Study On The Effect Of Dietary Energy Level On Production Performance And Reproductive Performance In Sichuan White Geese During Early Laying Period

Three experiments were conducted to determine the suitable energy requirement during early laying period in Sichuan white geese,and study the effect of dietary energy level on production performance and reproductive performance in Sichuan white geese and its possible mechanism.Expt.1: The experiment was conducted to study the effect of dietary energy level on production performance and egg quality in Sichuan white geese in order to obtain energy requirements in early laying period.Two hundred fifty 26 weeks old female Sichuan white geese were randomly allotted to five dietary treatments with five dietary metabolizable energy levels(9.14 MJ/kg,10.01MJ/kg,10.88MJ/kg,11.75MJ/kg,12.62MJ/kg),each containing 10 replicate pens with 5 birds per pen.The experiment lasted for 12 weeks.According to repeating groups to recording feed intake,egg weight and egg number everyday.At the end of experiment,weighting the geese to examined the effect of dietary energy level on the production performance in Sichuan white geese during early laying period.Selected 6 female geese to slaughter,examined the effect of dietary energy level on liver weight and abdominal fat weight.Two goose eggs from each repeating group were selected to study the effect of dietary energy level on egg quality in Sichuan white geese during early laying period.The results showed that:1)The final body weight and average daily gain of Sichuan white geese during early laying period were significantly improved with the increase of dietary energy level(P<0.01).The final body weight of 10.88MJ/kg,11.75MJ/kg and 12.62MJ/kg ME were significantly higher than 9.14MJ/kg and 10.01MJ/kg ME(P<0.01).The average daily gain of 10.88MJ/kg ME were very significantly higher than 9.14MJ/kg ME(P<0.01),and higher than 10.01MJ/kg ME(P<0.05).The feed intake and feed conversion ratio of Sichuan white geese during early laying period were very significantly decreased with the increase of dietary energy level(P<0.01).The daily feed intake of 12.62MJ/kg ME was significantly lower than the other four groups(P<0.01).The feed conversion ratio of 10.88MJ/kg ME was significantly lower than 9.14MJ/kg(P<0.01)and10.01MJ/kg ME(P<0.05).2)Dietary energy level significantly affected liver weight,abdominal fat weight and abdominal fat index of Sichuan white geese during early laying period(P<0.01),had no significant effect on liver index(P>0.05).Geese that were fed the diet containing 11.75MJ/kg ME had higher liver weight,abdominal fat weight and abdominal fat index than those fed the diet containing 9.14 MJ/kg and 10.01MJ/kg ME(P<0.01).3)The average egg weight,daily laying rate and average number of laying eggs of Sichuan white geese during the early laying period were significantly improved with the increase of dietary energy level(P<0.01),but increased to11.75MJ/kg turn to decreased.The feed egg ratio of Sichuan white geese were significantly decreased with the increase of dietary energy level(P<0.01),and in 11.75MJ/kg ME it was lowest,significantly lower than 10.01MJ/kg and 10.88MJ/kg ME(P<0.01).And the dietary energy level had no significant effect on the day in the first laying and the egg weight in the first laying of Sichuan white geese(P>0.05).4)The albumen height and haugh unit of Sichuan white geese were improved first and then decreased with the increase of dietary energy level(P<0.01),10.88MJ/kg ME was highest,significantly higher than 9.14MJ/kg and 12.62MJ/kg ME(P<0.01).The yolk color of Sichuan white geese during the early laying period were significantly improved with the increase of dietary energy level(P<0.01),and 11.75MJ/kg ME was best,was significantly higher 9.14MJ/kg and 10.01MJ/kg ME(P<0.01).The 10.88MJ/kg and 11.75MJ/kg ME had higher egg specific gravity than 9.14MJ/kg ME(P<0.01).Dietary energy level had no significant effect on the egg shape index,eggshell strength,eggshell thickness,egg white and yolk proportion of Sichuan white geese(P>0.05).5)According to quadratic or cubic curve model analysis,the energy requirement model of Sichuan white geese from 26 to 38 week of age for final body weight,average daily gain,average egg weight and daily laying rate were Y1=-0.056X2+1.371X-4.829(P=0.027,R2=0.973);Y2=-0.697X2+17.261X-91.924(P=0.011,R2=0.989);Y3=-1.434X3+45.948X2-484.15X+1798.6(P=0.036,R2=0.999);Y4=-1.816X3+57.864X2-607.98 X +2113.17(P=0.022,R2=0.969),respectively.The optimal energy requirements were 12.31MJ/kg,12.37MJ/kg,11.93MJ/kg and 11.91MJ/kg,respectively.Expt.2: The experiment was conducted to study the effect of dietary energy level on hatching performance and reproductive organ development in Sichuan white geese in order to obtain energy requirements.The experiment design and experiment diet were as Expt.1.At the end of experiment,six female geese from each group were selected to study the effect of dietary energy level on reproductive organ development and the number of follicles in Sichuan white geese.Select all eggs to hatching in experiment to examining the effect of dietary energy level on fertility,hatchability of fertile eggs in Sichuan white geese during the early laying period.The results showed that:1)Dietary energy level had no significant effect on oviduct weight,oviduct index,uterus weight and uterus index of Sichuan white geese during the early laying period(P>0.05),but significantly improved oviduct length of Sichuan white geese(P<0.05).The oviduct length of 12.62MJ/kg ME was significantly higher than 9.14 MJ/kg and 10.01MJ/kg ME(P<0.05).2)Dietary energy level had no significant effect on the number of small yellow follicles and large yellow follicles of Sichuan whitegeese during the early laying period(P>0.05),but had a significant effect on the number of small white follicles,large white follicles and preovulatory follicles of Sichuan white geese(P<0.05).The number of preovulatory follicles in 11.75MJ/kg ME was significantly higher than in 9.14 MJ/kg and10.01MJ/kg ME(P<0.05).The number of small white follicles in 9.14MJ/kg and 10.01MJ/kg ME were significantly higher than 10.88MJ/kg and 12.62MJ/kg ME(P<0.05).The number of large white follicles in 11.75MJ/kg and 12.62MJ/kg ME were significantly higher than 9.14MJ/kg ME(P<0.05).3)Dietary energy level had no significant effect on fertility of Sichuan white geese in early laying period(P>0.05),but had significant effect on the hatchability of fertilized eggs(P<0.01).The hatchability of fertilized eggs was the highest in 11.75MJ/kg ME,very significantly higher than9.14MJ/kg and 10.01MJ/kg ME(P<0.01),significantly higher than 12.62MJ/kg ME(P<0.05).4)According to cubic curve model analysis,the energy requirement model of Sichuan white geese from 26 to 38 week of age for hatchability of fertilized eggs was Y=-4.558X3+144.28X2-1499.9X+5189.3(P=0.032,R2=0.999),and the optimal energy requirement was 11.83MJ/kg.Expt.3: The experiment was conducted to study the possible mechanism of dietary energy level on laying performance and reproductive performance in Sichuan white geese.On the basis of the expt.1,two energy levels(10.01MJ/kg and 11.75MJ/kg)were selected to finish it.At the end of experiment,two geese from each repeating group were selected to study the effect of dietary energy level on serum biochemical indices and reproductive hormone in Sichuan white geese.Six geese from each group were selected to collecting hypothalamus,pituitary and ovary by RT-PCR to study the mechanism of energy on related gene mRNA expression of HPG axis in Sichuan white geese.The results showed that: 1)Dietary energy level had no significant effect on blood metabolic substrate triglyceride,total cholesterol,high density lipoprotein and low density lipoprotein of Sichuan white geese(P>0.05).11.75MJ/kg ME significantly promoted the secretion of GnRH,E2 and IGF-1 in Sichuan white geese(P<0.05).But Dietary energy level had no significant effect on LH,FSH,P,PRL and INS concentration in Sichuan white geese(P>0.05).2)11.75MJ/kg ME significantly increased LHR and GnRH mRNA level in the hypothalamus of Sichuan white geese(P<0.05),decreased PRL m RNA level in the hypothalamus(P<0.05).At the same time,11.75MJ/kg ME significantly increased PR and ER mRNA level in the pituitary(P<0.05),significantly increased FSH mRNA level in the pituitary(P<0.01).Dietary energy level had no significant effect on LH mRNA level in the pituitary(P>0.05).The E2 mRNA expression level in the ovary of 11.75MJ/kg ME was significantly higher than that 10.01MJ/kg ME(P<0.05).Therefore,increased dietary energy level to 10.88MJ/kg significantly increased average daily weight gain,promoted it to laying,decreased feed egg ratio and increased egg quality.Increased dietary energy level to 11.75MJ/kg ME significantly promoted growth of liver and abdominal fat,improved hatchability of fertile eggs et al.The mechanism may be to promote the gene expression and secretion of GnRH,E2 in Sichuan white geese.According to regression analysis,the energy requirements of Sichuan white geese from 26 to 38 week of age for final body weight,average daily gain,average egg weight,daily laying rate and hatchability of fertile eggs were 11.83 MJ/kg~12.37MJ/kg ME.