An overview of active vitamin D form and natural triterpenes supplementation in sows

Modern intensive swine husbandry requires appropriate nutrition, careful herd management, and systematic evaluation of reproductive performance to maintain productivity in breeding herds (Patterson and Foxcroft, 2019). Adequate vitamin D nutrition is important for pubertal development and normal female reproductive physiology (Dicken et al., 2012). Maternal vitamin D status may also influence offspring metabolic health (Belenchia et al., 2018) and has been associated with farrowing duration, piglet birth weight, and mortality rates (Zhang et al., 2017).

During gestation and lactation, calcium requirements increase substantially due to fetal mineralization, maternal tissue accretion, and milk production (Halloran et al., 1979). Calcium transfer from maternal circulation into milk further elevates this demand (Ardeshirpour et al., 2015). Excessive skeletal mobilization may compromise bone reserves and increase the risk of locomotor disorders, including reduced bone integrity, lameness, and fractures (Kirk et al., 2005; Weber et al., 2014).

Cutaneous vitamin D synthesis induced by ultraviolet B radiation is a major natural source of vitamin D in animals; however, it is often insufficient in intensive indoor systems where sunlight exposure is limited. Therefore, dietary vitamin D supplementation is required, particularly during late gestation and lactation. Under current European regulation, vitamin D₃ supplementation in pig feed is permitted up to 2,000 IU/kg complete feed (EU Commission Implementing Regulation, 2017).

Vitamin D is central to whole-body calcium homeostasis through coordinated regulation of intestinal absorption, renal reabsorption, bone turnover, and parathyroid gland signaling, maintaining serum calcium within a narrow physiological range (Fleet, 2017). Vitamin D also contributes to development and optimal function of the immune system (Tousignant et al., 2013).

Cholecalciferol (vitamin D₃), synthesized in the skin or provided via the diet, is biologically inactive and requires metabolic activation. The first hydroxylation occurs in the liver, producing 25-hydroxycholecalciferol (calcidiol), the primary circulating marker of vitamin D status (Bikle, 2014). A second hydroxylation in the kidney generates 1,25-dihydroxycholecalciferol (calcitriol), the hormonally active form that binds the vitamin D receptor and regulates calcium and phosphate metabolism (Alonso et al., 2022). Both calcidiol and calcitriol are catabolized to inactive metabolites (e.g., calcitroic acid), maintaining metabolic balance (Encyclopedia MDPI, 2022).

Optimizing vitamin D supplementation via combined dietary administration of vitamin D₃ and active vitamin D form has become a topic of increasing interest (Hasan et al., 2023).

Active vitamin D form and natural triterpenes

Glycosylated 1,25-dihydroxycholecalciferol (calcitriol glycosides) represents a plant-derived form of active vitamin D with improved solubility characteristics. Calcitriol glycosides occur in several plant species, including Solanum glaucophyllum, Trisetum flavescens, Cestrum diurnum, and Nicotiana glauca (Jäpelt and Jakobsen, 2013). To exert biological activity, glycosidic bonds must be cleaved by bacterial β-glycosidases, generally occurring in the large intestine of monogastric animals (Zimmerman et al., 2015). A proposed advantage of active vitamin D form supplementation is reduced dependence on hepatic and renal activation steps and supporting calcium absorption during periods of high physiological demand.

Ursolic acid (UA) and oleanolic acid (OA) are pentacyclic triterpenes widely distributed in plants and characterized by antimicrobial and antiparasitic activities (Cangiano et al., 2022). UA and OA have also been described as immunomodulators in vivo and in vitro models. These effects are commonly linked to modulation of NF-κB-related signaling pathways, with potential suppression of pro-inflammatory cytokines and stimulation of anti-inflammatory mediators across tissues (Renda et al., 2022).

Active D (Phytobiotics Futterzusatzstoffe GmbH) is a plant-based source of calcitriol glycosides combined with natural triterpenes (UA, OA) and glucosamine. The nutritional concept is to provide an active vitamin D form that can support intestinal calcium uptake without full dependence on endogenous vitamin D activation capacity (independent from liver and kidneys), thereby improving calcium availability during late gestation and lactation. In parallel, UA and OA may provide additional support via immunomodulatory, hepatoprotective and nephroprotective effects.

Active D and its effect on the metabolism of vitamin D and calcium were tested in sows during demanding periods such as gestation and lactation where the need for these nutrients is significantly increased.

Study in Italy

A study conducted in Italy evaluated 24 third-parity Landrace × Large White sows. Animals were enrolled 7 days before the predicted farrowing date (day 108 of gestation) and housed in individual farrowing crates until the end of lactation. Sows were allocated to three groups (n = 8 per treatment): a control group (CTR) fed a standard basal diet supplemented with cholecalciferol at 1,800 IU/kg complete feed; treatment group 1 (TG1) fed the control diet plus 400 mg/kg of a premix composed of golden oat grass meal with ursolic and oleanolic acids; and treatment group 2 (TG2) fed the control diet plus 600 mg/kg of the same premix.

Farrowing duration was reduced in TG1 and TG2 by 25.36% and 23.26%, respectively, compared with CTR (p < 0.05) (Table 1).

Table 1. Total farrowing time of sows, Italy 2024 (a, b p<0.05).

Litter weights were higher in TG1 and TG2 and evidenced increases of 23.87% and 25.65% in comparison to the CTR group was seen (p < 0.05). The piglet birth weight was improved in both treatment groups. Piglet mortality was significantly lower in TG1 compared with CTR (p < 0.05), whereas TG2 showed a numerical reduction. The number of weaned piglets tended to be higher (p = 0.07) in TG1 and TG2 compared with CTR. Both average litter and piglet weights at weaning were improved in TG1 and TG2 in comparison to CTR (Table 2).

Table 2. Litter consistency and growth performance, Italy 2024 (A, B p<0.01; a, b p<0.05).

Study in Thailand

A second study conducted in Thailand enrolled 60 sows (second to third parity), divided into three experimental groups (n = 20 per treatment): control (CTR), test group 1 (TG1) and test group 2 (TG2). Treatment diets included 50 ppm (TG1) and 75 ppm (TG2), respectively, of the premix composed of golden oat grass meal with ursolic and oleanolic acids.

Both TG1 and TG2 exhibited significantly shorter farrowing duration than CTR (reductions of 23.56% and 23.26%, respectively; p < 0.05) (Table 3).

Table 3. Total farrowing time of sows, Thailand 2024 (a p<0.05).

TG1 showed improvements in total born and total born alive relative to CTR, and the number of weaned piglets was higher in TG1 compared with CTR (Table 4).

Table 4. Litter consistency and growth performance, Thailand 2024.

Conclusion

These two studies, with supplementation with a plant-based premix providing calcitriol glycosides in combination with ursolic and oleanolic acids (Active D) during late gestation and lactation was associated with reduced farrowing duration and improvements in litter performance metrics.

These findings are consistent with the hypothesis that supporting vitamin D activity and calcium metabolism during periods of high physiological demand may enhance sow and litter outcomes in intensive production systems, which may also positively influence sow body condition for the following cycle.

References available upon request.