J. Anim. Sci. 2004. 82:2964-2971
© 2004 American Society of Animal Science
Effects of additional starch or fat in late-gestating high nonstarch polysaccharide diets on litter performance and glucose tolerance in sows1,2
C. M. C. van der Peet-Schwering*,3,
B. Kemp
,
G. P. Binnendijk*,
L. A. den Hartog
,
P. F. G. Vereijken
and
M. W. A. Verstegen
* Applied Research Division of Animal Sciences Group, Wageningen UR, 8203 AD Lelystad, The Netherlands;
and
Wageningen Institute of Animal Sciences, Wageningen UR, 6700 AH Wageningen;
and
Nutreco Agriculture Research and Development, 5830 AE Boxmeer, The Netherlands; and
and
Biometris, Wageningen UR, 6700 AC Wageningen
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Abstract
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The effects of feeding additional starch or fat from d 85 of gestation until parturition on litter performance and on glucose tolerance in sows that were fed a diet with a high level of fermentable nonstarch polysaccharides (NSP) were studied. The day after breeding, 141 multiparous sows were assigned to the experiment. At d 85 of gestation, sows were assigned to the treatments. Sows were fed 3.4 kg/d (as-fed basis) of a high-NSP diet or the same quantity of the high-NSP diet and an additional 360 g of starch (from wheat starch) daily, or the same quantity of the high-NSP diet and an additional 164 g of fat (from soybean oil) daily. During lactation, all sows were given free access to the same lactation diet. Approximately 1 wk before the expected time of parturition, an oral glucose tolerance test was performed in 38 randomly chosen sows by feeding pelleted glucose (3 g/kg BW0.75). Blood samples for glucose analyses were taken at –10, 10, 20, 30, 40, 50, 60, 70, 80, 90, 105, and 120 min after glucose was fed. The supply of additional dietary starch or fat did not increase piglet birth weight or total litter weight at birth. Sows that were fed the high-NSP diet had more (P = 0.097) live-born piglets and fewer (P = 0.084) stillborn piglets than did sows that were fed additional fat, whereas sows that were fed additional starch were intermediate for these variables. Piglet mortality after birth was not affected by dietary treatment. Body weight and backfat gains in the last month of gestation were higher for sows fed additional starch or fat than for sows fed the high-NSP diet (P < 0.001 and P = 0.017, respectively). Feed intake in lactation was greatest by sows fed the high-NSP diet, least by sows fed additional starch at the end of gestation, and intermediate by sows fed additional fat (P = 0.099). The differences in lactation feed intake did not result in differences in BW and backfat losses during lactation. Sows that were fed additional fat had the greatest glucose area under the curve (P = 0.044), indicating that these sows were less tolerant to glucose. In conclusion, feeding additional energy (starch or fat) in late-gestating sows that are fed a high-NSP diet did not increase litter weight at birth or piglet survival, but did increase maternal gain. Feeding sows additional energy from fat might induce glucose intolerance, whereas feeding sows additional energy from starch did not induce glucose intolerance.
Key Words: Fiber • Glucose Tolerance • Polysaccharides • Reproduction • Sows
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Introduction
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High levels of fermentable nonstarch polysaccharides (NSP) in diets for gestating sows reduce stereotypical behavior, probably due to decreased hunger (Vestergaard, 1997
; Van der Peet-Schwering et al., 2003b). Piglet birth weight, however, is lower in sows fed a high-NSP diet during gestation than in sows fed a starch diet (Van der Peet-Schwering et al., 2003a). A deficiency in glucogenic energy in sows fed a high-NSP diet, especially at the end of gestation, might explain the lower birth weight of the piglets. Glucose is required for fetal development (Père et al., 2000). In high-NSP diets, the starch content is generally low and, therefore, these diets may provide insufficient glucogenic energy to sustain optimal fetal growth at the end of gestation. It can be hypothesized that in case of a shortage of glucogenic energy, feeding sows additional starch (glucogenic energy) at the end of gestation will increase the birth weight of the piglets, whereas feeding sows additional fat (lipogenic energy) would not affect birth weight. To meet the increasing demand for glucose by the fetuses, insulin sensitivity and glucose tolerance in sows decrease after 85 d of gestation (Schaeffer et al., 1991; Père et al., 2000). The rate of glucose use by maternal tissues decreases, which allows for improved placental transfer of glucose. This improved placental transfer may result in hyperinsulinism and hyperglycemia in the fetuses. Hyperinsulinism can cause extreme hypoglycemia 1 to 1.5 h after birth, resulting in postnatal death (Sepe et al., 1985). Indeed, Kemp et al. (1996) reported greater piglet mortality in sows that were less glucose tolerant. Feeding sows additional energy at the end of gestation may induce glucose intolerance in sows (Kemp et al., 1996). Therefore, this experiment was conducted to determine the effects of feeding additional starch or fat from d 85 of gestation to parturition on litter performance and on glucose tolerance in sows that are fed a high-NSP diet.
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Materials and Methods
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Animals, Experimental Design, and Housing
The day after breeding, a total of 141 rotationally bred (involving the breeds: Dutch Landrace; Finnish Landrace; and Dutch Large White) multiparous sows were allotted to the experiment. At d 85 of gestation, sows were assigned to the treatments based on parity number and BW. Mean parity number of the sows was 4.8 (SD = 0.4). Three treatments were applied from d 85 of gestation until parturition. Sows in the control group were fed a high-NSP diet. Sows in the extra-starch group received an additional 580 g of wheat starch daily (equivalent to 500 g of starch containing 6.7 MJ of glucogenic NE; glucogenic energy mainly comes from glucose) compared with the control group. Sows in the extra-fat group received an additional 200 g of soybean oil daily (equivalent to 198 g of fat containing 6.7 MJ of lipogenic NE; lipogenic energy mainly comes from lipids) compared with the control group. The wheat starch and soybean oil, respectively, were not top-dressed but were incorporated in the total diet. Due to differences in the calculated and analyzed contents of starch and fat in the diets and due to feed refusals, the contrasts between treatments were somewhat smaller than intended. Daily starch and fat intakes were 270 and 176, 630 and 171, and 282 and 340 g, respectively, in sows that were fed the high-NSP, extra-starch, or extra-fat diet. Thus, sows in the extra-starch and extra-fat groups received additional daily amounts of starch and fat of 360 g and 164 g, respectively, rather than 500 g and 198 g, respectively. During gestation, sows were housed individually in stalls of 2.00 x 0.64 m. The stalls had partly slatted floors that consisted of a 0.90-m concrete solid floor and a 1.10-m concrete-slatted floor. Approximately 10 d before the expected time of parturition, sows were moved to farrowing rooms, each with six 2.20 x 1.80 m pens. The concrete solid floor (1.00 x 1.80 m) was equipped with floor heating. Crossfostering of piglets took place within 3 d of parturition and occurred only among sows of the same experimental treatment. Crossfostering was used in cases where large or small litter sizes occurred. Piglets were weaned at an average age of 27.5 d (SD = 2.3). All rooms were equipped with computer-controlled heating and mechanical ventilation systems. The care and treatment of the sows were according to Dutch animal welfare legislation. The institutional Animal Care and Use Committee of the Wageningen University approved all experimental protocols.
Diets and Feeding
Until d 85 of gestation, all sows were fed the high-NSP diet. From d 85 of gestation until parturition, sows were fed the high-NSP diet, the extra-starch diet, or the extra-fat diet (Table 1). The extra-starch diet contained (as-fed basis) 85.4% of the high-NSP diet and 14.6% of wheat starch. The extra-fat diet contained (as-fed basis) 94.5% of the high-NSP diet and 5.5% of soybean oil. Gestating sows were fed twice per day (0800 and 1500). The daily amount of feed (as-fed basis) increased during gestation (d 0 to 60: 2.5 kg/d; d 60 to 85: 2.9 kg/d). From d 85 to parturition, sows were fed 3.40 kg/d of the high-NSP diet (according to Van der Peet-Schwering et al., 2003a), 3.98 kg/d of the extra-starch diet (equivalent to 3.40 kg of the high-NSP diet and 0.58 kg of wheat starch), or 3.60 kg/d of the extra-fat diet (equivalent to 3.4 kg of the high-NSP diet and 0.20 kg of soybean oil), respectively. Due to feed refusals, the actual daily feed and energy intakes from d 85 of gestation until parturition were 3.38 kg and 28.5 MJ of NE, 3.89 kg and 34.6 MJ of NE, and 3.54 kg and 34.8 MJ of NE, respectively, in sows that were fed the high-NSP diet, the extra-starch diet, or the extra-fat diet. From parturition until weaning, all sows were fed the same lactation diet (Table 1). Sows were fed on an ascending scale from parturition until d 6 after parturition and were given free access to the lactation diet from d 6 after parturition until weaning. All feeds were given in the pelleted dry form. During gestation, drinking water was supplied twice daily for 1 h (0800 to 0900 and 1500 to 1600). In the farrowing room, sows were given free access to drinking water. Piglets were given free access to a commercial creep feed (CHV-Landbouwbelang, Veghel, The Netherlands; 9.82 MJ of NE/kg; 177 g of CP/kg; 10.5 g of ileal digestible lysine/kg; 3.5 g of digestible P/ kg) from d 11 after birth until weaning.
Measurements
Feed and Feed Intake.
Experimental diets were sampled weekly. The weekly samples were pooled over a 3-mo period. Feed was analyzed every 3 mo for DM, ash, CP, crude fat, starch, and sugars. All samples were analyzed in duplicate. The contents of DM, ash, CP, and crude fat were analyzed according to standard methods ISO 6496 (ISO, 1999b), ISO 5984 (ISO, 1978), ISO 5983 (ISO, 1979), and ISO 6492 procedure B (ISO, 1999a), respectively. The starch content was analyzed enzymatically by the method of Brunt (2000). The sugar content was analyzed by the method of Luff Schoorl (EG, 1971). Dietary NSP was calculated as dietary DM minus dietary ash, CP, crude fat, starch, and sugars. Feed intake of the sows was recorded from d 85 of gestation until parturition and during wk 1, 2, 3, and 4 of the lactation period, respectively. In addition, creep feed intake of the piglets was recorded.
Sow and Piglet Performance.
Individual BW and back-fat thickness of the sows were measured at d 84 of gestation, at the day of transfer to the farrowing room and at weaning. Backfat thickness was measured ultrasonically at three points 5 cm left of the median as described by Vesseur et al. (1997). The number of total piglets born (live-born piglets plus stillborn piglets plus mummies) and the individual weights of the live-born piglets and stillborn piglets were recorded within 16 h of parturition. Time and cause of piglet mortality during the suckling period were recorded. At weaning, the number of weaned piglets and individual weights of the weaned piglets were recorded.
Oral Glucose Tolerance Test.
Approximately 1 wk before the expected time of parturition, an oral glucose tolerance test was performed in 65 randomly chosen sows. Twenty-seven of the 65 sows did not eat the total amount of glucose administered within 10 min postfeeding and were therefore omitted from the statistical analysis. After an overnight feed withdrawal, sows were fed pelleted glucose (3 g/kg BW0.75) at 0800. Blood samples were taken (after making a small incision in the tail) from the sows at –10, 10, 20, 30, 40, 50, 60, 70, 80, 90, 105, and 120 min after glucose was fed (Kemp et al., 1996). Glucose concentration in each blood sample was measured immediately using the Glucosemeter Elite (Bayer Diagnostics, Mijdrecht, The Netherlands; accuracy = 7.5%). For each sow, the following characteristics were calculated: basal (–10 min sample) glucose concentration, maximum increase in glucose concentration, time of the maximum concentration, area under the entire 120-min curve, and area under the curve for the first 70 min (Kemp et al., 1996). The glucose peak ended approximately 70 min after glucose was fed; therefore, area under the curve for the first 70 min was calculated. The maximum increase in glucose concentration was calculated by subtracting the basal glucose concentration from the maximum glucose concentration achieved. The areas under the curves (AUC) from 0 to 120 min and from 0 to 70 min were calculated as the area above basal glucose concentrations by integrating the observed glucose concentrations (minus the basal glucose concentration) using the extended trapezoidal rule formula (Abramowitz and Stegun, 1965).
Statistical Analyses
Body weight and backfat thickness of the sows, changes in BW and backfat thickness, number of total piglets born, piglet birth weight, total litter weight at birth (birth weight of live-born piglets plus birth weight of stillborn piglets), piglet weaning weight, and feed intake by sows and piglets during lactation were analyzed by means of F-tests using generalized linear models for the fixed effects of dietary treatment during the last month of gestation, genotype, and parity of the sow (Parity 3, 4, 5, or 
6). Number of total piglets born was used as a covariate in the analysis of piglet birth weight and total litter weight at birth. The BW at d 84 and backfat thickness at d 84 were used as covariates in the analysis of BW gain and BW loss, and backfat gain and backfat loss, respectively. Live-born piglets, stillborn piglets, postnatal deaths from birth to d 3 and from birth to d 7, and weaned piglets were analyzed by means of F-tests using logistic regression (McCullagh and Nelder, 1989) for the fixed effects of dietary treatment during the last month of gestation, genotype, and parity of the sow. Live-born piglets and stillborn piglets were expressed as a fraction of total piglets born. Piglet mortality from birth to d 3 was expressed as a fraction of live-born piglets. Piglet mortality from birth to d 7 and weaned piglets were expressed as a fraction of live-born piglets after fostering. Response variables with repeated measurements, such as weekly feed intake during lactation, were analyzed by using a split-plot model. The fixed effect of week and the random effect of sow were added to the model. The random sow effect was considered to be normally distributed with mean equal to 0 and variance equal to 
. Glucose characteristics were analyzed by means of F-tests using generalized linear models for the fixed effects of dietary treatment during the last month of gestation and genotype. Estimates of fixed effects in the model and components of variance were obtained using the residual maximum likelihood procedure. Fixed effects were assessed using 
2 for the Wald statistics. After a significant overall test, pairwise differences between treatment means were tested using a t-test. All analyses were performed using the statistical program GenStat (2000).
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Results
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Litter Performance
The number of total piglets born, birth weigh of live-born piglets, birth weight of stillborn piglets, total litter weight at birth, number of piglets after fostering, piglet mortality from birth to d 3 or 7 after birth, weaned piglets (expressed as percentage after fostering), and piglet weaning weight did not differ among sows that were fed a high-NSP diet and sows that were fed additional starch or fat at the end of gestation (Table 2). Live-born piglets (expressed as percentage of total born piglets) was higher in sows that were fed the high-NSP diet than in sows that were fed additional fat at the end of gestation, whereas it was intermediate in sows that were fed additional starch (P = 0.097; Table 2). Stillborn piglets (expressed as percentage of total born piglets) was lower in sows that were fed the high-NSP diet than in sows that were fed additional fat, whereas it was intermediate in sows that were fed additional starch (P = 0.084; Table 2).
Body Weight and Backfat Thickness
Body weight gain from d 84 of gestation until the day of transfer to the farrowing room was higher in sows fed additional starch or fat at the end of gestation than in sows fed the high-NSP diet (P < 0.001; Table 3). Backfat gain from d 84 gestation until the day of transfer to the farrowing room was higher in sows fed additional fat at the end of gestation than in sows fed the high-NSP diet, whereas it was intermediate in sows fed additional starch (P = 0.017; Table 3). Body weight and backfat losses in the farrowing room were not affected by dietary treatment in the last month of gestation (Table 3).
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Table 3. Body weight and backfat thickness of sows as affected by dietary treatment from d 85 of gestation until parturition
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Feed Intake
In wk 1 and 2 of lactation, feed intake by the sows was not affected by dietary treatment during the last month of gestation. In wk 3 of lactation, however, sows fed the high-NSP diet ate more than sows fed additional starch or fat in the last month of gestation (P = 0.014; Table 4). In wk 4 of lactation, sows fed additional starch at the end of gestation ate less than did sows in the other two experimental treatments (P = 0.078). Overall feed intake during 4 wk of lactation was greatest by sows fed the high-NSP diet, least by sows fed additional starch at the end of gestation, and intermediate by sows fed additional fat (P = 0.099).
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Table 4. Feed intake (as-fed basis) of sows and piglets as affected by dietary treatment from d 85 of gestation until parturition
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Glucose Tolerance
Basal glucose concentration, maximum increase in glucose concentration, and time of the maximum concentration were not affected by dietary treatment in the last month of gestation (Table 5). Areas under the entire 120-min curve and under the curve for the first 70 min were higher in sows fed additional fat in the last month of gestation than in sows fed the high-NSP diet or in sows fed additional starch (P = 0.044 and P = 0.098, respectively). The highest glucose concentrations were measured at 40 min after glucose was fed (Figure 1).
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Table 5. Glucose characteristics in sows at d 108 of gestation as affected by dietary treatment from d 85 of gestation until parturition
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Figure 1. Mean glucose concentrations (mmol/L) before and after glucose was fed to sows (from –10 to 120 min) at d 108 of gestation as affected by dietary treatment from d 85 of gestation until parturition. Sows were fed 3.4 kg/d of a high-nonstarch polysaccharide (NSP) diet (high NSP) or the same quantity of the high-NSP diet and an additional 360 g of starch (from wheat starch) daily (extra starch), or the same quantity of the high-NSP diet and an additional 164 g of fat (from soybean oil) daily (extra fat).
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Discussion
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The supply of additional dietary fat in late-gestating sows fed a high-NSP diet did not increase piglet birth weight or total litter weight at birth. These results are in agreement with those found by Sinclair et al. (2001) and Averette Gatlin et al. (2002). In a review, Pettigrew and Moser (1991) also reported that fat supplementation during late pregnancy had no effect on piglet birth weight. Moreover, the supply of additional dietary starch in late-gestating sows fed a high-NSP diet did not increase piglet birth weight or total litter weight at birth. This finding suggests that the supply of glucogenic energy in late-gestating sows that are fed a high-NSP diet is sufficient for fetal growth. Daily starch plus sugar intake in the last month of gestation in sows that were fed the high-NSP diet, the added-starch diet or the added-fat diet were 534, 895, and 542 g/d, respectively. Thus, a daily intake of approximately 550 g of starch plus sugar in late-gestating sows seems sufficient for fetal growth. Van der Peet-Schwering et al. (2003a) reported a lower birth weight of the piglets in sows that were fed a high-NSP diet during gestation compared with those that were fed a starch diet. In that study, the higher number of live-born piglets in sows that were fed the high-NSP diet probably explains the lower piglet birth weight.
The number of stillborn piglets was greatest in sows that were fed additional fat. These results contrast those of Shurson et al. (1986) and Stahly et al. (1986). In their studies, the number of stillborn piglets was not affected by supplemental dietary fat at the end of gestation. Averette Gatlin et al. (2002), however, reported an increase in the number of stillborn piglets when late-gestating sows were fed a diet with 10% supplemental fat; however, they did not have an explanation for this increase in stillborn piglets. It might be that sows that are fed additional fat in late gestation are less glucose tolerant and that therefore stillborn piglets are increased. Sows that were fed additional fat at the end of gestation had the greatest glucose AUC (Table 5
), which indicates that these sows were less tolerant of glucose. Studies in rodents have also shown that high-fat feeding results in an increase in insulin resistance and consequently in an increase in glucose intolerance (Kraegen et al., 1991). Schaeffer et al. (1991) reported that the number of stillborn piglets tended to be higher in sows that were less glucose tolerant.
Weldon et al. (1994) indicated that feeding gestating sows extra energy might cause glucose intolerance. In our study, however, feeding additional starch at the end of gestation did not increase glucose intolerance in sows. The glucose AUC in sows that were fed additional starch was not increased compared with sows that were fed the high NSP-diet. In a study with grazing mares that were fed supplemental dietary energy (starch and sugar or fat and fiber) similar results were found (Hoffman et al., 2003). Mares that were fed supplemental starch and sugar had higher basal glucose concentrations, lower glucose AUC, and a more rapid glucose clearance rate than mares that were fed additional fat and fiber. These results indicated that mares that were fed supplemental starch and sugar had a superior glucose tolerance. An adaptation to high starch levels in mares and sows that were fed additional starch and sugar (mares and sows were adapted to the diets for 4 mo and 3 wk, respectively) probably explains the improved glucose tolerance. Thus, it seems that feeding late-gestating sows extra energy from fat may induce glucose intolerance, but that feeding sows extra energy from starch does not induce glucose intolerance.
Kemp et al. (1996) reported increased piglet mortality in the first 7 d after birth in sows that were less glucose tolerant at d 104 of gestation. In our study, sows that were fed additional fat were less glucose tolerant and, therefore, higher piglet mortality could be expected. Piglet mortality, however, was not affected by gestation feeding regimen (Table 2). Moreover, the reason for mortality was not affected by gestation feeding regimen. In fact, in most studies, there was no effect of feeding supplemental dietary fat in late gestation on piglet mortality after birth (Pettigrew, 1981; Azain, 1993). Moreover, in some studies, survival rate among piglets was increased, especially when late-gestating sows were fed medium-chain triglycerides (Azain, 1993; Jean and Chiang, 1999). Medium-chain triglycerides are rapidly metabolized to ketone bodies that can readily cross the placenta and probably spare glucose for glycogen synthesis and, hence, increase the glycogen stores (Jean and Chiang, 1999).
Body weight and backfat gains in the last month of gestation were higher in sows that were fed additional starch or additional fat than in sows that were fed the high-NSP diet. The higher BW and backfat gains can be explained by higher daily energy intakes. It has frequently been demonstrated that a higher energy intake during gestation increases backfat thickness at farrowing and decreases voluntary feed intake of the sows during lactation (Dourmad, 1991; Revell et al., 1998). Our results agree, although voluntary feed intake during lactation was only slightly decreased in sows that were fed additional starch or additional fat in late gestation. Revell et al. (1998) found that an increase in backfat thickness at parturition from 17.9 to 24.3 mm resulted in a decrease in lactation feed intake of 1.6 kg/d. In our study, the differences in back-fat gain were 0.7 and 1.2 mm for sows that were fed additional starch or additional fat, respectively, compared with the high-NSP diet. Therefore, only small differences in lactation feed intake could be expected. Probably as a result of the only small differences in feed intake during lactation, BW and backfat losses during lactation were similar in sows that were fed the high-NSP diet and in sows that were fed additional starch or additional fat.
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Implications
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The supply of additional energy (starch or fat) in late-gestating sows that are fed a diet with a high level of nonstarch polysaccharides did not increase litter weight at birth, but it increased maternal gain. This suggests that a daily intake of approximately 550 g of starch and sugar in late gestation is sufficient for fetal growth and that it is not necessary to supply additional energy to late-gestating sows that are fed a diet with a high level of nonstarch polysaccharides. Feeding late-gestating sows additional energy from fat tended to increase stillborn piglets (expressed as a percentage of total born piglets) and increased the area under the curve for glucose, indicating that feeding additional fat may result in sows that are less glucose tolerant. Feeding late-gestating sows additional energy from starch did not affect glucose tolerance.
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Footnotes
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1 This research was financially supported by the Institute of Sugar Beet Research (Bergen op Zoom, The Netherlands), by Danisco (Copenhagen, Denmark), and by the Netherlands Agency for Energy and the Environment (Sittard, The Netherlands). 
2 The technical assistance of H. Diepstraten is gratefully acknowledged.
3 Correspondence: P.O. Box 2176 (phone: +31-32029 3211; fax: +31-32024 1584; e-mail: carola.vanderpeet{at}wur.nl).
Received for publication October 7, 2003.
Accepted for publication June 30, 2004.
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Abstract
Introduction
