The aim of this study was to explain the cholesterol-lowering mechanism of dietary dried purslane leaves meal and essential phospholipids in egg-yolk and hen muscle tissues. Seventy two Inshas laying hens were randomly divided into 4 groups (3 replicate pens of 6 hens each) housed individually in one cage. Birds were fed from 28 to 40 weeks of age, either the control diet (based on corn-soybean meal) or the control diet with 10% purslane leaves meal with or without 450 mg essential phospholipids (EPL) /kg diet. Feed and water were offered ad libitum, feed intake, feed egg mass ratio, egg number and egg weight were recorded weekly. Birds were injected at 11th week of the experiment with Sheep Red Blood Cells (SRBC's) for immune test. At end of the experiment, sensory evaluation of hard boiled eggs was conducted for teste and flavor evaluation, cholesterol levels in each of egg-yolk, liver breast, thigh muscles and serum were determined. The activity of the rate-limiting enzymes in cholesterol biosynthesis was also determined. Four birds/group were slaughtered for sampling analysis.
Results obtained showed that feeding laying hens on 10% purslane leaves supplemented diet produced the best values of egg production, egg number, egg mass and feed conversion compared with the other dietary treatment groups. Dried purslane leaves, EPL and purslane + EPL diets decreased (P<0.05) serum total lipids by 3.05, 6.55 and 9.40% ; serum cholesterol by 16.74, 23.25 and 29.30% and serum triglycerides by 6.72, 8.93 and 14.55%, while, serum high density lipoprotein was significantly (P<0.05) increased by 5.35, 6.96 and 8.48%, respectively, and hens fed 10% purslane leaves diet increased (P<0.05) serum low density lipoprotein by 3.06% compared with the control group. Moreover, no significant effects were observed on serum AST and ALT as well as taste and flavor of hard boiled eggs at end of the experimental period. Antibody response to SRBC's and leucocytes (WBC's) and lymphocytes counts were increased (P<0.05) by feeding the purslane diets. Cholsterol level was decreased (P<0.05) by feeding purslane or purslane + ELP diets, in thigh, breast, liver, yolk and serum and this decrease (P<0.05) was more pronounced by feeding the purslane + EPL diet.
Supplementation of purslane or EPL to the laying hen diets significantly (P<0.05) decreased the relative weight of liver and oviduct. Abdominal fat percentage of groups while bile volume of gall bladder was significantly (P<0.05) increased compared with the control group. The activity of the rate-limiting enzymes in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl CoA reductase was suppressed (P<0.05) by feeding purslane or EPL and purslane + EPL diets. Fatty acid synthetase activity was not significantly affected by dietary treatment groups. Both purslane and EPL diets reduced cholesterol -7-a-hydroxylase activity.
This study indicates that purslane and EPL inhibit cholesterol biosynthesis by a similar mechanism.