Research Supervisors:
Dr Frank Dunshea (Victorian Institute of Animal Science (VIAS) and Farrer Centre), Dr Morley Muralitharan (CSU) and Reg Cross (Swinburne University of Technology)

Research Staff:
Ewa Ostrowska (Victorian Institute of Animal Science, Swinburne University of Technology and FarrerCentre)

Funding:
$55,000 PRDC and a PhD scholarship from Swinburne University of Technology

Duration:
1997-1999

Project Summary:
One of the major constraints to the Australian pig industry is the excessive deposition of fat and associated poor feed conversion efficiency. A further constraint is the growth depression that can occur in animals that are immunologically challenged. Technologies that can remove or reduce these constraints should improve the efficiency of pig production in Australia. The aim of the present study was to investigate the effect of dietary CLA on growth performance, body composition and immune function in finisher pigs.

Conjugated linoleic acid (CLA) is fatty acid component found in appreciable levels in dairy products. It has been established as a cancer inhibitor with apparent antioxidant activity in several animal models. In addition CLA has been shown to reduce the catabolic effects of immune stimulation in mice, rats and chickens without adversely affecting immune function. More recently CLA has been shown to increase liveweight gain and improve feed efficiency in rats, mice and chickens and decrease carcass fat content in mice. For instance the feed:gain of male and female rats were improved by 5 and 7%, respectively. However, little is known about the effects of CLA in pigs.

Major Research Findings:
The pertinent results are presented in point form below:
1. Dietary CLA had no significant effect on average daily gain or feed intake.

2. Feed:gain was improved by 0.2 units by dietary CLA with the responses being most pronounced over the first 4 weeks.

3. Backfat at the P₂ site decreased linearly with increasing dose of CLA. The maximum reduction in P₂ was almost 6 mm (-24%) at a CLA inclusion rate of 10.0 g/kg.

4. Carcass fat content decreased linearly with increasing dose of CLA. The maximum reduction in carcass fat content was 60 g/kg (-20%) at a CLA inclusion rate of 10.0 g/kg.

5. Carcass lean content increased linearly with increasing dose of CLA. The maximum increase in carcass lean content was 60 g/kg (+9%) at a CLA inclusion rate of 10.0 g/kg.

6. Carcass fat deposition decreased linearly with increasing CLA inclusion rates. At the highest level of CLA investigated carcass fat deposition was reduced by 86 g/d (-31%).
7. Meat quality was not altered by dietary CLA.

8. Dietary CLA decreased blood oesonophils and circulating levels of IgG suggesting improvements in some immune functions.

Conclusions:
Dietary CLA supplementation can effectively decrease carcass fat at all levels of CLA supplementation and may improve feed efficiency. Meat quality is unaltered by dietary CLA. Some aspects of immune function are altered by dietary CLA and the implications need to be investigated. The most cost effective dose of CLA very much depends upon what the producer wants CLA for (ie. maximum growth performance or reduction in fat) but is most likely to be an intermediate dose, possibly 5.0 g/kg.