Evaluation of the gene expression and Delta 6-desaturase activity in different chicken strains.

In chickens, body fatty acids (FA) are derived from dietary uptake, de novo synthesis and/or bioconversion. Among the different fatty acid classes, n-3 long-chain PUFA (n-3 LC-PUFA) are of particular interest due to their positive role on human health. Domestic animals are unable to synthesize long chain-PUFA, but they can convert dietary linoleic and α-linolenic acid through a pathway catalyzed by elongation and desaturation enzymes. Meat from animal species is characterized by different FA composition; within the same species the FA profile reflects the endogenous biosynthesis as well as the composition of the diet. The relatively low efficacy of the desaturation enzymes in poultry allows for further consideration on the selection of genotypes able to synthesize a higher PUFA amount. In this study, the liver messenger RNA copies and enzyme activity of the Δ6-desaturase were evaluated in three chicken strains (slow-SG, fast-growing- FG and SG x FG crossing-SFG). Three groups of laying hens for each genotype were fed with a standard diet. Chickens were slaughtered at hatch, and liver was taken for analysis. A relationship between genotype and desaturation ability was evidenced. The FG strain showed a lower mRNA copies of FADS2 gene than the SG one (P>0.01). However, RNA expression was two or three-hundred times higher in SFG than SG and FG strains, respectively (P<0.01). Even the enzyme activity confirmed what shown by mRNA. The Δ6-desaturase activity was significantly higher in SG than FG (172.0 vs. 63.56 pmol in 30 min/mg prot), whereas in SFG was at intermediate level (136.66 pmol in 30min/mg prot). However, the enzyme activity of SFG was not significantly different from SG (P>0.01). SG chicken in comparison to FG strain showed a higher desaturase activity (P<0.05), whereas there were no significantly differences between Δ6- desaturase activity in SG and SFG. Even mRNA copy number was widely affected by genotype. Indeed, SFG showed a much higher mRNA abundance, whereas SG does not show significant differences. Data herein reported showed that the Δ6-destaurase activity is strongly affected by genotype. However, several other factors involved in the process of expression/translation, can be assessed. Gene expression may follow certain design principles for optimal evolutionary fitness as demonstrated by the high mRNA copies of the SFG.