The Effects Of Energy Levels And Sources On Concentration Of Metabolism Substrate, Hormone Secretion In Plasma And Follicular Fluid Microenvironment In Gilts

The present study was conducted to investigate the effects of different energy levels and sources on the plasma energy metabolic substrates(Triglyeride,Total Cholesterol and Glucose),metabolic hormones(insulin,IGF-1 and leptin),reproductive hormones(E₂,FSH and LH) and the follicle microenvironments(Triglyeride,Total Cholesterol,Glucose and IGF-1,leptin,E₂) in gilts.According to 3×2 experimental design,54 F1(Landrace×Large White) crossbred gilts(59±4.2 kg) were randomly allocated to six treatment groups. Three energy levels were 87.5%,100%and 112.5%of recommendatory energy requirements by NRC(1998),maize starch-riched(provided 72%of DE) or fat-riched(provided 29%of DE) were respectively contained in each of the three energy allowance level treatment.The standing heat day of the 2nd estrus cycle was designated as dl.Blood samples were collected consecutively at 30-min intervals for 8h on d18. Additional blood and follicular fluids samples were withdrawn from(diameter＞3mm) the precaval vein and large follicles immediately after slaughtered on d19,and the ovaries were weighed and the corpora lutea were counted after the removal of the ovaries.The metabolic substrates from plasma and follicular fluid were determined by biochemistry autoanalyser and the hormones were analyzed by ELISA.The results indicated that:1.The concentrations of plasma Triglyeride(TG) and Total Cholesterol(TC) were significantly higher in fat group than the starch group(P＜0.01),there were no differences on the concentrations of plasma glucose(GLU) between fat and starch fed groups(P＞0.05). No effects of energy levels and energy allowance levels×energy sources on plasma metabolic substrates were observed(P＞0.05).2.Plasma energy metabolic hormone concentrations were affected by different energy levels.Plasma insulin AUC were significantly higher(P＜0.01) in high energy diet-fed gilts than low energy level diet-fed gilts,there was no difference between medium energy level diet-fed gilts and the other two groups(P＞0.05).IGF-I concentrations of high and low energy level diet-fed gilts were significantly higher than the medium energy level-fed gilts (P＜0.01 and P＜0.05,respectively),but there was no difference between high-energy level diet and the low-energy level diet-fed gilts(P＞0.05).Concentrations of Leptin were significantly higher in gilts fed the high-energy level diet compared with gilts fed the medium energy level diet(P＜0.01),but there were no differences between low-energy level diet fed gilts and the other two treatment groups(P＞0.05).The plasma IGF-1 concentration were higher in starch-fed group than fat fed group which were subjected to low energy-fed level(P＜0.01),but no variations were detected between starch and fat gilts subjected to medium and high-energy level fed groups(P＞0.05).However,the insulin AUC and leptin concentration were not affected by different energy source-treated groups(P＞0.05).There was no clear interaction of energy sources×levels on plasma energy metabolic hormones.3.The effects of different energy levels on plasma reproductive hormones were observed. Concentrations of E₂ were significantly higher(P＜0.01) in the low energy level diet-fed gilts compared with gilts fed the medium energy level diet,but there was no difference (P＞0.05) between high energy level diet group and the other two energy-feeding level diet groups.The FSH pulses were not affected between different energy level-fed gilt(P＞0.05). LH pulses were higher in high energy level-fed gilts diet than the gilts fed the other two energy-feeding level diets(P＜0.05),and there was no difference(P＞0.05) between low energy level diet and the medium energy level diets group(P＞0.05).There were significant effects of energy source treatment on the plasma E₂ concentrations.In low-energy level fed gilts,no difference of E₂ concentrations were shown(P＞0.05). However,concentration of E₂ were significantly higher in fat fed gilts than the starch fed gilts which were subjected to the medium and high-energy fed level(P＜0.01 and P＜0.05,respectively).No treatment effects of energy sources on FSH and LH pulses were observed(P＞0.05).There was no interaction of energy-feeding levels×energy sources on plasma reproductive hormones(P＞0.05).4.The Pearson correlation analysis between plasma energy metabolic substrates and hormones indicates that there was no significant(P＞0.05) association between fatty acid (TG and TC) and metabolic hormones(the basic concentration of preprandial Insulin,Leptin)(P＞0.05),but positive relationship between the concentration of Glu and the basic preprandial Insulin concentration and Leptin concentration were identified(P＜0.01). There was positive relationship between the concentration of TC and E₂(P＞0.05).5.Treatment effects of energy levels were detected to be imposed on the reproductive tracts.The initiation of estrus were not affected by different energy levels,regardless of energy source treatment(P＞0.05).There was more large follichles(diameter＞3mm) in high energy-fed gilts than the other two energy level-fed gilts(P＜0.01),but with no treatment effects between medium and low energy-fed gilts(P＞0.05);The ovary weight of high and medium energy-fed gilts were greater than the low energy-fed gilts(P＜0.05),but no difference were found between high and medium energy level group(P＞0.05).The number of corpora lutea(CL) in high energy starch-fed gilts were more than that in low energy-fed gilts(P＜0.05),and the CL were greater in high energy fat-fed gilts than the other two feeding level treatment groups(P＜0.05).No effects of energy source and energy level×energy source on the number of large follicles,ovary weight and CL were observed (P＞0.05).6.There was no significant effect of different energy-feeding levels metabolic substrates in follicular fluid(P＜0.05).However,the concentration of IGF-1 and E₂ in follicular fluid were affected by energy allowance levels,IGF-1 concentrations in follicle fluid were higher(P＜0.05) in gilts fed the high energy level diet compared with gilts fed the medium energy level diet,with the absence of variation between low energy level-fed group and the other two groups(P＞0.05).There was a higher E2 concentration in the high energy-fed gilts than the medium energy-fed gilts,but there was no difference between low-energy level and the other two energy-feeding groups(P＞0.05).The leptin concentration in follicular fluid were similar between different energy feeding level groups(P＞0.05).No interactions of energy allowance levels×energy sources between follicular fluid energy metabolic substrates and concentration of IGF-1,Leptin and E₂ established(P＞0.05).The conclusion:(1) The TC concentration was higher as the increasing dietary fat content which enhanced the E2 concentration,thus stimulated the initiation of estrus in gilts. (2)The follicular development and ovulation rate were promoted due to the greater concentrations of blood metabolic hormones(Insulin,IGF-land Leptin) and LH secretion induced by the increasing energy feeding level or starch content.(3)The higher IGF-1 and E₂ concentrations in follicular fluid generated by increasing energy allowance level contributed to the enhancing oocyte quality,although no effects of energy sources on the energy substrates IGF-1 E₂ and Leptin in follicular fluid were observed.