Effects of time of feeding during gestation on sow’s performance

Abstract

The aim of this study was to investigate the effect of different feeding time regimes given similar energy intake per kilogram live BW^0.75 during gestation on sow’s performance. One hundred and seventy-four sows [Topigs TN 70 (Landrace × Large White, Topigs USA); parity 3.81 ± 0.16; initial BW = 211.57 ± 3.34 kg; backfat (BF) 13.70 ± 0.42 mm] were blocked by parity, farrowing date, balanced for BW and randomly assigned to 1 of 3 treatments in a randomized complete block design. Treatments included sows fed corn-soybean meal-based diet once at [0730 (control, T1), 1130 (T2), or 1530 h (T3)], with daily feed quantity kept at 1.25× maintenance energy intake [100 × (BW)^0.75] kcal ME/d. Sows received 6,758, 7,434, and 8,110 kcal ME/d from days 30 to 60, days 61 to 90, days 91 to 109 of gestation, respectively. The gestation diet was formulated to contain 3,379 kcal of ME/kg, 0.70% Ca, 0.61% total P, 0.58% SID Lys, 0.26% SID Met, 0.45% SID Thr, 0.12% SID Trp, and 0.48% SID Met+Cys. Body weight and BF were recorded on days 30, 60, 90, and 109 of gestation, 24 h after farrowing and at weaning. Results showed that feeding times evaluated did not alter BW changes from day 30 to day 109 of gestation (P = 0.81) or from day 30 to weaning (P = 0.87). Similarly, feeding sows daily at 1130 h did not influence BF gains and sow reproductive performance relative to the control sows (P > 0.10). Sows fed once daily at 1530 h gained more BF compared with the control (3.69 ± 0.47 vs. 2.12 ± 0.50 mm, P = 0.04) from day 30 to day 109 of gestation. From day 30 of gestation to weaning, treatments did not influence BF gain (P = 0.24). Feeding sows daily meal at 1530 h had propensity to increase (P = 0.09) the number of piglets weaned by 0.54 piglets compared with the control sows. In conclusion, the present study demonstrated that feeding pregnant sows at 1530 h altered energy and nutrient metabolism improving their BF gain and exhibited a potential to increase the number of weaned piglets compared with conventional feeding regime.

INTRODUCTION

Nutritional intervention to control body composition of sows is of utmost importance. Feed restriction during the day constrains metabolism to alternate between storage and use of nutrients to ensure a continuous supply of energy to cells between meals (Le Naou et al., 2014). Supply of nutrients to cells may be coordinated with endogenous physiological rhythms such as glucose tolerance to optimize mammalian production and health (Nikkhah, 2012). Glucose tolerance in human dwindles as the day comes into night signifying the importance of meal timing. Wang et al. (2014) reported that consumption of more than 33% of daily energy intake as evening meal increased the risk of obesity compared with consumption of more than 33% of energy intake at or before 12:00 h. Also, nutritional outcomes differed by the timing of food intake under isocaloric conditions in mice (Arble et al., 2009). Furthermore, feeding time favorable for total growth (0730 h) differed from that auspicious to fattening (1600 h) in channel catfish (Noeske-Hallin et al., 1985). Conversely, evening and night feeding benefited ruminants through increased postprandial rumen VFA, surges of blood insulin, lactate, and beta-hydroxybutyrate secretions leading to increased milk fat synthesis and energy production (Nikkhah, 2012). Taking together, these studies suggest that timing of meals is a major external cue during the wake cycle and probably affects body weight regulation and production differently in different species. Data on how timing of meal affects pregnant sows under limit-fed condition are not known. We hypothesized that feeding the same amount of energy per kilogram live BW^0.75 at different time of day could alter energy and nutrient metabolism of gestation sows to influence their performance. The objective of this study was to investigate the effect of feeding time based on similar energy intake per kilogram live BW^0.75 during gestation on sow’s performance.

MATERIALS AND METHODS

Animals, Housing, and Management

The study was carried out at the swine unit of University of Minnesota Southern Research and Outreach Center, Waseca, MN. University of Minnesota Institutional Animal Care and Use Committee (IACUC) approved all protocols used in the study IACUC Number 171011961. Five cohort group of sows of Topigs Norsvin (Landrace × Large White); total N = 174; initial average BW 211.55 ± 3.42 kg; and average parity 3.8 ± 0.16 (with a range of 0 to 9) were artificially inseminated twice, 24 h apart during estrus using fresh diluted semen from Duroc boar (Compart Boar Store, Nicollet, MN).

Multiparous and nulliparous sows constituted 5 separate cohort groups: (cohort 1; n = 35), (cohort 2; n = 35), (cohort 3; n = 35), (cohort 4; n = 34), and (cohort 5; n = 35) derived from 2 farrowing herds out of the station’s 10 breeding groups. One of the 2 herds were sampled thrice (cohort groups 1, 3, and 5), whereas the other was sampled twice (cohort groups 2 and 4) from March 2016 to February 2017. Sows were kept in individual conventional gestation stalls with fully slatted floor measuring (2.1 m × 0.59 m × 0.97 m) under temperature-controlled environment (21 to 23 °C) on a 9 h of light and 15 h of dark schedule, with the light on at 0730 h and turned off at 1630 h. On the day 30 of gestation, sows were weighed individually before feeding and backfat (BF) thickness was measured using an ultrasound machine (Lean-Meater, Renco Corp., Minneapolis, MN). Measurements were taken at the last rib about 5 cm lateral from the dorsal midline on both left and right sides using soybean oil as coupling fluid, and the 2 readings were averaged. Sows that returned to estrus were excluded from the experiment after pregnancy check on day 35 postcoitum with the aid of ultrasonic pregnancy checker (Classic medical supply, Inc., FL). The conception rate was 88.3% for the 5 cohort groups sampled during the study. Throughout the experiment, sows had ad libitum access to water through nipple drinkers fitted to each pen or crate. On day 109 of gestation, sows were washed and transferred from gestation stalls to environmentally controlled farrowing rooms and placed in individual farrowing crates (213 cm × 97 cm × 66 cm) where they received a common lactation ration. Sows received 2.27-kg diet regardless of treatments from day 109 of gestation until parturition. After parturition, feeders were checked daily in the morning. Sows were fed twice daily at about 0800 and 1430 h daily. Feed offered was weighed and marked on individual sow card during feeding and the amount of feed offered increased gradually to allow for ad libitum feed intake without accumulation of feed in the feeder. Surplus feed was weighed and recorded once for each sow on the day of weaning.

Neonatal pigs were cross-fostered within treatment to equalize litter size of about 12 across sows within and limited to 24 h post-partum if it was required. Standard piglet management processing procedures of the farm includes intramuscular injection of 1-mL iron dextran shots, tail docking, cutting, and disinfection of naval cords within 72 h post-farrow. Supplemental heat lamp was provided to maintain a constant temperature for piglets after birth for 48 h while they had access to floor heat pads until weaning. The farrowing barn was maintained at 24 ± 2 °C during lactation. Piglets did not receive creep feed but had access to the dam’s feed. Surgical castration of the male piglets was accomplished between 5 and 12 d of age. Piglets were vaccinated 4 d prior to weaning. Weaning occurred between at 0800 and 1000 h on 18.9 ± 0.37 d post-partum. At weaning, sow BW and ultrasound BF thickness were recorded before transferring them to stalls in an environmentally controlled breeding facility where they were checked daily for signs of estrus using a mature boar housed in Contact-O-Max boar cart (Hog Slat Inc., Newton Grove, NC). Estrus was recorded when sows exhibited standing heat on exposure to the mature boar and estrous interval from weaning recorded. Removal of sows from the batch included failure to conceive after second mating, anestrous exceeding 8 d post-weaning, consecutive abortions, and difficulty to carry body weight on limbs. Feed offered to sows was restricted to 2 kg from weaning through breeding to 30 d, which is considered optimal for sows and gilt during that phase.

Experimental Design, Dietary Treatments, and Feed Line Calibration

Sows were blocked by parity, breeding date, and balanced for body weight and randomly allocated to 1 of 3 treatments with 11 to 12 replicates per batch in a randomized complete block design. All 5 cohort groups of sows received a common corn-soybean meal-based diet during gestation and lactation. Nutrients met or exceeded NRC (2012) nutrient requirements for gestation and lactation sows. The chemical compositions of diets are presented in (Table 1). Experimental treatments were imposed from 30 d of gestation until day 109 of gestation. Body weights on days 30, 60, and 90 were used to adjust the amount of feed fed between days 30 to 60, days 61 to 90, and days 91 to 109 of gestation, respectively. To standardize ME intake per kilogram live BW^0.75, the daily quantity of feed fed was scaled to the BW^0.75 live weight (Le Naou et al., 2014) and fed at 1.25 times (Prunier and Quesnel, 2000) the maintenance requirements for sows (100 × BW^0.75 kcal ME/d; NRC, 2012). On average, sows received 6,834; 7,434; and 8,110 kcal ME/d during the days 30 to 60, days 61 to 90, and days 91 to 109 of gestation, respectively. To provide a daily energy intake, sows received on average 2.0, 2.2, and 2.4 kg, from days 30 to 60, days 61 to 90, and days 91 to 109 of gestation, respectively. Sows were fed individually by raising the feeder ball valve of an Accu-Drop Feed Dispenser (AP Systems, Assumption, IL) to drop the required amounts of feed into the feeding troughs. The Accu-Drop feed dispensers were calibrated at the days 30, 61, and 91 at various set points and related the volume of feed dispenser (Y, cm³) to kilogram weight of feed (x) delivered as: Y = 5.4864x + 1.9087; R² = 0.9892. The required daily feed allowance was provided once daily at 0730 h (control, T1), 1130 h (T2), or 1530 h (T3).

Table 1.

Composition and nutrient analysis of gestation and lactation diets, as-fed basis

Ingredients, %	Gestation diet	Lactation diet
Corn, yellow dent	65.35	61.28
Soybean meal, dehulled, solvent extracted	10.00	17.20
Corn DDGS1, >6 but <9% oil	20.00	15.00
Choice white grease	1.50	3.00
Dicalcium phosphate	1.20	1.15
Limestone, ground	1.00	0.88
Sodium chloride	0.35	0.35
l-Lys-HCL	0.10	0.46
l-Thr	0.00	0.13
dl-Met	0.00	0.01
l-Trp	0.00	0.04
Swine breeder premix2 (EB Plus3)	0.50	0.50
Total	100.00	100.00
Analyzed composition
DM, %	89.34	89.60
GE, kcal/g	4,431.00	4,576.00
CP, %	15.70	17.90
NDF, %	13.30	12.00
ADF, %	4.80	4.50
Calculated nutrient composition
SID ME, kcal/kg	3,379.00	3,456.20
SID Lys, %	0.58	1.03
SID Met, %	0.26	0.28
SID Met+Cys, %	0.48	0.53
SID Thr, %	0.45	0.65
SID Trp, %	0.12	0.19
Total available P	0.61	0.61
Ca, %	0.70	0.66
Crude fat, %	6.30	7.40
SID Lys/ME, g/Mcal	1.71	2.96

¹DDGS = Dried distiller’s grains with solubles.

²Swine breeder premix was supplied by Agric-Nutrition Services, INC., Shakopee, MN.

³Mineral and vitamin mixture supplied per kilogram of diets: 15 mg of Cu (as CuSO₄); 124 g of Fe (as FeSO₄·7H₂O); 40 mg of Mn (as MnO); 124.7 mg of Zn (as ZnO); 2.2 mg of I (as Ca(IO₃)₂); 0.30 mg of Se (as Na₂SeO₃); 11,000 IU of vitamin A; 2,750 IU of vitamin D3; 55 IU of vitamin E; 4.4 mg of vitamin K3; 1.1 mg of thiamin; 9.9 mg of riboflavin; 55 mg of nicotinic acid; 33 mg of d-pantothenic acid; 2.2 mg of pyroxidine; 0.06 mg of vitamin B12; 2.6 mg of folic acid; and 0.22 mg of biotin; and 1.92 mg of Na.

Collection of Sow Performance and Reproductive Data

Sow performance and reproductive data were recorded during gestation and after farrowing, respectively. This includes total born, piglets born alive, number of stillbirth, count of mummified fetuses, birth weight, number weaned, and weaning weight. Return to estrous interval was recorded for each sow. Sow BW and BF thickness were recorded on days 30, 60, 90, and 109 of gestation, within 24 h of farrowing, and at weaning. These gestational stages were chosen as they represent completion of placentation process (day 30), midpoint of a period of high fetal death due to intrauterine competition (day 60), a period of rapid fetal demands for nutrients (day 90), and a point close to farrowing (day 109; Mesa et al., 2012). Approximately, 35 sows farrowed per batch and neonates from these sows were weighed within 24 h after farrowing. Three birth weight categories were used. Piglets weighing less than 1.25 kg (the minimum BW was 870 g), from 1.26 to 1.59 kg, and from 1.6 to 2.01 kg were classified as low birth weight, intermediate birth weight, and high birth weight, respectively (Douglas et al., 2014). Feed not consumed on the day of weaning was subtracted from the total feed offered to determine lactation feed disappearance. Sow lactation feed efficiency was measured as sum of sow BW loss (or gain) and litter weight gain relative to feed disappearance (Rosero et al., 2012). Sow and piglet mortality events were recorded daily.

Chemical Analysis

Duplicate samples of basal diets were analyzed for DM, GE, CP, NDF, and ADF and maintained a laboratory coefficient of variation of less than 5%. Moisture content of feeds was determined by the oven-drying method (method 934.01) as indicated by AOAC (2006). Gross energy was determined by bomb calorimeter using IKA WERKE c2000 basic bomb calorimeter (IKA Werke GmbH and Co. KG, Staufen, Germany) with benzoic acid in the samples for a standard. The CP content (N × 6.25) in the basal diet was determined using the Kjeldahl method (method 984.13, AOAC, 2006; Kjeltec 2300 Analyzer, Foss, Höganäs, Sweden). Determination of crude fat was by ether extract (method 920.39; AOAC, 2006) using an ANKOM XT15 extraction system (ANKOM Technology, Macedon, NY). Analysis for NDF and ADF was carried out using filter bag technique (ANKOM 2000 fiber analyzer, methods 12 and 13; ANKOM Technology, Macedon, NY; methods 973.18 and 973.19; AOAC, 2006). To determine the total ash content, samples of basal diet were weighed before and after ashing in a high-temperature muffle furnace at 600 °C for 6 h (Isotemp Muffle Furnace, Thermo Fisher Scientific Inc., Hampton, NH).

Statistical Analysis

Normality of the data sets was checked using PROC Univariate procedure of SAS 9.4 (SAS Inst., Inc., Cary, NC). Number of mummified fetuses, number of stillborn, 72-h mortality, and preweaning mortality data had excessive zeros and exhibited overdispersion. The data sets were analyzed using PROC GENMOD procedure of SAS with negative binomial distribution. The model provided deviance values of 0.73, 1.14, 0.87, and 0.81, respectively, for goodness-of-fit criteria. Other count and continuous sow reproductive data were analyzed as a randomized complete block design using PROC GLIMMIX with Poisson distribution and PROC MIXED procedures, respectively. The models included treatment group (time of feeding) as a fixed effect and block (batch of sows) as a random effect. Sow was the experimental unit in all analysis. Data collected repeatedly throughout sow’s gestation and lactation (BW, BF, BW changes, and BF changes) were analyzed as repeated measures ANOVA using the PROC MIXED procedure of SAS (SAS Inst. Inc., Cary, NC). The model included fixed effects of treatment, gestation day, and treatment × gestation day interaction while block was considered as random effects. Sow BW and BF at day 30 were used as covariate in the repeated measures model. Autoregressive process of first order was used to model repeated observation within sow as covariate structure (Littell et al., 1998). Least squares means of fixed effects with their corresponding SE were calculated using the LSMEANS statement of SAS. The estimation method was based on residual maximum likelihood. A chi-square test of homogeneity was used to determine the proportion of birth weight category amongst the treatments using the FREQ procedure of SAS. Data are presented as least squares means ± SEM. Differences between least squares means were requested using PDIFF option of SAS, and significant differences were declared at P ≤ 0.05, whereas a trend considered between 0.05 < P ≤ 0.10. The P values were adjusted for multiplicity based on the Tukey–Kramer method.

RESULTS

Treatment did not influence either sow BW or sow BW change in gestation or lactation (P > 0.05; Table 2). Sows fed once daily at 1130 and 1530 h had similar BF thickness at day 109 of gestation, farrowing, and weaning compared with the control group (P > 0.05). Sows that received their daily ration at 1130 h did not differ in terms of BF gain relative to the control sows during either gestation or lactation (P > 0.05). Conversely, sow fed once a day at 1530 h gain BF from day 30 to day 109 of gestation (P = 0.04), but not at the complete reproductive cycle (day 30 to wean; P = 0.24) compared with the control (0730 h) sows. Sow gestation ADG, lactation ADFI, wean to estrous interval, and efficiency of feed utilization during lactation were not affected by treatment and averaged 0.462 kg/d, 5.65 kg/d, 5.5 d, and 0.466, respectively (P > 0.05; Table 3). No differences in total piglet born, live piglet born, average piglet birth weight, number of piglets with low viability, number of mummified fetuses, number of stillborn, average weaning weight, piglets ADG, and adjusted litter weight gain were observed among treatment groups (P > 0.10). Number of piglets weaned tended to be 0.54 more piglets in sows fed once daily at 1530 h compared with the control group (10.87 vs. 10.33; P = 0.09). Treatment did not influence the proportion of birth weight category evaluated (χ² = 2.49; P < 0.64).

Table 2.

Main effect of treatment during gestation on sow performance (least squares means)¹

	Treatment
Item	T12	T23	T34	P-value
Number of sows	58	57	59	—
Body weight, kg
Initial day 30	211.97 ± 3.445	211.29 ± 3.42	211.40 ± 3.39	0.85
At day 109	247.97 ± 3.34	248.95 ± 3.42	247.35 ± 3.39	0.78
Farrowing	224.13 ± 3.34	227.42 ± 3.43	224.56 ± 3.39	0.56
Weaning	232.80 ± 3.34	230.86 ± 3.42	231.55 ± 3.37	0.86
Body weight gain6, kg
Days 30 to 109	37.03 ± 3.86	37.38 ± 3.83	35.88 ± 3.80	0.81
During lactation	8.34 ± 3.30	3.18 ± 3.74	7.04 ± 3.23	0.71
Day 30 to wean	20.79 ± 4.66	19.21 ± 4.64	19.92 ± 4.61	0.87
Sow BF, mm
Initial day 30	13.69 ± 0.42	13.64 ± 0.41	13.46 ± 0.41	0.66
At day 109	15.81 ± 0.42	16.18 ± 0.41	17.16 ± 0.40	0.19
At farrowing	13.70 ± 0.58	14.67 ± 0.54	15.35 ± 0.52	0.83
At weaning	13.81 ± 0.42	13.68 ± 0.41	14.64 ± 0.40	0.81
BF gain or loss6
Days 30 to 109	2.12 ± 0.50a	2.58 ± 0.50ab	3.69 ± 0.47b	0.04
During lactation	0.17 ± 0.47	−0.66 ± 0.45	−0.73 ± 0.45	0.17
Day 30 to weaning	0.11 ± 0.52	0.07 ± 0.52	1.02 ± 0.51	0.24

^a–bMeans within a row of treatment with uncommon superscripts differ (P ≤ 0.05).

¹Feed drops were adjusted on days 30, 61, and d 91 based on the BW of pigs on days 30, 60, and 90 of gestation, respectively.

²Received full daily ration of feed at 0730 h.

³Received full daily ration of feed at 1130 h.

⁴Received full daily ration of feed at 1530 h.

⁵Least squares means ± SE.

⁶BW and BF gain or loss were calculated as the difference between the final and the initial value.

Table 3.

Main effects of treatment on sow and reproductive performance during gestation and lactation (least squares means)¹

	Treatment
Item	T12	T23	T34	P-value
Number of sows	58	57	59	—
Initial BW, day 30	211.97 ± 3.335	211.58 ± 3.32	211.16 ± 3.37	0.85
Lactation length, d	19.70 ± 0.36	20.15 ± 0.36	19.78 ± 0.35	0.26
ADFI6 (days 1 to 18), kg	5.59 ± 0.31	5.58 ± 0.31	5.77 ± 0.31	0.71
ADG (days 30 to 109), kg	0.459 ± 0.05	0.474 ± 0.05	0.454 ± 0.05	0.81
Wean to estrous interval, d	5.47 ± 0.35	5.56 ± 0.35	5.54 ± 0.35	0.77
Sow lactation G:F	0.479 ± 0.03	0.441 ± 0.03	0.479 ± 0.03	0.20
Total pigs born	14.62 ± 0.61	14.08 ± 0.60	15.04 ± 0.58	0.36
No. born alive	12.02 ± 0.62	12.09 ± 0.61	13.00 ± 0.59	0.25
Mummified fetuses	0.32 ± 0.10	0.39 ± 0.12	0.34 ± 0.10	0.85
No. of stillborn	2.30 ± 0.36	1.59 ± 0.27	1.91 ± 0.29	0.40
Average birth weight, kg	1.39 ± 0.03	1.37 ± 0.04	1.38 ± 0.03	0.85
Litter size after cross-fostering	12.42 ± 0.41	12.49 ± 0.41	12.60 ± 0.40	0.91
72-h mortality, %	4.78 ± 1.66	5.58 ± 1.88	3.81 ± 1.21	0.63
Preweaning mortality, %	8.04 ± 1.98	7.99 ± 1.91	6.06 ± 1.37	0.40
Low viability piglets	1.04 ± 0.26	0.94 ± 0.26	0.83 ± 0.25	0.65
Pigs weaned7, days 18	10.33 ± 0.23x	10.78 ± 0.23xy	10.87 ± 0.22y	0.09
Average weaning weight, kg	6.00 ± 0.13	5.93 ± 0.13	5.99 ± 0.13	0.90
Adjusted litter weight gained	44.88 ± 1.75	46.71 ± 1.76	48.02 ± 1.68	0.32
Piglet ADG6, kg	0.233 ± 0.01	0.229 ± 0.01	0.233 ± 0.01	0.81

^x–zMeans within a row of treatment with uncommon superscripts tend to differ (P ≤ 0.10).

¹Feed drops were adjusted on days 30, 61, and 91 based on the BW of pigs on days 30, 60 and 90 of gestation, respectively.

²Received full daily ration of feed at 0730 h.

³Received full daily ration of feed at 1130 h.

⁴Received full daily ration of feed at 1530 h.

⁵Least squares means ± SE.

⁶Lactation length was used as covariate for average lactation feed intake and piglet ADG.

⁷Litter size after cross-fostering was used as covariate for number of piglets wean.

DISCUSSION

Nutritional outcomes differed by the timing of feed intake in many animal models under isocaloric conditions. The present study reports the impact of feeding pregnant sows at different time of the day under limit-fed conditions on sow’s performance.

Effect of Time of Feeding on Sow BW and BF Changes

The effect of time of feeding in pregnant sows and nutrient utilization by the gravid pig has not been studied. Under isocaloric conditions per kilogram live metabolic weight, feeding time did not influence sow BW and BW gain during either gestation or lactation. Excessive BW loss during lactation adversely impairs subsequent reproductive performance by extending the weaning to estrous interval (De Bettio et al., 2016). Consumption of total daily energy intake per kilogram live metabolic weight (BW^0.75) during gestation at different times of the day resulted in similar BW gain during lactation. Subsequently, wean to estrous interval did not differ with reference to feeding time ostensibly due to similar lactation feed intake observed. It was reported that BW loss greater than 12% during lactation extends the weaning-to-service interval in pigs (Eissen et al., 2003; Thaker and Bilkei, 2005). It can be inferred that the nutritional needs of the sows for energy were not compromised at the various feeding times in this study.

Sows fed once a day at 1530 h had increased BF gain during gestation. Feed restriction during the day constrains metabolism to alternate between storage and use of nutrients to ensure a continuous supply of energy to cells between meals (Le Naou et al., 2014). Supply of nutrients to cells may be coordinated with endogenous physiological rhythms such as glucose tolerance to optimize mammalian production and health (Nikkhah, 2012). Glucose tolerance in human dwindles as the day comes into night signifying the importance of meal timing. Backfat gained in sows fed at 1530 h could be attributable to time of feeding with its associated regulation of plasma triacylglycerols (TAG). Animal fats, including lard, are primarily composed of TAG, diacylglycerols, FFA, phospholipids, sterols, tocopherols, carotenoids, and fat-soluble vitamins, with the TAG being the main components (Rohman et al., 2012). In human studies, eating at night resulted in increased plasma TAG that remains elevated for longer period than response to the same meal given during the day (Sopowski et al., 2001; Johnston, 2014). Similarly, postprandial response to lunch provided approximately 50% less change in plasma TAG concentration than breakfast, although the plasma TAG fraction did not differ in palmitic acid concentration which was included in each meal (Burdge et al., 2003). Therefore, Burdge et al. (2003) concluded that the physiological basis for differences in postprandial TAG response could be independent of absorption or mobilization from the gut but rather to meal timing. It was reported that meal timing alters lipid profile postprandial and regulates adiposity by synchronizing local circadian rhythms in metabolically active tissues (Johnston, 2014). If this phenomenon is applicable to swine, we speculate that the increase BF thickness observed in sows fed at 1530 h could be attributed to elevated levels plasma TAG concentration, but the physiological mechanism for this observation remains to be elucidated and warrant further studies.

Although this study was conducted under limit-fed regime, our result resonates with a study reported by Wang et al. (2014) who stated that morning food intake was not related to obesogenic conditions in human but consumption of more than 33% of daily energy intake as evening meal increased the risk of obesity compared with consumption of more than 33% of energy intake at or before 12:00 h. However, for ethical reasons, direct quantification of adipose tissues mass gain associated with such feeding time is not usually undertaken in human studies making a direct comparison with our result difficult.

Effect of Time of Feeding on Sow Reproductive Performance

Neonatal piglet survival rate has declined and remains a major economic and welfare concern in modern pig production (Theil et al., 2014; Baxter and Edwards, 2018). One of the major findings in the current study was that sows fed once daily at 1530 h, tended to wean 0.54 more piglets per litter than sows fed once daily at 0730 h, although the total number of piglets born and litter size after cross-fostering were similar. This seems to be the first study to report the effects of feeding time on sow reproductive performance and definitive explanation for the tendency to increase the number of piglets wean are not clear to us. However, more than 50% of piglet preweaning mortality occurs during the first 3 d after farrowing (Hales et al., 2014; Phillips et al., 2014) due to inadequate colostrum intake, starvation and hypothermia (Kirkden et al., 2013). In addition, neonates have low reserves of glucose and fat at birth and therefore rely exclusively on colostrum and milk intake for their survival (Koketsu et al., 2017). An interesting observation made in this study was that sows fed once at 1530 h had increased BF thickness compared with the other sows that received the same amount of energy at other feeding times. It was also documented that besides dietary effects, the chemical composition of the colostrum and milk of sows depends on the body condition of the sows (Jin et al., 2018). Sows in good condition produced more milk, energy, and protein than thin sows (Klaver et al., 1981). It is therefore speculated that sows fed once daily at 1530 h exhibited high energy reserves to support colostrum and milk synthesis to enhance the piglet’s survivability during the first 3 d of life. Healthy piglets in the postnatal period are paramount to preweaning outcomes and likely to offset the negative impact associated with superprolific breeding programs to achieve production targets of 35 to 40 piglets per sow per year (Baxter, 2018).

The present study demonstrates that time of feed consumption is a critical regulator of body condition. The literature concerning the effects of time of feeding in pregnant sows to the best of our knowledge is absent, but our data suggest beneficial effect of BF gains in gestation sows under limit-fed condition. Similarly, evening and night feeding benefited ruminants through increased secretions of VFA, surges of blood insulin, lactate, and beta-hydroxybutyrate leading to increased energy production and milk fat synthesis (Nikkhah, 2012). Conversely, feeding at “inappropriate” time entrains rhythms in liver triglycerides and proteins into a phase opposite to the phase of physiological rhythms dictated by the master biological clock. Misalignment of the circadian rhythms resulted in reduction in glucose tolerance, downregulation of satiety hormone leptin in human (Scheer et al., 2009), inefficiency in energy expenditure, hepatic fat accumulation, physical inactivity, and adiposity in rat (Adamovich et al., 2014; Yasumoto et al., 2016). Therefore, further studies are required to evaluate potential welfare implications of such feeding times, metabolic profile, and its underlying circadian mechanisms in pregnant sows.

CONCLUSION

Under limit-fed conditions, feeding pregnant sows once daily at 1130 h did not change sow BW, BF, and reproductive parameters relative to sows fed at 0730 h. Consumption of total daily energy intake once daily at 1530 h was more beneficial for BF gained during gestation, tended to improve the number of piglets weaned, and supported normal reproductive performance in sows compared with conventional feeding time. Therefore, linking nutritional management techniques to time of feeding may enhance BF gains and number of piglets weaned during gestation and lactation, respectively.