Safety Evaluation Of Phytosterols As Dietary Supplements For Hens And Their Impact On Cholesterol Metabolism

In mammals, phytosterols are reported to have many effects on plasma cholesterol-lowing, anti-oxidative stress, promoting growth, anti-cancer and so on. But it’s unclear whether they are safe for hens as dietary supplements and what their effect on cholesterol metabolism. Therefore, this study was conducted to investigate the security of phytosterols and their effects on cholesterol metabolism in laying hens.1 Safety evaluation of phytosterols as dietary supplementsThis study was conducted according to safety evaluation method of feed additive in the Ministry of Agriculture, China.540 25-week-old HY-LINE Variety Brown hens were divided into 5 groups. Each dietary treatment was assigned to 6 replicate groups of 18 hens (with 6 cages and 3 hens per cage). The hens were fed diets containing 0,20,80,400 or 800 mg/kg phytosterol over a 70-day period.The results showed that, addition with phytosterol had no significant effect on egg weight, laying rate and feed to egg ratio of hens in 5 or 10 weeks.Adding phytosterol had no significant effect on visceral index of hens’heart, liver, spleen, lung and stomach. But, visceral index were increased when hens were fed 80 mg/kg phytosterol compared to the hens in the 400 mg/kg phytosterol group.In addition, phytosterol had no effect on plasma antioxidant activity. Addition with 80 mg/kg phytosterol to diets had the trend to decrease plasma AST concent (P=0.098) compared to the control.The result of tissue pathological slices showed that phytosterol had no side effect on the histopathological changs of heart, liver and spleen. Laying production, visceral index, plasma antioxidant activity and tissue pathological slices of hens proved the safety of phytosterols.2 Effect of phytosterols as dietary supplements on cholesterol metabolismPrevious explorations of the effect of phytosterols on cholesterol metabolism are controversial in poultry. It is valuable to understand the mechanisms of action of phytosterols on cholesterol metabolism in hens.In order to investigate whether phytosterols can decrease cholesterol in laying hens and its possible mechanism, this study was conducted to determine the effect of phytosterols on the plasma biological parameters, egg yolk, liver and intestinal cholesterol concentration and cholesterol metabolism-related gene expression.Phytosterol enhanced plasma TC, TG and VLDL significantly (P<0.05),400 mg/kg and 800 mg/kg phytosterol increased the content of plasma LDL-C (P<0.05) during the 5 weeks. At the end of the experiment, compared with the control,20 mg/kg phytosterol enhanced plasma HDL-C concentration (P<0.05),80 mg/kg phytosterol increased the content of plasma AST and HDL-C (P<0.05).Feeding with 400 mg/kg and 800 mg/kg phytosterol significantly increased hepatic, duodenal and ileal cholesterol concentration of hens compared to the control (P<0.05). And supplementation of 800 mg/kg phytosterols significantly increased jejunal cholesterol concentration (P<0.01) of hens.Diets added with phytosterol did not affect yolk cholesterol concentration.Real-time PCR results shown that 800 mg/kg phytosterol had no significant effect on hepatic expression of cholesterol-7alpha-hydroxylase (CYP7A1), low density lipoprotein receptor (LDLR), sterol regulator element-binding protein 2 (SREBP-2), apolipoprotein B (apoB), ATP-binding cassette transporter (ABC), liver X receptor (LXR), acyl-coenzyme A cholesterol acyltransferase 1 (ACAT1),3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGR). Jejunal, duodenal and ileal HMGR、ABCG5、ABCG8、ACAT2、LDLR and LXR mRNA expression had no significantly change between control group and 800 mg/kg phytosterol group.