Three experiments were conducted to study the influence of dietary fatty acids on the production performance and immune response of chickens. In experiment I, forty day-old broiler chicks were fed diets containing 5% of either animal fat + conjugated linoleic acid (CLA) (Diet I), sunflower oil (Diet II), flax oil (Diet III) or fish oil (Diet IV). No significant differences (P>0.05) were observed between the live weight of birds. The liver tissue total fat content was lower (P<0.05) in treatment I and II. The fatty acid composition of breast and thigh muscle, liver, heart, pericardial fat, plasma, splenocytes and gut associated lymphoid tissue differed (P<0.05) between treatments. The thiobarbituric acid reactive substances (TBARS) of breast and thigh muscle, liver and heart tissue were lower (P<0.05) in Diet I fed birds. Serum antibody activity was decreased (P<0.05) in Diet II fed birds. In experiment II, 120 day-old broiler chicks were fed diets containing 3.5% of either animal fat + conjugated linoleic acid (CLA) (Diet I), sunflower oil (Diet II), linseed oil (Diet III) or fish oil (Diet IV). Body weight gain was higher (P<0.05) in Diets III and IV compared to Diets I and II fed birds. Feed intake was increased (P<0.05) in Diet IV fed birds. Birds fed Diets III and IV had higher (P<0.05) n-3 fatty acids in all tissues studied. A preferential incorporation of CLA was observed in spleen mononuclear cells. TBARS were higher (P<0.05) in the breast and thigh muscle of Diet IV fed birds. Serum anti-BSA antibody content was higher (P<0.05) in birds fed Diets III and IV. Delayed type hypersensitivity (DTH) response was increased (P<0.05) in Diets IV and III fed birds. Lymphocyte and spleen mononuclear cell CD4⁺, CD8⁺ and IgM⁺ cell population did not differ (P>0.05) among treatments. In experiment III, 120 layer birds were fed diets containing 3% of CLA+animal fat (Diet I), sunflower oil (Diet II), canola+flax oil (Diet III) or fish oil (Diet IV). Egg production, feed consumption and feed efficiency did not differ (P>0.05) among treatments. Birds fed Diets III and IV had higher content of n-3 fatty acids in eggs. Eggs from hens fed Diet I incorporated higher (P<0.05) CLA and saturated fatty acids with a concomitant reduction in (P<0.05) monounsaturated fatty acid content. A preferential incorporation of CLA was observed in eggs over other tissues. TBARS were higher (P<0.05) in breast and thigh muscle of Diet IV fed birds. Egg TBARS content did not differ (P>0.05) among treatments. Serum and yolk anti-BSA antibody contents were higher (P<0.05) in birds fed Diets III and IV. DTH response was increased (P<0.05) in Diets IV and III fed birds. Lymphocyte and spleen mononuclear cell CD4⁺, CD8⁺ and IgM⁺ cell population did not differ (P>0.05) among treatments. Feeding n-3 fatty acids increased antibody mediated immune response while n-6 fatty acids and CLA increased cell mediated immune response. / Graduation date: 2003

Three potential probiotics, Lactobacillus acidophilus, Lactobacillus casei and the fungus Scytalidium acidophilum were prepared in different ways. They were evaluated for their effects on performance and immune responses in broiler chickens in two 6-week trials. In the first trial, probiotics were orally administered at the ages of day 1 and day 8. There were no differences between live and disrupted cells. However, cobalt-containing cells had improved effects numerously in comparison with non cobalt-containing cells. As a result, these three disrupted probiotics, each in two different concentrations, were sprayed onto a mash basal feed before pelleting in the second trial. Improved feed intake (up to 6%) and body weight gain (up to 7%) were observed in all probiotic treatments. The anti-KLH IgA and IgG titers of probiotic-treated chickens were not significantly different from the negative controls in both trials. In summary, disrupted and cobalt-containing probiotics were proved to enhance the performance of broiler chickens and are promising for commercial application. In addition, a new fungal mycelium, Scytalidium acidophilum, was suggested to be a good probiotic to improve the growth of broilers.

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