| Modern lactating sows have a large demand for energy and nutrients for supporting the large litter.However,the feed intake of lactating sows is often not sufficient to fulfil the energy demands for maintenance and milk production,which resulted in high lactational weight loss(HWL).Excessive lactational weight loss negatively influences weaning to estrus interval and subsequent reproductive performance of sows due to insufficient restoration of follicle development.The metabolic status may be the main factor contributing to the restricted follicular development of HWL sows.However,the causes and under lying mechanisms of compromised subsequent reproductive performance by HWL are not completely clear.During lactation,amino acids(AA)metabolism is fluctuant,and HWL leads to severe protein mobilization.However,it is not clear whether AA can improve the follicular development and return to estrus through normalizing the metabolic status of sows with HWL.In the current study,therefore,the difference of physiological profiles manifested in plasma originating from high and low lactational weight loss sows will be investigated,then the dynamic absorption and metabolism of AA of sows should be studied.Further,the effects and underlying mechanism of AA on follicular development and return to estrus of sows with HWL will be investigated.Last,the effect of AA supplementation before mating on reproductive performance of sows will be verified by large-scale trial.Based on these hypothesis,five experiments were included as follows:Exp.1 Comparative study on the physiological and metabolic profiles between high and low lactational weight loss sowsThe aim of this study was to investigate the differences of physiological and metabolic profiles between sows with high lactational weight loss(HWL)and low lactational weight loss(LWL).A total of 64 multiparous sows(parity 3 to 4)were used in this study.Based on the median of the percentage of weight loss during lactation,sows were retrospectively divided in a low weight loss(LWL,<10.15%of body weight)or high weight loss(HWL,>10.15%of body weight)groups.Only 20 sows(n=10 for LWL,average body weight loss was 2.89%;and n=10 for HWL,average body weight loss was 12.65%)were used to study effects of lactational weight loss on plasma metabolome,reproductive hormone,and antioxidant parameters.Results showed as follows:(1)Sows with HWL had lower feed intake and higher lactational weight loss and prolonged WEI,but had similar litter performance and milk composition compared to LWL sows.(2)Sows with HWL had lower plasma insulin-like growth factor 1 at weaning,while higher plasma fibroblast growth factor 21,non-esterified fatty acids,malondialdehyde,and aspartate aminotransferase concentrations than that of LWL sows.(3)Metabolomic analysis revealed differences in 46 compounds between HWL and LWL sows,18 compounds related to AA metabolism among them,and the identified compounds were enriched in metabolic pathways related to AA metabolism,fatty acids oxidation metabolism,bile acids biosynthesis and nucleoside metabolism.These results indicated that HWL led to severe oxidative stress and metabolic damage,as accompanied by excessive protein breakdown and lipids mobilization at weaning,especially in AA metabolism,which resulted in delayed WEI.Exp.2 Study on the dynamic absorption and metabolism of amino acids in multiparous sows during late gestation and lactationBased on Exp.1,AA metabolism is different between HWL and LWL sows.The objectives of the present study were to quantify AA fluxes and heat production across portal-drained viscera(PDV)and liver in multiparous sows during transition and lactation.Eight second parity sows were fitted with indwelling catheters in the femoral artery and in the mesenteric,portal and hepatic veins.Eight hourly sets of blood samples were taken starting 0.5 h before feeding at-10,-3,+3,and+17 d in milk(DIM).Blood gases,plasma metabolites and apparent total tract digestibility(ATTD)of nutrients were measured.Results showed as follows:(1)Feed intake,the ATTD of DM,energy,nitrogen,fat and crude fiber changed with DIM(P<0.001).(2)Except for Glu,O2,and urea,all net portal fluxes were positive,and all were affected by DIM(P<0.05)and by sampling time(P<0.01).Compared with pre partum levels,net portal uptake of AA was 3-63%lower at+3 DIM but 40-100%higher at+17 DIM.Net portal fluxes of AA peaked at 1.5 to 2.5 h after feeding except for Glu,and they were positively correlated with changes in sow feed intake across DIM.The net portal recovery was low for Met(49%),Thr(54%),and His(54%)and high for the remaining essential AA(63-69%)and none of them differed across DIM.(3)Net hepatic uptake(i.e.hepatic oxidation)of Lys,Thr,Ile,Leu and Phe peaked at 0.5to 2.5h after feeding,whereas uptake of Trp,Val,and His was constant,while that of Met was close to zero.In conclusion,the net portal recovery was substantially lower for Met,Thr,and His than the remaining essential AA.Hepatic AA oxidation peaks 0.5 to 2.5h after feeding.The heat production in PDV and liver was approximately two-fold higher at peak lactation compared to other stages.The study suggests that lysine was the limiting AA in peak lactation but not in early lactation.Exp.3 Effects of energy and amino acids intake during gestation on reproductive performance,endocrine,redox status and lactational weight loss of sowsThe purpose of this study was to investigate the effects of energy and AA intake during gestation on reproductive performance,milk composition,blood biochemical parameters,placental nutrient transport and antioxidant related genes expression of high-parity sows.Meanwhile,the model of sows with HWL can be got from this experiment.A total of 72LY sows(seventh through ninth parity)were randomly assigned to dietary treatments,which consisted of combinations of 2 AA levels and 2 energy levels in a 2×2 factorial design.After parturition,all sows were fed a standard lactation diet.Blood and placenta samples were collected and analyzed for parameters on metabolism,redox status and nutrients transport.Results showed as follows:(1)High energy intake during gestation reduced the number of born alive piglets(P<0.05),while increased piglet birth weight(P<0.05).Moreover,plasma progesterone concentration at d 30 and 60 of gestation,and plasma GSH-Px and T-SOD concentrations at d 90 of gestation were decreased by high energy intake(P<0.05).The fat content in the colostrum of sows and average daily weight gain(ADG)of piglets during lactation were increased by high energy intake(P<0.05).(2)High AA intake during gestation had a tendency to increase litter birth weight and protein content of colostrum(P<0.10),and increased plasma urea nitrogen at d 110 of gestation and plasma T-SOD concentration at d 90 of gestation(P<0.05).(3)High energy intake during gestation decreased m RNA expression of GPX but increased m RNA expression of GLUT3 in the placenta(P<0.05),while high AA intake during gestation increased m RNA expressions of placental ESOD and SNAT1(P<0.05).(4)In addition,both energy and AA intake during gestation increased body weight gain(P<0.05).However,high energy and AA intake during gestation reduced feed intake and increased lactational weight loss of sows(P<0.05).In conclusion,high energy intake during gestation impaired fetal survival by reducing progesterone concentration and antioxidant capacity,however,high energy intake increased piglets birth weight by improving placental nutrient transport.Moreover,high AA intake during gestation improved the capacity of antioxidant and placental AA transport.In addition,increased energy and AA intake during gestation reduced feed intake of sows,which led to high lactational weight loss.Exp.4 Effect of amino acid intake after weaning on follicular development and return to estrus of sows with different lactational weight loss and its underlying mechanismThe purpose of this study was to investigate the effects of dietary AA intake on weaning to estrus interval and follicular development of sows with different lactational weight loss.Thirty-two sows with high(11.33%,received from High Energy-High AA group in Exp.3)and low(2.48%,received from Low Energy-Low AA group in Exp.3)lactational weight loss were fed either high(1.0%Lys)or low(0.5%Lys)AA diets from weaning to estrus.Blood and tissues samples were collected and analyzed for parameters on hormone,redox status,AA profiles,and genes expression.Results showed as follows:(1)Sows with HWL decreased protein concentration,RNA:DNA ratio and protein:DNA ratio of longissimus dorsi,increased weaning to estrus interval(P<0.05),and had a tendency to decrease the volume of follicular fluid(P<0.10).Moreover,HWL decreased plasma concentration of IGF-1 at weaning,and E2 concentrations in plasma and follicular fluid at estrus(P<0.05),and had a tendency to decrease the concentrations of IGF-1 in plasma and follicular fluid at estrus(P<0.1).(2)High AA intake increased the protein content of longissimus dorsi(P<0.05),and the concentrations of Leu,Ile,Val and Arg in follicular fluid(P<0.05),and the volume of follicular fluid and number of large follicles(P<0.05),as well as the plasma IGF-1 and E2 concentrations,and E2 concentrations in follicular fluid at estrus(P<0.05).(3)High lactational weight loss decreased m RNA expression of Kiss-1 in AVPV and ER?in ARC and liver,and Cyp17A1 and BMP-15 in ovary(P<0.05).High AA intake increased the m RNA expression of kiss-1 in AVPV,ER?in ARC,and IGF-1R,Cyp19A1,and BMP-15 in ovary,as well as IGF-1 in liver(P<0.05).In conclusion,sows with HWL had increased protein mobilization,insufficient hormone secretion,and inhibition of gene expressions in hypothalamus-pituitary-gonadal axis,which resulted in impaired follicular development and prolonged weaning to estrus interval.However,high AA intake after weaning improves follicular development by regulating hormone secretion and activating gene expressions in hypothalamus-pituitary-gonadal axis.Exp.5 Effects of nutritional supplementation before mating on subsequent reproductive performance,endocrine and amino acids profile of sowsThe purpose of this study was to investigate the effect of pre-mating nutritional supplementation on subsequent reproductive performance of sows.A total of 320 sows were randomly assigned to four treatments:(1)the control diet;(2)the control plus oil diet;(3)the control plus amino acids diet;and(4)the control plus compound diet,from the third week of lactation to mating.Results showed as follows:(1)Pre-mating nutritional supplementation tended to reduce within-litter variation of piglet birth weight(P=0.08),but had no effect on piglet birth weight and litter size.(2)The plasma concentrations of GGT and TP at 2 days before weaning,and plasma concentrations of urea and NEFA at 2 days after weaning were affected by pre-mating nutritional supplementation(P<0.05).Plasma concentrations of Leu,Ile,Val,Asp,Glu and Ser concentrations were increased by pre-mating nutritional supplementation at 2 days after weaning(P<0.05).The concentration of plasma IGF-1 at 2 days after weaning was affected by pre-mating nutritional supplementation(P<0.05).In conclusion,pre-mating nutritional supplementation can reduce within-litter variation of piglet birth weight by regulating plasma AA profiles and metabolic hormones of sows.Collectively,high lactational weight loss led to increased protein and fat mobilization of sows.Accordingly,severe oxidative stress and metabolic damage impaired follicular development and delayed weaning to estrus interval of sows.High AA intake after weaning improved follicular development through regulating hormones secretion and gene expressions in hypothalamus-pituitary-gonadal axis.In addition,nutritional supplementation using both AA and energy can reduce subsequent within-litter variation of piglet birth weight. |
PDF Full Text Request