Comparative Impact of Selenium Selenite and Nano‐Selenium on Physiological Functions in Male Goat Kids

ABSTRACT

The present experiment was conducted to study the effects of nano‐selenium (Se‐NP) supplementation on nutrient utilization, growth, immune responses, antioxidant status, and reproductive performance in male goat kids over a 150‐day experimental period. Twenty‐four growing male goats were randomly allocated to three groups: control (T1), and two treatment groups receiving dietary Se‐NP at graded levels (T2‐0.15 ppm and T3‐0.30 ppm). Dry matter intake (DMI), nutrient digestibility, and the plane of nutrition remained statistically comparable (p > 0.05) across all groups, indicating no adverse effect of Se‐NP on feed acceptance or digestion. Growth performance metrics including average daily body weight gain and feed conversion ratio were also unaffected by the treatments. Haematological and serum biochemical parameters, including glucose, total protein, and creatinine, remained within normal physiological limits, though significant day‐wise variations (p < 0.05) were witnessed in glucose, cholesterol, total protein and creatinine. Antioxidant enzyme activity revealed a marked increase (p < 0.01) in Glutathione peroxidase (GPx) activity in T3(22.12 ± 2.21) and T2(11.99 ± 0.93), suggesting enhanced oxidative defence, while Superoxide dismutase (SOD) and Catalase (CAT) activities were unchanged. Notably, serum Triiodothyronine (T3) concentration increased significantly (p < 0.05) in T3(4.32 ± 0.24) and T2(4.21 ± 0.23) groups, accompanied by a reduction in Thyroxin (T4) and T4:T3 ratios, indicating potential modulation of peripheral thyroid hormone metabolism. Immune profiling demonstrated enhanced humoral (p < 0.05) and cell‐mediated immune responses (p < 0.01) in Se‐NP groups, particularly T3, as evidenced by higher haemagglutination titres and delayed‐type hypersensitivity reactions. Reproductive assessment showed no differences in scrotal size; however, sperm quality parameters‐mass motility, live sperm percentage, and hypo‐osmotic swelling test response‐were significantly improved (p < 0.01) in Se‐NP supplemented goats. In conclusion, Se‐NP supplementation, especially at higher levels (T3), positively influenced antioxidant status, immune competence, and seminal quality without compromising growth or metabolic health, demonstrating its potential as a functional micronutrient to enhance reproductive and immunological resilience in male goats.

1. Introduction

Selenium (Se) is a vital trace element with multifaceted roles in animal physiology, particularly in antioxidant defence, immune modulation, and reproductive function (Surai 2002). As a cofactor for essential selenoproteins such as glutathione peroxidase (GSH‐Px), Se contributes significantly to cellular protection against oxidative damage (Hoffmann and Berry 2008; Cai et al. 2012; Jung et al. 2023; Dalia et al. 2020). In poultry and other livestock, adequate Se supplementation has been correlated with, enhanced immunity, and redox homeostasis, (Liao et al. 2012; Skřivan et al. 2012). However, conventional inorganic selenium sources, such as sodium selenite, are constrained by poor bioavailability, a narrow margin of safety, and potential pro‐oxidant effects at higher dosages (Zhou et al. 2021) raising concerns about their long‐term efficacy.

Advancements in nanotechnology have led to the development of selenium nanoparticles (SeNPs), which offer a promising alternative due to their unique physicochemical characteristics, including increased surface area, improved solubility, and enhanced cellular uptake‐SeNPs have demonstrated superior bioavailability and biological efficacy across various animal models (Surai 2024; Hu et al. 2012). Studies across various species have demonstrated that SeNP supplementation can elevates antioxidant enzyme activity, and strengthens immune competence (Salam et al. 2021; Ghasemi et al. 2023; Li et al. 2024). Moreover, SeNPs have been reported to modulate thyroid hormones and key antioxidant biomarkers such as superoxide dismutase (SOD), glutathione peroxidase (GPx), and total antioxidant capacity (TAC), thereby influencing metabolic and reproductive pathways (Eid et al. 2019; Ahmed et al. 2020; Aitken 2022). Se yeast effectively attenuates diet‐induced oxidative stress and apoptosis in rumen epithelium via modulation of antioxidant enzymes and apoptotic gene networks, linking selenium nutrition with gut health and productivity (Shahid 2025). Despite these promising outcomes, the application of SeNPs in enhancing reproductive function‐particularly in male goats (bucks)‐remains insufficiently explored. Recent studies indicate that selenium nanoparticles (SeNPs) incorporated into semen extenders enhance sperm preservation primarily through improved antioxidant protection and mitochondrial stability. In boars, SeNPs at 1 µg mL⁻¹ maintained motility, membrane and DNA integrity during liquid storage and improved conception rates after artificial insemination (Paul et al. 2024). Mechanistic nanoconjugate approaches further confirm reduced ROS and lipid peroxidation with concurrent gains in post‐thaw fertility and embryo development (Piri et al. 2024). Selenium plays a crucial role in spermatogenesis, sperm motility, and the protection of sperm DNA integrity against reactive oxygen species (ROS)‐induced damage (Aitken 2022; Shi et al. 2020). Analogous male‐focused investigations show that nano‐form selenium and zinc enhance male reproductive function by improving testicular perfusion, antioxidant capacity, endocrine balance, and semen quality under stress conditions, (NasrEldeen et al. 2025; Horky et al. 2023). Complementary extender‐based studies demonstrate that Se‐NPs directly stabilize sperm during storage and cryopreservation through mitochondrial and redox protection, preserving motility and membrane‐DNA integrity and improving conception outcomes in boars and bucks (Paul et al. 2024); (Ibrahim et al. 2025). Mechanistic nanoconjugate evidence further confirms reduced ROS generation and lipid peroxidation with concurrent gains in post‐thaw fertility and embryo development (Piri et al. 2024). Collectively, these findings establish SeNPs as functionally validated nano‐antioxidant modulators of male reproductive efficiency. Additionally, selenium status is intimately linked with thyroid hormone metabolism, which is known to impact reproductive and metabolic efficiency (Winther et al. 2020). Emerging evidence also indicates that SeNPs may exert protective effects on testicular cells under pathophysiological stress, including inflammation‐induced Leydig cell dysfunction (Li, Wang, Feng,et al. 2025). Most existing SeNPs research has been limited to monogastric and laboratory animal models, such as poultry and rodents, with minimal focus on ruminants‐particularly indigenous goat breeds. Goats possess distinct physiological and digestive adaptations that influence trace mineral metabolism and face unique reproductive challenges, including seasonal breeding cycles and environmental stressors. In selenium‐deficient regions like the Indian subcontinent‐where goats form a vital component of rural livelihoods‐there is a pressing need to develop species‐specific nutritional strategies that can improve reproductive efficiency and metabolic resilience. Incorporating SeNPs into such strategies may offer a sustainable and scientifically grounded solution to address these challenges in an environmentally responsive manner.

2. Materials and Methods

2.1. Study Location and Duration

The present experiment was performed to evaluate the efficacy of selenium (Se) nanoparticles on growth performance, nutrient utilization, antioxidant, immune status, and reproductive performance in male goat kids. The study was carried at Mineral and Vitamin Nutrition Laboratory, Animal Nutrition Division, ICAR–Indian Veterinary Research Institute (IVRI), Izatnagar, India.

2.2. Experimental Animals and Design

Experiment involved 24 growing male goat kids (Capra hircus), aged 5–6 months with an initial average body weight of 10.96 ± 0.32 kg. The animals were randomly allocated to three treatment groups (T1, T2, and T3; n = 8 per group) using a completely randomized block design for 150 days duration.

• T1 (control): Basal diet consisting of wheat straw and concentrate mixture containing 0.3 ppm selenium from sodium selenite.

• T2: Similar basal diet supplemented with 0.15 ppm selenium as selenium nanoparticles.

• T3: Similar basal diet supplemented with 0.3 ppm selenium as selenium nanoparticles.

2.3. Synthesis and Characterization of Selenium Nanoparticles

2.3.1. Synthesis

Selenium nanoparticles were synthesized via a wet chemical reduction method. A 0.4 M ascorbic acid solution was added dropwise to a vigorously stirred 0.1 M aqueous solution of SeO₂, resulting in the formation of a red precipitate. The precipitate was washed, filtered, dried under vacuum, and stored at room temperature.

2.3.2. Characterization and Quantification

The particle size and morphology of the synthesized selenium nanoparticles were analyzed using transmission electron microscopy (TEM). Total selenium concentration in SeNPs was determined using graphite furnace atomic absorption spectroscopy (GF‐AAS; ECIL 4141, ECIL, India). Samples were digested with trace‐metal grade nitric acid and hydrogen peroxide using a closed digestion system until clear, then diluted to volume with ultrapure water. Se was measured at 196.0 nm with a palladium‐magnesium matrix modifier. Quantification was performed using external calibration standards prepared in the same acid matrix. The calibration curve showed excellent linearity (R ² > 0.999). Method accuracy was verified by spike recovery (95%–105%), and all samples were analyzed in triplicate with reagent blanks included.

2.3.3. Feeding and Management

All animals were individually in well ventilated house with free access to clean drinking water. The concentrate mixture was formulated as provided in Table 1, following ICAR feeding standard (Indian Council of Agricultural Research 2013) targeting an average daily gain of 50 g. The mineral mixture used was specifically formulated to exclude selenium and zinc to ensure controlled supplementation. The proximate principle in feed, faeces and residue were calculated by following the methods as per AOAC (Association of Official Analytical Chemists 2000) standard methods. The fibre fractionation of the feeds, residue, faecal samples were done by following the methods of Van Soest (Van Soest et al. 1991).

Table 1.

Physical composition of concentrate mixture for growing goat kids.

Ingredients	Amount (%)
Crushed maize	34
Deoiled soybean meal	38
Wheat bran	25
Mineral mixturea	2
Common salt	1

^a A Se and Zn free mineral mixture was formulated containing calcium carbonate −30.69%, Dicalcium phosphate −68.38%, KI −0.50%, MnSO₄ −0.27%, CuSO₄ −0.14%, CoSO₄ −0.04%.

2.3.4. Blood Collection and Processing

Blood samples were collected from the jugular vein on Days 0, 75, and 150 of the experimental period, prior to morning feeding. Samples were centrifuged at 3000 rpm for 15 min to separate serum and plasma, which were aliquoted into sterile Eppendorf tubes and stored at –20°C until analysis.

2.3.5. Blood Haematological Analysis

Hemoglobin (Hb) and packed cell volume (PCV) were estimated using a veterinary hematology analyzer (HA‐22/20/Vet; Clindiag System BVBA) following the manufacturer's protocol.

2.3.6. Blood Biochemical Analysis

Serum samples were analyzed for glucose, total protein, albumin, globulin, urea, creatinine, and total cholesterol using commercial diagnostic kits (CREST BIOSYSTEMS, Coral Clinical Systems, Goa, India), as per the manufacturer's instructions.

2.3.7. Serum Globulin

It was calculated by subtracting serum albumin from TP.

$$\mathrm{Globulin}\mathrm{in}\mathrm{g}/\mathrm{dL}=\mathrm{total}\mathrm{protein}(\mathrm{g}/\mathrm{dL})-\mathrm{albumin}(\mathrm{g}/\mathrm{dL})$$

2.3.8. Albumin/Globulin Ratio (A: G)

The serum albumin value and corresponding globulin values of individuals in each group were utilized to get the A: G ratio.

2.3.9. Analysis of Enzymes in Serum Samples

Serum concentrations of tri‐iodothyronine (T3), thyroxine (T4), thyrotropin (TSH), testosterone, and insulin were estimated using LDN‐T3 ELISA 2nd Generation kits (Nordhorn, Germany). Absorbance was measured at 450 nm using an ELISA reader.

2.3.10. Estimation of Enzyme Activity in Serum Samples

Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were estimated according to the method described by (Reitman and Frankel 1957), using diagnostic kits manufactured by Span Diagnostics Limited, Surat, India. Alcohol dehydrogenase activity was assessed using BioVision's alcohol dehydrogenase assay kit (Catalog K787‐100; 100 reactions; storage at −20°C).

2.3.11. Estimation of Antioxidant Enzyme Activity in Serum Samples

Catalase, superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities were measured using ELISA‐based assay kits (Cayman Chemical Company, Ann Arbor, MI, USA).

2.4. Immunological Studies

2.4.1. Humoral Immune Response

Humoral immune response was assessed using a micro‐hemagglutination assay. Each goat was intravenously injected with 1 mL of 20% suspension of washed chicken red blood cells (CRBC) as described by Wegman (Wegmann and Smithies 1966).

2.4.2. Sample Collection

Blood samples were collected via venipuncture on Day 0 (preinjection), and on Days 7, 14, 21, and 28 postinjections. Serum was separated and stored at −20°C until analysis.

2.4.3. HA Titre Measurement

Antibody titres against CRBC were determined by two‐fold serial dilution of heat‐inactivated serum (30 min at 56°C) in PBS. Each well of a microtiter plate received 50 µL of PBS, and 50 µL of serum was added to the first well. Serial dilutions were performed by transferring 50 µL from one well to the next. Finally, 50 µL of 2% CRBC suspension was added to each well. Plates were incubated at 37°C for 30 min. The titre was expressed as log₂ of the reciprocal of the highest serum dilution showing agglutination.

2.4.4. Cell‐Mediated Immune Response

Cell‐mediated immunity was assessed through an in vivo delayed‐type hypersensitivity (DTH) reaction using phytohaemagglutinin‐P (PHA‐P) as a mitogen.

2.5. Procedure

Skin areas on both sides of the neck were shaved 24 h before testing. A 1 cm² area was marked on each side, and skin thickness was measured using a Vernier caliper (0 h, baseline). Each animal received an intradermal injection of 125 µL of saline (control) on one side and 125 µL of PHA‐P solution on the other side. Skin thickness was measured at 12, 24, 48 and 72‐h postinjection (Masucci et al. 2011).

2.6. Reproductive Traits of Male Goats

2.6.1. Mass Motility

Mass motility was calculated by placing a drop of freshly collected, neat semen on a clean, grease‐free, pre‐warmed glass slide (37°C) and examined under low‐power (10x) phase‐contrast microscope with a thermostatically controlled stage (B5 Professional Series, Motic Ltd.). Motility was scored as follows:

Mass motility score
Very vigorous forward motion, extremely rapid waves and eddies, with 90%–100% active sperms	Excellent	+5
Vigorous, progressive movement with rapid and abruptly forming waves and eddies with about 70%–80% sperms are motile	Good	+4
Progressive rapid movement of sperm with slow moving waves and eddies and 50%–60% sperms are motile	Fair	+3
Oscillatory or rotary movement, no waves and eddies, 30%–40% progressively motile sperms	Poor	+2
Stationary bunting or weak rotary movements, 10%–20% scattered progressive sperms	Very poor	+1
Immotile sperm	All dead	0

2.6.2. Percent Live Spermatozoa

Live sperm percentage was determined using Eosin‐Nigrosin differential staining as per the method as prescribed by Lasley (Lasley et al. 1942).

2.6.3. Membrane Integrity Test (HOST)

Hypo‐osmotic swelling test (HOST) was conducted following Jeyendran (Jeyendran et al. 1984) with minor modifications. Spermatozoa were classified according to the swelling pattern of the tail membrane:

• Pattern A: No swelling (membrane damage)

• Pattern B: Swelling at tail tip

• Pattern C: Hairpin‐like swelling

• Pattern D: Complete tail swelling

Patterns B, C, and D were considered indicative of functionally intact sperm membranes (HOST‐positive).

2.7. Statistical Analysis

Data were analyzed using SPSS software (version 20.0; IBM Corp., USA). The experiment followed a completely randomized design with three dietary treatments. Variables related to feed intake, nutrient digestibility, growth performance, feed efficiency, and semen characteristics were analyzed by one‐way ANOVA with treatment as a fixed effect using the model: Yᵢⱼ = μ + Tᵢ + εᵢⱼ, where Yᵢⱼ is the observed response, μ is the overall mean, Tᵢ is the treatment effect, and εᵢⱼ is the residual error.

Parameters measured repeatedly over time (hematological, biochemical, antioxidant, hormonal, and immune indices) were evaluated using a mixed‐effects repeated‐measures model including treatment, period, and treatment × period interaction as fixed effects, with animal nested within treatment as a random effect and period as the repeated factor. The covariance structure was selected based on the lowest Akaike Information Criterion (AIC). Data normality was assessed using the Shapiro–Wilk test, and antibody titres were log₂‐transformed when required to meet model assumptions. Multiple comparisons among means were performed using Tukey's post hoc test. Results are presented as least squares means ± SEM. Differences were considered statistically significant at p < 0.05, and values of 0.05 ≤ p ≤ 0.10 were interpreted as trends (Jones 1994).

3. Results

3.1. Synthesis, Characterization and Quantification of Se Nano Particles

3.1.1. Characterization of Se Nano Particles

A high resolution TEM image of the synthesized selenium particles showed that most of them were spherical in shape and their size were between 15 and 60 nm (all below 100 nm) as depicted in Figure 1.

Figure 1.

Transmission electron microscopy image of nano selenium. [Color figure can be viewed at wileyonlinelibrary.com]

3.1.2. Quantification of Se Nano Particles

The concentration of the Se in the synthesized product as determined by Atomic Absorption Spectroscopy with hydride‐generation ranged between 23.51% and 25.62% with an average value of 24.56%. In this study ascorbic acid was used as a reducing agent as it is biocompatible and has good reducing properties forming a spherical nanoparticle having a size range of 15–60 nm (all below 100 nm) (Figure 1). The selenium concentration in different product batches, as measured by Atomic Absorption Spectroscopy (AAS), ranged from 23.51% to 25.62%, averaging 24.56%.

3.1.3. Chemical Composition of Feeds

The chemical composition of the concentrate mixture and wheat straw offered to the growing goat kids is presented in Table 2. The analyzed nutrient composition remained within the expected range and was uniform across dietary treatments.

Table 2.

Chemical composition of feeds (% DM basis) offered to goat kids.

Attributes	Concentrate mixture	Wheat straw
Organic matter	91.67	92.13
Crude protein	24.74	3.21
Ether extract	2.11	0.76
Total ash	8.33	7.87
NDF	61.97	58.71
ADF	9.35	52.02
Ca	1.23	0.50
P	0.68	0.17
Zn (ppm)	36.60	27.02
Se (ppm)	0.069	0.014

3.1.4. Nutrient Utilization and Growth Performance

The mean daily dry matter intake (DMI) of kids during different fortnights of the experimental period across treatment groups is presented in Table 3. The overall mean DMI did not differ significantly (p > 0.05) among groups T1, T2, and T3, indicating similar feed intake across treatments throughout the study period.

Table 3.

Effect of dietary nano‐Se on feed intake (gd^{− 1}) and digestibility of goat kids.

Parameters	Treatments			SEM	p value
	T1	T2	T3
Average daily intake (gd− 1)	424 ± 14.8	426 ± 14.3	424 ± 12.9	7.45	0.995
Total intake (kg)	69.9 ± 2.45	70.2 ± 2.36	70.0 ± 2.14	1.23	0.995
Dry matter intake (gd− 1)	477 ± 28.7	479 ± 18.1	467 ± 17.2	11.2	0.917
DM digestibility (%)	56.1 ± 2.81	56.5 ± 3.29	59.2 ± 0.40	1.37	0.633
OM digestibility (%)	60.2 ± 2.67	60.9 ± 2.94	62.9 ± 0.37	1.24	0.689
CP digestibility (%)	70.3 ± 2.72	72.6 ± 3.10	72.1 ± 2.86	1.59	0.859
NDF digestibility (%)	58.3 ± 3.13	61.9 ± 4.30	62.8 ± 2.40	1.90	0.641
ADF digestibility (%)	43.8 ± 1.72	46.1 ± 2.06	42.2 ± 2.71	1.30	0.484

3.1.5. Intake and Digestibility of Nutrients

The intake and digestibility coefficients of dry matter, organic matter, crude protein, ether extract, neutral detergent fibre, and acid detergent fibre measured during the metabolic trial are presented in Table 3. Both nutrient intake and digestibility coefficients were comparable among the three groups, with no significant treatment effect observed (p > 0.05).

3.1.6. Growth Performance, Feed Intake, and Feed Conversion Ratio

The fortnightly mean body weight, body weight gain, feed intake, and feed conversion ratio of growing kids in different groups are presented in Tables 3 and 4. These performance parameters did not differ significantly (p > 0.05) among treatments at any stage of the experiment, indicating comparable growth rate and feed conversion efficiency across groups.

Table 4.

Effect of dietary nano‐Se on growth and FCR of goat kids.

Attributes	Treatments			SEM	p value
	T1	T2	T3
Body weight (kg)
Initial	11.0 ± 0.64	10.9 ± 0.63	11.1 ± 0.60	0.33	0.979
Final	17.1 ± 0.74	17.7 ± 0.73	17.7 ± 0.66	0.39	0.834
Total gain	6.17 ± 0.34	6.85 ± 0.33	6.62 ± 0.23	0.18	0.327
ADG (gd− 1)	37.4 ± 2.09	41.5 ± 1.98	40.1 ± 1.40	1.07	0.325
Feed intake
Total DMI (kg)	69.9 ± 2.45	70.2 ± 2.36	70.0 ± 2.14	1.23	0.995
DMI (gd− 1)	424 ± 14.8	426 ± 14.3	424 ± 12.9	7.45	0.995
Feed: Gain ratio	11.4 ± 0.66	10.3 ± 0.46	10.6 ± 0.42	0.29	0.355

3.1.7. Hematological Parameters

The mean haemoglobin concentration and packed cell volume of growing kids in different groups are presented in Table 5. No significant differences (p > 0.05) were observed among the three groups, and values remained within normal physiological limits across the experimental period.

Table 5.

Effect of dietary nano‐Se on hematological profile in goat kids.

Treatments	Periods			Mean ± SE	p value
	0 days	75 days	150 days		T	P	T*P
Hb (g/dL)
T1	11.6 ± 0.33	11.9 ± 0.61	12.3 ± 0.36	11.9 ± 0.26	0.851	0.518	0.948
T2	11.9 ± 0.45	12.1 ± 0.40	12.4 ± 0.56	12.1 ± 0.26
T3	12.0 ± 0.59	12.4 ± 0.39	12.1 ± 0.53	12.1 ± 0.28
Mean ± SE	11.8 ± 0.26	12.1 ± 0.26	12.3 ± 0.27
PCV (%)
T1	36.2 ± 1.08	36.8 ± 1.85	38.7 ± 1.15	37.2 ± 0.80	0.889	0.253	0.937
T2	36.5 ± 1.48	36.7 ± 1.23	38.5 ± 1.65	37.2 ± 0.82
T3	37.0 ± 1.96	37.8 ± 0.79	38.3 ± 1.84	37.7 ± 0.83
Mean ± SE	36.6 ± 0.79	37.1 ± 0.75	38.5 ± 0.85

3.1.8. Blood Biochemical Parameters

Serum biochemical parameters, including glucose, total protein, albumin, globulin, A:G ratio, urea‐N, and creatinine, are presented in Table 6. Most parameters were statistically comparable among dietary groups (p > 0.05). However, serum glucose, total protein, total cholesterol, and creatinine showed significant differences toward the completion of the experiment, particularly in the later sampling period.

Table 6.

Effect of dietary nano‐Se on biochemical profile in goat kids.

Treatments	Periods			Mean ± SE	p value
	0 days	75 days	150 days		T	P	T*P
Glucose (mg/dL)
T1	52.6 ± 1.01	60.1 ± 1.62	63.8 ± 1.32	58.8 ± 1.35	0.733	0.000	0.955
T2	52.3 ± 1.29	61.2 ± 1.70	64.6 ± 1.85	59.4 ± 1.54
T3	53.8 ± 0.95	61.6 ± 1.94	64.0 ± 1.23	59.8 ± 1.31
Mean ± SE	52.9c ± 0.61	61.0b ± 0.97	64.1a ± 0.81
Total protein (g/dL)
T1	6.18 ± 0.91	6.94 ± 0.31	6.84 ± 0.32	6.65 ± 0.17	0.732	0.001	0.928
T2	6.19 ± 0.24	7.21 ± 2.85	6.92 ± 0.23	6.78 ± 0.17
T3	6.12 ± 0.16	6.77 ± 0.18	6.93 ± 0.40	6.61 ± 0.17
Mean ± SE	6.16b ± 0.11	6.97a ± 0.15	6.90a ± 0.18
Albumin (g/dL)
T1	4.06 ± 0.10	4.13 ± 0.03	3.89 ± 0.08	4.03 ± 0.05	0.183	0.575	0.092
T2	3.97 ± 0.08	3.85 ± 0.08	3.92 ± 0.07	3.91 ± 0.04
T3	3.99 ± 0.08	3.87 ± 0.08	4.05 ± 0.07	3.97 ± 0.05
Mean ± SE	4.01 ± 0.05	3.95 ± 0.05	3.95 ± 0.05
Globulin (g/dL)
T1	2.95 ± 0.33	2.80 ± 0.31	3.20 ± 0.27	2.99 ± 0.17	0.711	0.848	0.729
T2	2.99 ± 0.25	3.37 ± 0.26	3.08 ± 0.20	3.15 ± 0.13
T3	2.94 ± 0.37	3.14 ± 0.23	2.81 ± 0.40	2.96 ± 0.19
Mean ± SE	2.96 ± 0.18	3.10 ± 0.16	3.03 ± 0.17
A:G
T1	1.48 ± 0.20	1.57 ± 0.18	1.26 ± 0.10	1.44 ± 0.10	0.405	0.770	0.401
T2	1.38 ± 1.22	1.18 ± 0.11	1.30 ± 0.09	1.28 ± 0.06
T3	1.49 ± 0.21	1.27 ± 0.10	1.70 ± 0.39	1.49 ± 0.15
Mean ± SE	1.45 ± 0.10	1.34 ± 0.08	1.42 ± 0.14
Cholesterol (mg/dL)
T1	67.1 ± 3.79	71.5 ± 1.11	73.8 ± 2.10	70.8 ± 1.55	0.975	0.018	0.993
T2	67.8 ± 2.71	71.0 ± 2.98	73.0 ± 2.38	70.6 ± 1.56
T3	67.7 ± 1.56	70.0 ± 2.04	73.4 ± 2.08	70.3 ± 1.18
Mean ± SE	67.5b ± 1.54	70.8ab ± 1.19	73.4a ± 1.19
Urea‐N (mg/dL)
T1	14.6 ± 0.64	16.0 ± 0.77	16.2 ± 0.55	15.6 ± 0.40	0.942	0.108	0.897
T2	14.9 ± 0.57	15.8 ± 0.72	16.0 ± 0.71	15.6 ± 0.38
T3	15.2 ± 0.72	15.5 ± 0.51	15.6 ± 0.51	15.4 ± 0.32
Mean ± SE	14.9 ± 0.36	15.7 ± 0.37	15.9 ± 0.33
Creatinine (mg/dL)
T1	0.72 ± 0.08	1.14 ± 0.17	1.12 ± 0.06	0.99 ± 0.08	0.673	0.002	0.595
T2	0.83 ± 0.20	0.97 ± 0.04	1.01 ± 0.06	0.94 ± 0.07
T3	0.75 ± 0.08	0.92 ± 0.07	1.08 ± 0.04	0.92 ± 0.05
Mean ± SE	0.77b ± 0.07	1.01a ± 0.06	1.07a ± 0.03

Note: ^abc means bearing different superscript in row differ significantly.

3.1.9. Serum Enzyme Profile

The activities of serum enzymes, namely aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP), are presented in Table 7. Overall, enzyme activities were comparable among the three treatment groups (p > 0.05). Period‐wise analysis showed that ALT values did not vary significantly across sampling days (p > 0.05), whereas AST and ALP levels at day 150 were significantly higher (p < 0.05) compared with Day 0. Values recorded at Day 75 remained statistically similar to both Day 0 and Day 150.

Table 7.

Effect of dietary nano‐Se on serum enzymes of goat kids.

Treatments	Periods			Mean ± SE	p value
	0 days	75 days	150 days		T	P	T*P
ALT (IUL−1)
T1	30.8 ± 1.33	33.7 ± 1.74	34.9 ± 1.49	33.1 ± 0.93	0.957	0.014	0.997
T2	30.1 ± 0.84	32.8 ± 0.93	35.2 ± 1.71	32.7 ± 0.83
T3	30.5 ± 2.46	33.0 ± 2.46	35.6 ± 2.99	33.0 ± 1.52
Mean ± SE	30.5b ± 0.92	33.2ab ± 0.99	35.2a ± 1.18
AST (IUL−1)
T1	93.8 ± 2.50	94.2 ± 2.02	96.2 ± 2.90	94.7 ± 1.38	0.990	0.559	0.999
T2	93.5 ± 3.06	94.5 ± 2.77	97.2 ± 1.94	95.1 ± 2.04
T3	94.0 ± 3.36	94.8 ± 3.15	96.3 ± 3.76	95.1 ± 1.87
Mean ± SE	93.8 ± 2.15	94.5 ± 1.46	96.6 ± 1.61
ALP (IUL−1)
T1	107 ± 3.98	111 ± 4.30	114 ± 3.29	111 ± 2.22	0.881	0.033	0.997
T2	107 ± 3.67	114 ± 3.42	117 ± 3.89	113 ± 2.39
T3	107 ± 3.56	113 ± 2.62	116 ± 4.16	112 ± 2.08
Mean ± SE	107b ± 2.22	113ab ± 1.92	116a ± 2.07

Note: ^ab means with different superscripts within a row differ significantly.

3.1.10. Antioxidant Enzyme Activity

Serum antioxidant enzyme activities (GPx, SOD, and catalase) are presented in Table 8. GPx activity was significantly higher (p < 0.01) in group T3, followed by T2, compared with T1. Period‐wise comparison showed a significant increase in GPx activity over time, with the highest values recorded at day 150, followed by Day 75 and Day 0 (p < 0.01). In contrast, SOD and catalase activities did not differ significantly among treatment groups (p > 0.05).

Table 8.

Effect of nano‐Se supplement on serum CAT, SOD, and GPX in goat kids.

Treatments	Periods			Mean ± SE	p value
	0 days	75 days	150 days		T	P	T*P
Catalase (nmol min−1 mL−1)
T1	40.1 ± 0.53	41.8 ± 0.33	43.5 ± 1.01	41.8 ± 0.50	0.471	0.001	0.858
T2	41.6 ± 1.38	42.1 ± 0.36	43.3 ± 0.59	42.3 ± 0.51
T3	40.2 ± 1.07	41.4 ± 0.58	42.9 ± 0.49	41.5 ± 0.49
Mean ± SE	40.6b ± 0.59	41.8b ± 0.24	43.2a ± 0.40
Superoxide dismutase (U mL−1)
T1	35.6 ± 3.44	38.3 ± 1.90	42.0 ± 2.76	38.6 ± 1.63	0.920	0.065	0.960
T2	36.8 ± 1.52	40.1 ± 1.55	41.5 ± 4.11	39.4 ± 1.53
T3	37.5 ± 1.73	39.0 ± 1.03	40.5 ± 1.44	39.1 ± 0.83
Mean ± SE	36.6 ± 1.31	39.1 ± 0.85	41.31 ± 1.62
Glutathion peroxidase (nmol min−1 mL−1)
T1	5.58 ± 0.28	6.39 ± 0.64	7.06 ± 0.49	6.72C ± 0.30@	< 0.001	< 0.001	< 0.001
T2	5.61 ± 0.78	9.77 ± 0.37	14.21 ± 0.81	11.99B ± 0.93@
T3	5.42 ± 0.33	16.66 ± 0.40	27.58 ± 0.72	22.12A ± 2.21@
Mean ± SE	5.54c ± 0.28	10.94b ± 1.07	16.28a ± 2.10

Note: @ means of 75 and 150 d values. ^abc means bearing different superscript in row differ significantly (p < 0.05), (p < 0.01). Means with different superscripts ^ABC within a column indicate significant differences at p < 0.01.

3.1.11. Serum Hormones

Serum concentrations of triiodothyronine (T3), thyroxine (T4), T4:T3 ratio, thyroid stimulating hormone (TSH), testosterone, and insulin are presented in Table 9. Serum T3 levels were significantly higher (p < 0.05) in groups T2 and T3 compared with T1. Serum T4 levels and T4:T3 ratio were significantly lower (p < 0.05) in T2 and T3 relative to T1. Period‐wise values of T4 and T4:T3 ratio were significantly lower at Day 150 compared with days 0 and 75 (p < 0.01). Serum insulin, TSH, and testosterone concentrations did not differ significantly among treatments or across periods (p > 0.05).

Table 9.

Effect of dietary nano‐Se on Hormone levels of goat kids.

Treatments	Periods			Mean ± SE@	p value
	0 days	75 days	150 days		T	P	T*P
T3 (nmol/L)
T1	2.80A ± 0.17	3.19B ± 0.19	4.38B ± 0.13	3.79B ± 0.19	0.029	< 0.001	0.025
T2	2.62A ± 0.21	3.76A ± 0.11	4.75A ± 0.10	4.21A ± 0.23
T3	2.60A ± 0.07	3.67A ± 0.08	4.97A ± 0.14	4.32A ± 0.24
Mean ± SE	2.68c ± 0.09	3.54b ± 0.10	4.70a ± 0.09
T4 (nmol/L)
T1	44.7A ± 2.70	48.4A ± 3.12	45.5A ± 1.12	46.9A ± 1.39	< 0.001	0.081	0.016
T2	44.0A ± 2.64	38.9B ± 2.55	43.2A ± 2.66	41.1B ± 1.52
T3	43.9A ± 2.94	35.2B ± 1.84	31.0B ± 1.04	33.1C ± 1.73
Mean ± SE	44.19a ± 1.50	40.83ab ± 1.93	39.89b ± 1.82
T4:T3
T1	16.3A ± 1.37	15.6A ± 1.60	10.5A ± 0.48	13.1A ± 0.93	0.001	< 0.001	0.009
T2	17.1A ± 1.35	10.4B ± 0.65	9.13B ± 0.60	9.76B ± 0.99
T3	16.9A ± 1.28	9.57B ± 0.39	6.25B ± 0.22	7.91C ± 1.16
Mean ± SE	16.8a ± 0.73	11.8b ± 0.85	8.61c ± 0.49
Insulin (µIU/mL)
T1	20.9 ± 0.54	26.0 ± 0.65	28.1 ± 0.66	27.1 ± 0.81	0.797	< 0.001	0.861
T2	21.4 ± 0.54	27.1 ± 1.54	27.4 ± 0.80	27.3 ± 0.88
T3	21.6 ± 0.48	27.1 ± 0.98	27.7 ± 0.82	27.4 ± 0.79
Mean ± SE	21.3b ± 0.29	26.7a ± 0.62	27.7a ± 0.42
TSH (µIU/mL)
T1	1.11 ± 0.04	1.91 ± 0.10	2.46 ± 0.07	2.19 ± 0.14	0.081	< 0.001	0.424
T2	1.03 ± 0.00	1.77 ± 0.05	2.41 ± 0.05	2.09 ± 0.14
T3	1.18 ± 0.15	2.20 ± 0.24	2.44 ± 0.05	2.32 ± 0.16
Mean ± SE	1.11 ± 0.05	1.96 ± 0.09	2.43 ± 0.03
Testosterone (ng/mL)
T1	2.19 ± 0.17	2.27 ± 0.13	2.44 ± 0.15	2.31 ± 0.09	0.078	0.875	0.191
T2	2.23 ± 0.12	2.40 ± 0.10	2.42 ± 0.28	2.41 ± 0.10
T3	2.13 ± 0.17	2.43 ± 0.18	2.62 ± 0.10	2.53 ± 0.10
Mean ± SE	2.18 ± 0.09	2.37 ± 0.08	2.49 ± 0.11

Note: @ means of 75 and 150 d values; ^abc means with different superscripts within a row differ significantly; ^ABC means with different superscripts within a column differ significantly.

3.2. Immunological Status

3.2.1. Humoral Immune Response

Humoral immune response assessed by micro‐hemagglutination assay against chicken red blood cells is presented in Table 10. Antibody titres were significantly higher (p < 0.05) in group T3 compared with T1, while T2 remained statistically comparable with both groups (p > 0.05). Period‐wise evaluation showed that titres increased significantly after antigen administration, with values at Days 7, 14, 21, and 28 higher than day 0 (p < 0.01). The peak response was observed at Day 14, whereas values at Days 7 and 21 were statistically similar.

Table 10.

Effect of dietary nano‐Se on humoral immune response/antibody titre (log₂) in goats.

Treatments	Periods					Mean ± SE@	p value
	0 days	7 days	14 days	21 days	28 days		T	P	T*P
T1	1.00 ± 0.00	2.17 ± 0.17	3.00 ± 0.26	2.33 ± 0.33	1.67 ± 0.21	2.29B ± 0.16	0.035	< 0.001	0.934
T2	1.00 ± 0.00	2.33 ± 0.22	3.33 ± 0.20.21	2.67 ± 0.21	1.83 ± 0.31	2.54AB ± 0.17
T3	1.00 ± 0.00	2.50 ± 0.22	3.67 ± 0.21	3.00 ± 0.26	2.00 ± 0.45	2.79A ± 0.20
Mean ± SE	1.00d ± 0.00	2.33b ± 0.11	3.33a ± 0.14	2.67b ± 0.16	1.83c ± 0.19

Note: Values expressed as log base 2 of the reciprocal of the highest serum dilution that caused agglutination of red blood cells. @ means of 7, 14, 21 and 28 days. ^abcd means with different superscripts within a row differ significantly. ^AB means with different superscripts within a column differ significantly.

3.3. Cell‐Mediated Immune Response

Cell‐mediated immune response assessed through delayed‐type hypersensitivity reaction to PHA‐P is presented in Tables 10 and 11. Dermal induration increased progressively over post‐inoculation time in all groups. Mean skin thickness differed significantly among treatments (p < 0.01), with the highest response observed in group T3, and followed by T2 and T1. When expressed as percentage increase, both T2 and T3 showed significantly greater responses than T1. Maximum average skin thickness was recorded at 12 h postinoculation, followed by a gradual decline at later intervals.

Table 11.

Effect of dietary nano‐Se on DTH response (skin thickness in mm) to PHA‐p in goat kids.

Treatments	Periods					Mean ± SE	p value
	0 h	12 h	24 h	48 h	72 h		T	P	T*P
T1	2.65 ± 0.03	4.31 ± 0.03	3.98 ± 0.03	3.28 ± 0.03	2.77 ± 0.04	3.40B ± 0.67	< 0.001	< 0.001	< 0.001
T2	2.58 ± 0.05	4.51 ± 0.13	4.02 ± 0.12	3.27 ± 0.11	2.66 ± 0.05	3.4B ± 0.80
T3	2.67 ± 0.02	5.03 ± 0.08	4.68 ± 0.06	3.84 ± 0.06	2.81 ± 0.08	3.80A ± 0.98
Mean ± SE	2.63e ± 0.09	4.61a ± 0.37	4.23b ± 0.38	3.46c ± 0.32	2.75d ± 0.17

Note: ^abcde means with different superscripts within a row differ significantly. ^AB means with different superscripts within a column differ significantly.

3.4. Reproductive Traits of Male Goats

The reproductive traits of male goats in different groups are presented in Table 12. Scrotal circumference and scrotal volume did not differ significantly among treatments (p > 0.05). However, semen quality parameters, including mass motility, percentage of live spermatozoa, and hypo‐osmotic swelling test (HOST) response, were significantly higher (p < 0.01) in the nano‐selenium supplemented groups (T2 and T3) compared with the control group (T1).

Table 12.

Effect of dietary nano‐Se on andrological parameters and semen quality of goat kids.

Attributes	Treatments			SEM	p value
	T1	T2	T3
Scrotal circumferences (cm)	18.6 ± 0.30	19.3 ± 0.38	19.5 ± 0.26	0.20	0.161
Scrotal volume (cm)	130 ± 2.86	135 ± 3.25	138 ± 1.82	1.66	0.168
Live spermatozoa (%)	88.1a ± 1.70	94.4b ± 0.22	93.9b ± 0.46	1.03	0.003
HOST response (%)	84.1a ± 1.33	89.1b ± 0.68	88.9b ± 0.63	0.85	0.007
Mass motility	3.50a ± 0.29	4.50b ± 0.29	4.75b ± 0.25	0.22	0.025

Values are expressed as Mean ± SEM. Means bearing different superscripts (a, b) within a row differ significantly at P < 0.05, while means sharing a common superscript do not differ significantly. Statistical significance among treatments was determined based on the corresponding P values.

4. Discussion

4.1. Synthesis and Characterization

Selenium nanoparticles show an enhanced uptake post‐ingestion as these SeNPs are smaller in size with larger surface areas and are more permeable through capillary walls, leading to superior epithelial cell uptake and enhanced bioactivity. Au et al. (2023) and Kirupagaran and Vedhi (2019) utilized ascorbic acid as a reducing agent in the synthesis of SeNPs, resulting in particle sizes between 56 and 75 nm. Dwivedi et al. (2011) reported sizes between 40 and 100 nm using an organic acid as the reducing agent. Bunglavan et al. (2013) noted that their synthesized Se particles were under 100 nm in size. In contrast, the higher selenium concentration in the current product suggests improved nanoparticle recovery, making the method more economical and efficient.

4.2. Nutrient Utilization and Growth Performance

Our findings suggest that Se‐NPs supplementation did not significantly influence growth performance in Black Bengal bucks. This observation is consistent with several earlier studies where selenium source or supplementation level did not elicit notable changes in body weight or growth rate across various species, including dairy cows (Gunter et al. 2003), pigs (Zhang, Zhao, et al. 2020; Rao et al. 2023), lambs (Cárdenas‐Ramírez et al. 2023), goats (Kumar et al. 2022) and broiler chickens (Payne and Southern 2005). Similarly, Gavidel et al (Gavidel et al. 2025). reported no improvement in growth parameters in calves supplemented with organic selenium sources, even at doses ranging from 1.2 to 3.19 mg/kg DM under standard husbandry conditions. However, the literature presents conflicting evidence regarding the efficacy of selenium, particularly in its nano form, on animal growth. For example, improved average daily gain was reported in selenium‐supplemented goats (Hamed et al. 2021; Mahmood et al. 2020) and sheep (Mousaie 2021; Paiva et al. 2019). Furthermore, (Moustafa et al. 2024) demonstrated that supplementation of nano selenium tends to increase the growth performances in rabbit. These disparities may arise from species‐specific responses, physiological status, baseline selenium levels, form and dose of selenium used, and environmental conditions including nutritional stressors and oxidative load. Our study, conducted under tropical Indian conditions using an indigenous ruminant model, reinforces the notion that the growth‐promoting effects of selenium—especially in nano form—are not universally consistent and may depend on the interaction between baseline nutritional status and physiological demand, rather than supplementation alone.

4.3. Haematological and Biochemical Profiles

The haematological and serum biochemical parameters assessed‐including total protein, albumin, glucose, urea, creatinine, and cholesterol‐remained within physiologically normal ranges and did not differ significantly among treatment groups. These outcomes are in alignment with (Saadi et al. 2025) who found no serum biochemical changes in Awassi ewes supplemented with SeNPs indicating no any disrupt metabolic homeostasis in healthy ruminants. Similar trends were reported by (Błażejak‐Grabowska et al. 2022) who observed no adverse effects on serum biochemistry in ewes administered selenium nanoparticles at varying concentrations. Comparable results were obtained in ewes by (Budak 2024) and in Holstein calves by (Żarczyńska et al. 2024), both reporting insignificant alterations in key biochemical markers upon nano‐Se supplementation. However, some contrasting results have been documented. Liu et al. (2024) reported elevated serum protein levels in Holstein cows administered 0.2 mg/kg DM of nano‐selenium, suggesting possible dose‐dependent effects. Al‐Janabi et al. (2023) observed a decrease in serum creatinine levels in animals receiving high levels (5 mg/kg feed) of selenium, pointing toward potential renal modulation or altered protein catabolism at supranutritional doses. Regarding lipid metabolism, previous reports have indicated inconsistent effects of selenium supplementation on cholesterol and triglyceride concentrations. For instance, while (Cold et al. 2015) noted no change in albumin levels in older population, whereas (Hamzah and Dawood 2024) and (Guo et al. 2020) observed reductions in blood cholesterol in lambs and human, respectively, when supplemented with selenium. Conversely, (Żarczyńska et al. 2021) found no significant impact on triglyceride and cholesterol levels in calves following intramuscular vitamin E and selenium administration.

4.4. Plasma Hormones and Immune Responses

Consistent with our findings, Kumar et al. (2013) demonstrated that dietary selenium supplementation significantly elevated serum T3 and T4 levels after 60 days, indicating enhanced thyroid hormone activity. Selenium, particularly in its organic forms, plays a pivotal role in thyroid hormone metabolism by activating iodothyronine deiodinases‐selenium‐dependent enzymes responsible for the conversion of thyroxine (T4) to its biologically active form, triiodothyronine (T3) (Wen et al. 2025). observed reduced T4 concentrations in Sel‐Plex‐fed ewes, likely due to increased deiodination of T4–T3, suggesting an upregulation of deiodinase activity. A deficiency in selenium is well‐known to impair this conversion, leading to reduced hepatic deiodinase activity, lower T3 levels, and compensatory elevation of T4 as observed by (Maurya et al. 2024) in barbari goats after Se supplementation.

Recent experimental studies have underscored the role of selenium nanoparticles (Nano‐Se) in modulating thyroid function. Mojadadi et al. (2025) reported that mice supplemented with Nano‐Se exhibited a two‐fold increase in plasma T3 concentrations, concurrent with elevated expression of thyroid deiodinase‐1 (DIO1) without alterations in thyroidal GPx‐1/4 levels. These effects were accompanied by a trend toward increased protein levels of GPX1, GPX4, and DIO1. Emerging evidence also suggests a critical interaction between selenium status, gut microbiota, and thyroid function. The intestinal mucosa expresses deiodinases that contribute to local T3 synthesis, a process modulated by resident microbiota. Nguyen (2022) and Ruswandi et al. (2024) reviewed and concluded that Se inclusion may affect the iodothyronine deiodinase 2 (DIO2) protein and regulation of different associated genes like thioredoxin reductase 1 (TXNRD1) (Bano et al. 2025). Further, (De Souza et al. 2025) explained that selenium enables precise thyroid hormone regulation in the form of selenocysteine (SeCys), which is essential for the catalytic activity of iodothyronine deiodinases (D1, D2, D3), which regulate thyroid hormone metabolism. These findings collectively highlight the complex interplay between selenium intake and thyroid regulation as mediated by gut microbes.

4.5. Selenium, Immune Modulation

Conversely to our results, (Mudgal et al. 2022) reported that the buffalo calves supplemented with Se (0.3 ppm) results in increased antibody titre however, the cell mediated and humoral immune response remains unaltered. However, similar to our observation, the DTH response was significantly (p < 0.05) higher in layer chicks fed with 0.3 mg/kg DM nano‐Se as compared to 0.3 mg/kg DM sodium selenite after 8th weeks of postfeeding (Mohapatra et al. 2014). Moreover, (Kumar et al. 2009) reported that Se addition to the diet of lambs results in increased humoral immune response. Similarly, (Ashrafi et al. 2024) reported that dietary Sel‐Plex at 0.30 and 0.45 mg Se/kg diet significantly upregulated gene expression of interleukin‐2 (IL‐2) and interferon‐γ (IFN‐γ), key cytokines involved in cell‐mediated immunity.

Dalia et al. (2018) found that Se supplementation in broilers (0.3 ppm) leads to enhanced IL‐2 expression and circulating levels of immunoglobulins (IgG, IgA, and IgM), indicating improved humoral immunity. Selenium supplementation has been shown to enhance T cell proliferation, natural killer (NK) cell cytotoxicity, and overall lymphocyte functionality. In murine models, selenium status significantly influences T cell and macrophage differentiation, B cell abundance, and immunoglobulin production (Huang et al. 2012). Additionally, (Mudgal et al. 2008) found that inclusion of Se with dose of 0.3 ppm improves the immune status in male buffalo calves. Qin et al. (2015) reported enhances cellular and humoral immunity with 02 ppm of Se addition to basal diet of rats. Zhu et al. (2022) reported that selenium stimulates immunoglobulin synthesis by enhancing lymphocytic secretion of IL‐1 and IL‐2, thereby supporting antibody production. Se tends to alter lymphocytes expression of IL‐5 and Neutrophil upregulation of IL‐1 and IL‐8 (Montgomery et al. 2012) thereby modulating immune system. Mechanistically, selenium is known to enhanced humoral immunity by promoting immunoglobulin synthesis and B cell function, while supporting DTH responses by modulating T cell proliferation and dendritic cell‐mediated antigen presentation (Li et al. 2021). These effects are mediated through selenoproteins such as SelK and SELENOK, which regulate intracellular signalling pathways including ERK, Akt, and RhoA/ROCK, as well as oxidative stress responses (Zhang et al. 2021).

4.6. Antioxidant Status

Antioxidant enzymes such as glutathione peroxidase (GSH‐Px), superoxide dismutase (SOD), and catalase (CAT) play pivotal roles in eliminating reactive oxygen species (ROS), thereby protecting cells from oxidative damage. In the present study, the highest activities of serum GSH‐Px, SOD, and CAT were observed in the nano‐selenium (NS)‐treated group, indicating a pronounced enhancement in systemic antioxidant capacity. This finding aligns with earlier studies Research across various ruminant species‐including calves, heifers, fattening bulls, lactating cows, camels, buffaloes (Mudgal et al. 2023), goats (Wang et al. 2023; Nurmala et al. 2024) sheep, and their young‐consistently reports elevated blood Se concentrations and increased GSH‐Px activity following selenium supplementation (Guo et al. 2018; Gong and Xiao 2016; Seboussi et al. 2010; Mousaie et al. 2014).

The beneficial effects of selenium (Se) in dairy animals are primarily mediated through the diverse biological roles of selenoproteins. Key components of the cellular redox balance and antioxidant defence systems‐including glutathione peroxidases (GSH‐Px), thioredoxin reductases (TrxR), and selenoprotein P‐depend on an adequate supply of dietary selenium. This ensures the availability of seleno‐amino acids such as selenocysteine (Se‐Cys) and selenomethionine (Se‐Met), which are essential for selenoprotein synthesis and function (Arshad et al. 2021). selenoproteins play crucial roles as antioxidants within the body, (Guillin et al. 2019). Among them, glutathione peroxidases (GPx1‐4 and GPx6) and thioredoxin reductases (TrxR1‐3) are notable for their selenium‐dependent activity (Zhang, Roh, et al. 2020). These antioxidant enzymes primarily act by neutralizing reactive oxygen species through reduction reactions.

4.7. Reproductive Performance

The present findings for sperm progressive motility, viability, plasma membrane integrity, and acrosomal integrity are in close agreement with earlier studies. Paul et al. (2024) and Nateq et al. (2020) demonstrated that supplementation of nano‐selenium (1 μg/mL) in ram semen significantly (p < 0.01) enhanced these sperm quality parameters compared to both untreated and higher‐dose (2 μg/mL) groups, suggesting a dose‐dependent optimization. Similarly, (Dorostkar et al. 2012) reported improved sperm characteristics in buffalo semen following in vitro supplementation with 1 and 2 μg/mL selenium in extenders. These improvements are likely due to selenium's potent antioxidant properties, which protect sperm cells from reactive oxygen species (ROS)‐induced damage during handling and storage. Additionally, (Domosławska et al. 2018) observed increased GSH‐P and TAC activity in spermatozoa of dogs after 6 µg/kg Se yeast addition in their diet.

Selenium (Se) is essential for maintaining male reproductive function, largely due to its potent antioxidant and anti‐inflammatory activities. These biological effects are mediated through various selenoproteins, including glutathione peroxidases (especially GPX4) and thioredoxin reductases (TrxRs), which mitigate oxidative stress in testicular tissue by neutralizing reactive oxygen species (ROS) (Qazi et al. 2019; Owumi et al. 2020). Testicular cells, particularly spermatozoa, are highly vulnerable to oxidative damage because their membranes are rich in polyunsaturated fatty acids (PUFAs), making them susceptible to lipid peroxidation (O'Flaherty, Scarlata 2022). The antioxidant enzymes GPX, superoxide dismutase (SOD), and catalase play crucial roles in neutralizing these ROS and preserving sperm viability and membrane integrity (Surai and Fisinin 2015). Selenium also supports testosterone biosynthesis, spermatogenesis, and acrosome reaction, which are key to male fertility (Vatanpour et al. 2024). Experimental studies confirm selenium's beneficial effects on reproductive performance. In goats, Ganabadi et al. (2010) observed that selenium supplementation increased both the percentage of spermatozoa in seminiferous tubules and total sperm count, suggesting a critical regulatory role in spermatogenesis. Similarly, Vatanpour et al. (2024) demonstrated that treatment with selenium nanoparticles (0.5 mg/kg) in mice significantly increased testicular weight, seminiferous tubule diameter, and epithelial height compared to controls. In human clinical trials, selenium has also shown therapeutic potential. Alahmar (Alahmar 2023) evaluated selenium supplementation (200 µg/day for 6 months) in 65 infertile men with idiopathic oligo‐asthenospermia and reported a significant increase in sperm concentration, progressive motility, and total motility compared to untreated subjects. Selenium also impacts sperm morphology. During spermatogenesis, deficiencies in SELENOP and its receptor ApoER2 reduce selenium transport to testicular cells, leading to morphological abnormalities in spermatozoa (Kehr et al. 2009). Additionally, selenium enhances the expression of fertility‐related genes and modulates antioxidant signalling pathways. For instance, in a study on sheep Leydig cells treated with selenium, Li, Wang, Ma, et al. (2025) reported the activation of the NRF2 antioxidant signalling pathway. This led to increased expression of HO‐1 and NQO1, with miR‐200a playing a pivotal role in regulating cell proliferation and apoptosis. Further, selenium supplementation in Longyan ducks was found to increase the expression of the SHMT1 gene, which is involved in DNA and RNA synthesis and supports antioxidant activity and healthy cell division‐key processes during spermatogenesis (Sarker et al. 2025). Maintaining selenium homeostasis is crucial for reproductive function. This involves not only adequate dietary intake but also efficient selenium transport and utilization via proteins such as SELENOP, MTF1, and ZIP8 (Kehr et al. 2009; Li, Wang, Ma, et al. 2025). Disruptions in these transport pathways can compromise selenium bioavailability in testicular tissues, impairing fertility outcomes.

5. Conclusion

This study provides compelling evidence for the successful synthesis, precise characterization, and targeted nutritional application of selenium nanoparticles (SeNPs) in growing male goats. The nanoparticles, characterized by uniform sphericity (15–60 nm) and a high elemental selenium content (24.56%), demonstrated nanoscale integrity and enhanced bioavailability. While baseline growth and nutrient utilization metrics remained stable, dietary SeNP supplementation significantly elevated glutathione peroxidase activity, modulated thyroid hormone profiles‐marked by increased triiodothyronine (T3) and decreased thyroxine (T4)‐and robustly enhanced both humoral and cell‐mediated immune responses. Notably, SeNPs improved key semen quality parameters without affecting basal nutrient intake, underscoring their systemic physiological influence. These findings position SeNPs as a potent, next‐generation micronutrient strategy with functional benefits that extend beyond growth performance‐particularly in supporting antioxidant resilience, endocrine balance, and reproductive competence under physiological or environmental stress. For the livestock industry, SeNPs offer a scalable, feed‐compatible solution for improving animal health and productivity, especially in selenium‐deficient regions. For the scientific community, this work advances the frontier of nano‐enabled trace element nutrition, providing a mechanistic framework for understanding the systemic effects of SeNPs in ruminant models. Further research is warranted to evaluate long‐term safety profiles, refine dosage thresholds, and explore novel delivery modalities, including their utility in reproductive biotechnology (e.g., semen extenders) and female/lactating animals. In the context of global efforts toward sustainable, efficient, and welfare‐oriented animal agriculture, selenium nanoparticles emerge as a promising biometal‐based intervention with substantial implications for metabolic health, reproductive performance, and resilient livestock production systems.

Ethics Statement

The experiment was conducted after getting the approval from the Institutional Animal Ethics committee with Approval No IAEC/10.05.2016/L5.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.