| Dietary fiber?DF?was commonly used in pig diets.Most of the gestating sow studies with DF supplementation focused only on the consequent performance,but with no attention on effects of DF and its metabolites on metabolism,intestinal microbial changes of sow itself as well as the growth and development of their offspring in the later life.In comparison,DF-rich ingredients were rarely included in lactating sow diet as high DF may compromise feed intake and nutrient utilization.However,locally available crops and their co-products which are high in DF may be cost-efficient alternatives to partly replace cereals in lactating sow diet,and the fermentative products SCFAs have been proven to involve in milk fat synthesis.These seem to provide the possibility to include DF in lactating sow diet.Therefore,this study was conducted to explain the mechanism under which gestating sows and their offspring were affected by DF supplementation from maternal metabolic and microbial change perspectives,as well as the mechanism under which lactational performances of sows were affected by DF supplementation from mammary nutrient uptake.The main results were presented as below:Exp.1 Effects of dietary fiber supplementation during gestation on the performance,nutrient metabolism and intestinal microbiota of gestating sowsThe experiment was a 2×2 experimental design with levels of inulin?0%or 1.5%?and fat?0%or 5%?addition as the fixed factors,the four treatments were low-fat diet?LFD?,low-fat diet with 1.5%inulin?LFD.Inu?,high-fat diet?HFD?,and high-fat diet with 1.5%inulin?HFD.Inu?.A total of eighty 2-3 parity Landrace×Yorkshire sows were used.Sows were allocated to one of four groups based on parity,body weight,and backfat thickness.Dietary treatments were through the whole gestation.During lactation,sows were fed with the same standard lactational diet.The results we obtained were:?1?The fat addition significantly increased the gestational weight gain,maternal weight gain and backfat gain?P<0.01?,while inulin addition decreased the maternal weight gain and backfat gain?P<0.05?;fat addition increased the total born piglets,live born piglets,and litter weight at birth?P=0.01?,but with no effect on the birth weight and stillborn rate,inulin addition showed significant effect on shortening the farrowing duration of sows?P=0.04?and improving the uniformity of newborn piglets?P?0.05?;inulin addition upon fat supplementation decreased piglet and litter weight at weaning?P<0.05?,and inulin addition decreased the body weight and backfat loss during lactation?P<0.05?.?2?Inulin addition markedly increased the CRL,and decreased the BMI of newborn piglets at birth?P<0.05?.Fat addition increased the carcass ether extract of newborn piglets,while inulin showed the opposite effect?P=0.02?.Inulin addition increased carcass content of ash,calcium and phosphorus as well as the serum glucose of neonatal piglets?P<0.05?.?3?Results related to nutrient metabolism showed that fat addition increased AUC120,decreased the glucose clearance rate?P<0.05?,while inulin addition decreased the peak glucose and AUC120,and increased the glucose clearance rate?P<0.05?.Inulin addition decreased the ATTD of ether extract,but increased the ATTD of calcium of gestating sows?P<0.05?.Inulin addition upon fat supplementation increased bile acids excretion in feces,and also increased the serum butyrate concentration of gestating sows?P<0.01?.?4?16S rRNA gene sequencing of the V3-V4 region showed that inulin addition increased the Simpson index?P=0.02?,and also showed interactive effect with fat addition?P=0.01?.On the phylum level,fat addition decreased the relative abundance of Proteobacteria?P=0.04?,and inulin addition increased the relative abundance of Lentisphaerae?P=0.02?;on the genus level,fat addition only increased the relative abundance of YRC22?P<0.01?,while inulin addition increased the relative abundance of Streptococcus?P=0.02?,Oscillospira?P=0.02?,Sphaerochaeta?P=0.02?and Phascolarctobacterium?P<0.01?,and decreased that of YRC22?P<0.01???5?Inulin addition decreased the circulating concentrations of pro-inflammatory cytokine IL-6,adipokine leptin and chemerin?P<0.05?.Collectively,inulin addition during gestation showed no effect on litter performance,but reduced the farrowing duration,and the gestational body weight gain and backfat gain of the gestating sows.These may related to the alterations of maternal metabolism and intestinal microbiota induced by inulin additionExp.2 Effect of dietary fiber supplementation during gestation on performance and meat quality of offspring and its mechanismsMaternal nutrition could affect fetal growth,metabolism and health later in life by“nutritional programming”.This study was conducted to evaluate the effect of SDF inulin supplementation during gestation on growth performance and metabolism of offspring pigs,and to explain epigenetic effects of inulin from the perspective of histone acetylation changes.After the piglets were weaned from Exp.1,fiver litters with 10 piglets per treatment were chosen to fattening.During the experiment,standard feed was adopted at all stages.The results we obtained were:?1?Due to the experiment design that weaned piglets from Exp.1 had lighter BW in the inulin group compared with non-inulin group,BW of piglets in the HFD.Inu group was lighter until d 110 of age,and then their BW was not significantly different from other groups until d 180 of age.The feed intake changes of piglets at different phases showed the same trend in accordance with the BW change.?2?Inulin supplementation during gestation increased the liver index of their offspring at both weaning and fattening stage?P<0.05?;maternal inulin addition upon fat supplementation decreased the abdominal fat index of weaning piglets?P=0.05?,and decreased the average backfat thickness of offspring at fattening stage?P<0.01?.?3?Inulin supplementation during gestation had no effect on the meat quality,except it decreased the lightness L*of longissimus dorsi of the offspring at slaughter?P=0.02?.?4?Inulin supplementation during gestation decreased the liver lipid deposition in offspring at birth and fattening,and increased the gene expression of fatty acids?-oxidation related PGC-1?and CPT1A in the liver?P<0.05?.?5?Inulin supplementation during gestation showed tendency to increase the serum butyrate concentration in neonatal piglets?P=0.06?,and significantly reduced the activity of histone deacetylases?HDACs?as well as enhanced acetylated H3 and H4 contents in the liver?P<0.01?.Collectively,these results indicated that maternal inulin supplementation showed no effect on carcass and meat quality,but it reduced the liver lipid deposition of their offspring at birth and fattening.This may be due to the fact that inhibition of HDACs activity followed by increased acetylated H3 and H4 content induced by the maternal-derived butyrate activated the expression of fatty acid?-oxidation related genes in the liver.Exp.3 Effect of dietary fiber on uterus and mammary nutrient uptake and lactational performance of sowsIn order to investigate the effect of DF addition on uterus and mammary nutrient uptake and lactational performance of sows,a total of 10 cross-bred?Danish Landrace x Danish Yorkshire?multiparous sows?parity 3 to 5?were included in the present study.On d 75±2 of gestation,sows were stratified for BW?276±18 kg,mean±SD?and parity to be allotted into1 of 2 groups,namely a control group or a high dietary fiber?DF?–supplemented group?fiber group?,and were surgically fitted with indwelling catheters.From d 102 to 108,sows in control group were continually fed the standard gestation diet?14.6%DF?,and sows in the fiber group were fed standard gestation diet partially replaced with high DF supplementary diet?39.1%DF?.From d 109 of gestation until parturition,sows in control group were fed standard transition diet?16.8%DF?,and sows in fiber group were fed standard transition partially replaced with high DF supplementary diet?39.1%DF?.Form d 5 of lactation,sows in the control group were fed a standard lactation diet which is low in DF content?control group,13.2%DF?,and sows in the fiber group were fed a high DF lactation diet?fiber group,18.6%DF?.Low feed intake?Low-FI?sows?n=3?were chosen to be the feed intake paired group.The results we obtained were:?1?DF supplementation during gestation significantly increased arterial concentration of acetate,propionate,butyrate and total SCFAs?P?0.01?,but had no effect on arterial-venous difference of these metabolites.The uterus extraction of glucose,lactate,NEFA,acetate and butyrate were not different between treatments,but butyrate showed a tendency to increase as the gestation progressed?P=0.07?.?2?DF supplementation during lactation had numerically lower reproductive performance of sows when compared with control sows.And Low-FI sows had severe BW loss?-76 kg?and body protein mobilization?11.2 kg??P=0.02?,and piglet performance including piglet weight at weaning,litter weight at weaning and piglet survival rate as well as milk yield were also reduced?P<0.05?.?3?Lactating sows in the DF supplementation group had decreased ATTD of GE,DM and OM compared to control group,but higher than the Low-FI sows?P<0.01?.?4?Lactating sows in the DF supplementation group had higher arterial concentration of glucose,acetate and propionate at d 7 of lactation?P<0.05?,and the similar concentrations as the control group at d 17 of lactation.?5?Mammary extraction of glucose,NEFA,triglycerides,acetate,propionate and butyrate of Low-FI sows were significantly lower than the other two groups?P<0.05?.?6?The mammary plasma flow was similar among groups.The control sows showed the numerical highest value of 7401 L/d,the fiber sows was the intermediate with a value of6551 L/d,while the Low-FI sows had lowest value of 5499 L/d.Meanwhile,Low-FI sows had negative mammary flux of acetate,propionate and butyrate which were significantly lower than the other two groups?P<0.05?.?7?The Low-FI sows had higher milk DM,fat,protein and energy content,and lower milk lactose content than the other two groups?P<0.05?.At peak lactation,fiber sows had the highest milk energy,DM and fat output?P<0.05?.Collectively,these results indicated the uterus extraction of butyrate was above 10%during late gestation,and also had a tendency to increase as the gestation progressed.The Low-FI sows mobilized massive body reserves to main milk yield which resulted in dramatical body weight loss.Fiber supplemented sows had numerical lower lactation performance than control sows which was possibly due to lower feed intake and nutrient digestibility.Exp.4 Effects of NSP-degrading enzyme supplementation on nutrient digestibility and lactation performance of sowsResults of Exp.3 showed that high DF addition to lactational diet showed negative effects on feed intake,nutrient digestibility and performance of sows.Hence,how to improve the negative effects of DF in lactational diet becomes a topic worth exploring.Supplementing non-starch polysaccharides?NSP?degrading enzymes has been found to improve the nutrient digestibility,feed efficiency and growth performance of poultry and young pigs,but has not been commonly tested in sows.A total of 30 cross-bred?Danish Landrace x Yorkshire?multiparous sows were used in the experiment.Sows were fed a standard gestation diet from mating until d 108 of gestation,and then stratified for BW and parity to receive 1 of 2 dietary treatments?Control and Enzyme group?until weaning at d 28 of lactation.The enzyme diet was made by adding 200 FXU xylanase per kg of feed?corresponding to 200 g per ton of feed?to the control diet.The diet was based on wheat and barley with a DF level about 15%.The results we obtained were:?1?Supplementation of xylanase showed no effect on the total born,live born and stillborn piglets at parturition,but decreased the body weight loss during lactation when compared with control sows?P=0.04?.?2?The ATTD of GE,DM,N,OM and total NSP were all increased by xylanase supplementation?P<0.05?.?3?Supplementation of xylanase increased the ADFI of lactating sows?P<0.01?.Individual piglet weight gain,litter weight gain,litter size,milk composition and milk yield did not differ between treatments.Collectively,these results indicated supplementing a mono-component xylanase to wheat-barley based lactation diet improved sow feed intake and nutrient digestibility,thereby reducing sow BW loss throughout lactation,whereas no significant benefits were found on piglet performance or sow milk yield.To sum up,the main conclusions of this thesis are:?1?The alterations of maternal metabolism and intestinal microbiota changes induced by inulin addition were the underlying mechanisms by which inulin affected gestational weight gain,fat accumulation and partial performance of gestating sows.?2?Maternal inulin supplementation changed offspring growth and liver lipid deposition induced by maternal high fat addition via histone acetylation modifications,and the stable effects caused by epigenetic modifications at birth could last to fattening stage.?3?Despite the same SDF intake,uterine SCFAs uptake was also affected by the fermentability difference of different SDF types.More prominent effects may be found with DF source with high fermentability.?4?Due to lower feed intake and nutrient digestibility,sows supplemented with IDF-rich grass meal had numerical lower mammary nutrient uptake and lactation performance,while supplementing NSP degrading enzyme to DF-rich lactational diet could eliminate the negative effect of DF. |
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