Application Of Phytosterols And Its Mechanisms In Regulation Of Cholesterol Metabolism In Meat-strain Ducks

The purpose of this work was to explore the effect of dietary supplement phytosterols (PS) on the performance and physiological function of meat-strain ducks. It focused on the mechanisms of phytosterols in regulating cholesterol metabolism. Some results from this work could supply information for further exploitation and optimal level of phytosterol as a new functional feed additive in poultry diets. The study included three experiments and the results were demonstrated as follows:In experiment one, two thousand 15-day-old commercial Cherry Valley meat-strain ducks were randomly allocated into the five groups with four replicates for each. The ducks were fed basal diet supplemented with 0 (control group), 10 mg/kg, 20 mg/kg, 40 mg/kg and 80mg/kg phytosterols, respectively. Up to 42 day of age, five drakes and ducks from each treatment were slaughtered to determine their carcass trait and ingredients in tissues, and performance of 42-day-old ducks was also determined. The results showed: (1) No significant influence of phytosterols supplementation on average daily gain(ADG),average weight and feed conversion rate (FCR) were detected. (2) Leg muscle rate and breast muscle rate slightly increased. Abdominal fat rate slightly decreased with the increasing levels of supplementary phytosterols, but intramuscular fat and sebum thickness decreased at 10mg/kg,20mg/kg treatment, and then increased at 80mg/kg treatment. (3)10mg/kg, 20mg/kg and 40mg/kg treatments significantly increased cholesterol level in liver of ducks (P<0.05), but the cholesterol levels in breast muscle were not significantly influenced. (4) Crude fat in 10mg/kg, 20mg/kg and 40mg/kg treatments of breast muscle significantly decreased (P<0.05).Experiment two studied the effects of supplementary phytosterols of different levels on blood biochemical parameters, antioxidation activity and immune-organs relative weight. The results showed: compared with control group, (1) The total cholesterol (TC) and low density lipoprotein cholesterol (LDL-C) concentration in serum were reduced with the increasing levels of supplementary phytosterols, and the 40mg/kg treatment decreased significantly (P<0.05), but at 80 mg/kg treatment, the decreasing effects were not significant. The triglyceride (TG) and high density lipoprotein cholesterol (HDL-C) concentration in serum were not significantly affected. (2) The activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) as well as the contents of glucose (Glu), total protein (TP), albumin (Alb), globulin (Glo) and the ratio of albumin/globulin (A/G) in serum were all unaffected by supplementary phytosterols of all levels. (3) phytosterols significantly improved the activities of total-superoxide dismutase (T-SOD) in ducks serum(P<0.05), maleic dialdehyde (MDA) content in 80mg/kg treatment group significantly decreased. (4) The immune-organs relative weight had increased and the relative weight of bursal in 10mg/kg and 20mg/kg treatment was significantly increased (P<0.05).Based on experiment one and two, 20mg/kg and 40mg/kg phytosterols supplementation treatments were selected for experiment three, another trial of three hundred 17-day-old commercial Cherry Valley meat-strain ducks were randomly allocated into three treatments, and fed basal diet supplemented with 0 (control group), 20mg/kg, 40mg/kg phytosterols, respectively. This experiment determined the lipoprotein cholesterol concentration in serum and the expression of ABCA1 mRNA levels within jejunum and liver tissues of 42-day-old ducks to investigate the possible mechanisms of phytosterols in regulation of cholesterol metabolism. The results showed that: compared with control group, (1) 40mg/kg supplemented phytosterols significantly reduced TC and LDL-C concentration in serum (P<0.05), but had no significant effect on HDL-C and TG (2) The expression of ABCA1 mRNA levels within jejunum and liver tissue tended to increase.In conclusion, this work indicated that phytosterols decreased cholesterol concentration in serum, increased activities of antioxidases and immune-organs relative weight with dose-effect relationship. But at higher dosages, these effects were not improved. And its potential mechanism in regulation of cholesterol metabolism could be conducted through inducing the up-regulation of mRNA expression of ABCA1 in jejunum and liver tissues.