g/100 g of fatty acids in May, which is four times the average concentration (0.34 g/100 g of fatty acids) of the northeast Iowa farms during the first quarter of the year. Farm A was followed by Farm E that showed its highest CLA concentration (1.03 g/100 g of fatty acids) in May. On the other hand, the milk from Farm B did not show any noticeable change in CLA concentration throughout the experimental period. Among the southwest Wisconsin farms, Farms G and H had the highest CLA concentrations in May and June, representing a 3- to 4-fold increase from their respective baseline concentration during the first quarter of the year, whereas Farm I did not show any change in CLA concentration throughout the experimental period. The increase in CLA concentration is influenced strongly by the intensity of grazing practice of the farm. Farms A, E, F, G, and H are intensive graziers, whereas both Farms B and I rely heavily on stored feeds and concentrates. Most farms showed a decrease in CLA concentration beginning in August, and the decline progressed toward the latter part of the year as pasture became limiting. Persistence of a relatively high CLA concentration also is dependent on feeds and feeding system adopted by a farm. Farms A, E and F practice intensive grazing even towards the later part of the year as long as pasture is available. Consequently, higher milk CLA concentrations on these farms were held for a prolonged period of time (until October) compared with that of Farms C, D, G, H, and K that resorted to feeding of stored forages and greater amount of concentrates beginning in August. As shown in Tables 1 and 2, more than 50% of the fatty acids in most pasture forages is linolenic acid. Linolenic acid is degraded to trans vaccenic acid during ruminal biohydrogenation. Trans vaccenic acid, is a precursor for endogenous synthesis of CLA by∆9 -desaturase activity in the mammary gland.

CLA Concentrations in Milk from Pastured Dairy Cows (Dairy Controlled Study)

The data on dairy controlled study were presented during the pasture walk in Dan Beard’s farm in May 2003. Figure 3 shows the CLA concentrations of milk collected from the two groups of cows. Milk from both groups of cows had about the same CLA concentrations after being fed the winter ration. The concentrations of CLA continued to rise as the grazing season progressed and were similar for both groups of cows until the May 18 sampling. However, a distinctly higher concentration of CLA in the milk fat from those cows being fed with pasture alone was observed on June 1.

The linolenic acid concentrations detected in the milk from the two groups of cows are shown in Figure 4. Linolenic acid, an omega-3 fatty acid, was 0.60 g/100 of total fatty acids at the initial sampling. The concentration of this fatty acid increased to 0.93 g/100g and 1.06 g/100 g of total fatty acids for group 1 and group 2 cows, respectively, and each group maintained this concentration for the rest of the sampling times. Pasture grasses are relatively rich in linolenic acid and can be used as a substrate for CLA synthesis. This acid also can be transferred to the milk; hence, this fatty acid increased in milk when cows were allowed to graze.

CLA Concentration of Ribeye Steaks From Different Farms of Varied Management Systems

The data on this study were presented during the pasture walk at Farm L on August 21, 2003 to beef and dairy producers in attendance. Total lipid content of the ribeye steaks from the three groups of cattle of Specht’s farm are shown in Table 4. Farm L’s group 1 cattle had the highest percentage of lipid (4.74%), whereas group 2 cattle had the lowest (3.82%). The ribeye steaks from Farm L had lower total lipid content compared with that of the other three farms.

The total CLA content of the ribeye steaks from the four beef farms are presented in Table 5. The highest ribeye steak CLA content was observed in the group 2 cattle of Farm L, and the lowest was observed for Farm O. Farm L’s pasture-based cattle finishing system with limited grain supplementation supported a higher CLA concentration compared with the drylot system of Farm O.

CLA Concentration of Beef from Cattle Finished Mostly on Pasture (Beef Controlled Study)

The performance data of cattle finished on pasture or drylot are presented in Table 6. The average starting weight of the pasture-fed cattle was slightly lighter than those in the drylot system. As both cattle were fed to choice grade, pastured cattle fed lesser grain supplementation had 55 days longer feeding time than did those in the drylot. The average final weight of the pasture-fed cattle was about 12 kg heavier than that of the drylot-finished cattle. Average daily gain of the pasture-fed cattle was significantly slower than those for cattle fed a higher percentage of concentrates in the ration. In the absence of an accurate estimate of pasture DM consumption, only the concentrates consumption was included in the calculation of feed to gain ratio. However, the feed to gain ratio of the drylot–fed cattle is still considered less efficient compared with current beef cattle industry standard.

The dry matter and total lipid contents of the different beef parts are presented in Table 7. The adipose tissue obtained subcutaneously from the rump area had the highest DM and total lipid contents, whereas the ribeye steak had the lowest values. Within a beef part, DM content did not differ significantly (p0.05) between pasture and drylot systems. Although total lipids of ribeye steak and adipose tissue from pasture-fed cattle were numerically higher, the differences were not significant (p>0.05). Only the trim lipid content was affected significantly by the finishing system of cattle where trim from drylot group had more than twice the concentration in trim from the pasture treatment.

The fatty acid composition of pasture grass, ground hay, and concentrate mixture are shown in Table 8. Linolenic acid (C18:3n-3) comprised the greatest percentage of the total fatty acids for pasture and hay forages, whereas linoleic acid (C18:2n-6) was the largest component among the fatty acids in the corn-based concentrate mix.

Presented in Table 9 is the fatty acid composition of the different beef parts. The monounsaturated oleic acid (C18:1) accounted for the greatest concentration of the fatty acids in all three beef parts. This fatty acid was followed by palmitic acid (C16:0) and stearic acid (18:0) in a descending order of percentage. Myristic acid (14:0), which is the most atherogenic of all fatty acids, was found to be highest in the adipose tissue. Consequently, AI of adipose tissue was observed to be higher than those in the steak and trim. Linoleic acid (18:2), an omega-6 fatty acid, was highest in the ribeye steaks and lowest in the adipose tissue. Docosapentaenoic acid (C22:5), an omega-3 fatty acid, was also highest in ribeye steaks and almost negligible in the adipose tissue. Within a beef part, most of the fatty acids did not differ significantly (p>0.05) between the two finishing systems. In all three beef parts, the omega-3 linolenic acid (18:3) was significantly higher in parts from the pasture-finished cattle than in those from drylot-fed cattle. This result indicates that some of the linolenic acid in the feed, which makes up about 44% of the total fatty acids of the pasture forage, was transferred effectively to animal tissues. On the other hand, linoleic acid (C18:2) content of adipose tissue was significantly higher in beef parts from the drylot-finished cattle than in parts from pasture-fed cattle. A similar trend was observed for this fatty acid in the ribeye steak as it tended to be higher significantly (p=0.053) with drylot-finished cattle. The ratios of omega-3 to omega-6 fatty acids were significantly higher for pasture-fed cattle compared with ratios in the drylot-finished cattle in all three beef parts.

Table 10 shows the trans vaccenic acid (C18:t11), and CLA concentrations of the different beef parts. Among the four CLA isomers determined, cis9 trans11 accounted for about 78% of the total CLA. Adipose tissue had the highest cis9 trans11 CLA followed in a decreasing order by the trim and ribeye steak. In all three beef parts, CLA concentrations were significantly higher in parts from the pasture-finished cattle, having more than twice those in parts from the drylot-finished cattle. These data are complemented by the higher concentration of trans vaccenic acid in parts from the pasture-fed cattle than in parts from the drylot-finished cattle; the differences were significant (p0.05) for the ribeye steak and adipose tissue. Trans vaccenic acid is a precursor for CLA synthesis in animal tissues. Linolenic acid coming from pasture may have supplied the additional trans vaccenic acid produced during ruminal biodydrogenation.

Research conclusions:

Impact of the Results

This research gave producers the opportunity to understand more about CLA and to understand which production systems would be most likely to result in high CLA levels in beef and milk products. It also raised awareness about the potential health benefits of this fatty acid to humans. The results of this study documented the variation in milk and beef CLA concentrations between farms with varied production systems. Pasture feeding was identified clearly as the strongest management factor that results in high CLA concentrations. Pasture is a rich source of linoleic acid which, upon ruminal biohydrogenation, can supply the precursor for additional CLA synthesis by the endogenous pathway. This information was disseminated to producers so they can utilize feedstuffs high in linoleic acid to sustain a high CLA concentration even during the non-grazing months of the year. It remains to be seen what impact on the marketplace this study will have. Although the results of this study will be more useful when the effects of human consumption of products with high CLA concentrations are more widely documented and distributed to the media, there are some impacts on local producers. Once the information was distributed to producers, NRCS reported an interest from graziers wanting to incorporate more on grass time and reduce cement time for their animals. These producers were also interested in improving their grazing systems, incorporating higher forage and establishing niche marketing for their product.

Economic Analysis

Economic Analysis

Research related to this study was conducted by Iowa State Extension in the 1990s. The ISU Extension research found that initial start up cost for grass based systems is less than initial start up cost for a confined system. Grass based systems were found to be a less expensive way to produce milk on a family size farm of 100 or fewer cows. The grass based producer does not have to build a free stall barn or have the planting, harvest, and chopping equipment that a confined system needs. If they can have someone provide a small amount of silage, then they can avoid the cost of a tractor. The grass based producer was also found to save on infrastructure costs, since they did not have to build a free stall barn.

The same systems that ISU Extension found to be more economical to start up and operate were also the systems that were found by this study to produce higher CLA concentrations. If further studies in human ingestion of high CLA products support the human benefits of CLA ingestion, then the lower cost production system may be found to produce a product that is ultimately worth not only a greater market share, but also a greater profit within that market share.

Farmer Adoption

Farmer Adoption

A brochure titled “Conjugated Linoleic Acid, An Important Nutraceutical in Foods” as well as a one page summary “Conjugated Linoleic Acid Project Summary, Studying the Health Benefits from Pasture-fed Cattle” were developed and printed for distribution at pasture walks, conferences and seminars. These materials were presented at the Midwest Dairy Conference, the Upper Mississippi Grazing Conference, the Kickapoo Get Away Organic Field Day, an Organic Producers Meeting and at twenty-three pasture walks conducted in Iowa, Minnesota and Wisconsin. An estimated 4,500 producers attended these events from all over the nation. Presentations concerning the project were also given at some of these events.

Since the results of this project indicate milk and beef from pasture-fed cattle contain greater concentrations of CLA (greater than two to four times the concentration found in previous studies) compared with the same foods from cattle fed stored feeds, farmers wanting to increase CLA concentrations should increase pasture time for beef and dairy cattle. Those producers willing to increase pasture time for increased CLA could benefit in the future as foods enriched with CLA increase in market value because of the potential health benefits of CLA. The increase in value for high CLA foods has the potential to benefit small family farms on steep terrain that have traditionally relied heavily on pastured systems for beef and dairy production.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:

Publications/Outreach

Beitz, D.C., A.H. Trenkle, R. Sonon, and W. Miller. 2003. Conjugated linoleic acid – An important nutraceutical in foods. Brochure prepared in the Department of Animal Science and Iowa Beef Center, Iowa State University, Ames, IA.
Beitz, D.C., A.H. Trenkle, and R.N. Sonon Jr. Modifying milk fat composition for improved manufacturing qualities and consumer acceptability. USDA W-181 Annual Report presented in Reno, Nevada on January 2004.
Sonon, R.N. Jr., D.C. Beitz, A.H. Trenkle, and D. Beard. 2003. CLA concentrations in milk from pastured dairy cows. Brochure prepared for a pasture walk at Dan Beard’s farm in May 2003.
Sonon, R.N. Jr., D.C. Beitz, and A.H. Trenkle. 2003. Conjugated linoleic acid (CLA) concentrations in ribeye steaks produced from different beef finishing systems. Brochure prepared for a pasture at Dan Specht’s farm on August 21, 2003.
Sonon, R.N. Jr., D.C. Beitz, and A.H. Trenkle. 2004. Improving health benefits of beef and milk: A field study. Animal Science Reports, Department of Animal Science, Iowas State University, Ames, IA (In press).

Project Outcomes

Recommendations:

Areas needing additional study

Research Questions Needing Additional Study

Does ingesting feeds high in linolenic acid, such as flax seed, increase both CLA and omega-3 linolenic acid concentrations in milk and beef?

What are the health benefits of CLA-enriched and omega-3 fatty acid-enriched dairy and beef food diets in humans – as documented by human feeding studies? Scientific study of the response of human systems to the consumption of high CLA enriched foods is the logical extension of this project

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.