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.