Maternal potassium-magnesium sulfate supplementation in low-protein diets improves performance and health of sows and suckling piglets

Abstract

Minerals such as magnesium and potassium in low-protein diets are critical for the relief of inflammation and enhancement of immune function in sows. This study investigated the potential of potassium-magnesium sulfate (PMS) supplementation on the performance and health of sows and their piglets from d 107 of gestation to weaning. A total of 120 Yorkshire × Landrace sows (parity 3–4; initial body weight 263.62 ± 3.60 kg; d 107 of gestation) were fed low-protein diets supplemented with 0.00 (control), 0.25%, 0.50%, and 0.75% PMS. Each of the 4 treatments included 30 replicate sows, each sow serving as an experimental unit. Compared with the control, 0.50% PMS significantly increased average daily feed intake (ADFI) in sows and average weaning weight in piglets, weight gain per litter, and average daily gain (ADG), while also reducing diarrhea incidence (P < 0.05). Furthermore, the weaning-to-estrus interval decreased linearly with increasing PMS supplementation (P = 0.022). Compared with the control, PMS supplementation elevated serum magnesium, potassium, immunoglobulin (Ig) A, IgG, and interleukin (IL)-10 levels in sows, and enhanced colostrum/milk magnesium, potassium, total solids, and IgG levels (P < 0.05). Compared with the control, PMS increased serum magnesium, potassium, IgA, IgG, IgM, and IL-10 levels, and reduced IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) levels during lactation (P < 0.05) in piglets. Microbiota analysis using linear discriminant analysis effect size (LEfSe) and t-tests showed that, compared with the control, 0.50% PMS enriched Ruminococcus_gauvreauii_group, Lachnospiraceae_AC2044_group, Subdoligranulum, and Butyrivibrio in the sow rectum (P < 0.05). Collectively, these results indicate that PMS supplementation in low-protein diets during lactation can improve the productivity and health of sows and their offspring by alleviating inflammatory responses, improving immune function, and increasing the abundance of short-chain fatty acids producing and other potentially beneficial microbiota in the rectum, with 0.50% PMS showing a favorable overall response.

1. Introduction

Sows commonly experience oxidative stress and metabolic disorders due to physiological and psychological stressors during lactation, which can provoke inflammatory responses and compromise immunity (Luo et al., 2019; Palm et al., 2013). Low-protein diets balanced with crystalline amino acids are widely applied in swine nutrition to improve nitrogen utilization, without compromising litter growth performance (Wang et al., 2018; Zhang et al., 2019). However, low-protein diets with reduced inclusion of soybean meal are often deficient in essential minerals such as magnesium and potassium (Aguirre et al., 2022; Batal et al., 2010). These deficiencies, combined with reduced protein intake, may exacerbate inflammation and impair immune function in lactating sows (Wang et al., 2018; Wei et al., 2023). Both magnesium and potassium contribute significantly to physiological activities, including immune regulation and inflammatory responses (Fiorentini et al., 2021; Stone et al., 2016).

Magnesium and potassium are crucial macronutrients for animals (Fiorentini et al., 2021; Stone et al., 2016). Magnesium is necessary for ATP synthesis, supports immune system function, and improves stress resistance (Apell et al., 2017). Studies have demonstrated that 200 to 600 mg/kg MgSO₄ supplementation increased plasma immunoglobulin (Ig) G level and colostrum and milk IgA in sows (Hou et al., 2014; Trawinska et al., 2013). Potassium helps maintain proper osmotic pressure in cells, balances body fluid pH, and plays a role in carbohydrate and protein metabolism (Stone et al., 2016). Dietary potassium supplementation has been shown to alleviate heat stress in animals (Ansari et al., 2020). Potassium-magnesium sulfate (PMS) is a compound that simultaneously supplies both magnesium and potassium. It has been reported to enhance antioxidant capacity and increase colostrum IgA level in sows (Wei et al., 2023), as well as promote growth, antioxidant defense, and intestinal immunity in weaned pigs (Cao et al., 2022). Although PMS supplementation is known to enhance antioxidant capacity and immune function in sows and weaned pigs, its effect on lactation performance, inflammatory responses, and immunity in sows and suckling piglets fed low-protein diets remains to be fully elucidated.

Given the additional mineral deficiencies associated with low-protein feeding, strategies to alleviate inflammation and enhance immune function in sows under these conditions are particularly needed. Thus, this study investigated the effects of PMS supplementation on the performance and health of sows and suckling piglets at graded levels of 0.00, 0.25%, 0.50%, and 0.75% in low-protein diets fed from d 107 of gestation through weaning using a sow-piglet model. It was hypothesized that PMS supplementation would improve sow lactation performance and health, enhance maternal immune status and colostrum and milk composition, modulate rectal microbiota composition, and ultimately promote growth and immune development in suckling piglets.

2. Materials and methods

2.1. Animal ethics statement

The experimental procedures in this experiment were reviewed and approved by the Institutional Animal Care and Use Committee of China Agricultural University (Aw90015202-1-1).

2.2. Feed additives

This study aimed to assess the commercial PMS additives (K₂SO₄·MgSO₄·6H₂O, 21.0% potassium and 6.5% magnesium, Qinghai Lanhushancheng Bio-tech Co., Ltd., Xining, Qinghai, China) in lactating sows under low-protein feeding.

2.3. Animals and husbandry

A total of 120 Landrace × Yorkshire sows (parity 3–4; initial body weight, 263.62 ± 3.60 kg), with similar backfat thickness (measured at the P2 position using Piglog105, SFK Technology, Helver, Denmark; 16.37–17.07 mm across treatments; Table 2), were randomly allocated to 4 different dietary treatments on d 107 of gestation. Each of the 4 treatments included 30 replicate sows, each sow serving as an experimental unit. The experimental period lasted from d 107 of gestation to weaning (d 21 of lactation). On d 107 of gestation, sows were transferred to farrowing stalls measuring 2.1 m × 0.6 m and were fed 2.76 kg of feed per day until farrowing. After farrowing, sows were given about 0.5 kg of feed on the first day, with daily allotments increasing by 1.0 kg until maximum intake was reached, after which they were allowed ad libitum access to feed. During the entire experiment, the piglets were solely fed sow’s milk, and both sows and piglets had ad libitum access to water via nipple drinkers. Within 24 h of farrowing, litter was adjusted to about 13 ± 1 piglets through cross-fostering in each treatment. The farrowing environment for sows was controlled at 20 to 23 °C, supplemented with heat lamps for the neonates. Suckling piglets received routine procedures, including tooth trimming, tail docking, iron dextran injections, and vaccination. The experiment was carried out at the Fengning Swine Research Unit of China Agricultural University (Chengde, Hebei, China).

Table 2.

Effects of potassium-magnesium sulfate (PMS) supplementation on lactation performance of sows fed a low-protein diet.

Item	Treatments3				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Backfat thickness, mm	16.87	16.73	16.47	16.37	0.340	0.952	0.567	0.981
ADFI, kg/d	7.08b	7.20a	7.23a	7.18ab	0.023	0.031	0.058	0.020
Constipation score	3.22	3.17	3.10	3.11	0.024	0.271	0.074	0.537
Weaning-to-estrus interval, d	5.63	5.43	5.40	5.33	0.046	0.110	0.022	0.460
Reproductive performance of sows
Number of piglets born per litter	14.77	14.63	14.30	15.10	0.230	0.584	0.784	0.265
Number of piglets born alive per litter	13.33	13.27	12.90	13.57	0.174	0.602	0.832	0.297
Number of piglets stillborn per litter	1.23	1.10	1.17	1.40	0.117	0.829	0.594	0.441
Number of mummified fetuses per litter	0.13	0.10	0.07	0.03	0.028	0.625	0.188	1.000
Litter weight of piglets born alive, kg	19.13	18.76	17.61	19.21	0.271	0.131	0.704	0.067
Average birth weight, kg	1.44	1.42	1.37	1.43	0.017	0.626	0.678	0.307
Growth performance of piglets1
Number of piglets weaned per litter	11.73	11.93	11.47	11.90	0.127	0.554	0.398	0.648
Litter weight of weaned piglet, kg	70.46	74.21	74.92	72.16	0.823	0.211	0.428	0.049
Average weaning weight, kg	6.02b	6.26ab	6.68a	6.11b	0.108	0.047	0.394	0.030
Weight gain per litter, kg	51.33b	55.45ab	57.31a	52.95ab	0.818	0.047	0.350	0.009
ADG, g/d	218.25b	230.46b	252.86a	222.86b	4.844	0.016	0.328	0.013
Diarrhea rate2, %	5.38a	2.34bB	1.28dD	1.45cC		<0.001 (χ²)

ADFI = average daily feed intake during lactation; ADG = average daily weight gain from farrowing to weaning; CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; n = 30.

¹After cross-fostering within treatment.

²Diarrhea rate (%) = (The number of diarrhea pigs × Diarrhea days)/(The total number of pigs × Experiment days) × 100. Diarrhea rate was analyzed using the Chi-square test (χ²).

³The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

2.4. Dietary treatments

The treatments in a completely randomized design consisted of one low-protein diet as control (CON) and 3 treatment groups to examine the effects of the PMS additive. The control group was a basal diet with 16% crude protein (CP), formulated to meet the GB/T 39235-2020 (China National Standard, 2020). This CP level is close to the minimal recommendation level for high-producing sows; further reduction below this range has been associated with lower feed intake and impaired litter performance (Tokach et al., 2019). The 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50%, and 0.75% to the basal diet. These inclusion levels were selected within the 0.15%–0.75% range that has been reported to improve growth performance, diarrhea incidence, and gut health in weaned piglets (Cao et al., 2022), and around the 0.45% PMS level successfully used in sows during late gestation and lactation (Wei et al., 2023). Diets were formulated as corn-soybean meal-based lactation diets (Table 1).

Table 1.

Ingredients and nutrient levels of lactation diets (%, as-fed basis).

Ingredients	Content	Calculated nutrients2	Levels	Analyzed nutrients	Levels
Corn	58.44	Net energy, MJ/kg	10.88	Dry matter	92.99
Soybean meal	5.00	Crude protein	16.00	Gross energy, MJ/kg	17.45
Wheat bran	10.00	Crude fiber	4.50	Crude protein	15.92
Rice bran	8.99	Calcium	0.86	Ether extract	5.67
Cottonseed meal	6.07	Total phosphorus	0.76	Crude ash	6.06
Extruded soybean	5.00	Available phosphorus	0.40	Organic matter	86.93
Fish meal	0.50	Total amino acids		Total amino acids
Whey powder	0.50	Lys	1.01	Lys	0.98
Soybean oil	1.73	Met	0.30	Met	0.28
Limestone	1.20	Thr	0.69	Thr	0.67
Dicalcium phosphate	1.10	Trp	0.20	Trp	0.20
Salt	0.50	Arg	0.60	Arg	0.55
L-Lys HCl	0.40	Val	0.88	Val	0.88
L-Val	0.07	SID amino acids
Premix1	0.50	Lys	0.84
Total	100.00	Met	0.23
		Thr	0.51
		Trp	0.16
		Arg	0.48
		Val	0.69

SID = standardized ileal digestibility.

¹The premix provided the following per kg of the diet: vitamin A, 25,000 IU; vitamin D₃, 5000 IU; vitamin E, 12.5 IU; vitamin K₃, 1 mg; thiamin, 8.0 mg; pyridoxine, 3.0 mg; vitamin B₁₂, 15 μg; riboflavin, 6.0 mg; niacin, 17.5 mg; D-pantothenic acid, 12.5 mg; folic acid, 0.25 mg; biotin, 0.1 mg; choline chloride, 0.4 mg; Fe, 165 mg as FeSO₄; Cu, 16.0 mg as Cu₂(OH)₃Cl; Zn, 30 mg as ZnSO₄; Mn, 30 mg as MnSO₄; I, 0.3 mg as Ca(IO₃)₂; Se, 0.3 mg as Na₂SeO₃.

²Calculated nutrient levels were based on the ingredient values from Nutrient requirements of swine (China National Standard, 2020).

2.5. Determination of sows’ feed sample

Feed samples were collected and stored at −20 °C for further analysis. Gross composition of feed was determined following the AOAC (2006). Crude protein was analyzed by the Kjeldahl method (method 990.03) using an automatic Kjeldahl analyzer (Kjeltec 8400, FOSS Analytical A/S, Hilleroed, Denmark). Ether extract (EE) was determined by method 996.01 using a fat analyzer (XT10i, ANKOM Technology Corporation, Macedon, NY, USA). Moisture was measured by method 930.15 using an electric blast drying oven (DHG-9070A, Shanghai Yiheng Scientific Instrument Co., Ltd., Shanghai, China), and crude ash was determined by method 942.05 using a box resistance furnace (MFL-2000, Beijing Zhongxing Weiye Instrument Co., Ltd., Beijing, China). Organic matter (OM) was calculated as the difference between dry matter (DM) and crude ash:

$$\text{OM}=\text{DM}-\text{Ash}\left(\%\text{as}-\text{fed}\right)\text{.}$$

Amino acid composition was analyzed by method 982.30 using an automatic amino acid analyzer (L-8900, Hitachi High-Technologies Corporation, Tokyo, Japan) after hydrolysis with 6 N HCl at 110 °C for 24 h. Tryptophan was quantified using the same analyzer after alkaline hydrolysis according to method 988.15. Gross energy (GE) was analyzed with an adiabatic bomb calorimeter (6400, Parr Instrument Company, Moline, IL, USA) according to ISO 9831:1998 (1998).

2.6. Determination of sow and litter performance

The feed intake and fecal score of sows and piglet diarrhea incidence were recorded daily during the entire lactation period (d 1–21). Sow fecal score was assessed immediately after defecation using a visual qualitative evaluation method: 1 = dry and pellet-like; 2 = soft, firm, and well-formed; 3 = soft and well-formed; 4 = soft but not firm; 5 = wet, unformed, and liquid (Wei et al., 2023). Diarrhea incidence in piglets was assessed using a fecal consistency scoring system: 0, firm, well-formed feces; 1, slightly soft; 2, soft, partially shaped; 3, loose, semi-liquid; 4, watery, unformed with mucus-like appearance. Diarrhea was defined as a score ≥ 3 (Peng et al., 2024). The piglets' anus was examined daily, and the number of piglets with diarrhea was recorded. Data were recorded on total piglets born, live piglets, stillbirths, mummified fetuses, and weaned piglets per litter, along with the individual birth and weaning weights of all piglets. The interval time between weaning and estrus was recorded.

2.7. Collection and analysis of blood samples

Blood was collected from the ear veins of six sows per treatment at farrowing and eleven sows per treatment weaning after fasting, and from the precaval veins of their piglets on d 7, 14, and 21 after farrowing. One piglet per litter was randomly selected for blood sampling at each time point to minimize selection bias and ensure that a representative sample of the litter’s health status and size was included. Serum was separated by centrifugation (1800 × g, 10 min, 25 °C) and stored at −20 °C until biochemical analysis. Serum potassium, magnesium, immunoglobulins (IgA, IgG, and IgM), and cytokines (interleukin [IL]-1β, IL-6, IL-10, and tumor necrosis factor [TNF]-α) were determined in sows and piglets. Potassium was analyzed using a tetraphenylborate turbidimetry kit (P-982-SH), magnesium was analyzed using a microplate assay kit (P-984-SH), and immunoglobulins and cytokines were determined using enzyme-linked immunosorbent assay (ELISA) kits (IgA, HB176-Pg; IgG, HB174-Pg; IgM, HB171-Pg; IL-1β, HB354-Pg; IL-6, HB347-Pg; IL-10, HB359-Pg; TNF-α, HB015-Pg) according to the manufacturer’s instructions (Shanghai Hengyuan Biotechnology Co., Ltd., Shanghai, China). Absorbance was measured using a microplate reader (Multiskan MK3, Thermo Fisher Scientific Inc., Vantaa, Finland).

2.8. Collection and analysis of colostrum and milk samples

Colostrum and milk were sampled manually from the anterior, middle, and posterior mammary glands of 6 sows per group. Colostrum was obtained within 12 h after farrowing without oxytocin, and milk was collected on d 21 of lactation after injection of 20 IU oxytocin at the ear base. Samples were stored at −20 °C for analysis. Milk fat and total solids were determined by the drying and gravimetric method, whereas milk protein and lactose concentrations were measured using a microplate reader (Multiskan MK3, Thermo Fisher Scientific Inc., Vantaa, Finland). Potassium was analyzed using tetraphenylborate turbidimetry kit (P-982-SH), magnesium by a microplate assay kit (P-984-SH), and IgA, IgG, and IgM concentrations were measured using ELISA kits (IgA, HB176-Pg; IgG, HB174-Pg; IgM, HB171-Pg) according to the manufacturer’s instructions (Shanghai Hengyuan Biotechnology Co., Ltd., Shanghai, China).

2.9. Collection and analysis of rectal microbiota from sows

On d 21 of lactation, rectal microbiota samples were taken manually by sterile cotton swab from 6 examined sows in the control and 0.50% PMS group, respectively and promptly stored in liquid nitrogen. The microbiota analysis was designed as a targeted comparison between the control and 0.50% PMS groups, as 0.50% PMS showed the greatest improvements in piglet growth performance and the lowest diarrhea rate among the PMS-supplemented diets. After DNA extraction and sequencing, samples that did not meet predefined minimal DNA quality and sequencing-depth criteria were excluded.

2.10. 16S rRNA-based microbiota analysis

Total DNA was extracted from the rectal contents of sows using the E.Z.N.A. Soil DNA Kit (Omega Bio-tek, Inc., Norcross, GA, USA) following the manufacturer’s protocol. The DNA quality was evaluated by 1% agarose gel electrophoresis, and concentration and purity were determined with a NanoDrop 2000 spectrophotometer (Thermo Fisher Scientific Inc., Wilmington, DE, USA). The bacterial 16S rRNA gene (V3–V4 region) was amplified by PCR on a T100 Thermal Cycler (Bio-Rad Laboratories, Inc., Hercules, CA, USA) with primers 338F (5′-ACTCCTACGGGAGGCAGCAG-3′) and 806R (5′-GGACTACHVGGGTWTCTAAT-3′). The PCR conditions were as follows: 95 °C for 3 min; 27 cycles of 95 °C for 30 s, 55 °C for 30 s, and 72 °C for 30 s; and a final extension at 72 °C for 10 min. The amplicons were purified by 2% agarose gel electrophoresis, quantified with a Synergy HTX microplate reader (BioTek Instruments, Inc., Winooski, VT, USA), and pooled for library construction using the NEXTFLEX Rapid DNA-Seq Kit (Bioo Scientific Corporation, Austin, TX, USA). Sequencing was performed on an Illumina NextSeq 2000 platform (Illumina Inc., San Diego, CA, USA). Raw reads were filtered with fastp (v0.19.6) (Chen et al., 2018) merged using FLASH (v1.2.11) (Magoč and Salzberg, 2011), and clustered into operational taxonomic units (OTUs) at 97% similarity with UPARSE (v11) (Edgar, 2013), following the conventional 97% similarity threshold (Stackebrandt and Goebel, 1994). Taxonomic classification was assigned using the RDP classifier (v2.13) (Wang et al., 2007a) against the SILVA 16S rRNA database (v138; 70% confidence). Alpha-diversity indices (Shannon, Simpson, and Chao1) were calculated using Mothur (v1.30.1) (Schloss et al., 2009). Beta-diversity was assessed through principal coordinate analysis (PCoA) and non-metric multidimensional scaling (NMDS) based on weighted UniFrac distances.

2.11. Statistical analysis

Data were analyzed by one-way ANOVA with least significant difference (LSD) multiple comparisons using IBM SPSS Statistics (v25.0, IBM Corp., Armonk, NY, USA). Data were evaluated for normality and homoscedasticity by the Shapiro–Wilk and Levene’s tests, respectively. For the one-way ANOVA, the data were modeled as:

$$Y_{ij}=\mu +J_i+e_{ij}\text{,}$$

where Y_ij is the measurement for the j-th sample under the i-th treatment; μ is the overall mean; J_i is the fixed effect of the i-th treatment (PMS treatment effect); and e_ij is the random error. The linear and quadratic effects of different PMS levels were assessed using orthogonal polynomial contrasts. Piglet diarrhea rate was analyzed using the Chi-square test, and pairwise comparisons were performed using Chi-square tests with Bonferroni correction.The relative abundance of rectal microbial data was analyzed using the Kruskal-Wallis test and two-tailed Wilcoxon rank-sum test. P < 0.05 is considered statistically significant, and P < 0.01 is considered extremely significant.

3. Results

3.1. Effects of PMS supplementation on lactation performance of sows fed a low-protein diet

Dietary PMS supplementation increased sow average daily feed intake (ADFI), with higher values in the 0.25% and 0.50% PMS groups than in the control group (Table 2; P = 0.031), and the response was quadratic ( P = 0.020). The weaning-to-estrus interval decreased linearly with increasing PMS supplementation (P = 0.022), although the overall treatment effect was not significant (P = 0.110). In addition, piglets’ average weaning weight, weight gain per litter, and average daily gain (ADG) responded quadratically to increasing PMS supplementation (P < 0.05). Specifically, the 0.50% PMS group showed a higher average weaning weight than the control and 0.75% PMS groups (P = 0.047), a higher weight gain per litter than the control group (P = 0.047), and a higher ADG than the other three groups (P = 0.016). Furthermore, compared with the control group, dietary PMS supplementation reduced the diarrhea rate in piglets, with lower values observed in the 0.50% and 0.75% PMS groups (P < 0.001).

3.2. Effects of PMS supplementation on serum potassium and magnesium levels of sows during lactation

At farrowing, serum potassium level showed a quadratic response to increasing PMS supplementation (Table 3; P = 0.017), whereas serum magnesium level increased linearly with increasing PMS supplementation (P < 0.001). At weaning, serum potassium level showed both linear and quadratic increases with increasing PMS supplementation (P P < 0.001), with the highest value observed in the 0.50% PMS group. At weaning, serum magnesium level also showed a quadratic response (P < 0.001), with the highest value observed in the 0.25% PMS group.

Table 3.

Effects of potassium-magnesium sulfate (PMS) supplementation on serum potassium and magnesium levels of sows during lactation (mmol/L).

Item	Treatments1				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Farrowing
Potassium	4.90	5.78	5.67	4.17	0.253	0.073	0.277	0.017
Magnesium	1.97cC	2.99abAB	2.72bB	3.31aA	0.124	<0.001	<0.001	0.154
Weaning
Potassium	3.82dC	5.45cB	8.13aA	6.37bB	0.279	<0.001	<0.001	<0.001
Magnesium	2.23cC	3.35aA	2.74bB	2.73bB	0.085	<0.001	0.111	<0.001

CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; the number of biological replicates was 6 per treatment at farrowing and 11 per treatment at weaning.

¹The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

3.3. Effects of PMS supplementation on serum immunoglobulin and inflammatory cytokine levels of sows during lactation

At farrowing, PMS supplementation increased serum IgA and IgG levels in sows, with all PMS-supplemented groups showing higher serum IgA and IgG levels than the control group (Table 4; P < 0.01). Regarding inflammatory cytokine levels, no significant differences were observed in serum IL-1β, IL-6, IL-10, or TNF-α levelswere not significantly affected by dietary PMS supplementation (Table 5; P > 0.05). Although serum IL-6 levels differed among treatments, no PMS-supplemented group differed significantly from the control group (P = 0.037). At weaning, PMS supplementation increased serum IL-10 level, with all PMS-supplemented groups showing higher serum IL-10 levels than the control group P < 0.001). However, no significant differences were observed in serum IL-1β, IL-6, or TNF-α levels among treatment groups at weaning (P > 0.05).

Table 4.

Effects of potassium-magnesium sulfate (PMS) supplementation on serum immunoglobulin (Ig) levels of sows during lactation (μg/mL).

Item	Treatments1				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Farrowing
IgA	34.01bB	39.75aA	40.25aA	39.65aA	0.696	<0.001	0.001	0.004
IgG	367.67cC	528.39aA	524.55aA	484.67bB	13.745	<0.001	<0.001	<0.001
IgM	52.69aA	52.58aA	51.73aA	41.30bB	1.065	<0.001	<0.001	<0.001
Weaning
IgA	27.33	27.85	27.47	28.20	0.686	0.974	0.736	0.941
IgG	265.70	277.57	289.61	264.53	11.741	0.875	0.939	0.459
IgM	34.83	34.88	33.86	33.99	0.503	0.852	0.459	0.970

CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, and means without a common superscript capital letter differ at P < 0.01; the number of biological replicates was 6 per treatment at farrowing and 7 per treatment at weaning.

¹The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

Table 5.

Effects of potassium-magnesium sulfate (PMS) supplementation on serum inflammatory cytokine levels of sows during lactation (ng/L).

Item	Treatments1				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Farrowing
IL-1β	43.02	43.96	44.17	41.91	0.412	0.197	0.386	0.057
IL-6	987.22ab	976.81b	1016.95a	961.11b	7.293	0.037	0.510	0.089
IL-10	202.02	202.01	209.17	204.42	2.211	0.655	0.489	0.608
TNF-α	348.59	357.66	341.35	353.23	2.286	0.060	0.898	0.734
Weaning
IL-1β	30.23	34.44	32.95	32.86	1.152	0.659	0.554	0.376
IL-6	641.88	674.01	618.80	700.84	19.142	0.474	0.489	0.526
IL-10	153.82bB	218.35aA	215.14aA	223.93aA	6.194	<0.001	<0.001	<0.001
TNF-α	263.08	293.40	275.61	271.43	8.384	0.656	0.926	0.330

IL = interleukin; TNF-α = tumor necrosis factor-α; CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; n = 6.

¹The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

3.4. Effects of PMS supplementation on colostrum and milk mineral levels, composition, and immunoglobulin levels of sows during lactation

Potassium levels in colostrum and milk, as well as magnesium levels in milk, showed both linear and quadratic responses to increasing PMS supplementation (Table 6; P < 0.01), whereas magnesium level in colostrum increased linearly (P < 0.001). In addition, all PMS-supplemented groups showed higher potassium levels in colostrum and milk than the control group (P < 0.01), and magnesium levels in milk were higher in all PMS-supplemented groups than in the control group (P < 0.001). Regarding milk composition (Table 7), colostrum total solids increased linearly with increasing PMS supplementation (P = 0.010), and the 0.75% PMS group had a higher colostrum total solids level than the other groups (P = 0.036). Milk total solids showed a quadratic response to PMS supplementation (P = 0.035). For immunoglobulins (Table 8), PMS supplementation increased colostral IgG level, with the 0.50% PMS group showing the highest value among treatments (P< 0.001). No significant effects of PMS supplementation were observed on colostral IgA or IgM levels, or on milk IgA, IgG, or IgM levels (P > 0.05).

Table 6.

Effects of potassium-magnesium sulfate (PMS) supplementation on potassium and magnesium levels of colostrum and milk of sows during lactation (mg/mL).

Item	Treatments1				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Colostrum
Potassium	1.40bB	1.80aA	1.75aA	1.78aA	0.039	<0.001	<0.001	<0.001
Magnesium	0.11bB	0.12bAB	0.12bAB	0.14aA	0.003	<0.001	<0.001	0.663
Milk
Potassium	1.28bB	1.58aA	1.58aA	1.62aA	0.033	<0.001	<0.001	0.001
Magnesium	0.11cC	0.18aA	0.18aA	0.16bB	0.006	<0.001	<0.001	<0.001

CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; n = 6.

¹The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

Table 7.

Effects of potassium-magnesium sulfate (PMS) supplementation on compositions of colostrum and milk of sows during lactation.

Item	Treatments1				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Colostrum
Protein, mg/mL	7.26	7.30	7.35	7.41	0.078	0.930	0.514	0.976
Lactose, mg/mL	28.49	29.16	29.26	29.17	0.603	0.972	0.712	0.770
Fat, %	8.12	9.51	9.57	10.34	0.400	0.269	0.068	0.696
Total solids, %	11.48b	11.90b	12.50b	16.36a	0.691	0.036	0.010	0.167
Milk
Protein, mg/mL	6.20	6.64	6.47	7.01	0.109	0.052	0.017	0.792
Lactose, mg/mL	22.18	22.50	23.89	24.17	0.655	0.661	0.237	0.988
Fat, %	8.49	8.88	9.36	9.48	0.262	0.545	0.164	0.794
Total solids, %	12.36	13.22	15.45	11.72	0.557	0.082	0.949	0.035

CON = control; SEM = standard error of the mean.

Within a row, means are not statistically significant difference at P > 0.05, means without a common superscript capital letter differ at P < 0.01; n = 6.

¹The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

Table 8.

Effects of potassium-magnesium sulfate (PMS) supplementation on immunoglobulin (Ig) levels of colostrum and milk of sows during lactation (μg/mL).

Item	Treatments1				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Colostrum
IgA	38.57	39.97	38.95	39.45	0.315	0.448	0.571	0.486
IgG	452.45bB	458.11bB	475.44aA	438.68cC	2.892	<0.001	0.012	<0.001
IgM	50.40	51.24	50.70	50.69	0.346	0.876	0.922	0.566
Milk
IgA	34.24	35.01	34.74	33.67	0.300	0.428	0.471	0.141
IgG	407.27	411.89	417.04	417.24	6.820	0.955	0.595	0.880
IgM	45.20	45.48	45.38	45.35	0.305	0.992	0.909	0.817

CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; n= 6.

¹The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

3.5. Effects of maternal PMS supplementation on serum potassium and magnesium levels of suckling piglets during lactation

At 7 d after farrowing, serum potassium and magnesium levels in piglets were higher in the 0.50% and 0.75% PMS groups than in the control and 0.25% PMS groups (Table 9; P < 0.05), and both variables increased linearly with increasing dietary PMS supplementation (P < 0.001). At 14 d after farrowing, serum potassium level increased linearly with increasing dietary PMS supplementation (P < 0.001), with the highest value observed in the 0.75% PMS group (P < 0.05). At 14 d after farrowing, serum magnesium level also increased linearly (P = 0.011), but no significant differences were observed among treatment groups (P = 0.060). At 21 d after farrowing, the 0.75% PMS group showed higher serum potassium and magnesium levels than the other groups, and both variables showed significant increases with increasing dietary PMS supplementation (potassium: P = 0.028; magnesium: P = 0.001). Furthermore, serum potassium level increased linearly with increasing dietary PMS supplementation (P = 0.013), whereas serum magnesium level showed both linear and quadratic responses to increasing dietary PMS supplementation (P < 0.001 and P = 0.015, respectively).

Table 9.

Effects of maternal potassium-magnesium sulfate (PMS) supplementation on serum potassium and magnesium levels of suckling piglets during lactation (mmol/L).

Item1	Treatments2				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
Potassium
7 d	5.57bC	5.66bBC	6.16aAB	6.26aA	0.089	0.003	<0.001	0.980
14 d	6.79cB	6.90cB	8.46bA	8.86aA	0.200	<0.001	<0.001	0.259
21 d	8.63b	8.48b	8.73b	9.28a	0.105	0.028	0.013	0.065
Magnesium
7 d	2.07bC	2.26bBC	2.59aA	2.55aAB	0.056	<0.001	<0.001	0.122
14 d	2.67	2.67	2.92	3.02	0.059	0.060	0.011	0.644
21 d	2.75bB	2.78bB	2.80bB	3.25aA	0.057	0.001	<0.001	0.015

CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, and means without a common superscript capital letter differ at P < 0.01; n = 6.

¹7 d, 14 d and 21 d refers to d 7, 14, 21 after farrowing.

²The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

3.6. Effects of maternal PMS supplementation on serum immunoglobulin and inflammatory cytokine levels of suckling piglets during lactation

At 14 d after farrowing, piglet serum IgA level increased linearly with increasing maternal PMS supplementation, with the highest value observed in the 0.75% PMS group (Table 10; P < 0.001), with the 0.25% and 0.75% PMS group showing higher IgA levels compared with the control group (P = 0.001). In addition, at 7 d after farrowing, piglet serum IgG level showed a quadratic response to maternal PMS supplementation (P = 0.003), whereas serum IgM level increased linearly (P = 0.018) and were higher in all PMS-supplemented groups than in the control group (P < 0.05). Maternal PMS supplementation reduced piglet serum IL-1β, IL-6, and TNF-α levels while increasing IL-10 level during lactation (Table 11). Specifically, serum IL-1β level was lower in PMS-supplemented groups than in the control group at 14 and 21 d after farrowing (P < 0.001), and lower in the 0.50% and 0.75% PMS groups at 7 d (P = 0.034). Serum IL-6 level was reduced by maternal PMS supplementation at 7 and 14 d after farrowing, whereas only the 0.75% PMS group showed a lower value than the other groups at 21 d after farrowing (P < 0.001). Serum TNF-α level decreased linearly with increasing maternal PMS supplementation at 7, 14, and 21 d after farrowing (P < 0.001). Furthermore, serum IL-10 level was increased by maternal PMS supplementation, with the highest value observed in the 0.50% PMS group at 7, 14, and 21 d after farrowing (P = 0.012, P < 0.001, and P < 0.001, respectively).

Table 10.

Effects of maternal potassium-magnesium sulfate (PMS) supplementation on serum immunoglobulin (Ig) levels of suckling piglets during lactation (μg/mL).

Item1	Treatments2				SEM	P-value
	CON	0.25%PMS	0.50%PMS	0.75%PMS		ANOVA	Linear	Quadratic
IgA
7 d	35.73	36.60	35.92	36.12	0.268	0.725	0.851	0.555
14 d	33.25cC	34.35abAB	34.01bBC	35.04aA	0.180	0.001	<0.001	0.897
21 d	32.48	33.14	32.57	32.00	0.195	0.238	0.248	0.120
IgG
7 d	440.75c	461.47ab	471.78a	447.88bc	3.918	0.013	0.286	0.003
14 d	438.69	422.76	429.26	435.95	3.410	0.368	0.955	0.111
21 d	384.41	386.16	396.06	396.82	3.703	0.539	0.177	0.948
IgM
7 d	40.17bB	46.52aA	44.17aAB	45.65aA	0.763	0.008	0.018	0.060
14 d	43.29	41.86	42.02	42.12	0.356	0.496	0.312	0.300
21 d	42.48	41.32	40.00	41.82	0.421	0.198	0.369	0.079

CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; n = 6.

¹7 d, 14 d and 21 d refers to d 7, 14, 21 after farrowing.

²The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

Table 11.

Effects of maternal potassium-magnesium sulfate (PMS) supplementation on serum inflammatory cytokine levels of suckling piglets during lactation (ng/L).

Item1	Treatments2				SEM	P-value
	CON	0.25% PMS	0.50% PMS	0.75% PMS		ANOVA	Linear	Quadratic
IL-1β
7 d	34.71a	32.74ab	31.07b	30.65b	0.566	0.034	0.005	0.442
14 d	44.35aA	33.26bB	35.28bB	35.56bB	0.980	<0.001	<0.001	<0.001
21 d	47.32aA	34.69bB	43.81cC	36.25cC	1.148	<0.001	<0.001	0.004
IL-6
7 d	878.83aA	803.33bA	617.87cB	642.89cB	24.368	<0.001	<0.001	0.015
14 d	820.22aA	742.04bB	608.81cC	750.47bB	17.152	<0.001	<0.001	<0.001
21 d	817.94abA	843.07aA	744.37bA	600.98cB	24.710	<0.001	<0.001	0.016
IL-10
7 d	181.31b	175.54b	201.08a	187.38ab	3.068	0.012	0.066	0.440
14 d	164.92D	185.02C	238.06A	209.81B	6.011	<0.001	<0.001	<0.001
21 d	190.43cC	190.27cC	236.18aA	207.02bB	4.273	<0.001	<0.001	0.001
TNF-α
7 d	357.86aA	307.25bB	290.57bcB	273.05cB	7.962	<0.001	<0.001	0.095
14 d	362.65aA	364.24aA	298.57bB	317.04bB	6.996	<0.001	<0.001	0.295
21 d	400.87aA	305.46bB	275.87cC	280.27cBC	11.019	<0.001	<0.001	<0.001

IL = interleukin; TNF-α = tumor necrosis factor-α; CON = control; SEM = standard error of the mean.

Within a row, means without a common superscript lowercase letter differ at P < 0.05, means without a common superscript capital letter differ at P < 0.01; n = 6.

¹7 d, 14 d and 21 d refers to d 7, 14, 21 after farrowing.

²The control group was a basal diet with 16% crude protein, the 3 PMS-supplemented diets were prepared by adding PMS at 0.25%, 0.50% and 0.75% to the basal diet.

3.7. Effects of PMS supplementation on the rectal microbiota of sows at weaning

Following quality control, a total of 201,631 and 202,337 high-quality sequences were obtained from the control and 0.50% PMS groups, respectively, revealing 858 OTUs. Among these, 316 OTUs were shared between the two groups, whereas 262 and 280 OTUs were unique to the control and 0.50% PMS groups, respectively (Fig. 1A). At the phylum level, Firmicutes, Bacteroidota, Campilobacterota, Actinobacteriota, Proteobacteria, Desulfobacterota, Spirochaetota, Verrucomicrobiota, Fibrobacterota, and Fusobacteriota were the ten dominant phyla in the rectum (Fig. 1B). At the genus level, Clostridium_sensu_stricto_1, Terrisporobacter, Lactobacillus, Porphyromonas, Anaerococcus, Turicibacter, Campylobacter, UCG-005, norank_f_Muribaculaceae and Ezakiella were the ten dominant genera in the rectum (Fig. 1C). Principal coordinate analysis showed that PCoA1 and PCoA2 explained 50.00% and 33.15% of the total community variation, respectively (Fig. 1H). Furthermore, the linear discriminant analysis (LDA) effect size (LEfSe) analysis indicated ten discriminative genera with LDA scores > 3.0. As shown in Fig. 1J, Mobiluncus, Ruminococcus_gauvreauii_group, Lachnospiraceae_AC2044_group, Solobacterium, norank_f_Erysipelotrichaceae, Subdoligranulum, Family_XIII_AD3011_group, Colidextribacter, Butyrivibrio, and Sarcina were enriched in the 0.50% PMS group compared with the control group (P < 0.05).

Fig. 1.

Effects of potassium-magnesium sulfate (PMS) supplementation on rectal microbiota composition in sows (n = 3). (A) Venn diagram of the operational taxonomic units (OTUs) in the sow rectum on d 21 of lactation. Microbial community bar plot at the phylum level (B) and genus level (C) on d 21 of lactation. Alpha diversity index, including Sob index (D), Chao1 index (E), Shannon index (F), and Simpson index (G). Beta diversity index, including principal coordinate analysis (PCoA) (H) and non-metric multidimensional scaling (NMDS) (I). (J) The linear discriminant analysis (LDA) effect size (LEfSe) analysis identified the biomarker bacterial species in 0.50% PMS group. CON = control group; PMS = 0.50% PMS group.

4. Discussion

Magnesium and potassium regulate animal health by influencing serum inflammatory cytokines and immunoglobulins (Apell et al., 2017; Stone et al., 2016), with their effects that are dose-dependent (Hou et al., 2014; Trawinska et al., 2013). However, low-protein diets, due to reduced soybean meal inclusion, may lead to deficiencies in these minerals (Aguirre et al., 2022; Batal et al., 2010). This study assessed the impact of graded PMS supplementation on the performance and health of sows and their piglets when low-protein diets with PMS were fed from late gestation (d 107 of gestation) through weaning. The results demonstrated that 0.50% PMS notably increased feed intake in sows and promoted growth in piglets, and PMS linearly shortened the weaning-to-estrus interval. Additionally, PMS supplementation alleviated piglet diarrhea and enhanced maternal immunity, colostrum and milk quality, as well as piglet immune development by mitigating inflammatory responses. The beneficial effects of 0.50% PMS were further supported by modulation of the rectal microbiota, with enrichment of beneficial bacterial taxa. These findings indicate that PMS at an optimal level can effectively improve the performance and health of sows and their offspring under low-protein feeding conditions.

The improvement of sow lactation and piglet growth performance is critical for swine production efficiency (Cai et al., 2025; Zeng et al., 2023). Previous research indicated that MgCl₂·6H₂O supplementation at a level of 1 g/100 kg body weight per d significantly increased litter size at weaning, total litter weight, average weaning weight, and body weight gain (Trawinska et al., 2013). The results revealed that, compared with the control, 0.50% PMS supplementation quadratically increased the average weaning weight, weight gain per litter, and ADG. Moreover, PMS supplementation linearly and quadratically decreased the diarrhea occurrence among suckling piglets during lactation. These findings showed that PMS positively influences the sow lactation outcomes and piglet growth performance.

Dietary composition influences the changes in mineral element levels in pig serum (Guo et al., 2019). Studies have shown that serum magnesium in sows responds inconsistently to changes in dietary magnesium intake. Researchers reported an increase in serum magnesium levels with dietary magnesium intake ranging from 0.015% to 0.060% (Hou et al., 2014; Zang et al., 2014), whereas a reduction was observed in growing pigs supplemented with 1 to 100 mg/L magnesium in drinking water (Svajgr et al., 1969). Lactating sows, with higher magnesium demand for milk synthesis, appear more responsive to moderate increases in dietary magnesium, whereas growing pigs receiving extra magnesium on top of an already adequate intake may divert the excess toward tissue deposition and renal excretion under homeostatic control, resulting in unchanged or even lower serum concentrations (Pinotti et al., 2021; Zang et al., 2014). Consistent with this, PMS increased sow serum magnesium levels at farrowing, and both serum potassium and magnesium levels at weaning, as well as potassium and magnesium levels in colostrum and milk, compared with the control. Furthermore, dietary supplementation with 0.75% PMS significantly increased piglet serum potassium and magnesium levels compared with the control throughout the lactation period, which is most likely mediated by improved maternal mineral status and subsequent transfer via colostrum and milk (Farmer et al., 2006).

From farrowing to weaning, injuries to the birth canal and uterus during labor, along with the significant catabolic and anabolic shifts from milk production (Zou et al., 2025), contribute to inflammatory responses in sows (Cindrova-Davies et al., 2007; Shen et al., 2015; Tan et al., 2018). Prolonged inflammation may lead to weakened immunity or even diseases (Luo et al., 2019). In this study, maternal PMS supplementation in a low-protein diet improved growth performance and health of sows and their suckling piglets, and linearly and quadratically increased serum IL-10 concentrations in both sows and piglets. These changes suggest that PMS may contribute to the observed improvements by suppressing the inflammatory response, thereby reducing the metabolic cost of inflammation and preserving more nutrients for productive functions. The IL-10 is considered a key cytokine during the resolution phase of the inflammatory response, functioning to downregulate pro-inflammatory activity derived from both innate and adaptive immunity pathways (Bernardini et al., 2005). By limiting excessive immune reactions, it protects tissues from damage and facilitates repair processes after infection or inflammatory events (Carlini et al., 2023). This outcome aligns with previous evidence showing that dietary magnesium supplementation at 2800 mg/kg diet alleviates arthritis severity and joint injury through the upregulation of IL-10 (Laragione et al., 2023). Magnesium deficiency promotes inflammation (Bernardini et al., 2005), as indicated by elevated IL-1β, IL-6, and TNF-α levels (Bernardini et al., 2005; Nakagawa et al., 2001), thereby contributing to the exacerbation of tissue damage and metabolic dysfunction (Bester and Pretorius, 2016; McCoy and Kenney, 1992). In addition to magnesium, higher dietary potassium intake attenuates salt-induced increases in the vascular inflammatory marker pentraxin-3 (Hu et al., 2018). Consistently, dietary potassium supplementation reduces renal inflammatory lesions and downregulates the expression of pro-inflammatory and pro-fibrotic mediators, such as TNF-α and transforming growth factor-β (TGF-β), in experimental models of chronic kidney disease (Wang et al., 2007b). In the present study, 0.50% PMS supplementation exhibited a linear and quadratic decrease in piglet serum IL-1β, IL-6, and TNF-α at 7 and 14 d after farrowing. This reduction in inflammatory markers is likely due to the enhancement of IL-10 production, suggesting that PMS supplementation may help suppress the inflammatory response (Bernardini et al., 2005).

Maternal immunity plays a crucial role in safeguarding piglet health and promoting growth performance (Devillers et al., 2011). Experimental magnesium deficiency has been shown to negatively impact the humoral immune system (Alcock and Shils, 1974; Kubena et al., 1989; Windhauser et al., 1991). The survival of newborn piglets relies heavily on maternal immune factors transferred via colostrum and milk (Kim, 1975). Colostrum serves as a primary source of maternal antibodies for neonatal piglets, mainly IgG (Bourne and Curtis, 1973), which are transferred from the bloodstream to the mammary gland (Salmon et al., 2009). In sows, the majority of colostrum IgG originates from serum (Bourne and Curtis, 1973). This process ceases shortly after farrowing, leading to a significant decline in colostrum IgG level as the colostrum transitions to milk (Klobasa et al., 1987). Immunoglobulin G predominantly mediates secondary antibody responses, whereas IgA is essential for mucosal immune defense (Ariza-Nieto et al., 2011). Consistent with the beneficial effects of PMS on performance and health, increasing PMS level linearly and quadratically elevated sow serum IgA and IgG at farrowing and colostrum IgG, as well as piglet serum IgA at d 14, and IgG and IgM at d 7 post-farrowing. These changes indicate that PMS enhanced humoral immunity in sows and improved the passive transfer of antibodies to piglets. Magnesium and potassium are known to support innate and adaptive immune responses by promoting immunoglobulin synthesis, complement activation, and phagocyte function (Galland, 1988; Meehan and Beiko, 2014; Zimowska et al., 2002), which is consistent with the antibody profile observed in the PMS groups. Under low-protein conditions, a stronger maternal humoral immune status and higher levels of circulating and colostral antibodies are expected to reduce infection pressure in piglets, allowing more nutrients to be used for growth and maintenance of health. In particular, increased IgA concentrations may better support mucosal protection in the gut, which fits with the rectal microbiota changes described below and may further contribute to the improved performance of piglets from PMS-supplemented sows.

Gut microbiota are strongly linked to the regulation of inflammation and exert substantial effects on host immune function (Tang et al., 2019; Zhao et al., 2022). Although no significant changes in α-diversity were observed between the two treatments, PCoA revealed distinct clustering, indicating different microbial composition changes in response to the control and 0.50% PMS groups. Firmicutes and Bacteroidetes are the predominant phyla in most mammals (Ley et al., 2008). In this study, these two phyla were also the most abundant in both groups, aligning with previous research (Ji et al., 2019; Ley et al., 2008). Furthermore, 0.50% PMS group was enriched with specific bacterial taxa such as Ruminococcus_gauvreauii_group, Lachnospiraceae_AC2044_group, Subdoligranulum, Family_XIII_AD3011_group, Colidextribacter, and Butyrivibrio. Ruminococcus_gauvreauii_group, belonging to the Lachnospiraceae family, contributes to intestinal epithelial health by strengthening barrier integrity and directly modulating T cells, thus influencing intestinal immune regulation (Cani et al., 2021; Meehan and Beiko, 2014; Van Hul et al., 2020). Lachnospiraceae_AC2044_group, Subdoligranulm, and Colidextribacter are recognized producers of short-chain fatty acids (SCFAs) that reinforce intestinal barrier integrity and suppress inflammatory responses in the host (Hu et al., 2019). Family_XIII_AD3011_group was reported to enhance disease resistance in pigs (Shang et al., 2022). Butyricicoccus has been shown to alleviate colitis and strengthen intestinal barrier function (Kwon et al., 2018). Taken together, these results indicate that 0.50% PMS modulates rectal microbiota composition of sows during lactation by enriching SCFA-producing and immune-associated bacterial taxa, which have been associated with improved barrier integrity and reduced intestinal inflammation (Nogal et al., 2021). Such a microbial profile is consistent with the anti-inflammatory cytokine and immunoglobulin responses observed in the present study and may contribute to a more favorable intestinal environment for nutrient utilization and defense against pathogens in sows, thereby supporting better lactational performance and, consequently, the improved growth and health of piglets from PMS-supplemented sows (Lin et al., 2023).

5. Conclusion

In summary, PMS supplementation in a low-protein diet during lactation may enhance sow and piglet health and performance by reducing inflammation, strengthening immune responses, and promoting the enrichment of beneficial rectal microbiota. A 0.50% PMS inclusion serves as an effective dietary strategy for achieving these benefits.

Credit Author Statement

Jiale Bao: Writing – review & editing, Writing – original draft, Project administration, Methodology, Investigation, Formal analysis, Data curation. Yanlong Li: Investigation. Bangxin Xue: Investigation, Data curation. Jun Huang: Formal analysis, Data curation. Xinyin Fan: Formal analysis, Data curation. Yueyang Meng: Formal analysis, Data curation. Yongxin Li: Writing – review & editing, Supervision. Wenjing Hei: Writing – review & editing, Supervision. Fuquan Bo: Writing – review & editing, Supervision. Xiangfang Zeng: Writing – review & editing, Supervision, Methodology, Funding acquisition, Conceptualization. Xiangzhou Zeng: Writing – review & editing, Supervision, Methodology.

Declaration of competing interest

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, and there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the content of this paper. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Yongxin Li, Wenjing Hei, and Fuquan Bo are currently employed by Qinghai Lanhushancheng Bio-tech Co., Ltd. (Xining, Qinghai, China).