**2. Bioavailability and clinical manifestation of enhanced CLA**

**CLA enhancing feed CLA content Reference** Pasture + extruded soybean 1.4 g/100 g fatty acid [16] Whole pasture 1.5 g/100 g fatty acid [17] Sunflower seed (11.2%) 400 (percentage increase) [23] Pasture 8.12 mg/100 g cheese [38] Pasture, 100 g/kg of sunflower oil/d 1.93 g/100 g fatty acid [41] Grass-fed animals 64·19 mg/100 g cheese [74] Fish oil (0.75% of dry matter) 2.41 g/100 g fatty acid [75] Natural spring pasture 0.76 g/100 g fatty acid [78] Pasture grazing 1.45 g/100 g fatty acid [79]

CLA represents two major CLA isomers of C18:2 cis-9, trans-11 and trans-10, cis-12 isomer, TMR: total mixed ration,

with unknown geometric position. However, the two major peaks in that commercial CLA mixture were assumed the isomers c9, t11 and t10, c12. Later on, further research advances turned out to achieve the possible isomerization with specific isomers ratios [82]. Propylene glycol isomerization was another method to produce CLA from monounsaturated and polyunsaturated oil fatty acids. The propylene glycol was used with KOH as a catalyst instead of ethylene alcohol for consumer safety reasons. Later, hexane was also used instead of ethylene/ propylene glycol to facilitate the purification of required CLA isomers. Thus, the mixture of CLA isomers was marketed as free acids instead of n-3 concentrates [83]. Isomerization of mono-alkyl ester is a relatively recent effective quantitative method to produce CLA isomers by isomerizing methyl and ethyl esters of linolenic acids in presence of very small quantity of catalyst and virtually no solvent. Besides, thermal sigma tropic rearrangement by preceding

Regarding the potential health effects, safe isomers selective processes are investigated for CLA production. Among these, bioprocess by microbial use is the potential method for production of CLA. Initially, the bacteria were divided into group A and group B depending on the type of reactions and the products as result of biohydrogenation. The bacteria of group A were able to hydrogenate linolenic acid and α-linolenic acid end product t11- C18:1. The group B bacteria were able to convert t11-C18:1 to end product stearic acid [84]. Besides ruminant bacteria, some bacterial strains from human/animal intestinal membrane, dairy products origins were isolated for CLA production. *Lactobacillus reuteri*, *Lactobacillus plantarum, Lactobacillus lrhamnosus, Lactobacillus brevis, Lactococcus lactis, Lactobacillus acidophilus, Propionibaterium freudenrehichii, Bifidobacterium, Streptococcus*, are capable for CLA production. Potential CLA producing strains such as bifidobacteria *Bifidobacterium*, lactobacilli, and pediococci have been selective for CLA production. The increasing interest in bifidobacteria as the natural inhabitant and

DM: dry matter, FA: fatty acid.

32 Bovine Science - A Key to Sustainable Development

*1.6.2. Microbial CLA*

**Table 3.** Effect of feed modification on CLA content in milk's cheese.

the reaction below 100°C results in CLA isomer production.

The general availability of CLA from food sources has been summarized in **Table 4**. Recently, the manipulation of fatty acid profile of milk, meat, cheese and butter has been shown to confer beneficial impacts on human health. There are very few experimental studies that indicate the kinetic behavior of dietary CLA from naturally enhanced diary and meat products. The studies on kinetic behavior of polyunsaturated fatty acids (PUFAs) showed that the bioavailability and disposition of PUFA could be altered in some biologic fluids after the intake of enriched PUFA-rich food products. For example, previous studies with high-fat diet and low-fat diet containing 1% rumenic acid show higher and lower bioavailability of CLA content respectively which in return was more bioactive in reducing hyperinsulinemia [95]. The experimental rats group fed on CLA enriched butter had sixfold higher CLA content in liver compared to that of the control group, without having difference in dietary intake. The naturally enriched CLA butter consumption leads to increase the c9, t11-CLA serum concentrations and will as other PUFA without influencing the cholesterol content and blood TG [96, 97]. de Almeida et al. showed that the animals with synthetic CLA supplement diet have lower level of hyperinsulinemia, hyperglycemia and inflammatory proteins in retroperitoneal adipose tissue with high level of plasma HDL cholesterol [95]. While, other studies in which synthetic CLA mixture was used, report unhealthy effect of synthetic CLA as compared to that of naturally enriched CLA products, several authors have reported that using synthetic CLA in animal developed insulin resistance, hyperinsulinemia [97–98]. Thus, it is important to differentiate the bioavailability of CLA from different production sources, which ultimately determine the bio-functionalities of CLA from the health point of view. As commercial commercially produced CLA has predominant with mixture of 10-, 9,11-, 10,12-, and 11,13-isomers while natural CLA has 80–90% of 9,11-isomer. This difference in isomers composition is a major determinant of biological activities of CLA in diet and thus source. Furthermore,


acid were 18.76 and 63.42 μg/mL in plasma and 7.60 and 26.66 μg/g in erythrocytes, respectively, suggesting that CLA-enriched dairy fat produced by dietary manipulation may be well absorbed for better health effects in humans as compared to synthetic CLA [9]. It was observed that the rats fed on butter selectively absorbed more CLA. The accumulation was fourfold more higher for total CLA in mammary gland and tissues compared to rats fed on synthetic free fatty acids while taking the same dietary intake [100]. The studies on transfer efficiency of a CLA showed that bioavailability of the 9, 11-CLA isomer was twofold more as compared to 10, 12-CLA isomer [97]. While feeding of commercial CLA to pigs showed that c9, t11-isomer preferentially incorporate to liver and c11, t13-isomer into heart. Another study showed that the serum bioavailability of synthetic CLA was low when was inducted to pig feed for 15 days dietary treatments. The results were in increase of 10–30-fold mono-CLA isomers (c9, t11-c15-18:3 + c9-t13-c15-18:3) in the heart, kidneys and liver indicating the trend of incorporation of conjugated CLA isomers, which depends on the structure and source of the conjugated fatty acids [47]. The rats fed during the mammary gland development period show that naturally enriched CLA was more potent in reducing 22% epithelial mass, 30% terminal end bud density, 30% proliferation and 53% tumor yield of mammary glands. The consumers have the options for choosing CLA to increase CLA intake from synthetic CLA pill or produced by diet modification in dairy and meat products. The relative health value benefits of CLA from ruminant, microbes, and synthetic sources are

Bovine Feed Manipulation, Enhancement of Conjugated Linoleic Acid and Its Bioavailability

http://dx.doi.org/10.5772/intechopen.79306

35

uncertain regarding the bioavailability and functional disposition in human [100, 101].

Enhanced or enriched dairy fats produced by dietary manipulation are considered wellabsorbed and bioactive source of essential fatty acids with beneficial health effects in humans. However, most of the studies related to effect of CLA on human health were conducted on commercial CLA that was differentially available and dispersed in body organs and tissues and hence have different health effects. Further, there are not conclusive studies on the moderation of CLA and its dietary source on average human intake. The extrapolation from rat animal models to human intake must be taken with cautions due to difference in dietary requirements. To meet recommended intake of CLA, several efforts have been made to enhance the level of CLA naturally and natural enhanced CLA in dairy food is more health effective. The manipulation of dairy ration type and composition seems to be one of the most suitable strategies for enhancement of CLA in enriched dairy products. Manipulation of the animal's diet can result in up to 8- to 10-fold increase in the concentration of CLA in milk. As consumers become more conscious of the link between diet and health, milk designed to have enhanced levels of CLA may provide new market opportunities for milk and milk products

We would like to acknowledge that Government College University Faisalabad and its IT department provided us kind permission to use digital library and access to research data.

**3. Conclusion**

such as butter and cheese.

**Acknowledgements**

**Table 4.** Availability of CLA content from food products.

the bioavailability of CLA is measured either the total contents of CLA in blood circulation after ingestion or the total contents of CLA disposition in the liver, mammary fat, peritoneal fat and plasma. The composition of CLA isomers mixture can also influence the incorporation and bioavailability of CLA to tissue and organs. To date, most of the human studies evaluated by only blood measurements, which are different from animal models regarding the bioavailability and distribution modes of CLA according organs, model of dietary supplementation or enrichment [97, 99].

A very recent study by Rodriguez-Alcala et al. (2015) was conducted on oral absorption and disposition of CLA isomers from naturally enriched goat milk cheese conducted to evaluate the bioavailability of CLA. The oral doses of 153 mg vaccenic acid, 46 mg rumenic acid were fed to rats on kilogram body weight basis. The maximum concentration value of vaccenic acid and rumenic acid were 18.76 and 63.42 μg/mL in plasma and 7.60 and 26.66 μg/g in erythrocytes, respectively, suggesting that CLA-enriched dairy fat produced by dietary manipulation may be well absorbed for better health effects in humans as compared to synthetic CLA [9]. It was observed that the rats fed on butter selectively absorbed more CLA. The accumulation was fourfold more higher for total CLA in mammary gland and tissues compared to rats fed on synthetic free fatty acids while taking the same dietary intake [100]. The studies on transfer efficiency of a CLA showed that bioavailability of the 9, 11-CLA isomer was twofold more as compared to 10, 12-CLA isomer [97]. While feeding of commercial CLA to pigs showed that c9, t11-isomer preferentially incorporate to liver and c11, t13-isomer into heart. Another study showed that the serum bioavailability of synthetic CLA was low when was inducted to pig feed for 15 days dietary treatments. The results were in increase of 10–30-fold mono-CLA isomers (c9, t11-c15-18:3 + c9-t13-c15-18:3) in the heart, kidneys and liver indicating the trend of incorporation of conjugated CLA isomers, which depends on the structure and source of the conjugated fatty acids [47]. The rats fed during the mammary gland development period show that naturally enriched CLA was more potent in reducing 22% epithelial mass, 30% terminal end bud density, 30% proliferation and 53% tumor yield of mammary glands. The consumers have the options for choosing CLA to increase CLA intake from synthetic CLA pill or produced by diet modification in dairy and meat products. The relative health value benefits of CLA from ruminant, microbes, and synthetic sources are uncertain regarding the bioavailability and functional disposition in human [100, 101].
