Conjugated Linoleic Acid Update

Conjugated linoleic acid (CLA) is continuing to keep researchers at a number of North American universities and research facilities busy trying to uncover its secrets. Since the discovery of its health benefits in the late 1970s at the University of Wisconsin, this fatty acid has generated a lot of attention. To date, research in mice, rats and pigs has shown that CLA can be a powerful tool in the fight against cancer and atherosclerosis, while repartitioning carcass fat to decrease body fat stores, increase lean body mass, improve feed efficiency, and enhance immune function.

CLA is produced naturally by rumen bacteria and is found in significant quantities in ruminant meat and dairy products. Meat from monogastric animals, like the pig, is relatively low in CLA by comparison. It is possible to synthesize CLA from linoleic acid but the high cost limits the potential for research and commercial application of any scale. Recently, large-scale commercial production of CLA from sunflower oil has made feeding trials with large animals possible.

Researchers at Agriculture and Agri-Food Canada's Lacombe Research Centre have reported positive results from feeding CLA. Finishing pigs fed 2% CLA tended to consume less feed, have better feed conversion, significantly more lean and less subcutaneous fat in the carcass compared to pigs fed 2% sunflower oil (See table). Based on the results of all of the research that has been conducted to date, it is reasonable to suggest that the expected response to CLA should be a 1.4% increase in percent lean and a 0.10 improvement in feed efficiency.

Table 1. Effect of CLA on Growth Performance and Carcass Characteristics of Finishing Pigs
  Diet Change
CLA Sunflower Oil
ADG (kg/day)
Feed Intake (kg/day)
Feed Efficiency
Total Lean (%)
Total Subcutaneous Fat (%)

Source: Agriculture and Agri-Food Canada, Lacombe Research Centre

With all the positive benefits associated with the feeding of CLA, researchers have turned their attention to the effects on the end-product, pork. Other repartitioning agents, like porcine somatotropin (pST) and ractopamine, have shown that they can dramatically increase lean yield but not without some negative impact on meat quality. Pork quality cannot be compromised for the sake of improvements in lean gain and feed efficiency so recent research has probed deeper into the effects of CLA on meat quality. The most dramatic response has been observed in increased firmness of the belly, allowing for improved sliceability, and increased bacon yield. For processors, this in itself may prove to be the most significant impact of CLA, since slicing soft bellies on commercial processing equipment is next to impossible. CLA also appears to improve other meat quality characteristics such as water holding capacity, subjective colour score, uniformity of colour, and marbling although results vary between researchers. The bottom line is that, to date, there is no evidence that CLA adversely affects pork quality.

In addition to the interest in meat quality aspects of the use of CLA, researchers have been investigating the impact that CLA has on the immune system. Research at Iowa State University has shown that CLA fed to nursery pigs causes an increase in cells vital in the development of the animal's response to viral infections. The results of this experiment have also shown that, in order to be biologically active, CLA needs to be progressively incorporated into cells, for a period of 42 days in this case, to become fully functional for enhancing immunity.

One important question that is difficult to address at this stage is whether or not feeding CLA will be cost effective. Dr. Jim Pettigrew, Pettigrew Consulting International, recently evaluated the economics of feeding CLA to finishing pigs in the US market. He estimated that benefits from feeding CLA would be determined based on a premium for leanness and the value of the reduction in feed costs (See table). Dr. Pettigrew's calculations do not include the cost of CLA, so the estimate could be used as an indication of what could be paid for CLA. It is important to note that the estimate does not attempt to quantify the added benefits associated with increases in belly firmness and immune function because of the difficulty in assigning dollar values for these improvements at this early stage.

Table 2. Economic Analysis of Feeding CLA to Finishing Pigs*

Lean Premium ($/pig)

Feed Saving ($/pig Total Benefit ($/pig)
$1.00 $1.20 $0.06 $0.10
$/cwt carcass $/lb feed
Sophisticated Feeding Program
$ 2.68
Traditional Feeding Program

* Based on $US
Source: Dr. Jim Pettigrew, Pettigrew Consultants International
Proceedings of the American Association of Swine Practitioners Annual Meeting, 1999

Research in pigs to date has been very positive, but a lot of ground still has to be covered before the book is written on CLA. Research continues in Alberta, Indiana, Iowa, Kansas and Wisconsin in the race to determine CLA's mode of action. Other research priorities include determining the optimum inclusion rate in diets, identification of the specific CLA isomers responsible for the positive results, and assessing the potential for value-added pork with anticarcinogenic properties. Who knows, maybe someday pork will be sold for its CLA-related medicinal properties.

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Author: Greg Simpson - Swine Nutritionist/OMAFRA
Creation Date: 18 August 2000
Last Reviewed: 29 Febuary 2012