Goats are an important small ruminant species in Thailand, with a rapidly expanding market and high consumer demand. Despite increasing demand and supportive policies, goat farming in Thailand continues to face several challenges, including persistently low productivity, recurring health problems, and rising feed costs. These constraints undermine profitability and sustainability and limit the ability of the sector to expand and meet market demand.

To address these concerns, previous studies have focused on improving goat production systems, with most research emphasizing enhanced nutrition and management to increase productivity (Mayberry et al., 2018);(Teixeira et al., 2024);(Aman et al., 2025) and the mitigation of health-related issues to reduce economic losses (Airs et al., 2023);(Rabee et al., 2025). Recently, plant by-products and plant-derived compounds have gained considerable attention as animal feed supplements, offering potential benefits beyond basic nutrition(Wójtowski et al., 2023);(Bouma & Noosen, 2024);(Rabee et al., 2025). The use of functional animal feed supplements is increasingly being considered a promising strategy for improving animal performance efficiency while reducing the reliance on expensive traditional feeds and synthetic additives. In particular, bioactive compounds derived from plants have gained attention because of their potential to improve nutrient utilization (Faniyi et al., 2021);(Rabee et al., 2024);(Peng et al., 2024), modulate metabolic processes (Tsiplakou et al., 2021)(Aldian et al., 2025), and support animal health without compromising its welfare (Jaber, 2025);(Jia et al., 2025);(Asfa et al., 2025).

Mangosteen (Garcinia mangostana L.) is a tropical fruit widely cultivated in India and Southeast Asia, especially in Thailand. Traditionally, extracts from the mangosteen peel have been used in herbal medicine due to their pharmacological properties, including anti-inflammatory, antimicrobial, and antioxidant effects (Suttirak & Manurakchinakorn, 2014). The mangosteen pericarp is particularly rich in several phenolic compounds such as xanthones, benzophenones, flavonoids, bioflavonoids, phenols, and tannins (Manimekalai et al., 2016);(Rohman et al., 2019). Among these, xanthones are considered the most distinctive group of compounds, as more than 50 different xanthones have been identified in mangosteen (Akao et al., 2008);(Adriani & Widjastuti, 2020). The most extensively studied xanthones in mangosteen are α-mangostin, β-mangostin, and γ-mangostin (Zarena & Sankar, 2009);(Wittenauer et al., 2012);(Rohman et al., 2019). However, xanthones have been reported to affect lipid metabolism, particularly suppressing de novo cholesterol synthesis (Adriani & Widjastuti, 2020). In addition, xanthones present in the mangosteen peel extract can suppress the intestinal absorption of cholesterol and bile acids, thereby reducing blood cholesterol levels (Kusmayadi et al., 2019). These dual effects on cholesterol synthesis and absorption suggest that mangosteen peel may have substantial potential to improve lipid metabolism and overall health in livestock.

Several in vitro and in vivo studies in ruminants have explored the functional potential of mangosteen peel supplementation. These studies demonstrated beneficial effects, such as enhanced rumen fermentation efficiency, increased nutrient digestibility, and improved antioxidant status, highlighting the potential of mangosteen peel as a sustainable feed additive in ruminant production systems (Pilajun & Wanapat, 2011);(Phesatcha et al., 2022). By improving nutrient utilization efficiency and reducing oxidative damage, mangosteen peel can help address two major challenges in goat production: increasing feed costs and animal health concerns. Moreover, natural feed additives can reduce the need for synthetic growth promoters and antibiotics, aligning with current trends toward safer and more environmentally sustainable livestock production.

In addition to its effects in the rumen, the biological activity of mangosteen peel has been demonstrated in various animal models. A systematic review of studies revealed that mangosteen pericarp extract can reduce oxidative stress, lipid peroxidation, and inflammation in animals exposed to toxins, unhealthy diets, and ultraviolet radiation. These protective effects are primarily mediated by increased endogenous antioxidant enzyme activity and reduced levels of oxidized low-density lipoprotein (LDL), highlighting the systemic antioxidant potential of mangosteen-derived compounds (Elmund & Hartrianti, 2020). Furthermore, mangosteen peel supplementation has been reported to improve growth performance, gastrointestinal health, nutrient efficiency, and immune responses in chickens (Kim et al., 2024). These findings suggest that the beneficial effects of mangosteen extend across animal species, highlighting its potential as a versatile feed additive.

Evidence indicates that mangosteen peel extract, rich in xanthones and other bioactive phytochemicals, can provide a practical solution to several challenges in goat production. By improving feed efficiency, enhancing health through antioxidant and antimicrobial activities, and reducing dependency on costly or synthetic inputs, mangosteen peel can contribute to more sustainable and profitable goat farming. Despite these promising preliminary findings, further systematic investigation is needed to clarify the specific effects of mangosteen supplementation on goat performance, metabolism, and health under practical production conditions.

Therefore, this study compared the effects of mangosteen peel powder (MPP) and mangosteen pulp extract containing 10% mangostin (MG10) on growth performance, hematological parameters, and serum metabolic profiles in growing meat goats.

The present study demonstrated that dietary supplementation with MPP and MG10 did not significantly affect growth performance, as indicated by initial and final BW or ADG, in growing meat goats. These results are consistent with those of previous studies, suggesting that dietary polyphenol or plant-derived extract supplementation does not necessarily result in measurable improvements in growth performance in small ruminants fed nutritionally adequate basal diets (Poli et al., 2021);(Giller et al., 2021);(Serra et al., 2021).

Interestingly, Ban et al. (2022) (Ban et al., 2022) reported that MPP, which contains flavonoids and cinnamic acids, can impart a pleasant flavor, whereas its condensed tannin content can impart a bitter and tangy taste. Therefore, supplementation with these nutrients may slightly reduce feed intake in meat goats. In this study, goats supplemented with MG10 exhibited significantly higher feed intake than the control group, whereas MPP supplementation had a moderate effect on feed intake. This suggests that mangostin-rich extracts can enhance palatability or stimulate appetite, likely by modulating taste perception or gastrointestinal microbial activity, as observed for other plant-derived bioactive compounds (Ban et al., 2022);(Fabela-Morón, 2024). However, the increase in voluntary feed intake did not result in substantial weight gain (Poli et al., 2025), indicating that additional feed consumption did not translate into enhanced growth. This may be attributable to the relatively short duration of the feeding trial or, alternatively, to the possibility that mangosteen supplementation did not substantially influence the nutrient utilization efficiency or the metabolic conversion of the additional feed.

Hematological parameters were not significantly affected by supplementation with either MPP or MG10 in growing meat goats. These results suggest that mangosteen-derived bioactive compounds do not adversely affect erythropoiesis or hemoglobin synthesis, supporting the hematological safety of the supplements under the conditions of this study (Soosean et al., 2010);(Kim et al., 2024). In contrast, ESR was slightly elevated in the MG10-1 group. Although significance was not reached, this finding could indicate transient, mild changes in plasma protein levels or erythrocyte aggregation (Harrison, 2015). The elevated ESR observed in the MG10-1 group may be associated with changes in plasma protein composition, particularly increases in acute-phase proteins and globulin fractions. These alterations could result from immunostimulation and modifications in hepatic protein metabolism induced by MG10-1 supplementation, thereby promoting erythrocyte aggregation and a higher sedimentation rate. Similar minor variations in the inflammatory status have been reported in ruminants supplemented with plant-derived bioactive compounds, likely reflecting short-term physiological adaptations rather than adverse effects (Kumprechtová et al., 2022). Overall, these results suggest that the dietary inclusion of MPP or MG10 is hematologically safe for growing meat goats. The slight increases in RBC count and Hb levels, along with the modest elevation in ESR observed in one group, warrant further investigation, potentially through longer-term supplementation or higher inclusion rates, to determine whether these trends have functional significance for oxygen transport or erythrocyte stability.

Notably, MG10 supplementation affected the counts of various WBC types. Mangosteen-derived products, particularly MG10, have been reported to exert immunomodulatory effects by altering the distribution of WBCs toward adaptive immunity. Bioactive compounds may enhance adaptive immunity by facilitating antigen presentation and T and B cell activation via cytokine signaling, thereby improving antigen-specific immune responses. Such modulation may strengthen the immune response, enhance disease resistance, and help maintain immune homeostasis during stress periods, such as weaning or exposure to high pathogen levels (Ban et al., 2022). A lower neutrophil-to-lymphocyte ratio, as observed in MG10-supplemented groups, could indicate reduced systemic inflammation and better immune homeostasis, consistent with the anti-inflammatory properties of α-mangostin reported in previous studies (Kim et al., 2017);(Herrera-Aco et al., 2019).

Serum biochemical indicators are critical parameters for assessing animal health, and dietary nutrient absorption and metabolism strongly influence their levels (Zaitsev et al., 2021). FBS, total cholesterol, HDL, and triglyceride levels are key indicators of energy metabolism (Graugnard et al., 2012). In the present study, MPP supplementation resulted in a slight increase in FBS levels, whereas MG10-2 significantly increased HDL and triglyceride concentrations without affecting total cholesterol or LDL levels. These findings suggest that mangostin-rich extracts can improve lipid mobilization and metabolism while modulating carbohydrate utilization (Ban et al., 2022). Elevated BUN, a marker of nitrogen metabolism, along with increased albumin levels, an indicator of hepatic protein synthesis, in MG10-supplemented goats, suggest enhanced hepatic protein metabolism and synthetic function (Ban et al., 2022). In contrast, the modest increase in AST levels observed in the MPP1 group remained within the normal physiological range, indicating no evidence of hepatotoxicity. These results align with previous reports indicating that plant-derived bioactive compounds, including xanthones and polyphenols, can support liver function, enhance protein synthesis, and improve metabolic efficiency in ruminants (Ban et al., 2022);(Kim et al., 2024).