Mechanism Of Soluble Fiber Inclusion In Gestation Diets Regulating Lactation Feed Intake Of Sows And Its Role In Improving Reproductive Performance Of Sows

The reproductive performance of sows is an important feature that affects the economic benefits of pig farms. Maximising feed intake during lactation is critical to improving overall sow performance, including productivity and longevity. It is well known that as the associated body weight gain during gestation increase, feed intake of sows during the subsequent lactation decreases. Thus, pregnant sows were recommended to be fed restrictively. However, these resulted in the development of abnormal behavior, and in turn have negative influence on the reproductive performance of sows.In this study, we firstly investigated the fibrous components levels, viscosity, hydration properties, fermentability and digestibility of different fibrous ingredients, and selected fibrous ingredients of high hydration properties and fermentability. Then, the inclusion of these fibrous ingredients in gestation diets of sows have increased postprandial satiety in pregnant sows without providing excess feed, improved insulin sensitivity, increased lactation feed intake of sows, improved reproductive performance of sows, and researched the possible mechanism. In order to provide theoretical guidance and support for inclusion of dietary fiber in gestation diet of sows. The main contents and results are as follows:In the first part, levels of CF, ADF, NDF, total fiber, soluble dietary fiber (SF) and insoluble fiber (ISF), viscosity, swelling and water-binding capacity of six fibrous ingredients were analyzed. In vitro fermentation of six ingredients, gas and short chain fatty acids production were monitored during fermentation. Pearson’s correlations were also conducted to determine significant correlations.The main results are as follows:1. There were significant differences among six fibrous ingredients in the levels of fibrous components, viscosity, swelling and water-binding capacity (WBC). KF had highest viscosity (22.36mPa-s), swelling (13.01g/g) and water-binding capacity (31.11ml/g) in six ingredients.2. Gas production patterns of ingredients were fitted to a biphasic model. For the rapidly fermented fraction, fermentation of konjac flour (KF) resulted in greatest VF1(P<0.01), and lowest (FRD0)1(P<0.05). However, as with the slow fraction, sugar beet pulp (SBP) had greatest VF2(P<0.05). 3. In vitro fermentation of KF, sugar beet pulp and apple pomace produced higher concentrations of SCFAs than fermentation of red jujube flour, alfalfa mea and wheat bran (P<0.05).Compared with sugar beet pulp, wheat bran, alfalfa mea, red jujube flour and apple pomace, fermentation of KF produced higher concentrations of acetic acid, propionate and total SCFA (P<0.05).4. The correlation coefficients for relationships between the level of soluble fiber and physicochemical properties showed viscosity (r=0.864, P<0.05), swelling (r=0.947, P<0.01), acetic acid (r=0.809, P<0.05), propionate (r=0.846, P<0.05) and total SCFA (r=0.822, P<0.05) concentrations were significant positive correlated with the level of soluble fiber.In the second part, we investigated the effects of inclusion three fibrous ingredients in diets on the physicochemical properties of diets. Three diets were formulated using wheat bran, konjac flour and sugar beet pulp. Three diets had the same level of DE, crude protein and NDF, but have different levels of soluble fiber. Six Yorkshire barrows fitted with a simple T-cannula at the terminal ileum were arranged as a replicated3×3latin square design. Ileal effluent was collected during the collection period. Viscosity, swelling and water-binding capacity of three diets and ileal effluent were analyzed. In vitro fermentation of three diets and ileal effluent. The main results are as follows:1. There were no differences between KF and SBP diets in viscosity. Compared with control group, KF and SBP diets had higher viscosity (P<0.05). The inclusion of KF or SBP significant increased the swelling and water-binding capacity of diets (P<0.01).2. The inclusion KF in diet had no effect of the viscosity, swelling and water-binding capacity of ileal effluent. Similarly, there were no differences between SBP and control diets in viscosity and water-binding capacity of ileal effluent. However, the inclusion SBP in diet increased the swelling of ileal effluent (5.37vs3.51mL/g, P<0.05).3. Gas production patterns of three diets were fitted to a biphasic model. KF diet had similar fermentation pattern with the control diet, and the gas mainly come from apidly fermented fraction. Whereas, the gas of fermentation of SBP diet mainly come from slowly fermented fraction. Fermentation of KF diet produced higher VF1of rapidly fermented fraction (P<0.01) than the control or SBP diets. Compared with the control and SBP diets, KF diet had lower (FRD0)1from rapidly fraction. For slowly fermented fraction, SBP diet group had higher VF2(P<0.05) than the control or KF diets group, there were no differences between the control diet and KF diet. 4. In vitro fermentation of KF diet produced higher concentrations of acetate (P<0.01), butyrate (P<0.01) and total SCFA (P<0.01) than the control and SBP diet groups, there were no differences between the control and SBP diet group.5. Gas production patterns of ileal effluent were fitted to a monophasic model. There were no differences in all gas production parameters between the control and SBP diets. However, in vitro fermentation of ileal effluent from pigs fed the KF diet produced higher VF than the control or SBP diets (P<0.05).6. Similarly, there were no differences in concentrations of SCFAs between the control and SBP diets. However, in vitro fermentation of ileal effluent from pigs fed the KF diet produced higher VFthan the control or SBP diet groups (P<0.05).In the third part, this study was conducted to investigate the effects of konjac flour (KF) inclusion in gestation diets of sows on nutrients digestibility, lactation feed intake, reproductive performance of sows. Two isoenergetic and isonitrogenous gestation diets were formulated:the control diet and the2.1%KF-supplemented diet (KF diet). Both diets had the same neutral detergent fibre (NDF) and insoluble fiber (ISF) levels, but the KF diet had higher soluble fiber (SF) level. The day after breeding,96multiparous sows were assigned to the two dietary treatments. Restrict-fed during gestation, in contrast, all sows were offered the same lactation diet ad libitum. Response criteria included nutrient digestibility, sow and piglets performance. The main results are as follows:1. Tthe digestibility of dry matter, gross energy, crude fibre and acid detergent fibre were not affected by the dietary treatments. The inclusion of KF in gestation diets increased NDF digestibility (P<0.05) and tended to increase the digestibility of crude protein (P=0.05) compared with the control diet group.2. Dietary treatment during gestation did not affect body weight and backfat gain during gestation, lactation weight, backfat loss or weaning-to-estrus interval of sows.3. Sows fed the KF diet consumed more (6.38vs5.88kg, P<0.05) lactation diet per day than sows in the control group.4. Dietary treatment during gestation did not affect litter size. However, sows fed the KF diet further showed greater average piglet weights on day21of lactation (6.59vs6.24kg,P=0.09), meanwhile the litter weight of sows fed the KF diet on day21of lactation increased by3.95kg compared with sows fed the control diet.In the fourth part, this study was conducted to investigate the effects of different levels of konjac flour (KF) inclusion in gestation diet on postprandial satiety in pregnant sows, lactation feed intake and reproductive performance of sows during two successive reproductive cycles. A total of140Landrace sows with average parities of3.97±1.74were used in this trial. Four isoenergetic and isonitrogenous gestation diets were formulated to contain KF levels of0(control diet),0.6(0.6%KF diet),1.2(1.2%KF diet), or2.2%(2.2%KF diet), respectively. All diets had the same levels of insoluble fiber and NDF, the soluble fiber levels increased with the increasing inclusion levels of KF. After breeding, sows were assigned to the four dietary treatments based on parity and BW. All sows were maintained on the same dietary treatments in cycle1and2. Restrict-fed during gestation, in contrast, all sows were fed with the same diet ad libitum during lactation. Response criteria included performance of sows and piglets. On d70,71and72of gestation during second reproductive cycle,20sows (5sows per dietary treatment) were observed, the parity for these sows was3.0. Before feeding and1postprandial on d90of gestation during the second reproductive cycle,20sows (5sows per dietary treatment), which had the same parity (3) were selected for blood sampling. Cortisol concentrations in plasma were determined using a commercial ELISA kit.The main results are as follows:1. Time spent on self-directed behavior of sows decreased linearly (P<0.01) with increasing inclusion levels of KF.2. There were no differences in plasma concentrations of pre-prandial cortisol of sows among four dietary treatments. However, the plasma concentration of cortisol1h postprandial of sows on d90of gestation was decreased (linearly, P<0.05) with increasing inclusion levels of KF.3. Dietary treatment during gestation had no effect on feed intake of sows during the first week of lactation. However, feed intake of sows during the second week of lactation (P<0.01) the third week of lactation (P<0.01) and entire lactation period (P<0.01) increased linearly with increasing inclusion levels of KF.4. The inclusion of KF in gestation diet of sows had no effect on BW or backfat thickness gain during gestation or loss during lactation, and weaning-to-estrus interval of sows. However, the number of piglets weaned (linearly, P<0.05), pre-weaning survival rate (linearly, P<0.01; quadratic, P<0.05), litter weights on day14of lactation (linearly, P<0.01), average piglet weights and litter weights on day21of lactation (linearly, P<0.01), ADG of suckling piglets of the third week (linearly, P<0.01) and entire lactation period (linearly, P<0.05) increased with increasing inclusion levels of KF. In the fifth part, this study was conducted to investigate the mechanism of soluble fiber inclusion in gestation diets regulate postprandial satiety in pregnant sows and lactation feed intake of sows. The fifth part has the same experimental animal, diet and design with the fourth part. Viscosity, swelling and water-binding capacity of four diets were analyzed, and in vitro fermentation of four diets. During the second reproductive cycle, before feeding and1,2and4h postprandial on day90of gestation; Before feeding on day7of gestation, day0,7,14,21of lactation.20sows (5sows per dietary treatment), which had the same parity (3) were selected for blood sampling. During the second reproductive cycle, we measured the plasma concentrations of SCFAs and EFA before feeding and4h postprandial on d90of gestation; concentrations of glucose, insulin and leptin on day7and90of gestation, day0,7,14,21of lactation; Glucagon-like peptide1(GLP-1) or Peptide-YY (PYY) concentrations before feeding,1h,2h or4h postprandial on day90of gestation.The main results are as follows:1. The water-binding capacity (WBC)(from1.78to1.97g/g; P<0.01), swelling capacity (1.34,1.70,2.06and2.16ml/g, respectively; P<0.01), and viscosity (from1.62to2.14mPa-s; P<0.05) of gestation diets increased linearly with the increasing inclusion levels of KF.2. The inclusion of KF in gestation diet had no effect on propionic acid concentration after the in vitro fermentation of gestation diet. However, increasing the levels of KF linear increased concentrations of acetic acid (from11.31to19.03mmol/L; P<0.05), butyric acid (from1.14to1.92mmol/L; P<0.05) and total SCFA (from20.41to30.44mmol/L; P<0.05) after the in vitro fermentation of gestation diet.3. During the second gestation, there were no differences in plasma concentrations of pre-prandial SCFAs and EFA of sows among four treatments. However, plasma concentrations of acetic acid (from342.92to480.72umol/L), propionic acid (from14.33to21.68umol/L), butyric acid (from11.95to23.22umol/L) and total SCFA (from369.20to525.62umol/L)4h postprandial of sows were increased linearly with increasing inclusion levels of KF (P<0.05), and plasma concentrations of EFA4h postprandial of sows were decreased linearly with increasing inclusion levels of KF (P<0.01).4. There were no differences among four dietary treatments in plasma concentrations of leptin before feeding on day7,90of gestation, and day0,7,14,21of lactation, and the plasma concentrations of pre-prandial GLP-1and PYY. The plasma concentration of GLP-12h postprandial on d90of gestation was increased linearly (P<0.01) with increasing inclusion levels of KF.5. The inclusion of KF in gestation diet had no effect on plasma concentrations of glucose and insulin before feeding andlh,4h postprandial on day90of gestation, the value of HOMA-IS and HOMA-IR of sows on day7of gestation and day0,14,21of lactation. However, the value of HOMA-IS of sows on day90of gestation (P<0.01) and day7of lactation (P<0.01) were increased linearly with increasing inclusion levels of KF. While, the value of HOMA-IR of sows on day90of gestation (P<0.01) and day7of lactation (P<0.01) were decreased linearly with increasing inclusion levels of KF.In conclusion, there were significant different among different sources fibrous ingredients in fibrous components and physiochemical properties, and inclusion of fibrous ingredients in diet changed the physiochemical properties of the diet. The inclusion of konjac flour in gestation diets has no negative effects on the digestibility of nutrition, whereas enhanced postprandial satiety in pregnant sows, and increased lactation feed intake of sows. Compared with one reproductive cycle, feeding sows with dietary fiber during gestation for two reproductive cycles may be beneficial to improve reproductive performance of sows. During the gestation, sows fed with dietary fiber may be beneficial to enhance postprandial satiety of pregnant sows by increasing gastric distension by expanding their volume in the stomach and increaseing the plasma concentration of GLP-12h postprandial. Feeding sows with fibrous diet during gestation may be beneficial to increase the feed intake of sows during lactation by improving insulin sensitivity during late gestation and early or midterm lactation. These results strongly suggested that inclusion of dietary fiber of high WBC, swelling capacity and fermentability in gestation diet was beneficial for enhancing postprandial satiety in pregnant sows, increasing lactation feed intake and improving sow reproductive performance.