1. Immunological challenge – increased cytokine activity – effects in growth
2. Mechanism – modulate eicosanoidproduction (arachidonic acid)
3. Effects of eicosanoids
4. PUFA – modulation of immunity
5. Fish Oil
It is well documented that a disease challenge in farm animals can result in a series ofphysiological changes, including increased body temperature, depressed feed intake, changes in plasma acute phase protein concentration and activation of the immune system (Johnson, 1997).Consequently, livestock exhibit a reduction in growth, increasing economic losses for producers.
One emerging view is that these changes are attributed to the release of proinflammatory cytokines (Johnson,1997; Webel et al., 1997), including tumor necrosis factor, interleukin-1, and interleukin-6. Cytokines are produced by macrophages and form the first line of defense against invading pathogens byactivating immune system cells to attack. In swine, it has been shown that a reduced feed intake, lean muscle accretion, and growth in immunologically challenged pigs are the result of increased cytokineactivity (Kelly et al., 1994; Webel et al., 1997). Overproduction of these cytokines can adversely affect growth and feed efficiency. Cytokines mediate the systemic effects of inflammation such as fever,loss of appetite, mobilization of protein and fat, and acute phase protein synthesis (Calder, 2001) and overproduction of these cytokines can adversely affect growth and feed efficiency. Therefore,the modulation of these cytokines may have benefits in alleviating the negative effects induced by immunological stress (Lang et al., 1996). There are two major classes of PUFAs, the n-6 and the n-3families. Linoleic acid is the precursor of the n-6 family, and it is found in plant oils, including corn and soybean oil. In animals, linoleic acid is converted to arachidonic acid, which can...