The Effect of Dietary Fat Composition and Age On Residual Yolk Sac Membrane, Liver and Gall Bladder Bile Lipid Composition In Broiler Chicks

Abstract

A study was carried out to investigate the effects of dietary fat composition and post-hatching age on lipid changes of the yolk sac membrane (YSM), liver and gallbladder bile. Two groups of ninety-day­ old male broiler chicks were fed diets containing a saturated fat (tallow oil) Diet 1 and unsaturated fat (soybean oil) Diet 2 for two weeks. Twelve birds from each treatment were sacrificed on days 1, 3, 6, 9, 12 and 14 post-hatch and samples of the YSM, liver and gall bladder bile were collected. Weight changes of the chick and tissues and lipid composition were also determined during the experimental period. About 75% decrease in YSM weight occurred during the first 3 days post-hatch in both groups. However, the rate of decline was highest in chicks fed Diet 1. The weight of the YSM was negligible by day 9 post­ hatch in both groups. Triglycerides (TG) formed major lipid component of the YSM at day 1 post-hatch (>60% of total lipid) but had declined to less than 2% on day 12 pos t-ha tch. The decreases in TG were accompanied by significant increases of cholesterol esters (CE). These changes were not affected by dietary treatment.  The liver constituted less than 3% of chick body weight at hatching but increased to about 6% by day 6 post-hatch and remained constant thereafter. The total lipid content of the liver increased gradually with post-hatching age. TG formed less than 4% at hatching and increased to about 50% of total lipid by day 12. In contrast CE formed about 75% of the total lipid on day 1 but declined to less than 2% on day 12 post-hatch. Similarly, decreases in phospholipids content with age were noted. Changes in liver lipid composition were influenced by both dietary fat composition and post­ hatching age. Phospholipids formed the major lipid component of the gallbladder bile on day 1 post-hatch, followed by free cholesterol. Variations in gallbladder bile lipid compositions with age and dietary fat composition were observed although they were inconsistent.