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. 2021 Feb 7;99(2):skab040. doi: 10.1093/jas/skab040

Optimal feed level during the transition period to achieve faster farrowing and high colostrum yield in sows

Takele Feyera 1, Sigrid J W Skovmose 1, Signe E Nielsen 1, Darya Vodolazska 1, Thomas S Bruun 2, Peter K Theil 1,✉
PMCID: PMC8489418  PMID: 33550387

Abstract

This study aimed to determine the optimal supply of lactation feed during the transition period to minimize farrowing duration (FD) and maximize colostrum yield (CY) and quality with the overall aim of reducing piglet mortality. A total of 48 sows were stratified for body weight and assigned to six levels of feed supply (1.8, 2.4, 3.1, 3.7, 4.3, and 5.0 kg/d) from day 108 of gestation until 24 h after the onset of farrowing. The number of total born, live-born, and stillborn piglets; birth time and birth weight of each piglet; and frequency of farrowing assistance (FA) was recorded, and blood samples were obtained from newborn piglets at birth. Live-born piglets were further weighed at 12 and 24 h after birth to record weight gain, which in turn was used to estimate intake and yield of colostrum. Colostrum samples were collected at 0, 12, 24, and 36 h after the onset of farrowing. FD was shortest (4.2 h) at intermediate (3.7 kg/d), longest (7.1 to 7.6 h) at low (1.8 and 2.4 kg/d), and intermediate (5.6 to 5.7 h) at high (4.3 and 5.0 kg/d) feed intake (P = 0.004; mean comparison). FA was lowest (0.7% to 0.8%) at intermediate feed intake (3.7 and 4.3 kg/d) and substantially elevated (4.3% to 4.7%) at both lower and higher feed intake (P = 0.01; mean comparison). The cubic contrast revealed 4.1 kg/d as the optimal feed intake to achieve the shortest FD and to minimize FA. Newborn piglets from second-parity sows were less vital than piglets from gilts as evaluated by blood biochemical variables immediately after birth. CY was greatest at 3.1 kg/d (P = 0.04), whereas the cubic contrast revealed 3.0 kg/d as the optimal feed intake to maximize CY. Concentrations of colostral components were affected by the diet, parity, and their interaction except for lactose concentrations. In conclusion, the study demonstrated the importance of proper feed level during the transition period on sow productivity. Moreover, this study estimated 4.1 and 3.0 kg/d as the optimal feed intake during the transition period to improve farrowing characteristic and CY, respectively, and these two feed intake levels supplied daily 38.8 MJ metabolizable energy (ME) and 23.9 g standardized ileal digestible (SID) lysine (3.0 kg/d) or 53.0 MJ ME and 32.7 g SID lysine (4.1 kg/d). The discrepancy of optimal feed intake for optimal farrowing and colostrum performance suggests that it may be advantageous to lower dietary lysine concentration in the diet fed prepartum.

Keywords: energy supply, farrowing kinetics, sow nutrition, stillbirth, transition period, vitality

Introduction

Intensive breeding in the swine industry resulted in increased litter size over the last decades. However, large litter size has been associated with longer farrowing duration (FD; Canario et al., 2006), which is a risk factor for incidence of stillbirth (Langendijk and Plush, 2019). Langendijk and Plush (2019) suggested adaptive feeding strategy to speed up the farrowing process and thereby reduce the stillbirth rate (SR) should be implemented before the onset of farrowing. Feeding during the transition period could be a feasible strategy to improve the farrowing process and thereby reduce the SR. Feed supply is commonly reduced a few days before expected farrowing to minimize the risk of constipation in sows (Tabeling et al., 2003). However, a recent study emphasized that sows may be depleted of energy prior to or during farrowing (Feyera et al., 2018), which in turn increased the FD, incidence of SR, and farrowing assistance (FA). Dose–response studies during the transition period to investigate the impact on farrowing kinetics have not been done. Thus, it is crucial to determine the optimal level of feed intake during the transition period to reduce FD, SR, and incidence of FA.

Colostrum intake is crucial for short- and long-term survival of the piglet (Devillers et al., 2011), but it is limited by the sow’s capacity to produce colostrum in hyperprolific sows (Krogh, 2017). Sow colostrum yield (CY) is highly variable and factors of this variability are not well known (Farmer and Quesnel, 2009; Quesnel, 2011). Feeding during the transition period could explain part of this variability because colostral fat and lactose are produced mainly after the onset of farrowing (Feyera et al., 2019), and colostral fat has been shown to vary from 2.9% to 9.2% (Vadmand et al., 2015). Colostral protein is produced mainly before the onset of farrowing (Jönsson, 1973). The present study hypothesized that feeding levels during the last week of gestation will affect the energy balance and thereby influence the FD, FA, and SR as well as the yield and composition of colostrum. Therefore, the aim of this study was to determine the optimal level of feed intake required during the last week of gestation to minimize FD and SR and to maximize CY.

Materials and Methods

Housing and care of experimental animals complied with Danish laws and regulations for the humane care and use of animals in research (The Danish Ministry of Justice, Animal Testing Act [Consolidation Act number 726 of September 9, 1993, as amended by Act number 1081 on December 20, 1995]). The Danish Animal Experimentation Inspectorate approved the study protocol and supervised the experiment.

Handling of sows and piglets

A total of 48 sows (24 first- and 24 second-parity; DanBred Landrace × DanBred Yorkshire) were included in the experiment from day 108 of gestation until 24 h after the onset of farrowing. Sows were fed a standard diet throughout gestation according to the Danish feeding standard for gestating sows (Tybirk et al., 2018) until they were moved to the farrowing unit on day 108 of gestation. On this day, the sows and gilts were stratified for body weight (BW) and randomly assigned to one of six dietary treatments and individually housed in the farrowing crate until weaning. Sows were included in the experiment in two blocks of 24 animals per block.

Sows and their litter were individually housed on partly slatted floor in non-bedded farrowing crates (2.7 × 1.7 m). The room temperature was kept at 20 °C, and the light was turned on from 0630 to 1830 hours and from 2230 to 0030 hours during the night meal. Around the time of farrowing, the light was turned on 24 h a day. Each farrowing crate had a separate creep area for piglets, including cover, floor heat, and an infrared heating lamp to keep the ambient temperature of the creep area around 32 °C during farrowing. All sows farrowed naturally without farrowing induction. Farrowing was strictly monitored from the onset until the end to record the number of live-born, stillborn, total born piglets in the litter, birth time and birth weight of each piglet, and the frequency of FA in each litter. Assistance was given when the birth interval exceeded 60 min. Each newborn piglet was grasped and ear-tagged; live-born piglets were dried by sawdust and paper towel; the umbilical cord was closed with a plastic strip to prevent bleeding, shortened to 10 to 15 cm, and disinfected with iodine solution; and piglets were weighed before first suckling. All live-born piglets were weighed again individually at 12 and 24 h after the onset of farrowing to determine weight gain during the colostrum period, which in turn was used to estimate piglet intake and sow yield of colostrum.

Diets and feeding

From day 108 of gestation until weaning, sows were fed a wheat-, barley-, and soybean meal-based lactation diet optimized according to Danish recommendations for lactating sows (Tybirk et al., 2018; Table 1), and the chemical composition of the experimental diet is presented in Table 2. The diet was formulated to contain 13.44 MJ metabolizable energy (ME), 151 g crude protein, and 8.56 g standardized ileal digestible (SID) lysine per kilogram feed. Sows were randomly assigned to six feed levels (eight sows/feed level) and fed either 1.8, 2.4, 3.1, 3.7, 4.3, or 5.0 kg/d from day 108 of gestation until 24 h after the onset of farrowing. According to the Danish recommendations, sows should be fed 3.3 kg/d until 3 d before expected farrowing, and then reduced to 2.9 kg/d until the day after farrowing (Anonymous 2020). The present feeding levels were designed to create divergent feed intakes during the last week of gestation to investigate the impact on sow and piglet performance. Sows were fed three meals per day of equal size at 0700, 1500, and 2300 hours using a Spotmix feeding system (SpotMix Schauer Agrotronic GmbH, Prambachkirchen, Austria). Feed leftover was collected daily between 0900 and 1000 hours after the morning meal and used to calculate the realized feed intake. Feed samples were collected at the beginning and the mid of the week, pooled together, and kept at −20 °C until analysis.

Table 1.

Dietary ingredient and calculated chemical compositions of the experimental diet

Ingredients, g/kg feed as-fed Composition
 Wheat 380
 Barley 350
 Soybean meal 138
 Oat 50.0
 Sugar beet pulp 30.0
 Monocalcium phosphate 14.5
 Vegetable oil, fat, and soy 14.1
 Limestone (granulated) 11.4
 Sodium chloride 5.4
   l-Lys HCL (98.5%) 3.58
 l-Thr 1.32
 dl-Met 0.72
 l-Val 0.07
 Vitamin premix1 1.1
Calculated chemical composition, g/kg as-fed
 DM, g/kg feed 877
 Crude protein 155
 Fat 38
 Ash 56
 Starch 433
 Crude fiber 44
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1Supplied per kilogram of diet: 8,960 IU retinol; 2,000 IU 25-hydroxy vitamin D3 (HyD, DSM Nutritional Products, Basel, Switzerland); 167 mg α-tocopherol; 2.27 mg thiamin; 5.62 mg riboflavin; 22.7 mg niacin; 167 mg pantothenic acid; 3.35 mg pyridoxine; 5.94 mg folic acid; 0.02 mg cobalamin; 0.43 mg biotin; 4.32 mg menadion; 88.99 mg iron (FeSo4); 13.0 mg copper (CuSO4); 45 mg manganese (MnO), 103 mg zinc (ZnO); 0.23 mg iodine (Ca(IO3)2), and 0.38 mg selenium (Na2SeO3).

Table 2.

Analyzed chemical compositions of the experimental diet (g/kg DM) unless otherwise stated

Ingredients Composition
 DM, g/kg feed 869
 Gross energy, MJ/kg DM 18.3
 Crude protein 184
 Fat 47.2
 Ash 56.4
 Starch 433
 Lignin 24.9
 Nonstarch polysaccharides 185
 Dietary fiber 210
Minerals
 Ca 9.6
 K 8.9
 P 6.1
 Na 2.7
 Mg 1.8
 Fe, mg/kg DM 462
 Zn, mg/kg DM 147
 Mn, mg/kg DM 97.5
 Cu, mg/kg DM 28.8
Amino acids1
 Lys 10.4 (9.2)
 Thr 7.1 (6.0)
 Ile 6.7 (5.7)
 Leu 12.2 (10.5)
 His 4.1 (3.5)
 Phe 8.2 (7.1)
 Phe + Tyr 13.3 (11.4)
 Val 8.3 (6.8)
 Met 3.1 (2.8)
 Met + Cys 6.2 (5.3)
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1Value in parentheses shows the SID content of amino acids. The SID content of the amino acids was calculated from the analyzed content in diet (g/kg DM) corrected for the ratio between SID and total amino acids content in the diet formulation.

Blood sampling from the piglets

A single blood sample was collected from every fourth piglet within the birth order to measure blood biochemical variables that could be used as a biomarker to assess piglet vitality at birth. From the total of 845 live-born piglets, a single blood sample was collected from 290 piglets within 2 min of birth from the jugular vein into a 4-mL heparinized vacutainer tube using a G22 × 1″ 0.7 × 25 mm needle. Afterward, the sample was drawn from the vacutainer tube into a heparinized blood gas syringe for immediate analysis of blood biochemical variables. Blood samples were analyzed for blood gases and different blood biochemical variables using RapidPoint 500 System Gas Analyzers (Siemens Healthcare Diagnostics Ltd., UK) immediately after sampling.

Colostrum sampling

Colostrum samples were collected from the sows by hand milking at 0 (within 30 min after the birth of the first piglet), 12, 24, and 36 h relative to the birth of the first piglet in the litter. Except at 0 h colostrum sampling, an intramuscular injection of 2 mL oxytocin (10 IU/mL; Boxmeer, Holland) was used to facilitate the letdown of colostrum. Approximately, 50 mL of colostrum was collected at each sampling time, filtered through gauze, and kept at −20 °C until analysis. The volume of colostrum samples collected for chemical analysis was not included when estimating the CY.

Analytical procedures

All chemical analyses on the diet were performed in duplicate except for lignin, which was analyzed without repetition. The dry matter (DM) content was determined by drying to a constant weight at 103 °C for 20 h in a forced-air oven. Analyses for crude ash, nitrogen, crude fat, minerals, and amino acids (EC 152/2009) were conducted according to the Official Journal of the European Union (European Commission, 2009). Starch, nonstarch polysaccharides, and lignin were analyzed according to Bach Knudsen (1997). Gross energy was determined in an Automatic Isoperibol Calorimetry system (Parr Instrument Company, Moline, IL). Concentrations of fat, protein, lactose, and DM in colostrum were analyzed in duplicate by infrared spectroscopy (Milkoscan 4000, FOSS, Hillerød, Denmark).

Calculations

Dietary ME intake was calculated according to Theil et al. (2020) based on the intake of energy (in feed units per day) and calculated ME concentration in the diet (MJ ME/kg DM = 4.121 + 9.096 MJ ME/FUsow × FUsow/kg DM). The two constants (4.121 MJ ME/kg DM and 9.096 MJ ME/FUsow) refer to the intercept and the slope when converting from FUsow to MJ ME (on a DM basis in lactation diets). The FUsow/kg DM is the energy concentration in feed unit per kilogram DM and amounted to 1.18 FU/kg DM. The SID lysine was calculated from the analyzed content in the diet and the expected ratio between SID and total lysine content in the diet formulation and multiplied with daily feed intake to derive the SID lysine intake. The crude protein content of the diet was calculated as nitrogen × 6.25. Dietary fiber was calculated as the sum of total nonstarch polysaccharides and lignin. FD was calculated as the time lap from birth of the first piglet to that of the last born piglet in the litter. Colostrum intake of individual piglets during the first 24 h after the birth of the first piglet was estimated according to Theil et al. (2014), and yield was calculated by summing up colostrum intakes of all piglets in the litter.

Experimental design and statistical analyses

This experiment was regarded as a complete randomized design in which sows were stratified for BW and assigned randomly to one of six dietary treatments. All statistical analyses were performed using the SAS procedure (version 9.3, SAS Institute Inc., Cary, NC). The average daily feed intake, ME intake, SID lysine intake, sow BW and backfat thickness, FD, live-born piglets, total born piglets, blood biochemical variables, litter birth weight, litter live weight during the first 24 h after birth, and CY were analyzed using the MIXED procedure including feed level (1.8, 2.4, 3.1, 3.7, 4.3, and 5.0 kg/d), parity (gilt and sow), and feed level × parity as fixed effects. The incidence of SR and frequency of FA were analyzed using the GLIMMIX procedure (assuming binomial distribution), including feed level, parity, and feed level × parity as fixed effects. Piglet birth interval, piglet birth weight, piglet live weight, and weight gain during the colostrum period and piglet colostrum intake were analyzed using the MIXED procedure including feed level, parity, and feed level × parity as fixed effects and sow as a random effect. Piglet birth interval was log-transformed to stabilize the residual variance before performing the statistical analysis. Concentrations of fat, protein, lactose, and DM in colostrum were analyzed using the MIXED procedure, including feed level, parity, time of colostrum sampling (time: 0, 12, 24, and 36 h), and interaction between feed level × parity as fixed effects and sow as a random effect. The interaction between feed level and time of colostrum sampling did not show a significant effect on concentrations of colostral components; thus, it was omitted from the final model. For the repeated measurements in the above models (piglet traits and colostrum composition at different time points), sow was included in the model as a random effect to account for repeated measurements within sow by using variance component as the covariance structure.

In all of the above models, orthogonal polynomial contrasts were used to evaluate the linear, quadratic, and cubic effects of feed level within the final model. Coefficients of the orthogonal polynomial contrasts were generated by the IML procedure of SAS using the realized feed level in each group. When the quadratic and/or cubic polynomial contrast showed significance or a tendency on sow and piglet performance traits, an optimal value of the feed level was regressed from the cubic effect. Data are presented as least squared means and largest SEM within feed level, parity, and time of colostrum sampling. For SR, FA, and birth interval, the 95% confidence intervals are presented. The statistical difference was declared at P < 0.05 and tendency at P ≤ 0.10.

Results

Impact of feed level on sow and litter performance

The average daily intake of feed, ME, and SID lysine differed as expected with increasing feed level (P < 0.001; Table 3). An interaction between feed level and parity was observed for average daily feed intake, with greater average daily feed intake in second-parity sows than in gilts at the highest feed supply (4.9 vs. 4.4 kg/d, respectively; P < 0.001) and a tendency for greater intake when 4.3 kg/d of feed supplied (P = 0.10; Figure 1). FD was shortest (4.2 h) at intermediate (3.7 kg/d), longest (>7 h) at lower (1.81 and 2.44 kg/d), and intermediate (>5.5 h) at highest (4.3 and 5.0 kg/d) feed intakes (P = 0.004; mean comparison). Increasing feed supplied tended to decrease FD in a curvilinear manner (P = 0.07), which then increased when feed level exceeded 4.1 kg/d. FA was lowest (0.7% to 0.8%) at 3.7 and 4.3 kg/d and substantially elevated (4.3% to 4.7%) at both the lowest and highest feed intake (P = 0.01; mean comparison). The feed level decreased the FA in a curvilinear (P = 0.02) manner until it increased again when the feed level exceeded 4.1 kg/d. CY was greatest at 3.1 kg/d of feed level (P = 0.04), whereas the cubic contrast revealed 3.0 kg/d as the optimal daily feed level to maximize CY. There was no evidence for effects of feed level on sow body, total born, live-born, SR, litter birth weight, and litter BW during the first 12 h after birth. Except for FD and SR, parity affected all other sow performance traits.

Table 3.

Impact of feed level during the last week of gestation on productive performance of the sows (n = 8 sows/feed level)

Feed level (FL), kg/d Parity (P) P-value
Item 1.8 2.4 3.1 3.7 4.3 5.0 SEM Gilt Sow SEM Trt P FL × P Linear Quadratic Cubic Optimum1
Feed allowance, kg/d 1.75 2.41 3.04 3.71 4.33 5.00 0.04 3.34 3.41 0.02 <0.001 0.008 0.04 <0.001 0.02 0.09
Feed intake, kg/d 1.75f 2.41e 3.01d 3.71c 4.27b 4.63a 0.06 3.21b 3.38a 0.03 <0.001 <0.001 0.02 <0.001 0.10 0.21
ME intake MJ/kg DM 22.6f 31.1e 39.0d 47.9c 55.1b 59.9a 0.84 41.5b 43.7a 0.42 <0.001 <0.001 0.01 <0.001 0.10 0.21
SID Lys intake, g/kg DM 14.0f 19.2e 24.1d 29.6c 34.1b 37.0a 0.52 25.6b 27.0a 0.26 <0.001 <0.001 0.01 <0.001 0.10 0.21
FD, h 7.58a 7.11a 5.76ab 4.21b 5.61ab 5.71ab 0.80 5.75 6.25 0.43 0.03 0.47 0.28 0.02 0.07 0.36 [4.1]
FA, % 4.33ab 4.68a 1.43bc 0.77c 0.74c 4.72a [0.16;9.66] 0.71 5.93 [0.25;8.91] 0.02 <0.001 0.84 0.08 0.004 0.02 [4.1]
Stillbirth, % 8.31 5.86 5.17 3.89 4.66 6.83 [1.71;14.3] 4.84 6.52 [3.10;9.17] 0.64 0.28 0.09 0.42 0.12 0.63
Sow BW day 108, kg 272 266 267 267 265 266 7.7 247b 287a 4.3 0.99 <0.001 0.99 0.63 0.77 0.82
Sow BW day 2, kg 250 244 249 256 261 252 7.1 238b 266a 4.2 0.63 <0.001 0.97 0.27 0.93 0.18
Sow backfat day 108, mm 14.0 14.0 14.4 16.2 15.9 15.1 0.80 16.0a 13.8b 0.41 0.09 <0.001 0.11 0.04 0.39 0.12
Sow backfat day 2, mm 18.8 17.1 17.5 17.2 18.1 17.9 1.3 18.9b 16.6a 0.66 0.87 0.02 0.96 0.84 0.37 0.54
Live born 19.1 19.5 20.4 18.1 19.6 18.4 0.96 18.1b 20.2a 0.54 0.54 0.008 0.85 0.51 0.50 0.65
Total born 20.9 20.8 21.5 18.9 20.6 19.7 0.90 19.1b 21.7a 0.50 0.32 <0.001 0.43 0.24 0.99 0.64
Litter BW, kg 23.1 25.1 24.6 22.5 23.9 23.8 1.1 20.7b 26.9a 0.55 0.38 <0.001 0.82 0.79 0.68 0.11
Litter BW 12 h, kg 21.8 24.1 24.6 22.6 23.3 23.0 1.1 20.5b 26.0a 0.62 0.49 <0.001 0.45 0.85 0.19 0.18
Litter BW 24 h, kg 21.1 23.3 24.2 22.7 22.8 22.9 0.96 20.4b 25.3a 0.54 0.31 <0.001 0.37 0.44 0.10 0.16 [2.9]
CY 0 to 24 h, kg/sow 5.33b 6.26a 6.62a 6.32a 6.06ab 6.17a 0.27 5.37b 6.88a 0.15 0.04 <0.001 0.53 0.13 0.008 0.08 [3.0]
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1Optimal daily feed level was estimated for cubic contrast when the quadratic and/or cubic contrast showed significance (P < 0.05) or a tendency (P ≤ 0.10). Only the optimum for the cubic function is presented.

a–fMeans within a row with different superscript differ (P < 0.05).

Figure 1.

Figure 1.

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Interaction between feed level and parity for average daily feed intake in gilts (open triangle) and second-parity sows (solid triangle) fed increasing feed level from day 108 of gestation until 24 h after the onset of farrowing. †P = 0.10, ***P < 0.00. Values are LSMEANS and SEM; n = 8 sows/feed level.

Increasing feed level increased piglet weight gain in the first 12 h after birth in a cubic manner (P = 0.04; Table 4) with an optimum at 2.9 kg/d. Piglet birth weight (P = 0.001) and weight gain (P = 0.04) during the colostral period and piglet colostrum intake (P = 0.05) were lower in gilts than in second-parity sows but birth interval (P = 0.009) was greatest in gilts. There was no evidence for effects of feed level on birth interval, piglet birth weight, piglet colostrum intake, piglet weight, and weight gain during the first 24 h after birth.

Table 4.

Impact of feed level during the last week of gestation on the performance of the piglets (n = 8 sows/feed level)

Feed level (FL), kg/d Parity (P) P-value
Item 1.8 2.4 3.1 3.7 4.3 5.0 SEM Gilt Sow SEM Trt P FL × P Linear Quadratic Cubic Optimum1
Birth interval, min 7.90 8.61 5.74 6.56 6.54 7.64 [4.38;11.3] 8.31a 6.07b [5.18;9.82] 0.28 0.009 0.14 0.44 0.15 0.44
Piglet birth weight, g 1,164 1,197 1,179 1,206 1,212 1,236 49 1,132b 1,266a 28 0.94 0.001 0.24 0.29 0.90 0.79
Piglet BW 12 h, g 1,213 1,264 1,231 1,246 1,252 1,302 52 1,177b 1,327a 30 0.90 <0.001 0.51 0.34 0.76 0.47
Piglet BW 24 h, g 1,212 1,262 1,258 1,271 1,279 1,330 52 1,193b 1,344a 30 0.77 <0.001 0.50 0.14 0.91 0.54
Piglet weight gain 0 to 12 h, g 26.1 58.6 55.8 45.9 45.2 59.1 11 39.6b 57.2a 6.1 0.24 0.04 0.86 0.20 0.34 0.04 [2.9]
Piglet weight gain 0 to 24 h, g 32.7 43.7 60.1 68.4 58.7 75.9 14 50.2b 62.9b 8.0 0.28 0.24 0.82 0.02 0.59 0.72
Piglet colostrum intake 0 to 24 h, g 302 321 333 350 341 357 21 317b 351a 12 0.46 0.05 0.95 0.04 0.61 0.83
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1Optimal daily feed level was estimated for cubic contrast when the quadratic and/or cubic contrast showed significance (P < 0.05) or a tendency (P ≤ 0.10). Only the optimum for the cubic function is presented.

a,bMeans within a row with different superscript differ (P < 0.05).

Impact of feed level on blood biochemical variables

Anion gap was lower in newborn piglets from sows fed 3.7 kg/d as compared with newborn piglets from sows fed 2.4 kg/d (P = 0.005; Table 5). Concentrations of oxygen (P = 0.09) and oxyhemoglobin (P = 0.06) tended to be lower in newborn piglets from sows fed the lowest and the highest feed levels, and greatest for intermediate feed levels. Newborn piglets from gilts had greater concentrations of oxygen (P < 0.001), anion gap (P = 0.03), oxyhemoglobin (P < 0.001), oxygen saturation (P = 0.06), and hematocrit (P = 0.05) than piglets from second-parity sows. Concentrations of glucose (P = 0.08), lactate (P = 0.05), oxygen (P = 0.008), oxyhemoglobin (P = 0.002), and oxygen saturation (P = 0.007) showed a quadratic increase with increasing feed levels, whereas anion gap (P = 0.05), hemoglobin (P = 0.02), and hematocrit (P = 0.004) showed a cubic increase.

Table 5.

Impact of feed level during the last week of gestation on blood biochemical variables of the piglets at birth (n = 8 sows/feed level)

Feed level (FL), kg/d Parity (P) P-value
Item 1.8 2.4 3.1 3.7 4.3 5.0 SEM Gilt Sow SEM Trt P FL × P Linear Quadratic Cubic
Glucose, mmol/L 2.20 2.56 2.55 2.80 2.94 2.48 0.23 2.65 2.53 0.11 0.15 0.59 0.79 0.10 0.08 0.38
Lactate, mmol/L 5.12 5.76 5.72 5.84 5.24 4.64 0.52 5.72 5.05 0.26 0.29 0.09 0.83 0.37 0.05 0.97
pH 7.36 7.34 7.32 7.33 7.35 7.34 0.02 7.35 7.33 0.01 0.34 0.10 0.50 0.66 0.13 0.40
O2, mmol/L 3.50 4.66 4.29 4.19 4.28 3.89 0.28 4.53a 3.74b 0.12 0.09 <0.001 0.28 0.62 0.008 0.11
CO2, mmol/L 29.7 28.1 28.6 29.3 28.9 30.5 1.26 28.8 29.6 0.59 0.60 0.19 0.64 0.48 0.19 0.77
Ca2+, mmol/L 1.42 1.43 1.42 1.44 1.43 1.43 0.02 1.40b 1.45a 0.01 0.93 <0.001 0.12 0.53 0.73 0.66
Na+, mmol/L 137 138 137 138 136 139 0.89 138 137 0.46 0.17 0.09 0.05 0.57 0.82 0.13
K+, mmol/L 4.43 4.54 4.38 4.27 4.58 3.85 0.18 4.25 4.43 0.09 0.06 0.06 0.28 0.05 0.12 0.22
Ca2+(7.4), mmol/L1 1.38 1.39 1.37 1.39 1.41 1.40 0.02 1.37b 1.41a 0.01 0.16 <0.001 0.42 0.10 0.69 0.65
Anion gap, mmol/L 13.1ab 14.1a 13.0ab 11.7b 12.5b 12.8ab 0.78 13.3a 12.4b 0.36 0.03 0.03 0.14 0.15 0.57 0.05
Hemoglobin, mmol/L 6.78 7.19 7.26 6.91 6.87 6.73 0.21 7.18 6.91 0.11 0.12 0.08 0.41 0.53 0.67 0.02
Oxyhemoglobin, % 50.9 62.5 59.8 59.7 62.1 51.9 3.42 62.2a 53.5b 1.71 0.06 <0.001 0.20 0.81 0.002 0.88
Deoxyhemoglobin, % 41.3 35.6 39.3 38.3 36.8 45.8 3.49 36.2b 42.9a 2.01 0.22 0.005 0.87 0.46 0.11 0.64
Oxygen saturation, % 53.1 61.5 59.4 60.9 60.2 52.5 3.79 63.0a 52.8b 1.70 0.11 <0.001 0.22 0.90 0.007 0.92
Hematocrit, % 32.3 34.8 34.3 32.8 32.6 34.9 1.03 34.3a 32.3b 0.53 0.08 0.05 0.19 0.56 0.86 0.004
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1Measured at pH of 7.4.

a,bMeans within a row with different superscript differ (P < 0.05).

Impact of feed level on colostrum composition

Interactions between feed level and parity were observed for all colostral components (Figure 2). Concentrations of colostral fat decreased from 8.7% to 6.1% in second-parity sows, but varied less in gilts and showed no distinct pattern related to feed level (Figure 2A). The colostral concentration of lactose was greater in gilts when fed 2.4 kg/d but lower when fed 4.3 kg/d compared with second-parity sows (Figure 2B). Colostral concentrations of protein (Figure 2C) and DM (Figure 2D) were greater in second-parity sows when fed 2.4 kg/d but lower when fed 4.3 kg/d compared with gilts. Sows fed the lowest feed level had greatest concentrations of fat in colostrum, whereas the reverse was true for those fed the highest feed level (P < 0.001; Table 6). Concentrations of protein (P = 0.008) and DM (P = 0.04) intermittently increased and decreased with increasing feed level. Colostrum from gilts had greater concentrations of fat (P < 0.001) but lower concentrations of protein (P = 0.03) as compared with colostrum from second-parity sows. Concentrations of colostral fat (P < 0.001) and lactose (P < 0.001) increased, but those of protein (P < 0.001) and DM (P < 0.001) decreased with the progress of time after the onset of farrowing.

Figure 2.

Figure 2.

Open in a new tab

Interactions between feed level and parity for colostral composition of fat (A), lactose (B), protein (C), and DM (D) in gilts (open triangle) and second-parity sows (solid triangle) fed increasing feed level from day 108 of gestation until 24 h after the onset of farrowing. *P < 0.05, **P < 0.01, and ***P < 0.001. Values are LSMEANS and SEM; n = 8 sows/feed level.

Table 6.

Impact of feed level during the last week of gestation on sow colostrum composition (n = 8 sows/feed level)

Feed level (FL), kg/d Parity (P) Time
Item 1.8 2.4 3.1 3.7 4.3 5.0 SEM Gilt Sow SEM 0 h 12 h 24 h 36 h SEM
Fat, % 9.09a 7.51b 7.68b 7.57bc 7.71b 6.88c 0.30 8.41a 7.06b 0.17 6.38d 7.14c 7.97b 9.45a 0.24
Lactose, % 3.95 3.98 4.06 4.07 4.04 4.05 0.04 4.02 4.02 0.02 3.31d 3.94c 4.35b 4.50a 0.03
Protein, % 9.47b 10.5ab 9.69b 9.69b 11.0a 9.88b 0.35 9.76b 10.3a 0.19 16.5a 10.2b 6.95c 6.51c 0.27
DM, % 23.4a 22.6a 22.2b 22.2b 23.2a 21.7b 0.43 22.9 22.2 0.24 27.2a 22.1b 20.0c 20.9c 0.34
P-value
Trt P Time FL × P Linear Quadratic Cubic
Fat <0.001 <0.001 <0.001 <0.001 <0.001 0.15 0.002
Lactose 0.27 0.94 <0.001 <0.001 0.05 0.17 0.96
Protein 0.009 0.03 <0.001 <0.001 0.17 0.53 0.87
DM 0.04 0.03 <0.001 <0.001 0.06 0.57 0.04
Open in a new tab

a–dMeans within a row with different superscript differ (P < 0.05).

Discussion

Impact of feed level on farrowing kinetics

The present study was designed to reveal the optimal level of daily feed during the last week of gestation that would ensure a rapid farrowing process with the ultimate goal of reducing SR and incidence of FA. Accordingly, this study demonstrated the significance of feed level during the transition period for the farrowing kinetics and supports that sows may be depleted of energy, as indicated in our previous study (Feyera et al., 2018). The present study showed that both FD and FA could be minimized by choosing the appropriate feed level during the transition period. Both shorter FD and minimal FA were achieved when sows and gilts were supplied 4.1 kg/d. Although SR was not decreased statistically due to fairly low sample sizes, the lowest SR was also observed around that feed level. Results indicate that energy intake was the most limiting factor for the farrowing kinetics at low feeding levels. A recent study observed a faster farrowing process at high (33.8 MJ ME/d) as compared with low (28.2 MJ ME/d) energy intake during late gestation (Che et al., 2019).

The total energy requirement of sows during farrowing is currently unknown but speculated to be comparable with the energy cost of moderate-to-heavy endurance exercise (van den Bosch et al., 2019). A lowered feed supply to 2.5 or 3.0 kg/d has previously been recommended in some European countries beginning 2 to 3 d before expected farrowing to reduce constipation (Tabeling et al., 2003) and health problems, such as metritis, mastitis, and agalactia (Cerisuelo et al., 2010). This study revealed that there is no need to reduce the feed level prior to farrowing and that it would be better to supply 3.5 to 4.0 kg/d the last days before parturition. Based on the optimal feed level from the cubic model and ME content of the diet, 53 MJ ME/d was calculated as the optimal energy intake for the farrowing sow result in shortest FD and minimal FA. If the sows used in this study weighed 270 kg and their maintenance energy requirement was 0.464 MJ ME per metabolic BW (Theil et al., 2002), then their daily maintenance energy requirement would be 32 MJ ME. In late gestating sows, activity-related heat production amounts to approximately 4 MJ/d (Theil et al., 2002). Assuming that the time sows standing approximately doubled during the last day before farrowing due to nest-building behavior, they would spend another 5 MJ ME on this behavior. Taking into account that fetal energy deposition should be minor on the day of farrowing, the current findings suggest that the energy cost of a sow farrowing is around 16 MJ ME. Consequently, the previous recommendation of supplying less feed the last few days before expected farrowing would be detrimental for sow performance. On the other hand, FD increased when feed supply exceeded the optimal level, suggesting that physical blockage of the birth canal (due to increased digesta fill in the hindgut) may have the opposite effect and compromise the farrowing process. In line with this, Danielsen (2003) reported an increased incidence of metritis–mastitis–agalactia in sows fed ad libitum (5.9 kg/d) during the last week of gestation compared with sows fed restrictedly (3.0 kg/d). The interaction between feed level and parity revealed that gilts had lower feed intake than second-parity sows at high feeding levels, most likely reflecting a lower gastric capacity. As a result, physical blockage of the birth canal could be speculated to be less pronounced in gilts than multiparous sows.

The negative impact of prolonged FD on SR was previously reported (Feyera et al., 2018; DeRouchey et al., 2019; Langendijk and Plush, 2019). The majority of stillborn piglets are presumable alive when the farrowing process starts but complications during farrowing, such as prolonged FD and asphyxia, could exacerbate intrapartum SR (Friendship et al., 1990; Peltoniemi et al., 2014). Management strategies to minimize the farrowing complications and thereby reduce SR have been suggested (Langendijk and Plush, 2019), and the present results show the potential beneficial impact of optimizing the feed supply during the transition period to improve the productivity of hyperprolific sows.

Impact of feed level on CY

Studies to maximize sow CY are very limited, and nutritional trials have not been very successful in improving CY. This could be associated with the recent indication that colostral lactose and fat are mainly produced after the onset of farrowing (Feyera et al., 2019). In the present study, CY was maximized at a feed level of 3.0 kg/d. Previously, Decaluwé et al. (2014) observed a tendency for increased CY in sows fed 4.5 kg/d compared with 1.5 kg/d during the last week of gestation. However, Wiegert (2019) did not observe any difference in CY from sows fed increasing feed levels (1.5, 3.0, and 4.5 kg/d) from day 104 of gestation until farrowing. Surprisingly, Mallmann et al. (2019) observed a linear decrease in CY in gilts fed increasing feed levels (1.8, 2.3, 2.8, and 3.3 kg/d) from day 90 of gestation until farrowing. Colostrum production is highly variable among sows (Farmer and Quesnel, 2009; Quesnel, 2011) and transition feeding alone could not explain such variations. Sow body condition during late gestation (Decaluwé et al., 2014), parity (Devillers et al., 2007), piglet characteristics (Quesnel, 2011), and plasma metabolites (Loisel et al., 2014) have been reported to influence CY. Loisel et al. (2014) reported a positive correlation between CY and plasma concentrations of creatinine and urea at late gestation. This is in contrast with current findings whereby urea concentrations were not correlated with CY and plasma concentrations of triglycerides were negatively correlated with CY (r = −0. 47; P = 0.003, data not shown).

The increase in CY with increasing feed level to a maximum at 3.0 kg/d suggests that lysine and in turn protein intake relative to energy intake may be more important for maximizing the CY than the feed level per se. According to the present study, the lysine requirement during the transition period to achieve maximum CY would be 24 g SID. Ji et al. (2005) and Samuel et al. (2012) determined 15.3 and 16.4 g/d SID lysine as a requirement during late gestation in sows bearing 10.5 and 14.6 litters, respectively. In the present study, litter size ranged from 14 to 26 with an average litter size of 20.4. In hyperprolific Danish sows with very large litter size, a greater demand for lysine during the transition period could be expected because fetal protein deposition accelerates in late gestation (McPherson et al., 2004; Samuel et al., 2012). Moreover, mammary growth increases rapidly during the last 10 d of gestation (Ji et al., 2006) along with increased synthesis of colostral bioactive components during these days (Jönsson, 1973; Palombo et al., 2018), thereby increasing the demand for lysine.

Impact of feed level on blood biochemical variables in piglets

In the present study, feed levels had no significant impact on the majority of blood biochemical variables in piglets, except for the anion gap. In human studies, an elevated anion gap (18 to 42 mmol/L) is an indicator of metabolic acidosis (Gabow, 1985; Kraut and Madias, 2007) and hypoxia during birth (Randolph et al., 2014). To the best of our knowledge, there is no reference on anion gap for the newborn piglets. However, it is unknown whether the risk of hypoxia is the same in human babies and piglets during the birth process, but it could be expected to be more severe in piglets since sows are litter-bearing mammals.

The impact of parity was more pronounced than that of feed levels on the concentrations of blood biochemical variables in piglets. Reduced piglet vitality has been associated with increased blood lactate and CO2 concentrations and reduced blood pH (Herpin et al., 1996). Concentrations of lactate and pH tended to be greater and lower, respectively, in piglets born from second-parity sows compared with piglets born from gilts. The lower concentrations of oxygen, hemoglobin, oxyhemoglobin, oxygen saturation, and hematocrit observed in this study in piglets born from sows compared with piglets born from gilts further support a lower vitality in piglets born from sows. The greater litter size and longer FD observed in sows vs. gilts could partly explain this. Greater concentrations of glucose and higher pH, hemoglobin, and hematocrit values in piglets at birth were reported to be associated with increased survival (Rootwelt et al., 2012).

Impact of feed level on colostrum composition

The present study showed a significant effect of feed level on concentrations of macronutrients in colostrum, except for lactose. Indeed, lactose is the least-variable colostral component and is hardly influenced by the diet (Declerck et al., 2015). The strong interactions between feed level and parity on colostrum concentrations of macronutrients in the present study reflect the differential response of gilts and sows to a similar feeding strategy. The concentration of fat was strongly affected by feed level, parity, and their interaction, and the linear decrease with increasing feed level was most pronounced in sows. A decrease in milk fat was also observed in lactating sows in response to increasing energy supply (Verstegen et al., 1985). The fact that sows fed the lowest feed level had greater concentrations of colostral fat could suggest that a low energy intake triggered fat mobilization and, consequently, increased colostral fat. Colostral fat is highly influenced by the type and amount of fat fed but not by the amount of feed supplied (Farmer and Quesnel, 2009). Similar to the present study, Pedersen et al. (2019) observed greater concentrations of fat in colostrum from gilts as compared with colostrum from sows. It is not obvious why gilts and sows responded so differently to increasing feed level with respect to colostral fat concentrations. It could be related to the fact that not only gilts have to prioritize between their own body growth and that of their offspring but it is also likely due to a slightly lower energy requirement of young gilts as compared with sows (~0.3 kg/d).

Optimizing FD and CY at similar feed level

The fact that FD and CY were optimal at different feed levels strongly suggests that a transition diet would be more adequate than the lactation diet commonly used in late gestation, which is rich in dietary nutrients (amino acids, minerals, and vitamins). In support of this, Pedersen et al. (2020) reported that sows produced 5% more colostrum when fed a gestation diet as compared with a lactation diet during the last week of gestation, and 2% more colostrum when sows were fed a 50:50 mixture. However, it should be emphasized that these differences were not statistically different. Since maximum CY was achieved at a lower feed level than minimum FD, it could be favorable to lower the dietary concentrations of lysine and (protein) when sows are fed a lactation diet in late gestation. The diet used in the current study was a lactation diet containing 9.2 g SID lysine/kg DM, which is substantially greater than the lysine content of the gestation diet (6.2 g SID lysine/kg DM) used by Pedersen et al. (2020). The use of two-component feeding strategy, a basal and a lactation component, as described by Feyera et al. (2020) could be an alternative approach to a transition diet because it allows the supply of energy and lysine to be partly separated by changing the daily proportion of each component at each meal.

Conclusions

The present study demonstrated that feed level in the transition period affects farrowing dynamics and CY in hyperprolific Danish sows. It was shown that, not only too low, but also too high, feed levels during the transition period had negative consequences on the farrowing process. The FD was shortest and FA was minimized at a feed level of 4.1 kg/d, and insufficient and excess feed intakes increased FD, FA, and SR. Furthermore, 3.0 kg/d was estimated as the optimal feed level to optimize sow CY. The disparity of optimal feed intake to meet the requirement of energy for the farrowing process and lysine for colostrum production suggests that it may be advantageous to lower lysine concertation of the lactation diet or use a transition diet intermediate in lysine and protein to maximize farrowing and colostrum performance at the same feed intake.

Acknowledgments

This research was supported by funds from the Danish Ministry for Food, Agriculture and Fishery (Grønt udviklings og demonstrationsprojekt, [GUDP, grant 34009-18-1340]). We would like to acknowledge Maria Eskildsen, Geonil Lee, Trine Friis Pedersen, Sophie van Vliet, Liang Hu, Uffe Krogh, and the stable personnel for their help during the practical experiment.

Glossary

Abbreviations

BW

body weight

CY

colostrum yield

DM

dry matter

FA

farrowing assistance

FD

farrowing duration

ME

metabolizable energy

SID

standardized ileal digestible

SR

stillbirth rate

Conflict of interest statement

The authors declare that there are no conflicts of interest.

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