Effects Of Sea Buckthorn Flavonoids On Egg Production Performance And Blood Biochemical Parameters Of Laying Ducks

Seabuckthorn is cold and drought resistant,abundant in production,and distributed all over the world,and it is mainly distributed in the northwest of China.As the main bioactive component,the development of sea buckthorn flavonoids into livestock feed additives may have positive effect on antioxidant capacity,immunity and lipid metabolism of livestock,thus improving the production performance of livestock.To this end,this experiment was conducted to investigate the effects of different levels of sea buckthorn flavonoids in the diets of Guangxi small hemp duck(laying ducks)on egg production performance,blood lipids,antioxidant and immune indexes,as well as to evaluate the effects of adding sea buckthorn flavonoids in the diets on egg quality,yolk cholesterol,amino acid and fatty acid contents in eggs.The effects of cholesterol deposition-related genes HMGCR,was investigated by the effect of tissue expression of HMGCR and CYP51 genes,which are related to cholesterol deposition.240 ducks of similar body weight and condition at 23 weeks of age were selected and divided into four groups using a completely randomized trial design,with six replicates of 10 ducks in each group.The control group was fed the basal diet,and the three experimental groups were supplemented with 0.5 g/kg,1.0 g/kg and 1.5g/kg of sea buckthorn flavonoids on top of the basal diet,respectively.During the pre-feeding period of 14 d and the regular feeding period of 70 d,daily feed intake,daily egg production and egg weight were recorded.Up to day 69 of the feeding trial,three fresh eggs(18 eggs per treatment group,72 eggs in total)were randomly selected from each replicate for egg quality analysis,and the eggs were collected in the same way to determine the yolk cholesterol content.On day 70,three ducks(18eggs per treatment group,72 eggs in total)were selected from each replicate for the determination of amino acids and fatty acids,and two ducks of similar body weight were selected from each replicate to collect blood and separate serum for the determination of blood lipids,antioxidants and immune parameters.Three laying ducks of similar body weight were selected from each group,liver and ovary tissues were taken after slaughter,and their total RNA was extracted and reverse transcribed for real-time fluorescence quantitative PCR.The results were as follows.1.The results showed that the mean egg weight of the 1.0 g/kg sea buckthorn flavonoid group was significantly higher(P < 0.05)compared with the control group;the feed-to-egg ratio of the 0.5 g/kg and 1.0 g/kg sea buckthorn flavonoid groups was significantly lower(P < 0.05).2.The results showed that the addition of 0.5 g/kg sea buckthorn flavonoid significantly increased the egg shell strength of duck eggs(P < 0.05);the addition of0.5 g/kg and 1.0 g/kg sea buckthorn flavonoid significantly increased the yolk weight of duck eggs(P < 0.05);the addition of 1.5 g/kg The addition of 1.5 g/kg of sea buckthorn flavonoid significantly increased the protein height and haugh unit of duck eggs(P < 0.05);the addition of 1.0 g/kg and 1.5 g/kg of sea buckthorn flavonoid significantly reduced the yolk cholesterol content(P < 0.05).3.The results showed that the diets supplemented with 0.5 g/kg,1.0 g/kg and 1.5g/kg sea buckthorn flavonoids significantly increased the content of total amino acids(P < 0.05)and highly significantly increased the content of essential amino acids(P <0.01)compared with the control group;the diets supplemented with 0.5 g/kg and 1.0g/kg sea buckthorn flavonoids significantly increased the content of non-essential amino acids(The addition of 0.5 g/kg and 1.0 g/kg of sea buckthorn flavonoids significantly increased the content of non-essential amino acids(P < 0.05)and highly significantly increased the content of fresh amino acids(P < 0.01).The addition of 1.0g/kg sea buckthorn flavonoid significantly reduced the content of total saturated fatty acids(P < 0.01);the addition of 0.5 g/kg,1.0 g/kg and 1.5 g/kg sea buckthorn flavonoid significantly increased the content of total bitter amino acids and monounsaturated fatty acids(P < 0.01)and significantly reduced the content of n-3polyunsaturated fatty acids and n-6 polyunsaturated fatty acids(P < 0.01).The addition of 1.0 g/kg and 1.5 g/kg sea buckthorn flavonoids significantly increased the content of total sweet amino acids and docosahexaenoic acid(DHA)(P < 0.01).4.The results were as follows: compared with the control group,the addition of1.0 g/kg and 1.5 g/kg of sea buckthorn flavonoids significantly reduced the total blood cholesterol and triglyceride levels(P < 0.05);the addition of 0.5 g/kg and 1.0 g/kg of sea buckthorn flavonoids significantly increased the total superoxide dismutase activity(P < 0.05)and the total antioxidant capacity(P < 0.01)of ducks’ blood;the addition of 0.5 g/kg and 1.0 g/kg of sea buckthorn flavonoids significantly increased the total antioxidant capacity(P < 0.01).The addition of 0.5 g/kg sea buckthorn flavonoids significantly increased the activity of blood glutathione peroxidase in laying ducks(P < 0.05)and significantly increased the levels of immunoglobulin G,immunoglobulin A and immunoglobulin M in laying ducks(P < 0.01);the addition of1.5 g/kg sea buckthorn flavonoids significantly decreased the level of LDL cholesterol in laying ducks blood(P < 0.01).5.HMGCR and CYP51 genes were expressed in both liver and ovarian tissues of laying ducks by real-time fluorescence quantitative PCR.The addition of 1.5 g/kg of sea buckthorn flavonoids significantly reduced the expression of HMGCR genes in liver and ovarian tissues of laying ducks(P < 0.01),and the expression of HMGCR genes in liver and ovarian tissues showed a decreasing trend.The addition of 0.5 g/kg sea buckthorn flavonoid significantly increased the expression of CYP51 gene in ovarian tissues of laying ducks(P < 0.05),and the addition of 1.0 g/kg sea buckthorn flavonoid significantly increased the expression of CYP51 gene in liver tissues of laying ducks(P < 0.05),and their expressions showed an inverted "V" trend.In conclusion,dietary supplementation of sea buckthorn flavonoids could increase the average egg weight and feed-to-egg ratio,improve egg quality,the composition of amino acids and fatty acids in eggs,enhance duck’s resistance to oxygenation and immunity,reduce blood cholesterol and yolk cholesterol content and regulate the expression of HMGCR and CYP51 genes in the cholesterol synthesis pathway.Diets supplemented with appropriate amounts of sea buckthorn flavonoids can improve the egg production performance,anti-oxidative energy and immunity of laying ducks.