The Mechanism Of The Effect Of Energy Intake On Growing Performance And Reproduction System Development In Peking Ducks

Maintaining a high level of egg production is crucial for the industry.Animal reproduction is strongly affected by the trade off of the energy balance.The relationship between energy metabolism and reproduction performance in the Peking duck is still elusive.Studies on other animal showed that energy intake could affect reproduction performance by lipid metabolism.A study was conducted to determine the effect of energy intake on ovary development and reproduction performance female Peking duck from 8 to 24 weeks of age and its subsequent effects on the laying performance from 25 to 34 weeks of age.A total of 240 8-week-old female Peking ducks were used in a completely randomized design divided to 5 dietary treatments to provide a range of apparent metabolizable energy(AME)content from 2400,2550,2700,2850 and 3000kcal/kg.Ducks were randomly allocated to 5 treatments of 48 birds each per treatment and fed in separate cages.The average energy intake was controlled at 390,415,440,465,and 490 kcal/d by restricted feeding.The weight gain,feed conversion efficiency and the yields of abdominal fat,breast meat,leg meat and ovarian of ducks from each treatment were measured every 4 weeks.Laying performance were measured from 24 to 34 weeks of age(free feed intake at this period).The results indicated that as dietary energy level increased from 10.00 to 12.60 MJ/kg,the weight gain of ducks increased(p<0.01)and the feed conversion efficiency decreased(p<0.01).A high dietary energy content did not affect(p>0.05)the percentage of leg meat in the carcass but the percentage of abdominal fat,breast meat,skin fat and ovarian increased(p<0.01)as dietary energy level increased.The result on the content of estradiol,follicle stimulating hormone and luteinizing hormone radioimmunity indicated that the plasma FSH concentration of high energy intake was significantly higher than low energy intake group,and reached the peak at 16 weeks of age;the plasma E2 concentration of high energy intake was significantly higher than low energy intake group,and reached the peak at 20 weeks of age;The concentration of LH in plasma peaked at 20 weeks of age and the concentration of LH in 2700 kcal/kg group is significant higher than other groups during this period.The concentration of triglyceride and low density lipoprotein in plasma were increased significantly(p<0.01)as the energy intake increase,however,the total protein was reduced(p<0.01).There were no significant difference in albumin?uric acid?cholesterol and high densitylipoprotein.Higher ovary percentage was observed(p<0.05)at 2700 and 3000 kcal/kg and it was also accompanied with larger follicle size according to histological morphology.There was a large number of fat vacuoles in liver tissue of Peking ducks at 20 weeks of age in the high energy intake group,and a great quantity cell necrosis in liver tissue were occurred at the age of 24 weeks.As for eggshell tissue section,there was no significantly different between 5 treatments.We sought to systematically explore the effect of energy intake on genetic regulation and metabolism through transcriptome analysis.The results indicated that there were 458 differentially expressed genes were obtained,of which 316 were up-regulated and the other 142 were down regulated genes.There were 221 extremely significant(p<0.01)differentially expressed genes and237 significant(0.01<p<0.05)differentially expressed genes in all the differentially expressed genes.Furthermore,ovary development might be controlled by gene regulation and it was supported by significant increase in gene expression of follicle-stimulating hormone receptor(FSHR),estrogen receptor(E2R)and leptin receptor(LEPR)at high energy intake.According to the broken-line regression analysis,the AME requirement of White Peking ducks 8 to 24 weeks of age for optimal feed conversion efficiency,abdominal fat ratio,ovarian ratio and TP concentration were 2919,2823,2700 and 2760 kcal/kg when dietary protein was 151g/kg,respectively.As for egg production the AME requirement was 2700 kcal/kg.The experiment consequence above showed that energy intake indirectly regulate the development of ovarian tissue by affecting the fat metabolism and the expression of related genes.