| Green tea is a traditional Chinese beverage,and its health benefits and the underlying mechanisms have been frequently investigated in recent years.By using laying hens and broilers the efficacies of green tea in alleviation of excessive abdominal fat deposition,melioration of chicken and egg qualities were examined in our lab,and the preliminarily mechanisms of these efficacies were also studied in the past few years.Based on our previous results,the present research is to further confirm the dose-effect of dietary green tea in ameliorating the egg nutritional qualities.Moreover,the effect of green tea on intestinal microbiotaand the hepatic lipid-metabolizing genes were also involved in our experiment.A total of 384 healthy Loman laying hens(26-weeks old)were randomly divided into four groups(with each group containing 3 replicates of 32 laying hens): control group,antibiotic-treated group,low-dose green tea treatment group and high-dose green tea treatment group.And there were 0.5%(w/w)and 1.5%(w/w)green tea powder in the basal diet of laying hens from low-dose green tea treatment group and high-dose green tea treatment group,respectively.The results were as follows:1.Green tea treatment did not affect the growth of laying hens.Dietary antibiotic,low and high doses of green tea did not affect the weight,liver index of laying hens.After8 weeks,the abdominal fat rate of laying hens significantly reduced by 37.70%(P<0.01)for low-dose green tea treatment and 38.49%(P <0.01)for high-dose green tea treatment.Besides,the 0.5% green tea treatment increased the egg production rate by5.84%(P <0.01)and 6.20%(P <0.05),respectively for 4 and 8 weeks trial.2.Green tea could significantly improve the nutrient composition and value of eggs,and had no significant effect on the performence of eggs.After treated with green tea for 4 and 8 weeks,the composition of egg yolk had a significant change,and the profile of cholesterol in egg notably decreased.Specifically,compared with the control group,the composition of saturated fatty acids(myristic acid,palmitic acid and total saturated fatty acids)in egg yolk significantly decreased by treated with1.5% greea tea,and the high dose green tea treatment also increased the composition of polyunsaturated fatty acids(arachidonic acid and docosahexaenoic acid)at 4 week trial.After 8 weeks treatment,the chage of composition of fatty acids in yolk for 1.5%green tea group was similar to the 4 weeks,except the increasing of total polyunsaturated fatty acid.In addition,after treated with 0.5% green tea for 8 weeks, the composition of fatty acids had an analogous effect to the 1.5% green tea treatment group.Compared with the control group,low-dose green tea treatment respectively decreased composition of myristic acid(52.94%,P<0.05),palmitic acid(13.08%,P<0.01),total saturated fatty acids(10.04%,P<0.05),and increased the composition of linoleic acid(23.08%,P<0.05),arachidonic acid(22.60%,P<0.05),docosahexaenoic acid(34.33%,P<0.05)and tatol polyunsaturated fatt acid(23.47%,P<0.05).Green tea treatment not only changed the fatty acid composition of eggs,but also reducing the profile of cholesterol in the yolk.The results showed that all doses of green tea treatemnt significant decreased the content of cholesterol in egg yolk and the tatol cholesterol content per egg,compared with control group.Specifically,0.5%and 1.5% green tea treatment significantly dreased the yolk cholesterol content by15.90%(P<0.01),17.20%(P<0.01);the two doses of green tea treatment also notably decreased the total conetent of cholesterol in each egg by 23.53%(P<0.01)and21.43%(P<0.01).3.Green tea treatment significantly improved the lipid metabolism of laying hens.Green tea had no significant effect on the serum lipid-metabolism-related index.Our results showed that the m RNA expression level for lipid anabolism genes(Fattyt Acid Synthase,Acetyl-Co A Carboxylase,Stearoyl-Coenzyme A Desaturase 1)in liver were notably down-regulated compared with that of control,and the hepatic expression level of fat catabolism gene(Carnitine Palmitoyl Transferase 1)was significantly up-regulated.The changes of these genes disappeared after 4 and 8 weeks treatment.Our data compliance with the law that expression level of functional genes was interfered before its related phenotype.4.Green tea treatment chaged the composition of gut microbiota.Specifically,Firmicutes,which is rich in the fat animals' gut,had a decreasing compared with that of control.The butyrate can improve the growth of intestinal epithelial cells and the absorb of energy,and it produced by Firmicutes.The composition of butyrate in the feces decreased by 25.13%(P<0.01)after the layers treated with dietary containing1.5% green tea for 4 weeks.At 8 week trial,the composition of feces butyrate decreased but not significant for all doses of green tea treatment.In short,green tea treatment significantly improved the egg production rate and the nutritional value of eggs,regulated lipid-metabolism-related genes and intestinal microflora.Our results suggest that green tea treatment might alleviate the body fat deposition through the improving of structure of gut microbiota. |
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