Effect of age on total lipid, cholesterol and fatty acids content in tissues of fast and slow growing chickens

The dependence of the content of total lipid, cholesterol and eighteen fatt y acids (FA) in breast muscle (BM), thigh muscle (TM) and skin (S) on age w as determined in cockerels of a slow (SG) and a fast (FG) growing hybrid. C hickens of both hybrids were fed with the same standard diet and were slaug htered successively at weekly intervals. Total lipids were extracted from t he separated tissues by a hexane/isopropanol mixture, cholesterol was deter mined in this fraction by the liquid chromatography and FA by the gas chrom atography. Total lipid content in BM and TM of FG hybrid (Y, % of the wet tissue) chan ged with the increasing age of birds (X, days) according to the equation Y = 3.8 - 0.08 X + 0.0007 X-2 (I-YX(2) = 69%, P < 0.01) and Y = 14.2 - 0.035 X + 0.0029 X-2 (I-YX(2) = 89%, P < 0.01), respectively. The interesting dec rease of this component from 5(th) to 8(th) week of the age of chickens is possibly related to the use of cockerels in the experiment. Cockerels depos it fat with lower intensity in comparison with female birds at this age. To tal lipids content in TM or S of SG hybrid was lower (P < 0.05) in comparis on with FG hybrid, but SG chickens deposited total lipids with higher inten sity with increasing age. The course of the changes of total PUFA (polyunsaturated FA) content in TM of FG hybrid (% of total FA) was opposite to that of total lipid in this ti ssue: Y = 12.5 + 0.59 X - 0.0049 X-2 (I-YX(2) = 54%, P < 0.05). FG chickens deposited more (P < 0.05) linoleic acid or total PUFAn6 in TM or Sand more alpha-linolenic acid in BM or S in comparison with SG hybrid. Cholesterol content (mg/100g wet tissue) in TM of FG and SG hybrid decrease d linearly within the whole time period: Y = 76.4 - 0.28 X (I-YX(2) = 77%, P < 0.01) and Y = 89.0 - 0.37 X (I-yx(2) = 83%, P < 0.01), respectively. Hi gher (P < 0.05) cholesterol concentration in total lipids of TM or S of slo wly growing hybrid confirmed a trend of more intensive deposition of choles terol in lipids with decreasing growth intensity, which is presumably conne cted with a shift of cholesterol distribution from the storage fraction to the membrane fraction of the lipid component of the tissues. It is possible to expect the same amount of total lipid (60 g), saturated F A (14 g), monounsaturated FA (20 g) or PUFA (10 g) and less cholesterol (40 0 mg in comparison with 500 mg) in BM + TM + S from the whole carcass of SG hybrids slaughtered at 13 weeks of age in comparison to FG hybrids slaught ered in 6 weeks.