Open Veterinary Journal, (2025), Vol. 15(7): 3206-3215

Research Article

10.5455/OVJ.2025.v15.i7.31

Effects of vitamin E supplementation on sow gestation: a meta-analysis

Ni Wayan Helpina Widyasanti¹, Sari Yanti Hayanti^2*, Cecep Hidayat^2,3, I. Putu Cahyadi Putra¹, Jonathan Anugrah Lase², Ragil Angga Prastiya⁴, Surya Surya², Maureen Chrisye Hadiatry², Marchie Astrid da Costa², Nandari Dyah Suretno², Reny Debora Tambunan², Franciscus Rudi Prasetyo Hantoro², Susana Insusila Watyning Rakhmani² and Yenny Yusriani²

¹Faculty of Veterinary Medicine, Udayana University, Denpasar, Indonesia

²Research Center for Animal Husbandry, Research Organization for Agriculture and Food, National Research and Innovation Agency of The Republic of Indonesia (BRIN), Cibinong Sciences Center, Cibinong, Indonesia

³Animal Feed and Nutrition Modeling Research Group, Faculty of Animal Science, IPB University, Bogor, Indonesia

⁴Departement of Health, Medicine, and Life Sciences, Faculty of Health, Medicine, and Life Sciences (FIKKIA), Universitas Airlangga, Surabaya, Indonesia

*Corresponding Author: Sari Yanti Hayanti. Research Center for Animal Husbandry, Research Organization for Agriculture and Food, National Research and Innovation Agency of The Republic of Indonesia (BRIN), Cibinong Sciences Center, Cibinong, Indonesia. Email: sari029 [at] brin.go.id

Submitted: 19/01/2025 Revised: 26/05/2025 Accepted: 16/06/2025 Published: 31/07/2025

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ABSTRACT

Background: Vitamin E is an antioxidant that plays a crucial function in the reproductive processes of pigs.

Aim: This study evaluated the reproductive efficacy of ɑ-tocopherol or vitamin E supplementation in pregnant sows.

Methods: Twenty-one articles from 1977 to 2021 were included in the database. There were eight parameters observed, such as concentration in the serum during gestation, colostrum concentration, number of piglets per litter at birth, number of stillborn piglets, number of piglets born alive, litter weight at birth, weight of each piglet at birth, and piglet serum concentration on day 1. The data were analyzed using the PROC MIXED procedure in SAS version 9.1.

Results: Vitamin E administration in sows led to a statistically significant rise in the level of α-tocopherol in the serum of both sows during gestation and the serum of piglets on the first day after birth. The injection of vitamin E did not yield a statistically significant effect on the observed variables, including an increase in the number of pigs per litter at birth, stillborn piglets, pigs born alive, litter weight at birth, vitamin E levels in colostrum, dan the weight of piglets at delivery.

Conclusions: Vitamin E supplements are advisable for female pigs to increase the concentration of α-tocopherol in serum throughout pregnancy and enhance α-tocopherol levels in the serum of piglets on the first day after birth.

Keywords: ɑ-Tocopherol, Antioxidant, Pregnancy, Swine.

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Introduction

Vitamin E, a lipid-soluble antioxidant, protects monounsaturated and polyunsaturated fatty acids (PUFA and MUFA) and cholesterol in cellular membranes from free radical damage (Zingg, 2023). This antioxidant exhibits fat-soluble characteristics in cell membranes. Because pigs cannot synthesize vitamin E endogenously, it must be incorporated into their diet (Lauridsen and Litta, 2018). Numerous food sources contain vitamin E, including vegetable oils, fruits, nuts, vegetables, oats, bran, barley, wheat, and palm oil (Neophytou and Constantinou, 2015; Zaaboul and Liu, 2022).

Research has demonstrated that vitamin E is essential for reproductive function in both male and female animals and humans (Siddiqui et al., 2021; Md Amin et al., 2022; Gao et al., 2023). Antioxidant properties contribute to the maintenance of normal female reproductive system function (Md Amin et al., 2022). In females, vitamin E influences menstruation, ovulation, oocyte quality, and maturation. Deficiency during pregnancy can result in miscarriage, premature birth, preeclampsia, and intrauterine growth restriction (IUGR) (Siddiqui et al., 2021).

Studies on vitamin E supplementation in pigs have yielded different outcomes. Some researchers have observed that supplementing sow feed with vitamin E during gestation increased its levels in serum (Chen et al., 2016; Jeong et al., 2019), colostrum (Chen et al., 2016), piglets born alive (Parraguez et al., 2021), weight at birth, and the number of total piglets born (Kumar et al., 2020). Conversely, other studies have reported no significant effects on vitamin E content in stillbirths, live-born piglets (Becerra, 2017; Santos et al., 2019; Jeong et al., 2019), total number of piglets born, piglet weight at birth, serum piglet weight at birth (Jeong et al., 2019), and piglet weight at birth (Wang et al., 2017; Jeong et al., 2019).

Despite these discrepancies, a comprehensive meta-analysis is required. Meta-analysis measures and investigates variations in study results, helping to identify potential sources of bias and apparent discrepancies (Mohapatra and Sengupta, 2016; Tatsioni and Ioannidis, 2024). The primary objective of this study was to conduct a meta-analysis to evaluate the impact of vitamin E oral and injection supplementation in pregnant sows on the reproductive performance of pigs.

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Materials and Methods

Ethics statements

This study was a meta-analysis review article; therefore, ethical approval was not required.

Database development

This meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) principles (Hidayat et al., 2020). The data were obtained from publications published between 1977 and 2021. A comprehensive literature search was conducted using keywords such as “Vitamin E,” “ɑ-tocopherol,” “pig,” “sow,” “gilts,” “reproductive performance,” “fertility,” “gestation,” and “pregnant” on search engines including Google Scholar, Scopus, PubMed, ScienceDirect, and Directory of Open Access Journals (DOAJ) to identify relevant articles.

Inclusion/exclusion criteria

The inclusion criteria were as follows: (1) articles published in English by reputable publishers such as Google Scholar, Scopus, PubMed, ScienceDirect, and DOAJ; (2) appropriate experimental design; (3) sufficient experimental and replication materials; (4) pig-specific animal experiments; (5) vitamin E dose in mg/day or convertible to mg/day; (6) reproductive performance parameters; (7) adequate sows (n); and (8) criteria for administering vitamin e orally or by injection.

Data extraction

Input data from selected articles included author name, publication year, journal name, pig type, number of pigs, vitamin E treatment dose, observed parameters, recommended dose, vitamin E source, parameter units, sampling technique, and measurement techniques. Thirty-three studies on vitamin E supplementation in sows were initially conducted. Twenty-one studies met the inclusion criteria based on titles and abstracts. Vitamin E studies were compiled using assessed variables, including serum gestational vitamin E levels, serum vitamin E levels in piglets on day 1, number of pigs per litter at birth, number of stillborn piglets, number of live-born piglets, litter weight at birth, colostrum vitamin E levels, and piglet weight at birth.

Following a comprehensive evaluation, 21 articles were selected and incorporated into the designated databases (Table 1). Sows undergo stages of pregnancy and postnatal period, during which they receive commercially manufactured feed supplemented with vitamin E at 0–39079 mg/day. Alternative dosing units were converted to mg per day for uniformity. Performance parameters for vitamin E included concentration in serum during gestation (µg/ml), concentration in colostrum (µg/ml), number of piglets per litter at birth, number of stillborn piglets, number of piglets born alive, weight of the litter at birth (kg), weight of each piglet at birth (kg), and concentration in day 1 (µg/ml). The dosage and performance characteristics were entered into the database. Statistical analysis was conducted after input of the dietary vitamin E dosage and gestational performance data. The article selection and evaluation processes are illustrated in Figure 1.

Statistics analysis

The data were processed using a mixed-model technique (Lagares et al., 2017; Hayanti et al., 2022). The analysis used the PROC MIXED function in SAS version 9.1. The dosage of vitamin E was determined as a fixed effect in specific investigations, whereas other studies considered it to have a random impact, as indicated in the RANDOM statement. The mathematical models employed were as follows:

Yij=β0 + β1 Level ij + Experiment i + Experiment i Level ij + eij (1),

Yij=β0 + β1 Level ij + β2 Level ij + Experiment + Experiment Level ij + eij (2).

This investigation examines two types of mathematical models within the linear mixed model (LMM) framework: LMM models of orders 1 and 2. Fixed effects are represented by β0 + β1 Level ij (Order 1) and β0 + β1 Level ij + β2 Level ij (Order 2). The models incorporated the effects of Experiments i and j. The variables are Level ij (level addition to random impacts in first and second sequences), β0 (overall intercept value across experiments), β1 (first-order linear regression coefficient), β2 (second-order linear regression coefficient), experiment (specific experiment conducted), and eij (unexplained residual error). Quadratic regression models with a p < 0.05 were considered significant. The statistical model used p-values and root mean square errors, with significance determined by assuming a threshold.

y=aX2 + bx + c, and

dy/dx=2ax + b=0 and

2ax + b=0

x=−b/2a

x=optimum vitamin E dose.

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Results

Vitamin E supplementation in sows resulted in a statistically significant increase (p < 0.05) in α-tocopherol concentrations in both sow serum during gestation and piglet serum on the first postpartum day. However, vitamin E supplementation did not significantly affect (p > 0.05) the number of piglets per litter at parturition, incidence of stillbirths, number of live-born piglets, total litter weight at farrowing, vitamin E concentrations in colostrum, and piglet birth weight. The effects of ɑ-tocopherol and vitamin E on the duration of sowing gestation are presented in Table 2.

Table 1. Studies included in the meta-analysis.

Fig. 1. Selection of articles and evaluation process using the PRISMA method. PRISMA=preferred reporting items for systematic reviews and meta-analyses.

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Discussion

The meta-analysis conducted in this study revealed a statistically significant increase in α-tocopherol concentrations in the serum of pregnant sows following vitamin E supplementation (Table 2). This was similar to the findings of Chen et al. (2016), who reported that α-tocopherol levels in serum on days 30, 60, and 90 and on day 11 of lactation increased when sows were fed diets with higher vitamin E levels. Becerra et al. (2017) also stated that during lactation, vitamin E levels in sows increased significantly after vitamin E supplementation through injection on day 107 of pregnancy and during lactation. The increase in vitamin E levels in the serum of gestating sows was consistent with the increase in vitamin E levels in day-old piglets in this meta-analysis (Table 2). High concentrations of vitamin E in sow diets increase α-tocopherol levels in the milk and plasma of sows, resulting in increased vitamin E levels in the plasma of piglets (Wang et al., 2017). Supplementing the diet of pregnant sows with high levels of vitamin E increased the antioxidant capacity of sows and piglets. This is evidenced by the increased activity of antioxidant enzymes, such as glutathione peroxidase and catalase, in piglets (Szczubial, 2015; Wang et al., 2017; Lauridsen et al., 2021). High vitamin E levels in the maternal diet improved the immune function of piglets. This includes increased concentrations of immunoglobulins (IgG and IgA) in sow plasma, colostrum, and milk, which are crucial for passive immunity in piglets (Wang et al., 2017). Furthermore, piglets from sows with high vitamin E intake show improved immunological responses, such as lower levels of inflammatory markers and better cytokine profiles (Lauridsen et al., 2021).

Table 2. Results of the meta-analysis.

The elevated serum vitamin E concentration in the supplemented sows can be attributed to the transport of vitamin E via lipoproteins into the bloodstream. These lipoproteins are macromolecular aggregates that carry triglycerides and cholesterol into the blood (Acuña–Aravena and Cohen, 2020). Wang et al. (2017) stated that the timing of peak levels of α-tocopherol in plasma of sows with vitamin E supplementation of 250 IU/kg occurred on day 21 of lactation, while Szczubial (2015) found significantly higher plasma vitamin E levels in sows 7 days postpartum when supplemented with 200 mg of vitamin E. van Kempen et al. (2016) noted that orally administered vitamin E appeared in plasma after a 56-minute delay, with a half-life of 2.6 ± 0.8 hours. In contrast, intravenous injection results in the rapid disappearance and reappearance of plasma substances. The initial peak’s half-life was 1.7 ± 0.3 minutes, while the second peak’s half-life was 5.9 ± 1.2 hours. In this meta-analysis study, the sows received daily dietary vitamin E intake, with some receiving additional vitamin E injections to maintain serum vitamin levels. Consequently, serum vitamin E concentrations were higher in supplemented sows than in non-supplemented sows.

This meta-analysis revealed a statistically significant increase in vitamin E (α-tocopherol) levels in the serum of 1-day-old piglets following vitamin E administration. Comparable fluctuations in serum vitamin E concentrations were observed by Jeong et al. (2019) in day-old piglets born to sows that were administered various doses of vitamin E supplements. Parraguez et al. (2021) demonstrated that piglets from vitamin E-supplemented sows exhibited higher serum α-tocopherol levels (4.05 ± 0.32 vs. 1.95 ± 0.18 µg/ml) than those in the control group. Wang et al. (2017) suggested that vitamin E supplementation (250 IU/kg) can increase plasma IgA and IgG levels, total antioxidant capacity, and catalase enzyme levels in piglets. The increased serum levels in piglets were attributed to the transfer of α-tocopherol across the placenta during pregnancy; however, this transfer is limited (Matte and Audet, 2020). The placenta has specific mechanisms for nutrient transfer, including the presence of lipoprotein receptors and α-tocopherol transfer protein (α-TTP), which selectively facilitates the transfer of RRR-α-tocopherol (the most biologically active form of vitamin E). However, this selective transfer is not very efficient, leading to lower α-tocopherol concentrations in fetal circulation compared with parental blood (Gázquez et al., 2023). However, vitamin E levels in piglets injected with vitamin E decreased from day 3 to day 25 (7.67 to 2.19 µg/ml), indicating that vitamin E injection in the mother did not sustainably increase vitamin E levels in the piglets. This may be due to the inefficient transfer of vitamin E through the placenta or milk (Berreca et al., 2017).

Vitamin E administration did not result in a significant decrease in the α-tocopherol concentration in colostrum. Several studies have shown that although vitamin E supplementation in dams increases serum α-tocopherol levels, its transfer to colostrum is not significantly increased in the early stages of lactation (Medeiros et al., 2016; Melo et al., 2017; Moghimi-Kandelousi et al., 2020). The concentration of α-tocopherol in colostrum tends to increase after supplementation; however, this increase is more pronounced in milk than in early colostrum (Medeiros et al., 2016; Silva et al., 2017). Vitamin E is a fat-soluble vitamin that is stored in adipose tissue and the liver; therefore, its release into the blood circulation is gradual (Bellés et al., 2019). This storage mechanism may delay the increase in vitamin E levels in postsupplementation colostrum. The efficiency of vitamin E transfer into colostrum is influenced by various factors, including maternal vitamin E status, the form of vitamin E used (natural vs. synthetic), and supplementation duration (da Silva et al., 2016; de Sousa Rebouças et al., 2019). Therefore, short-term supplementation may not be sufficient to significantly increase vitamin E levels in colostrum, given that vitamin E must be mobilized from storage (Melo et al., 2017). In contrast, long-term supplementation is more effective for gradually increasing vitamin E levels in colostrum (de Sousa Rebouças et al., 2019). Vitamin E supplementation in sows is required to maintain stable vitamin E concentrations in colostrum and milk. This is because newborn piglets are highly susceptible to vitamin E deficiency owing to low tissue reserves at birth and limited transfer of vitamin E through the placenta and colostrum. This susceptibility can lead to conditions such as “white muscle disease,” which is characterized by degeneration and necrosis of the skeletal muscle (Shastak and Pelletier, 2025).

The research findings indicate that the addition of Vitamin E did not have a statistically significant effect on litter size at birth. Similar results were reported by Chen et al. (2016), who found that administration of vitamin E at doses of 30 IU and 90 IU in combination with selenium sourced from organic or inorganic sources did not increase litter size at birth. Santos et al. (2019) reported similar results in which the administration of 45 mg/kg vitamin E in the gestation phase and 125 mg/kg in the lactation phase to sows in combination with other multivitamins did not increase litter size at birth. However, Kumar et al. (2020) reported different results, where sows orally supplemented with Vitamin E 1g/sow/day and Selenium 2 mg/sow/day for 7 days before the estimated calving date and 7 days after calving showed a higher litter size at birth in the treatment group than in the control group. König et al. (2021) and Chen et al. (2023) suggested that achieving an optimal litter size requires an increase in both ovulation rate and placental efficiency. A higher ovulation rate is essential for a larger litter size, as it sets the upper limit for the number of piglets that can be born (Chen et al., 2023). Efficient placental development and vascularization are crucial for fetal growth. Breeds such as the Chinese Meishan pig, which have high placental efficiency, can support larger litters despite having smaller uterine sizes (König et al., 2021). However, Chen et al. (2016) found no significant interaction between vitamin E levels and selenium sources on reproductive performance, including serum progesterone levels.

Supplementing sows with vitamin E did not have a statistically significant effect on the number of stillborn or live-born piglets. These results are supported by Wang et al. (2017), who reported that the administration of vitamin E (250 IU/kg) to sows on gestational day 107 did not increase the number of piglets born alive. Furthermore, Chen et al. (2016) also supported our findings, stating that the administration of vitamin E up to 90 IU/kg and selenium from both organic and inorganic sources had no effect on the number of live and stillborn piglets but rather affected the body weight of the piglets. In contrast, Kumar et al. (2020) reported that the administration of vitamin E (1 g/sow/day) and selenium (2 mg/sow/day) reduced the number of stillbirths in sows. However, in the study by Kumar et al. (2020), the number of samples used was insufficient to represent these results compared with those of Wang et al. (2017) and Chen et al. (2016).

Vitamin E supplementation in sows may enhance their immune capacity, potentially supporting embryo development and providing antioxidant protection (Shastak and Pelletier, 2025). Despite this potential, the current study found no significant effect of vitamin E on the numbers of stillborn or live-born piglets. Typically, stillborn pigs constitute 3%–8% of the total piglets at birth (Rangstrup-Christensen et al., 2017). The causes of stillbirth in piglets are multifactorial and involve genetic, environmental, and management factors. Intrapartum stillbirth accounts for 75% of all stillbirths in pigs. Factors such as piglet size and shape, litter size, birth order, gestation length, and birth weight deviation are significantly associated with increased intrapartum stillbirths (Nam and Sukron, 2021; Lanh and Nam, 2022).

Vitamin E supplementation did not result in a significant increase in birth weight. This finding is consistent with that of Jeong et al. (2019), Berreca (2017), Wang et al. (2017), Sosnowska et al. (2012), and Shelton et al. (2012), who reported no significant difference in litter weight at birth with vitamin E supplementation. Jeong et al. (2019) observed no statistically significant variation in litter weight at birth when sows were supplemented with vitamin E supplementation. However, Kumar et al. (2020) reported contrasting results, noting the significant effect of vitamin E supplementation on piglet birth weight.

Vitamin E supplementation is correlated with enhanced feed conversion ratios (gain-to-feed ratio), suggesting that pigs can more effectively convert feed into body mass. Improving feed efficiency plays a crucial role in increasing weight gain in pigs. Nevertheless, this weight gain was observed in pigs during the weaning and finishing phases (Rao et al. 2023; Wang et al. 2023). This discrepancy can be attributed to various factors that influence the observed phenomenon. As noted by Assan (2013), the birth weight of pigs may be affected by both genetic and nongenetic factors. Furthermore, it is crucial to acknowledge that the birth weight of a pig may be affected by a range of environmental factors, including the composition and nutritional quality of the feed and the overall practices of animal husbandry.

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Conclusion

The administration of vitamin E supplements to gestating sows is recommended to enhance α-tocopherol concentrations in maternal serum during pregnancy and in neonatal piglet serum.

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Acknowledgments

The authors thank the Research Center for Animal Husbandry, Research Organization for Agriculture and Food, National Research and Innovation Agency of the Republic of Indonesia (BRIN), and Faculty of Veterinary Medicine, Udayana University, for providing the necessary facilities for the study.

Conflict of interest

The authors declare no conflicts of interest.

Funding

The authors did not receive any funding for this study.

Authors contributions

NWHW and SYH conceptualized, designed, and wrote the original draft. NWHW, IPCP, JAL, RAP, SS, MCH, MAC, NDS, RDT, FRPH, and SIWR searched the literature and collected and processed the data. NWHW and CH analyzed the data. SYH, CH, and YY supervised the research. SYH and YY critical review of the manuscript. IPCP, JAL, RAP, SS, MCH, MAC, NDS, RDT, FRPH, and SIWR performed the necessary editing. All authors have read and approved the final manuscript.

Data availability

All data required to substantiate the findings of this research are included in the manuscript.

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