Precision Feeding in Lactating Sows Improves Growth Performance and Carcass Quality of Their Progeny

Abstract

The use of electronic sow feeders (ESFs) during lactation has been associated with weaning of heavier piglets when compared to traditional feeders, with a lower amount of sow feed per kg of weaned piglet, improved welfare of the sow, and no negative effects on body condition or metabolic traits at weaning or subsequent reproductive yields. However, there have been no studies assessing the possible effects of ESF use on the lifelong development of the progeny. This study reveals that piglets weaned from sows fed with ESFs were heavier than those from sows fed with traditional feeders (5.91 ± 1.45 vs. 5.58 ± 1.23 kg, p < 0.005), with a lower amount of feed per kg of weaned piglet (2.41 ± 0.42 vs. 1.88 ± 0.28 kg, p < 0.0005). Subsequent differences in body weight increased due to a higher average daily weight gain during both the periods of nursery (0.332 ± 0.92 vs. 0.312 ± 0.80 kg/day, p < 0.01) and growing–finishing (0.921 ± 0.11 vs. 0.871 ± 0.09 kg/day, p < 0.001). Finally, the weights of the carcasses and primal pork pieces (ham, shoulder, loin, and belly) were also higher in pigs from sows fed with ESFs (p < 0.001 for all).

1. Introduction

Nutrition and feeding strategies are the main factors affecting the outputs and profitability of swine production [1]. Specifically, maternal nutrition and feed intake during lactation are critical for ensuring the viability and adequate growth of the suckling offspring, leading to heavier piglets at weaning [2]. Moreover, adequate nutrition—and, hence, better body condition of the sows at weaning—will result in a shorter weaning to estrus interval and thus higher fertility, prolificacy, and productivity of the following cycle [3].

At present, the profitability of swine production is boosted by the use of hyperprolific sows, which are characterized by increased numerical productivity (i.e., the number of piglets weaned per productive sow and year) but are more prone to nutritional and metabolic disorders, compromising the viability and growth of their piglets and the resumption of reproductive activity after weaning [4]. Hence, it is necessary to adopt specialized nutritional strategies to fulfill the nutritional needs of these sows.

In this scenario, precision livestock feeding (PLF) approaches—specifically electronic sow feeders (ESFs)—have emerged in response to this need, serving as tools that allow for continuous monitoring of a sow’s intake and, therefore, adaptation of the feeding strategy to the body condition and reserve mobilization of the sow during lactation [5,6,7]. Sows fed with ESFs wean heavier piglets than those fed with traditional feeders, leading to remarkable decreases in both feed wastage (i.e., fewer kilograms of feed per weaned piglet) and body weight losses, such that the return to estrus and productive outputs in the following cycle are not diminished (and may even be improved) [8,9].

Weaning heavier piglets improves their later performance during the periods of nursery and growing–finishing; in particular, heavier piglets require simpler and cheaper diets and achieve higher feed intake, lower mortality, and the target weight in a shorter time to [10,11,12]. Most existing studies on the use of ESFs in lactating sows have focused on the growth and production costs of piglets during the suckling phase; however, to the best of our knowledge, there have been no studies assessing the possible long-term effects on the developmental traits of the piglets.

Given these considerations, the present work aimed to determine possible differences in the growth patterns and metabolic and welfare status—from lactation to slaughterhouse—of pigs whose mothers were fed with either ESFs or traditional feeders. In addition, our study also assessed possible differences in the characteristics of the carcass and primal pork pieces (i.e., ham, shoulder, loin, and belly).

2. Materials and Methods

2.1. Ethics Statement

This research was carried out in 2024, according to the European Union Directive and the Spanish Policy for Animal Protection RD53/2013. The Committee of Ethics in Animal Research of the Universidad Complutense de Madrid (UCM) assessed and approved the experimental procedures (CEEAH2788M2).

2.2. Animals, Management, and Experimental Procedure

A total of 942 Danbred × Pietrain crossbred pigs were born from 45 multiparous sows (from second to seventh parity) housed in farrowing crates from one week before delivery to the day of weaning. These sows were distributed equally in two experimental groups, according to their productive history and body weight and condition. Therefore, the first group of sows were housed in farrowing crates with traditional feeders (Group CON; n = 24 sows and 501 piglets), with the possibility of feeding twice per day (at 8:00 and 14:00 h), while the remaining females were housed in farrowing crates with electronic feeders (Group ESF; Gestal SOLO+, Jyga Technologies Inc., Quebec City, QC, Canada; n = 21 sows and 441 piglets), with the possibility of feeding six times per day (5:00, 8:00, 11:00, 14:00, 17:00, and 20:00 h). The diet consisted of a standard grain and soy-based food diet (16.1% crude protein, 5.0% fat, and 2.36 Mcal/kg metabolizable energy; see Supplementary Table S1). The amount of feed served to and refused by each sow during the lactation period, from the day of farrowing to the day of weaning, was individually recorded daily (manually in Group CON and automatically by the electronic feeder in Group ESF), in order to determine the amount of feed disappearance (including feed intake and wastage, as previously described [8,9]) and thus the amount of feed per weaned piglet and per kg of weaned piglet.

Immediately after birth, the number of total, live, and stillborn piglets and the mean litter weight at farrowing (recorded using a litter scale; MPigData, Mensoft, Madrid, Spain) were recorded per sow. All living piglets were immediately sexed, individually identified with electronic ear tags, and weighed. Subsequently, within-group cross-fostering and allocation to mothers were performed at a rate of 16 piglets/sow, with similar birth weights. Hence, further studies involved 384 piglets in Group CON and 336 piglets in Group ESF. Creep feeding was offered to the piglets from 14 days of age.

At weaning (at 24 days old), all piglets in both groups (342 piglets in CON and 304 piglets in ESF) were mixed together, allowing for the same conditions during the subsequent periods, and moved to a nursery farm, where they remained for 42 days (to around 68 days old). Subsequently, all pigs in both groups (314 pigs in CON and 281 pigs in ESF) were moved to a growing–finishing farm until being processed at the slaughterhouse at 192 days old. At the nursery, all the piglets were fed the same standard diet (18% crude protein, 4.5% fat, and 3.35 Mcal/kg of metabolizable energy; see Supplementary Table S2). At the growing–finishing farm, all the pigs were fed with the same diet (15.1% crude protein, 2.8% fat, and 3.08 Mcal/kg of metabolizable energy; see Supplementary Table S3).

2.3. Growth-to-Target

The piglets were individually weighed at birth, at weaning (at 24 days old, when starting the nursery period), and at the beginning and end of the growing–finishing period (at around 68 and 192 days old, respectively). At 14 days old, when creep feeding was allowed, a subset of 180 piglets was selected to be weighed again and sampled in order to assess possible differences in metabolic and welfare status. These piglets were randomly selected among a representative population in each litter (n = 4 in each litter, avoiding the smallest and largest piglets). The average daily weight gain (ADWG; for the intervals of 0–14 and 14–24 days old in these piglets, and 0–24, 24–68, and 68–192 days old) was individually determined in all piglets using the formula ($\left[\mathrm{f}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}-\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\right]/\mathrm{n}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r} \mathrm{o}\mathrm{f} \mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}$).

2.4. Metabolic and Welfare Status

Saliva and blood samples were obtained in the selected subset of 180 piglets for determination of their welfare and metabolic status.

Saliva samples were used to assess the welfare status during the lactation and nursery periods. At 14 days old, samples were collected with sterile dry swabs attached to a polypropylene tube (Deltalab, Plz. Verneda 1, Pol Ind La Llana, 08191 Rubí, Barcelona, Spain) for assessment of the cortisol concentration via enzyme immunoassay (ELISA) using a previously described technique [13]. At 31 days old (i.e., one week after weaning), in the nursery, the pigs were larger, and the samples were collected with polypropylene sponges (Koronis ref. SKU 030004, La Griega E. Koronis, Madrid, Spain) clipped to flexible thin metal rods, which were placed in each pig’s mouth to be chewed. The sponges were then immediately placed into Salivette^® tubes (SARSTEDT S.A.U., La Roca del Vallès, Spain), centrifuged at 3500× g for 10 min at room temperature (around 20 °C), and the saliva was then immediately stored at −80 °C until analysis via ELISA for quantification of the salivary cortisol (Expanded Range High Sensitivity Salivary Cortisol Enzyme immunoassay Kit, Salimetrics, Carlsbad, CA, USA) and alpha-amylase (Salivary Alpha-Amylase Kinetic Enzyme Assay Kit, Salimetrics, Carlsbad, CA, USA [14]).

Blood samples were taken to assess the metabolic status at weaning. At 24 days old, just prior to weaning, samples were drawn via puncture of the cranial vena cava (cava cranialis) using EDTA vacuum tubes (Vacutainer Systems Europe, Meylan France) and immediately centrifuged at 1500× g for 15 min (Nahita-Blue, Innovagen, Madrid, Spain) at room temperature (around 20 °C). The plasma was immediately separated and stored at −80 °C until further analysis. The plasma concentrations of glucose, fructosamine, total protein content, and lipids (total cholesterol, high- and low-density lipoprotein cholesterol [HDL-c and LDL-c, respectively], and triglycerides) were assessed using a clinical analyzer (Konelab 20i, Thermo Fisher Scientific, Madrid, Spain) [15].

2.5. Productive Yields at Slaughterhouse

At the slaughterhouse, the carcass weights were recorded for 295 pigs in Group CON and 264 pigs in Group ESF, and the carcass yields were obtained using the formula ($[\mathrm{c}\mathrm{a}\mathrm{r}\mathrm{c}\mathrm{a}\mathrm{s}\mathrm{s} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}/\mathrm{b}\mathrm{o}\mathrm{d}\mathrm{y} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}]/100$). An evaluation of the carcass quality was carried out using Autofom (Frontmatec-Intecal S.A.U, Hospitalet de Llobregat, Spain). Autofom is a fully automatic 3D ultrasound scanner for carcasses that provides information on the total lean percentage of the carcass, backfat depth, loin depth, subcutaneous fat depth of the ham, and main yields (total weight with and without bone, lean percentage and total lean weight) of the primal pork pieces (ham, shoulder, loin, and belly) [16,17].

2.6. Statistical Analysis

The data were analyzed using SPSS 22.0 (IBM, New York, NY, USA). The analyses assessed the effects of the maternal feeding system (CON vs. ESF) on the developmental traits (changes in weight over time), the metabolic and welfare status, and the productive yields (weight and quality of the carcass and main pieces) of the piglets, which were considered the experimental unit; the model also took sex into consideration. For a comparison of single-point data, parametric analysis of variance (ANOVA) or the non-parametric Mann–Whitney U-test were performed, according to the data distribution. Changes over time were assessed via ANOVA for repeated measures, considering time and sex as fixed effects, after using a Kolmogorov–Smirnov test for verification of normal distribution. Variables that did not fit a normal distribution were analyzed using a non-parametric Kruskal–Wallis test. Possible effects of birth weight on the development, homeostasis or productive performance of the piglets were assessed via both analyses of covariance and Pearson correlation tests. All data are presented as the mean ± SD, with statistical significance being accepted from p < 0.05, whereas 0.10 > p > 0.05 was considered a trend.

3. Results

3.1. Growth to Target

At farrowing, there were no significant differences between the sows in Groups ESF and CON in terms of the mean number of piglets (19.71 ± 3.03 vs. 20.12 ± 5.57 piglets, p = 0.120) or the weight of either the total litter (24.55 ± 3.31 vs. 24.65 ± 3.90 kg, p = 0.655) or individual piglets (1.22 ± 0.28 vs. 1.20 ± 0.26 kg, p = 0.162); see

Table 1. Mean (±SD) body weight and average daily weight gain of piglets born from sows fed with electronic or traditional feeders during lactation.

Group	BW Day 0	BW Day 14	ADWG 0–14	BW Day 24	ADWG 14–24	ADWG0–24
ESF	1.22 ± 0.28	4.11 ± 0.86	0.207 ± 0.06	5.91 ± 1.45	0.226 ± 0.10	0.205 ± 0.05
CON	1.20 ± 0.26	3.64 ± 0.74	0.180 ± 0.06	5.58 ± 1.23	0.191 ± 0.13	0.182 ± 0.05
p-Value	0.162	<0.001	0.448	0.002	0.045	0.059

ESF: electronic sow feeders; CON: traditional feeders; BW: body weight (kg); ADWG: average daily weight gain (kg/day, $\left[\mathrm{f}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}-\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\right]/\mathrm{n}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r} \mathrm{o}\mathrm{f} \mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}$).

.

The assessment of changes in the body weight of the piglets during the lactation period showed a higher increase in relation to their birth weight for Group ESF (4.50 ± 1.32 kg vs. 4.30 ± 1.11 kg in Group CON; p < 0.05). Piglets in Group ESF were heavier than those in Group CON at both mid-lactation and weaning (p < 0.005 for both), due to changes in the ADWG. Overall, differences in the ADWG during the first half of lactation (0–14 days old) did not reach statistical significance between the groups, but were found to be affected by sex, with ESF males showing similar higher ADWG (and, thus, body weight) than their CON counterparts (p < 0.05 for both). The ADWG was significantly higher in both males and females of Group ESF than in their CON counterparts during the second half of lactation (0–14 days old; p < 0.05).

The amount of feed required to produce weaned piglets differed between the groups (

Table 2. Mean (±SD) of feed disappearance, feed per weaned piglet, feed per kg of weaned piglet, mean number of weaned piglets and mean weight of weaned piglets, with respect to sows fed with electronic and traditional feeders during lactation.

Group	Feed Disappearance	Feed per Weaned Piglet	Feed per kg of Weaned Piglet	Weaned Piglets (n)	Weight of Weaned Piglets
ESF	155.37 ± 18.77	11.31 ± 2.13	1.92 ± 0.33	13.95 ± 1.63	5.91 ± 1.46
CON	187.83 ± 12.35	13.35 ± 1.94	2.43 ± 0.48	14.25 ± 1.45	5.58 ± 1.23
p-Value	<0.001	0.002	<0.001	0.520	<0.002

ESF: electronic sow feeders; CON: traditional feeders; Feed Disappearance (kg): total amount of feed served to the sow; Feed per Weaned Piglet (kg): $(\mathrm{F}\mathrm{e}\mathrm{e}\mathrm{d} \mathrm{d}\mathrm{i}\mathrm{s}\mathrm{a}\mathrm{p}\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e} \mathrm{p}\mathrm{e}\mathrm{r} \mathrm{s}\mathrm{o}\mathrm{w})/(\mathrm{n}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r} \mathrm{o}\mathrm{f} \mathrm{w}\mathrm{e}\mathrm{a}\mathrm{n}\mathrm{e}\mathrm{d} \mathrm{p}\mathrm{i}\mathrm{g}\mathrm{l}\mathrm{e}\mathrm{t}\mathrm{s})$; Feed per kg of Weaned Piglet (kg): $(\mathrm{F}\mathrm{e}\mathrm{e}\mathrm{d} \mathrm{d}\mathrm{i}\mathrm{s}\mathrm{a}\mathrm{p}\mathrm{p}\mathrm{e}\mathrm{a}\mathrm{r}\mathrm{a}\mathrm{n}\mathrm{c}\mathrm{e} \mathrm{p}\mathrm{e}\mathrm{r} \mathrm{s}\mathrm{o}\mathrm{w})/(\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{t}\mathrm{e}\mathrm{r} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t} \mathrm{a}\mathrm{t} \mathrm{w}\mathrm{e}\mathrm{a}\mathrm{n}\mathrm{i}\mathrm{n}\mathrm{g} \mathrm{p}\mathrm{e}\mathrm{r} \mathrm{s}\mathrm{o}\mathrm{w})$.

). Sows fed with electronic feeders showed a significantly lower total feed disappearance during lactation than those fed with traditional feeders, so the amount of feed per weaned piglet was significantly lower. Furthermore, given their higher weaning weight, the amount of feed per kg of weaned piglet was significantly lower in Group ESF than in Group CON.

Differences in the ADWG and body weight of the piglets during lactation were also observed during the nursery and growing–finishing periods (

Table 3. Mean (±SD) body weight and ADWG at the end of the nursery and the growing–finishing periods for pigs born from sows fed with electronic and traditional feeders during lactation.

Group	BW Day 68	ADWG 24–68	BW Day 192	ADWG 68–192
ESF	20.59 ± 4.21	0.332 ± 0.92	128.54 ± 14.56	0.921 ± 0.11
CON	19.35 ± 4.06	0.312 ± 0.80	121.12 ± 12.53	0.871 ± 0.09
p-Value	<0.001	0.006	<0.001	<0.001

ESF: electronic sow feeders; CON: traditional feeders; BW: body weight (kg); ADWG: average daily weight gain (kg/day, $\left[\mathrm{f}\mathrm{i}\mathrm{n}\mathrm{a}\mathrm{l} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}-\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l} \mathrm{w}\mathrm{e}\mathrm{i}\mathrm{g}\mathrm{h}\mathrm{t}\right]/\mathrm{n}\mathrm{u}\mathrm{m}\mathrm{b}\mathrm{e}\mathrm{r} \mathrm{o}\mathrm{f} \mathrm{d}\mathrm{a}\mathrm{y}\mathrm{s}$).

). The assessment of possible sex-related effects during the nursery period in the study population showed that ESF males had an ADWG similar to their female littermates and CON counterparts (0.334 ± 0.096 vs. 0.327 ± 0.092 and 0.320 ± 0.083 kg/day, respectively) but significantly higher than the CON males (0.295 ± 0.078 kg/day, p < 0.005). Conversely, there were no significant sex-related differences during the growing–finishing period.

3.2. Metabolic and Welfare Status

The assessment of salivary biomarkers for welfare status during the lactation and nursery periods, determined in terms of cortisol levels at 14 days after farrowing and 7 days after weaning, together with alpha-amylase levels at 7 days after weaning, indicated no differences between the two groups of piglets (

Table 4. Mean (±SD) cortisol and alpha-amylase concentrations at mid-lactation and 7 days after weaning in piglets born from sows fed with electronic and traditional feeders during lactation.

	Day 14	Day 31
Group	Cortisol (μg/dL)	Cortisol (μg/dL)	Alpha-Amylase (U/L)
ESF	2.73 ± 2.29	0.18 ± 0.86	5004.01 ± 3917.27
CON	2.67 ± 2.12	0.18 ± 0.88	4594.42 ± 2194.25
p-Value	0.903	0.563	0.770

ESF: electronic sow feeders; CON: traditional feeders.

).

The assessment of plasma biomarkers for metabolic status at weaning, taken as the mean concentrations of indices for glucose, lipids, and protein metabolism, showed significantly higher values of total and LDL cholesterol and triglycerides (p < 0.05 for all), as well as a trend for proteins (p = 0.052), in the piglets of Group ESF (

Table 5. Mean (±SD) plasma concentrations of indices for glucose, lipids, and protein metabolism at weaning in piglets from sows fed with electronic and traditional feeders during lactation.

Group	Glucose (mg/dL)	Fructosamine (µmol/L)	Cholesterol (mg/dL)	HDL-c (mg/dL)	LDL-c (mg/dL)	Triglycerides (mg/dL)	Proteins (g/dL)
ESF	132.2 ± 18.15	379.93 ± 50.94	128.05 ± 26.93	49.97 ± 7.52	64.82 ± 18.46	89.42 ± 38.48	4.98 ± 0.47
CON	126.98 ± 14.44	382.35 ± 49.02	115.73 ± 32.65	47.6 ± 12.20	55.85 ± 13.79	75.62 ± 34.7	4.8 ± 0.32
p-Value	0.166	0.790	0.028	0.129	0.015	0.043	0.052

ESF: electronic sow feeders; CON: traditional feeders.

).

3.3. Productive Yields at Slaughterhouse

Assessment of the productive yields at the slaughterhouse showed that pigs in Group ESF showed a higher carcass weight, with higher values for backfat depth and loin diameter (

Table 6. Mean (±SD) values for weight, yield and lean content of the carcass, as well as backfat depth and loin diameter, in pigs born from sows fed with electronic and traditional feeders during lactation.

Group	Carcass Weight (kg)	Carcass Yield (%)	Carcass Lean (%)	BFD (mm)	Loin Diameter (mm)
ESF	105.17 ± 15.92	80.63 ± 5.89	62.31 ± 4.92	16.2 ± 3.10	73.08 ± 8.13
CON	97.98 ± 20.25	80.36 ± 3.01	61.39 ± 10.95	15.03 ± 3.57	69.78 ± 13.69
p-Value	<0.001	0.684	0.325	0.003	0.010

ESF: electronic sow feeders; CON: traditional feeders; BFD: backfat depth.

), but with similar carcass yield and lean content when compared to pigs in Group CON. Similarly, the subcutaneous fat depth of the ham (measured at two different points) showed higher values in Group ESF (10.55 ± 2.31 vs. 9.48 ± 2.53 mm, and 18.27 ± 3.73 vs. 16.61 ± 4.10 mm; p < 0.001 for both).

Assessment of the weights and lean content of the primal pieces (loin, ham, shoulder, and belly;

Table 7. Mean (±SD) weights of the primal cuts (ham, shoulder, loin, and belly) in pigs born from sows fed with electronic and traditional feeders during lactation.

Group	Loin W	Loin WT	Loin L	Ham W	Ham WT	Ham L
ESF	9.08 ± 1.35	8.13 ± 1.24	5.93 ± 0.71	13.56 ± 1.74	12.77 ± 1.62	10.51 ± 1.27
CON	8.35 ± 1.81	7.45 ± 1.63	5.55 ± 1.12	12.67 ± 2.59	11.85 ± 2.41	9.84 ± 1.98
p-Value	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001
Group	Shoulder W	Shoulder WT	Shoulder L	Belly W	Belly WT	Belly L
ESF	7.88 ± 1.06	7.15 ± 0.98	5.57 ± 0.70	4.84 ± 0.69	4.50 ± 0.66	2.99 ± 0.36
CON	7.24 ± 1.52	6.65 ± 1.40	5.20 ± 1.07	4.44 ± 0.94	4.12 ± 0.89	3.00 ± 0.57
p-Value	<0.001	<0.001	<0.001	<0.001	<0.001	<0.001

ESF: electronic sow feeders; CON: traditional feeders; W: weight with bone; WT: weight without bone; L: total lean weight. All values are expressed as kg.

) showed that all of the weights (both with and without bone) were greater in the pigs of Group ESF. The lean content of these primal cuts was similar in both groups, so the total lean content was also higher in Group ESF.

4. Discussion

The results of this study support previous data addressing the fact that piglets weaned from sows fed with ESFs during lactation are heavier than piglets weaned from sows fed with traditional feeders. This higher weaning weight, confirming the results of previous studies, was obtained with less feed disappearance; therefore, the amount of feed per kg of weaned piglet was remarkably lower. Assessment of the post-weaning growth of the pigs (performed for the first time in the current trial, to the best of our knowledge) revealed that the differences in body weight and ADWG remained during the nursery and growing–finishing periods. Ultimately, the carcass weight and quality of carcasses were also greater in pigs from sows fed with ESFs during lactation.

At the beginning of this study (i.e., at farrowing), both the total weight of the litter and the individual body weights of the piglets were similar between the groups. Subsequently, the better performances in Group ESF, initially observed at the first sampling time at two weeks of age and then throughout the lifecycle of the pigs, were related to consistently better ADWG during this study.

First, piglets in Group ESF had a higher weight gain during the suckling period and, therefore, a higher weaning weight, confirming the results of previous studies reporting that precision feeding has a positive impact on the performance of the breeding sows and their litters by weaning heavier piglets [8,9,18]. The possible causes of such differences were not addressed in this study, but previous authors have suggested that they may be related to better milk quality and/or higher milk intake [19,20], related in turn with higher milk production [21], a higher number of successful suckles of the piglets when sows move more times to eat [22], and/or a greater ability of the sow herself and the farm staff to adjust the daily ration to the sow’s needs, minimizing over- or undernutrition [23]. The presented results support better nutrition of the piglets, as plasma biomarkers for both lipids and protein metabolism at weaning were higher in the piglets of Group ESF. The plasma values of proteins and lipids were primarily affected by the nutritional value of the feed [24,25]. Therefore, given that all piglets had free availability of food during the creep-feeding period, we can hypothesize a higher nutritional value of the milk in Group ESF. However, we should note that there were no significant differences in these parameters in a previous study [8], which reinforces the main importance of management when implementing precision feeding [9].

In any case, the weaning of heavier piglets in our study was obtained with lower feed consumption (or wastage)—at around 32 kg of feed per lactation—and, thus, lower feed spending. Therefore, from an economic point of view for a breeding farm, the sows fed with ESFs in the present trial required a significantly lower amount of feed per weaned piglet (around 2 kg), equating to EUR 0.68 per weaned piglet under the current feed cost of 0.337 EUR/kg and around EUR 20,135 per year in a farm with 1000 breeding sows. These data are highly similar, and therefore, strengthen the results obtained in our previous studies [8,9].

The higher weight gain in the piglets of Group ESF continued during the nursery period, which may be related to the fact that piglets weaned at higher weights have a higher feed intake and achieve a better growth rate during the nursery period than smaller piglets [10,26,27]. It is important to note the effect of sex in our current study: the performances of males in Group ESF during the maternity and nursery periods were similar to those of the ESF and CON females, and higher than those of the males in Group CON. This is an significant finding, as it is well known that females start suckling sooner than males and suck more and faster than males [28]; hence, females grow faster during lactation [29]. Subsequently, in the immediate post-weaning period, males continue to eat less and grow slower than their female littermates [30]. Conversely, at later stages (until they were slaughtered at 113 kg), males were found to grow faster than gilts [31]. Therefore, at first glance, our results indicate that the use of ESFs in lactating sows benefitted the early-life development of their male offspring, such that they reached similar growth rates with respect to their female littermates during the lactation and nursery periods. These findings, which cannot be explained under the conditions of this study, are remarkable and deserve further research.

Furthermore, the better performance of Group ESF also continued during the growing–finishing period, which may be in agreement with previous data supporting the remarkable impact of weaning weight on lifetime growth performance and the time to achieve market weight [12,23].

The translation of the technical data in our study to economic estimations indicates that the higher weight reached at the end of the finishing period in pigs from sows fed with ESFs during lactation (around 7.5 kg greater carcass weight), considering the current price of 1.565 EUR/kg, means an extra benefit of EUR 11.61 per pig and around EUR 31,350 per year in a farm with 1000 growing pigs and 2.7 cycles/year. In other terms, calculating the benefits of slaughtering pigs when reaching the target weight (115 kg live weight), pigs in Group ESF would reach such a weight around 5.71 days earlier than those in Group CON. At a current cost per day of stay of EUR 0.40, such a difference means another extra benefit of EUR 2.3 per pig and around EUR 6200 per year in a farm with 1000 growing pigs and 2.7 cycles per year.

The effects of feeding lactating sows with ESFs were also observed when comparing the qualities of the carcasses. In brief, pigs in Group ESF had a significantly higher weight (quantity) of all the primal cuts (ham, shoulder, loin, and belly). The positive economic impact in a slaughterhouse processing one million pigs per year may be estimated at around EUR 20.2 million (based on current prices in Spain as of March 2025; loin: 5.74 EUR/kg, ham: 3.22 EUR/kg, shoulder: 2.29 EUR/kg, and belly: 3.9 EUR/kg).

5. Conclusions

Precision feeding during the lactation period of sows was shown to have a positive impact on the growth of their piglets during all raising periods (i.e., lactation, nursery, and growing–finishing phases). These pigs reached slaughter weight earlier and presented higher weights and better pork quality (in terms of total lean content), both in the carcass and the different primal cuts.