N-6 and n-3 fatty acids in different beef adipose tissues depending on the presence or absence of the gene responsible for double-muscling

Abstract

Levels of n-6 and n-3 PUFAs, including those with 20 and 22 carbon-chains, in concentrate-fed Asturiana de los Valles (AV) yearling bulls with and without the double muscling gene <I>(mh/mh</I> = 24, <I>mh</I>/+ = 26, +/+ = 25) were measured to examine if this gene influences the pattern of PUFA deposition in different adipose tissues. Fatty acid compositions of muscle tissue (<I>longissimus thoracis</I>) and intermuscular and subcutaneous adipose tissues were determined by gas chromatography. The composition of intramuscular fat was unique compared to the other two adipose tissues which were similar in composition. In general, n-6 and n-3 fatty acid elongation and desaturation products were affected by AV genotype and this effect was most evident in n-3 PUFAs of the intramuscular fat of <I>mh/mh</I> (n-6/n-3 = 11.8 and 18:2n-6/18:3n-3 = 25.3) compared to <I>mh</I>/+ and +/+ animals (mean values of n-6/n-3 = 9.86 and 18:2n-6/18:3n-3 = 15.5). PUFA elongation and desaturation end products did not accumulate to any great extent in intermuscular and subcutaneous adipose tissues. Beef from <I>mh/mh</I> cattle showed greater deposition rates of n-3 elongation and desaturation products but their absolute content of total n-3 fatty acids was lower (21 mg/100 g meat) in comparison with <I>mh</I>/+ and +/+ cattle (mean value of 25 mg/100 g meat).