Dietary biotic supplementation modulates growth performance, anticoccidial efficacy, oxidative status, and intestinal histomorphology in Eimeria tenella–challenged broilers

Abstract

This study investigated the comparative effects of dietary prebiotic, probiotic, and synbiotic supplementation on growth performance, anticoccidial efficacy, oxidative status, intestinal morphohistology, carcass traits, and meat quality of broilers experimentally challenged with Eimeria tenella (E. tenella). The novelty of this study lies in the simultaneous comparison of these three biotic strategies under the same controlled challenge model while integrating productive, physiological, intestinal, and meat quality responses. Broiler chicks were randomly allocated to six treatment groups consisting of a non-challenged control (CONN), a challenged control (CONP), an anticoccidial drug group supplemented with robenidine (0.5 g/kg of diet), and three challenged groups receiving either a prebiotic [Thepax®; an inactivated Saccharomyces cerevisiae yeast product rich in mannan oligosaccharides and β-glucans; 0.75 g/kg of diet], a probiotic [B-ACT®; Bacillus licheniformis DSM 28710, 3.2 × 10⁹ CFU/g; 0.50 g/kg of diet], or a synbiotic (Thepax® 0.75 g/kg + B-ACT® 0.50 g/kg of diet) supplementation. At 15 days of age, birds in the challenged groups were orally inoculated with sporulated E. tenella oocysts. Growth performance indices, anticoccidial indices, carcass traits, breast meat physicochemical properties, intestinal histomorphology, and antioxidant status were evaluated. The results showed that dietary supplementation with biotics, particularly probiotics and synbiotics, improved performance indices compared with CONP (P < 0.05). Supplemented birds also showed reduced lesion scores, oocyst excretion, and anticoccidial index (ACI). In addition, supplementation enhanced antioxidant capacity and improved intestinal morphology, as indicated by increased villus length and villus length-to-crypt depth ratio. Responses in carcass and meat quality traits were selective but generally favorable. In conclusion, dietary biotic supplementation, particularly probiotic and synbiotic, represents a promising nutritional strategy to mitigate the negative effects of E. tenella infection and enhance health and productivity in broilers.

Introduction

Coccidiosis is one of the most economically important enteric diseases affecting the global poultry industry (Aziz-Aliabadi et al., 2026; Mathis et al., 2025). It is caused by intracellular protozoan parasites of the genus Eimeria, which invade and damage the intestinal epithelium, resulting in impaired nutrient absorption, reduced growth performance, and increased susceptibility to secondary infections (Chen et al., 2025; Sharma and Kim, 2024). Among the pathogenic species, E. tenella is considered one of the most virulent, predominantly infecting the ceca and inducing severe hemorrhagic lesions, intestinal inflammation, and high morbidity in broilers (Mohammed et al., 2025; Qaid et al., 2021a). Consequently, E. tenella infection can markedly reduce feed efficiency, body weight gain, and overall production efficiency in commercial broiler operations (Choi et al., 2021; Qaid et al., 2021b; Qasem et al., 2020).

Traditionally, coccidiosis has been controlled through prophylactic anticoccidial drugs and ionophore antibiotics included in poultry diets (El-Saadony et al., 2026; Mathis et al., 2025; Qasem et al., 2020). Although these strategies have been effective in reducing the severity of infection, their continuous use has led to the emergence of drug-resistant Eimeria strains and increasing concerns regarding antimicrobial resistance and drug residues in poultry products (Chapman and Blake, 2022; Flores et al., 2022). Moreover, growing regulatory restrictions and consumer demand for antibiotic-free poultry production systems have intensified the search for natural and sustainable alternatives to conventional anticoccidial agents (Soromou, 2026; Tsiouris et al., 2023).

In recent years, dietary supplementation with functional feed additives, as potential alternatives to conventional antimicrobial agents in poultry nutrition, such as prebiotics, probiotics, and synbiotics has attracted increasing attention in poultry nutrition (Abdulazeez et al., 2025; Assaf et al., 2025; Khomayezi and Adewole, 2022; Yadav et al., 2022). Prebiotics are non-digestible dietary components that selectively stimulate the growth and metabolic activity of beneficial intestinal microorganisms, thereby improving gut microbial balance and intestinal health (Al-Baadani et al., 2022; Mousa et al., 2025; Rastall et al., 2022). Probiotics consist of live beneficial microorganisms that can exert multiple positive effects in the host, including competitive exclusion of pathogenic bacteria, enhancement of mucosal immunity, modulation of inflammatory responses, and improvement of intestinal barrier integrity (Al-Abdullatif et al., 2025b; Mercado‐Monroy et al., 2025; Murshed et al., 2024). Synbiotics, which combine prebiotics and probiotics, may provide synergistic benefits by simultaneously promoting the growth and activity of beneficial microbes in the gastrointestinal tract (Al-Habsi et al., 2024; Murshed et al., 2024; Reddy and Muraleedharan, 2026).

Previous studies have demonstrated that these biotic additives can enhance growth performance, improve nutrient utilization, strengthen immune responses, and support intestinal morphology in broilers (Assaf et al., 2025; Khomayezi and Adewole, 2022; Salehimanesh et al., 2016; Sulaiman et al., 2025). Furthermore, several reports suggest that dietary supplementation with prebiotics, probiotics, or synbiotics may mitigate the negative effects of coccidial infection by improving gut health, reducing oxidative stress, and enhancing host resistance to intestinal pathogens (Mohsin et al., 2022; Ogwiji et al., 2024). However, comparative studies evaluating the efficacy of these three nutritional strategies under controlled Eimeria challenge conditions remain limited, particularly regarding their combined effects on antioxidative status, carcass characteristics, and meat quality parameters.

Oxidative stress is a critical pathological consequence of coccidial infection, as intestinal inflammation and tissue damage stimulate excessive production of reactive oxygen species, leading to lipid peroxidation and impairment of cellular antioxidant defense systems (Al-Quraishy et al., 2020; Mishra and Jha, 2019; Ogwiji et al., 2024; Razavi et al., 2024). Therefore, evaluating antioxidant markers can provide valuable insights into the physiological responses of broilers to dietary interventions under pathogenic stress conditions.

Although previous studies have reported beneficial effects of individual prebiotics, probiotics, or synbiotics in poultry, direct comparative evaluations of these three biotic strategies under the same controlled Eimeria tenella challenge conditions remain limited. In addition, few studies have simultaneously examined their integrated effects on productive performance, anticoccidial efficacy, oxidative status, intestinal histomorphology, carcass traits, and meat quality characteristics within a single experimental model. It was hypothesized that these dietary biotic additives would differ in their capacity to alleviate the detrimental effects of coccidial infection by improving intestinal health and antioxidant defense mechanisms. Therefore, the present study aimed to comparatively evaluate the effects of dietary prebiotic, probiotic, and synbiotic supplementation on growth performance, anticoccidial responses, antioxidant status, intestinal morphology, carcass traits, and breast meat physicochemical quality of broilers experimentally challenged with E. tenella.

Materials and methods

The study was approved by the King Saud University Scientific Research Ethics Committee (KSU- SE-21–47) and followed institutional animal care guidelines.

Experimental design and birds

A total of 672 one-day-old Ross broiler chicks were obtained from a commercial hatchery, individually weighed upon arrival, and randomly assigned to six dietary treatments, followed a completely randomized design, each with eight replicates of 14 birds (6 × 8 × 14). Birds were reared until 28 days of age at the animal facility of the Animal production Department, King Saud University, under standard management and environmental conditions. The experimental period was intentionally limited to 28 days because the acute phase of Eimeria tenella infection, including lesion development, peak oocyst shedding, oxidative stress, and intestinal damage, occurs mainly during the starter–grower phase after challenge; therefore, a 28-day model is commonly used to evaluate early biological and nutritional responses under standardized conditions.

Housing and management

Chicks were reared in a climate-controlled poultry facility in floor cages for the entire experimental period. Each cage measured 1 m^² of floor area per cage. With fourteen birds per cage, the stocking density (SD) was 0.0714 m² per bird, which is within accepted limits for broiler research under controlled conditions.

Temperature, ventilation, and lighting were managed in accordance with breeder recommendations. The ambient temperature was maintained at 35 °C on day 1 and gradually reduced by approximately 2 °C every three days until reaching 22-24 °C by day 24, after which it was maintained at this level until day 28. Continuous lighting (24 h/day) was provided during the first week, followed by a lighting regimen of 23 h light and 1 h dark per day for the remainder of the experiment. Feed and water were supplied ad libitum throughout the study. Birds were vaccinated at the hatchery against infectious bronchitis (IB), Newcastle disease (ND), and infectious bursal disease (IBD) according to standard commercial vaccination protocols.

Experimental diets and treatments

A corn–soybean meal–based diet was formulated to meet or exceed the nutrient requirements of broilers during the starter (0-14 d) and grower (15-28 d) phases, in accordance with National Research Council recommendations (NRC, 1994). The ingredient composition of the basal diets is presented in Table 1. All feed additives were thoroughly incorporated into the basal diet to ensure homogenous distribution. Diets were offered in mash form. The six dietary treatment groups were assigned as follows:

• 1.Non-challenged control group (Control negative: CONN): Basal diet without additives, non- challenged with E. tenella.
• 2.Challenged control group (Control positive: CONP): Basal diet without additives, challenged with E. tenella.
• 3.Anticoccidial standard drug group: Basal diet supplemented with the coccidiostat robenidine (Robenz) at 0.5 g/kg in both starter and grower phases, challenged with E. tenella.
• 4.Prebiotic group: Basal diet supplemented with the Thepax® at 0.75 g/kg, challenged with E. tenella.
• 5.Probiotic group: Basal diet supplemented with B-ACT® at 0.50 g/kg, challenged with E. tenella.
• 6.Synbiotic group: Basal diet supplemented with Thepax® and B-ACT® at 0.75 and 0.50 g/kg, respectively, and challenged with E. tenella.

Table 1.

Diet composition and amount of feed required of broiler's basal diets (%).

Ingredient	Starter (1-14 days)	Grower (15-28 days)
Corn, %	53.84	61.43
Soybean meal (48% CP), %	38.24	30.52
Soybean oil, %	3.43	4.40
Monocalcium phosphate, %	1.59	1.28
Limestone, %	1.54	1.28
DL-methionine, %	0.37	0.28
L-lysine HCL, %	0.25	0.15
L-threonine, %	0.16	0.08
Common salt, %	0.38	0.38
Vitamin premix1, %	0.10	0.10
Mineral premix2, %	0.10	0.10
Total	100	100
Nutrient
Calculated chemical composition
Dry matter (DM, %)	88.91	88.92
Metabolizable energy, kcal/kg	3000	3100
Crude protein, %	22.58	19.51
True protein, %	20.73	17.71
Ethe extract, %	6.18	7.30
Crude fiber, %	2.55	2.42
Ca, %	0.96	0.79
Total phosphorus, %	0.71	0.61
Available phosphorus, %	0.48	0.40
Na, %	0.16	0.16
Chlorine (Cl), %	0.26	0.26
Choline, %	0.17	0.15
Folate mg/kg	2.08	2.07
d Lysine, %	1.28	1.03
d Methionine, %	0.67	0.55
d Total sulfur amino acids, % (TSAA)	0.95	0.80
d Threonine, %	0.86	0.69
d Tryptophan, %	0.24	0.20
d Arginine, %	1.32	1.12
d Valine, %	0.91	0.79
d Leucine, %	1.80	1.58

¹Vitamin premix supplied per kg of premix: Vitamin A = 2,400,000 IU; Vitamin D₃ = 1,000,000 IU; Vitamin E = 16,000 IU; Vitamin K₃ = 800 mg; Vitamin B₁ = 600 mg; Vitamin B₂ = 1,600 mg; Vitamin B₆ = 1,000 mg; Vitamin B₁₂ = 6 mg; Biotin = 40 mg; Folic acid = 400 mg; Niacin = 8,000 mg; Pantothenic acid = 3,000 mg.

²Mineral premixes supplied per kg of premix: Cobalt = 80 mg; Copper = 2,000 mg; Iodine = 400 mg; Iron = 1,200 mg; Manganese = 18,000 mg; Selenium = 60 mg; Zinc = 14,000 mg.

All products were commercially procured from Biochem (Küstermeyerstraße, Germany) and were supplied with detailed chemical composition and analytical specifications. The additives were applied according to the manufacturers’ recommendations. B-Act® is a powdered probiotic preparation containing a minimum declared concentration of 3.2 × 10⁹ colony-forming units (CFU) of Bacillus licheniformis DSM 287107 per gram of additive. The formulation consists of approximately 3% spore concentrate and 97% calcium carbonate as a carrier (Bampidis et al., 2019). The commercial prebiotic Thepax® is derived from inactivated and stabilized baker’s yeast (Saccharomyces cerevisiae var. ellipsoideus), providing prebiotic activity at a concentration of 1 × 10¹⁰ cells/g. The yeast cell wall is rich in mannan oligosaccharides (MOS) and β−1,3-glucans, which are widely recognized for their functional prebiotic properties (Al-Baadani et al., 2023; Boostani et al., 2013).

Eimeria tenella oocysts

Unsporulated oocysts of E. tenella were obtained from naturally infected chickens and processed as described by El-Ashram and Suo (2017). Oocysts were sporulated in 2.5% potassium dichromate at 25 °C for 72 h, purified by salt flotation, and stored at 4 °C until use. Species identification was confirmed based on morphological characteristics, lesion patterns, and molecular analysis of the internal transcribed spacer 1 partial region (ITS-1 region) and sequences analysis by our colleague's researchers at the parasitology laboratory at the Department of Zoology, KSU.

To obtain a pure and infective inoculum, E. tenella oocysts derived from a field isolate were maintained and serially passaged two to three times in coccidia-free broiler chicks. Virulence was evaluated in a preliminary trial to determine a challenge dose capable of inducing consistent cecal lesions without excessive mortality.

Broilers were reared under standard conditions until day 14. On day 15, birds in the challenged groups were orally gavaged with 1/2 mL suspension of distilled water containing 20,000 E. tenella sporulated oocysts per bird, following Wang et al. (2026), while the non-challenged group received distilled water only.

Performance indices

Birds and feed were weighed on a replicate basis at 0, 7, 14, 21, and 28 days of age to evaluate growth performance. The assessed parameters included average daily gain (ADG; g/bird/day), average daily feed intake (ADFI; g/bird/day), and feed conversion ratio (FCR; calculated as ADFI / ADG). Mortality was recorded daily, and growth performance data were adjusted accordingly to account for mortality when applicable.

Anticoccidial indices and lesion scoring

Anticoccidial efficacy was evaluated using the anticoccidial index (ACI), calculated based on bloody diarrhea score, fecal oocysts per gram (OPG), relative body weight gain (RBWG), lesion score, and survival rate, following Qaid et al. (2021b), and classified according to Lan et al. (2016). ACI values were interpreted as: <120 = inactive, 120–140 = slight, 140–160 = moderate, 160–180 = marked, and >180 = excellent.

Bloody diarrhea, a characteristic sign of E. tenella infection, was assessed daily from 4 to 7 d post-infection. Bloody fecal spots were counted after removal of previous excreta, and scores were assigned on a scale of 0-4 (0 = normal; 1-4 = increasing severity). The fecal score percentage was calculated relative to the positive control, as following:

$$\left[\text{Highest}\text{fecal}\text{score}\text{in}\text{the}\text{CONP}\text{group}-\text{highest}\text{fecal}\text{score}\text{in}\text{the}\text{treated}\text{group}\right]/\text{highest}\text{fecal}\text{score}\text{in}\text{the}\text{CONP}\text{group}\times 100.$$

Oocyst shedding was determined on day 7 post-infection. Fecal oocyst counts were determined using a direct smear method with volumetric correction. Briefly, 1 g of fresh fecal sample was homogenized in 1 mL of distilled water to obtain an approximately 1:1 (w/v) suspension. The mixture was thoroughly vortexed to ensure uniform distribution of oocysts. An aliquot of 10 µL of the homogenized suspension was transferred onto a microscope slide and examined under an olympus compound microscope equipped with a digital camera (Olympus 6.0, Tokyo, Japan). The number of oocysts within the entire aliquot was counted manually. Oocyst concentration was calculated by converting the counted number to oocysts per milliliter and then adjusting for the total suspension volume. The final results were expressed as oocysts per gram of feces (OPG) using the following calculation:

$$\text{OPG}=\left(\text{Number}\text{of}\text{oocysts}\text{counted}\times \text{Total}\text{suspension}\text{volume}\right)/\text{Volume}\text{examined}$$

Based on this approach, counts were standardized to reflect the number of oocysts per gram of the original fecal material. The inhibition rate was calculated as:

$$\text{Inhibition}\text{rate}(\%)=\left[\left(\text{OPG}\text{in}\text{CONP}-\text{OPG}\text{in}\text{treated}\text{group}\right)/\text{OPG}\text{in}\text{CONP}\right]\times 100.$$

Clinical signs and mortality were recorded daily, and survival rate was expressed as the percentage of surviving birds.

At 21 d of age (7 d post-infection), one bird per replicate (n = 8 per treatment) was necropsied after 10 h feed withdrawal. Following humane slaughter, ceca were examined, and lesion scores (0-4) were assigned based on severity (0 = normal; 4 = severe hemorrhage with darkened ceca).

Ileal histomorphology

Immediately after slaughter at 28 d of age, approximately 2 cm of ileal tissue was collected from 8 birds per treatment group (3 point for each replicate). Samples were rinsed with phosphate-buffered saline (PBS), fixed in 10% neutral buffered formalin, and processed for histological analysis. After dehydration in graded ethanol, tissues were embedded in paraffin, sectioned at 5 μm using a microtome (Leica RM2255 Microtome; Leica Microsystems, Germany), and mounted on glass slides in a 50 °C water bath. Sections were stained with hematoxylin and eosin and examined an olympus compound microscope and a digital camera (Olympus 6.0, Tokyo, Japan) to measure villus length, width, and crypt depth. Villus surface area and the villus length-to-crypt depth ratio were calculated by Al-Baadani et al. (2025).

Blood sampling and antioxidative marker analysis

On day 28, approximately 3 mL of blood was collected from the wing vein of eight birds per treatment using non-anticoagulant tubes. Samples were centrifuged at 3,000 × g for 30 min to obtain serum, which was stored at −80 °C until analysis. Serum total antioxidant capacity (TAC), malondialdehyde (MDA), and superoxide dismutase (SOD) were quantified using commercial assay kits (Cayman Chemical Company, USA) following the manufacturer’s instructions. Absorbance was measured using an ELISA microplate reader (MR-96A Microplate Reader; Mindray, Shenzhen, China), as previously described (Al-Baadani et al., 2025; Humam et al., 2020).

Carcass traits

At 28 d of age, one bird per cage (8 birds per treatment) was randomly selected, fasted for 10 h, and weighed to obtain pre-slaughter body weight. Birds were then individually slaughtered under standardized conditions. Carcass weight was recorded immediately after slaughter, and dressing percentage was calculated as (carcass weight / pre-slaughter weight) × 100, as described by Al-abdullatif et al. (2025a). Carcass parts were weighed and expressed as a percentage of carcass weight (carcass part weight / carcass weight × 100) following the method of Mousapoor et al. (2023).

Breast physicochemical traits

Physicochemical quality parameters (pH and color) were evaluated in the pectoralis major muscle at 30 min postmortem. For each sample, two pH- and -color readings were taken at different locations on the inner surface of the muscle and averaged. The pH was measured using a digital pH meter (model pH 211, Hanna Instruments, Woonsocket, RI, USA) that had been calibrated with pH 4 and pH 7 buffers.

Breast meat color parameters-lightness (L*), redness (a*), and yellowness (b*)-were measured using a CR-400 Chroma Meter (Konica Minolta, Tokyo, Japan) based on the CIELAB color space system. In addition, total color difference (ΔE), chroma (saturation index), hue angle, whiteness index (WI), and browning index (BI) were calculated to provide a more comprehensive assessment of meat color attributes, following the method described by Al-Abdullatif et al. (2023).

Statistical analysis

Data were analyzed using a completely randomized design with SAS (2012) (SAS Institute Inc., Cary, NC, USA). A one-way analysis of variance (ANOVA) was conducted using the General Linear Model (GLM) procedure, with dietary treatment included as the fixed effect. The statistical model was expressed as follows:

$${\gamma }_{ij}=\mu +T_i+e_{ij}$$

Where Y_ij represents the individual observation, μ is the overall mean, T_i denotes the effect of the i^th treatment, and e_ij is the random residual error. Prior to statistical analysis, data were evaluated for normality using the Kolmogorov-Smirnov test and for homogeneity of variances to verify compliance with ANOVA assumptions. The replicate pen was considered the experimental unit for growth performance parameters, whereas individual birds served as the experimental units for other measurements. When significant treatment effects were identified, means were separated using Tukey’s multiple comparison test. Results are expressed as means ± standard error of the mean (SE), and differences were considered statistically significant at P < 0.05.

Mean comparisons for each parameter were conducted using orthogonal contrasts to evaluate: (1) the effect of infection with E. tenella under a basal diet without supplementation (CONP vs. CONN), and (2) the effect of dietary supplements under constant infection conditions (CONP vs. robenidine, prebiotic, probiotic, or synbiotic, and the combined biotic "prebiotic + probiotic + synbiotic" treatments.

Results

Performance indices

The effects of dietary treatments on performance indices are presented in Table 2. ADG was unaffected during the starter phase (P > 0.05), but differed during the grower phase and overall period (P < 0.05). All biotic-supplemented groups and CONN groups showed higher ADG than CONP, with synbiotic and probiotic groups recording the greatest gains. Combined contrasts also showed superior ADG for biotic treatments versus CONP.

Table 2.

Effects of dietary treatments on performance indices of broilers challenged with E. tenella.

Treatment1	ADG (g/day)			ADFI (g/day)			FCR
	0-14	15-28	0-28	0-14	15-28	0-28	0-14	15-28	0-28
CONP	31.59	76.38b	54.24b	37.87	114.71	76.29	1.20	1.49a	1.40a
Robenidine	31.78	78.03b	54.90b	35.95	113.72	74.83	1.13	1.46a,b	1.36a,b
Prebiotic	32.41	80.69a	56.68a	37.81	114.10	75.95	1.17	1.41b,c	1.34b,c
Probiotic	32.69	82.44a	57.57a	38.07	116.85	77.46	1.16	1.42b,c	1.35b,c
Synbiotic	32.15	82.88a	57.86a	37.33	114.28	75.81	1.16	1.38c	1.31c
CONN	32.70	81.13a	56.91a	37.22	115.78	76.50	1.14	1.43b,c	1.34b
SEM	0.184	0.482	0.265	0.278	0.385	0.231	0.009	0.008	0.006
Source of variance (P value)
Treatment	0.489	0.001	<0.0001	0.275	0.466	0.235	0.300	0.001	<0.0001
CONP vs. CONN	0.594	0.001	<0.0001	0.154	0.744	0.348	0.365	0.002	0.003
CONP vs. Robenidine	0.193	0.391	0.316	0.188	0.240	0.112	0.874	0.214	0.257
CONP vs. Prebiotic	0.791	0.017	0.016	0.050	0.569	0.164	0.304	0.040	0.051
CONP vs. Probiotic	0.368	0.049	0.0103	0.057	0.825	0.282	0.224	0.001	0.008
CONP vs. Synbiotic	0.193	0.002	0.0002	0.301	0.077	0.104	0.307	0.002	0.045
CONP vs. Biotic	0.426	0.043	0.025	0.105	0.293	0.405	0.076	0.001	0.046

¹Treatments: Basal diet supplemented with a prebiotic, probiotic, or synbiotic; compared with a basal diet containing an anticoccidial drug (robenidine), and an unsupplemented basal diet under either challenged (CONP) or non-challenged (CONN) conditions. n = 8 replicated cages per group.

^a-cMeans within the same column with different superscripts differ significantly (P < 0.05). ADG: Average daily gain. ADFI: Average daily feed intake. FCR: Feed conversion ratio. SEM: Standard error of mean.

ADFI was not affected during any phase (P > 0.05), indicating that performance differences were not due to feed consumption. In contrast, FCR differed during 15-28 d and overall (P ≤ 0.001). Synbiotic birds had the lowest FCR, followed by prebiotic, probiotic, and CONN groups, whereas CONP showed the poorest efficiency. Overall, dietary biotic supplementation, particularly synbiotic and probiotic, alleviated the growth-depressing effects of E. tenella challenge, mainly through improved gain and feed efficiency.

Anticoccidial efficacy

The effects of dietary treatments on anticoccidial indices in broilers challenged with E. tenella are presented in Table 3. Oocyst shedding differed markedly among treatment (P < 0.0001). CONP had the highest output (19.25 × 10³ oocysts/g), whereas no oocysts were detected in the CONN. All supplemented groups and robenidine significantly reduced oocyst shedding compared with CONP, with no significant differences among the treated groups. The greatest inhibition rate among challenged birds was observed in the prebiotic group (83.12%).

Table 3.

Effects of dietary treatments on anticoccidial indices of broilers challenged with E. tenella.

Treatment1	Oocyst/g* 10^3	Inhibition rate (%)	Bloody diarrhea (Score)	RBWG	Survival rate (%)	Lesion score	Oocyst value	ACI
CONP	19.25a	0.00c	2.54a	76.32c	96.4	2.50a	100.00a	70.2c
Robenidine	4.75b	75.32b	1.00b	83.58b	99.1	0.94b	24.68b	157.1b
Prebiotic	3.25b	83.12b	1.25b	87.58b	100.0	1.00b	16.88b,c	169.7b
Probiotic	5.25b	72.73b	1.08b	101.68a	98.2	0.88b	27.27b	171.7b
Synbiotic	4.75b	75.32b	0.75b	97.45a	99.1	0.50b,c	24.68b	171.4b
CONN	0.00c	100.0a	0.00c	100.00a	100.0	0.00c	0.00c	200.0a
SEM	0.946	4.92	0.121	1.49	0.388	0.131	4.915	6.19
Source of variance (P value)
Treatment	<0.0001	<0.0001	<0.0001	<0.0001	0.065	<0.0001	<0.0001	<0.0001
CONP vs. CONN	-	-	0.017	<0.0001	-	0.049	-	0.029
CONP vs. Robenidine	0.0003	<0.0001	<0.0001	<0.0001	0.483	0.001	0.0003	<0.0001
CONP vs. Prebiotic	<0.0001	<0.0001	<0.0001	0.002	0.060	<0.0001	<0.0001	<0.0001
CONP vs. Probiotic	0.021	0.046	0.018	0.041	0.483	0.008	0.021	0.035
CONP vs. Synbiotic	0.047	0.047	0.044	<0.0001	0.483	0.048	0.046	0.025
CONP vs. Biotic	<0.0001	<0.0001	0.0001	0.010	0.391	0.015	<0.0001	0.0004

¹Treatment: As described in Table 2. n = 8 replicated cages per group.

^a-cMeans within the same column with different superscripts differ significantly (P < 0.05). ACI: anticoccidial index. RBWG: relative ratio of body weight gain compared with the control group. SEM: Standard error of mean.

Clinical severity was also reduced by supplementation, as indicated by lower intestinal bloody diarrhea and lesion scores (P < 0.0001). Although synbiotic shared similar superscripts with the other treated groups, it exhibited the lowest numerical bloody (0.75) and lesion scores (0.50) among challenged birds, approaching CONN values (0.00) and indicating superior intestinal protection.

The RBWG differed among treatments (P < 0.0001). CONP had the lowest RBWG, whereas probiotic (101.68%) and synbiotic (97.45%) restored growth to levels comparable with CONN. Prebiotic and anticoccidial treatments also improved RBWG relative to CONP. Survival rate was not significantly affected (P = 0.065), although numerically lowest in CONP.

Oocyst value and anticoccidial index (ACI) were strongly influenced by treatment (P < 0.0001). All supplemented groups showed reduced oocyst values compared with CONP. CONP had the lowest ACI (70.2), whereas probiotic, (171.7), synbiotic (171.4), prebiotic (169.7) and robenidine (157.1) markedly improved ACI, indicating substantial anticoccidial efficacy. Overall, dietary biotics effectively mitigated the pathological and parasitological effects of E. tenella infection.

Intestinal microscopic parameters

The effects of dietary treatments on intestinal morphohistology are summarized in Table 4. All measured variables were affected by treatment (P < 0.05). Villus length (VL) was markedly reduced in the CONP (665 μm), confirming mucosal damage after infection. Biotic supplementation significantly increased VL (P < 0.001) compared to the other groups, with synbiotic birds exhibiting the highest numerical value (934 μm).

Table 4.

Effects of dietary treatments on intestinal morphohistology of broilers challenged with E. tenella.

Treatment1	Villus length (μm)	Villus width (μm)	VSA (mm2)	CD (μm)	VL/CD
CONP	665c	129b	0.266d	90.8b	7.63c
Robenidine	805b	120b,c	0.304c	84.8b,c	9.70b,c
Prebiotic	917a	108c	0.312a,b,c	77.5c	12.1a,b
Probiotic	905a	113c	0.325a,b,c	79.9b,c	12.8a
Synbiotic	934a	115c	0.336a,b	80.7b,c	11.9a,b
CONN	752b	154a	0.363a	109a	7.02d
SEM	11.7	2.22	0.006	1.54	0.314
Source of variance (P value)
Treatment	<0.0001	<0.0001	0.002	<0.0001	<0.0001
CONP vs. CONN	<0.0001	0.036	0.018	0.036	0.017
CONP vs. Robenidine	0.037	0.183	0.003	0.179	0.063
CONP vs. Prebiotic	<0.0001	0.021	0.064	<0.0001	0.046
CONP vs. Probiotic	0.000	0.041	0.057	0.101	0.008
CONP vs. Synbiotic	0.001	0.027	0.061	0.269	0.001
CONP vs. Biotic	0.031	0.048	0.057	0.564	0.017

¹Treatment: As described in Table 2. VSA: Villus surface area; CD: crypt-depth; VL/CD: Villus length/ crypt depth. n = 8 samples/treatment (3 point for each replicate).

^a-cMeans within the same column with different superscripts differ significantly (P < 0.05). SEM: Standard error of mean.

Villus width and villus surface area (VSA) were also influenced by treatment (P ≤ 0.002). CONN displayed the widest villi (154 μm) and the largest VSA (0.363 mm²), while CONP had the lowest VSA (0.266 mm²). Experimental groups showed lower villus width values than CONP, indicating reduced mucosal swelling and epithelial hyperplasia, which are typically associated with intestinal inflammation and tissue damage. Biotic treatments improved villus surface area relative to CONP, indicating partial restoration of absorptive structures.

Crypt depth differed among treatments (P < 0.0001), with shallower crypts observed in supplemented groups compared with CONP, suggesting reduced epithelial turnover and improved intestinal health. Consequently, the villus length-to-crypt depth ratio (VL/CD ratio), an indicator of absorptive efficiency, was significantly higher in prebiotic, probiotic, and synbiotic groups than in CONP, with the highest ratio in probiotic birds. Overall, dietary biotic supplementation alleviated E. tenella-induced intestinal damage by improving villus architecture and mucosal integrity, indicating enhanced absorptive capacity.

Antioxidative markers

As shown in Table 5, serum antioxidative markers (TAC, MDA, and SOD) were all affected by treatment (P < 0.0001). TAC was lowest in the CONP (14.38), indicating oxidative stress, whereas probiotic (20.04) and synbiotic (19.58) treatments showed the highest values, followed by prebiotic (17.82), anticoccidial (18.90), and CONN groups (17.14). All biotic treatments improved TAC compared with CONP. Pairwise contrasts indicated a significant increase in TAC for an individual and combined comparison of biotic groups vs. CONP showed a significant improvement (P < 0.05). MDA concentrations were highest in CONP (7.08), reflecting increased lipid peroxidation. Probiotic (1.92) and synbiotic (2.60) supplementation markedly reduced MDA, while prebiotic (4.58) and CONN (4.58) groups showed intermediate values, indicating strong antioxidative protection. SOD activity was highest in CONP (40.60), likely reflecting a compensatory response to oxidative stress, but reduced in all supplemented groups to levels comparable with the CONN (21.24), suggesting alleviation of oxidative stress (P < 0.0001). Overall, dietary biotics mitigated E. tenella-induced oxidative stress in broilers, with probiotic and synbiotic treatments showing the strongest effects-higher TAC and lower MDA-while SOD did not differ among biotic groups.

Table 5.

Effects of dietary treatments on serum antioxidative markers of broilers challenged with E. tenella.

Treatment1	Total antioxidant capacity (TAC; µmol/ mL)	Malondialdehyde (MDA; nmol/mL)	Superoxide dismutase (SOD; U/mL)
CONP	14.38c	7.08a	40.60a
Robenidine	18.90a,b	4.88b	21.90b
Prebiotic	17.82a,b	4.58b	22.29b
Probiotic	20.04a	1.92c	22.77b
Synbiotic	19.58a	2.60c	20.78b
CONN	17.14b	4.58b	21.24b
SEM	0.371	0.263	1.18
Source of variance (P value)
Treatment	<0.0001	<0.0001	<0.0001
CONP vs. CONN	0.048	<0.0001	0.049
CONP vs. Robenidine	0.041	0.041	0.041
CONP vs. Prebiotic	<0.0001	<0.0001	<0.0001
CONP vs. Probiotic	0.017	0.042	0.051
CONP vs. Synbiotic	0.021	<0.0001	0.046
CONP vs. Biotic	0.035	0.024	0.001

¹Treatment: As described in Table 2.

^a-cMeans within the same column with different superscripts differ significantly (P < 0.05). SEM: Standard error of mean.

Dressing and carcass yields

The effects of dietary treatments on carcass traits of broilers challenged with E. tenella are presented in Table 6. Significant treatment effects were observed for carcass weight, dressing yield, and relative weights of leg, thymus, liver, and intestine (P < 0.05), whereas relative weights of breast, bursa, spleen, and cecum were unaffected (P > 0.05). Carcass weight was the lowest in CONP (1050 g) and highest in CONN (1236 g). All supplemented groups improved carcass weight relative to CONP, with probiotic treatment showing the greatest increases. Dressing yield followed a similar pattern, with highest values in CONN (68.6%) and lowest in CONP (64.4%). Leg percentage was higher in challenged groups than CONN, whereas breast yield was unchanged. Thymus weight increased in probiotic (0.85%) and synbiotic (0.76%) groups compared with CONP (0.35%), suggesting improved immune status. Liver relative weight was higher in the robenidine group than in synbiotic and CONN groups, with CONP, prebiotic, and probiotic showing intermediate values. Intestinal relative weight was highest in CONP, followed by robenidine, while prebiotic, probiotic, and CONN groups showed the lowest values; synbiotic was intermediate, indicating attenuation of infection-related intestinal enlargement and improved gut health in supplemented birds (P < 0.001).

Table 6.

Effects of dietary treatments on carcass characteristics of broilers challenged with E. tenella.

Treatment1	Carcass weight (g)	Dressing yield (%)	Relative organ weights (% of carcass weight)
			Leg	Breast	Thymus	Bursa	Spleen	Liver	Intestine	Ceca
CONP	1050c	64.4c	37.7a	40.6	0.35b	0.36	0.17	3.54a,b	7.98a	0.88
Robenidine	1067b,c	65.4b,c	37.4a	39.9	0.62a,b	0.42	0.21	3.73a	7.30b	0.89
Prebiotic	1158a,b	67.6a,b	37.8a	38.8	0.64a,b	0.32	0.16	3.20a,b	6.43c	0.98
Probiotic	1185a	66.7a,b,c	38.1a	38.1	0.85a	0.39	0.21	3.20a,b	6.56c	1.00
Synbiotic	1159a,b	66.9a,b	37.1a	39.3	0.76a	0.36	0.18	3.11b	6.71b,c	1.09
CONN	1236a	68.6a	35.0b	38.1	0.66a,b	0.3	0.16	3.08b	6.60c	1.15
SEM	13.5	0.291	0.244	0.375	0.040	0.014	0.008	0.058	0.113	0.041
		Source of variance (P value)
Treatment	<0.0001	<0.0001	0.001	0.322	0.003	0.297	0.177	0.001	<0.0001	0.333
CONP vs. CONN	0.013	0.043	0.001	0.604	0.232	0.324	0.222	0.001	0.049	0.153
CONP vs. Robenidine	<0.0001	0.225	0.622	0.174	0.698	0.144	0.064	0.001	0.021	0.075
CONP vs. Prebiotic	0.047	0.001	0.749	0.596	0.867	0.182	0.077	0.260	0.027	0.915
CONP vs. Probiotic	0.014	0.090	0.607	0.401	0.027	0.080	0.064	0.300	0.005	0.533
CONP vs. Synbiotic	0.002	0.099	0.327	0.160	0.053	0.663	0.930	0.003	0.015	0.455
CONP vs. Biotic	0.032	0.197	0.459	0.480	0.956	0.150	0.128	0.004	0.048	0.605

¹Treatment: As described in Table 2.

^a-cMeans within the same column with different superscripts differ significantly (P < 0.05). SEM: Standard error of mean.

Cecum weight was not affected by treatment (P = 0.333). Overall, dietary biotics partially alleviated the adverse carcass effects of E. tenella, with probiotic and synbiotic treatments showing the most consistent benefits.

Breast physicochemical traits

The effects of dietary treatments on the pH and color characteristics of broiler breast meat are presented in Table 7. Initial pH, lightness (L*), color difference (ΔE), and whiteness index (WI) were affected by treatment (P < 0.05), whereas redness (a*), yellowness (b*), chroma, hue angle, and browning index (BI) were unaffected. Muscle pH was highest in the robenidine group (5.91) and CONN (5.83), lowest in the synbiotic group (5.37), and intermediate in the other groups. Lightness was lowest in CONP and highest in probiotic (55.9) and CONN (55.5) groups. Color difference (ΔE) was highest in CONP and lower in probiotic and CONN groups, indicating improved color stability. Likewise, WI was lowest in CONP and highest in probiotic and CONN groups. Chroma, hue angle, and BI were not affected (P > 0.05), indicating that the saturation and tonal attributes of meat color remained relatively stable among treatments. Overall, dietary biotic supplementation moderately improved breast meat color quality, particularly by increasing lightness and whiteness and reducing color deviation in broilers under E. tenella challenge.

Table 7.

Effects of dietary treatments on initial pH, color quality and its derivatives of breast muscle measured at 30 minutes post-mortem in broilers challenged with E. tenella.

Treatment1	Initial pH	Initial color component			Initial color derivatives
		L*	a*	b*	ΔE	Chroma	Hue angle	BI	WI
CONP	5.64a,b	51.2b	2.02	13.5	44.1a	13.6	81.6	32.9	49.4b
Robenidine	5.91a	53.0a,b	1.30	13.5	42.4a,b	13.6	84.4	30.8	51.0a,b
Prebiotic	5.79a,b	53.4a,b	1.77	13.2	41.9a,b	13.3	82.1	30.2	51.5a,b
Probiotic	5.64a,b	55.9a	1.48	14.0	39.7b	14.1	84.0	30.0	53.7a
Synbiotic	5.37b	54.6a,b	1.89	13.4	40.8a,b	13.5	82.1	30.4	52.6a,b
CONN	5.83a	55.5a	0.80	13.2	39.8b	13.3	86.5	27.8	53.5a
SEM	0.050	0.400	0.143	0.202	0.383	0.202	0.604	0.585	0.376
Source of variance (P value)
Treatment	0.025	0.003	0.135	0.912	0.003	0.905	0.156	0.269	0.003
CONP vs. CONN	0.200	0.040	0.221	0.813	0.030	0.910	0.259	0.826	0.029
CONP vs. Robenidine	0.620	0.183	0.302	0.662	0.172	0.614	0.321	0.135	0.164
CONP vs. Prebiotic	0.096	0.162	0.136	0.904	0.150	0.977	0.171	0.310	0.151
CONP vs. Probiotic	0.451	0.019	0.330	0.618	0.021	0.684	0.245	0.769	0.021
CONP vs. Synbiotic	0.102	0.703	0.710	0.577	0.669	0.551	0.811	0.702	0.647
CONP vs. Biotic	0.099	0.568	0.246	0.980	0.583	0.929	0.258	0.889	0.573

¹Treatment: As described in Table 2.

^a-cMeans within the same column with different superscripts differ significantly (P < 0.05). SEM: Standard error. L*: Lightness, a*: Redness, b*: Yellowness; ΔE: Delta E color difference, and BI: Browning index; WI: Whiteness index.

Discussion

Coccidiosis caused by E. tenella is one of the most economically important enteric diseases affecting broiler production, primarily due to intestinal damage, impaired nutrient absorption, oxidative stress, and reduced growth performance (Choi et al., 2021; Mohammed et al., 2025; Qaid et al., 2021a; Qasem et al., 2020).

Experimental infection with E. tenella negatively impaired growth performance, as reflected by reduced body weight and poorer feed efficiency in the challenged control group. This outcome is consistent with the pathogenic nature of E. tenella, which damages the cecal epithelium, disrupts nutrient digestion and absorption, and induces intestinal inflammation (Choi et al., 2021; Guo et al., 2025; Tomal et al., 2023). The resulting intestinal inflammation and tissue damage typically lead to reduced growth rate and inefficient feed utilization in infected broilers.

In the current study, birds receiving dietary biotic supplementation exhibited improved ADG during the grower phase (15-28 d) and enhanced overall performance (0-28 d) compared with the challenged control. These findings agree with previous studies indicating that prebiotics and probiotics can enhance nutrient utilization and support intestinal health in broiler chickens under enteric disease challenge (Alqhtani et al., 2024; Blokker et al., 2022; Obianwuna et al., 2023). For example, several studies have reported improved ADG and FCR in broilers supplemented with probiotics or synbiotics during coccidial infection, suggesting that beneficial microorganisms can partially offset the negative effects of intestinal damage caused by Eimeria species (Chhetri et al., 2026; Javanmiri et al., 2024; Ogwiji et al., 2024). The improvement in growth performance observed in the present study may therefore be attributed to several mechanisms, including modulation of gut microbial balance, improved digestive efficiency, and improved intestinal barrier function resulting from biotic supplementation (Assaf et al., 2025; Chowdhury et al., 2025; Sulaiman et al., 2025). Also, the improved FCR observed particularly in the probiotic and synbiotic groups further supports the suggestion that combining beneficial microbes with fermentable substrates promotes a more stable, functional gastrointestinal microbial ecosystem, and nutrient digestion efficiency (Atuahene et al., 2025; Yadav and Jha, 2019; Yang et al., 2025).

The anticoccidial index results confirmed the effectiveness of the experimental challenge model. The challenged control group exhibited high oocyst shedding, severe lesion scores, and reduced relative weight gain, which are classical indicators of cecal coccidiosis. In contrast, birds receiving dietary biotics showed markedly reduced oocyst output, lower lesion scores, and higher anticoccidial indices. The reduction in lesion severity and oocyst shedding, together with the improvement in anticoccidial indices in birds receiving dietary biotics, supports the protective role of these additives against coccidial infection. Similar findings have been reported in broilers challenged with Eimeria spp., where probiotic or synbiotic supplementation reduced intestinal lesion scores and parasite shedding (Chalalai et al., 2025; Chhetri et al., 2026; Ogwiji et al., 2024). These effects are commonly attributed to modulation of the intestinal microbiota, competitive exclusion of pathogens, stimulation of host immune responses, and the production of antimicrobial metabolites and short-chain fatty acids that help maintain intestinal integrity and limit pathogen proliferation (Calik et al., 2019; Javanmiri et al., 2024). Overall, these results indicate that modulation of gut microbiota by prebiotics, probiotics, and synbiotics can reduce parasite burden and enhance disease resistance in broilers infected with coccidia.

Intestinal morphohistological parameters provide important insights into nutrient absorption capacity and gut health (Azizi et al., 2026; Khan et al., 2025; Rus et al., 2025). In the present study, intestinal morphology was also markedly influenced by both infection and dietary supplementation. Birds in the challenged control group showed shorter villi and altered villus-to-crypt ratios, indicating impaired absorptive capacity due to epithelial damage caused by coccidial infection. In contrast, dietary biotic supplementation significantly improved villus length and villus-to-crypt ratio, with the probiotic and synbiotic groups showing the greatest improvements. Enhanced villus architecture reflects improved epithelial regeneration and nutrient absorption, which likely contributed to the better growth performance observed in supplemented birds (Fritzlen, 2025). Moreover, improved intestinal architecture may also strengthen the mucosal barrier and reduce pathogen invasion, thereby limiting the severity of coccidial infection (Calik et al., 2019; McKnight et al., 2019).

Oxidative stress represents an important pathological consequence of coccidial infection (Razavi et al., 2024; Zhao et al., 2025). In the present study, infected birds exhibited increased lipid peroxidation, reflected by elevated malondialdehyde levels, indicating enhanced oxidative stress that may impair cellular function, reduce nutrient utilization, and aggravate intestinal damage. In contrast, probiotic and synbiotic supplementation enhanced total antioxidant capacity and reduced lipid peroxidation compared with the challenged control group, suggesting improved antioxidant defense.

These findings agree with previous reports that probiotics and synbiotics can enhance antioxidant status and mitigate oxidative stress in broilers exposed to pathogenic or environmental challenges (Atuahene et al., 2025; Mohsin et al., 2022; Zhao et al., 2025). The reduction in oxidative stress may be associated with microbial production of antioxidant metabolites and stimulation of host antioxidant enzymes (Li et al., 2025; Zhou and Hatzios, 2025). Improved oxidative balance may also protect intestinal tissues, support immune responses, and facilitate recovery from intestinal damage caused by E. tenella, thereby enhancing physiological resilience during infection (Wickramasuriya et al., 2022).

As expected, the results of this study demonstrate that E. tenella challenge adversely affected carcass traits, as evidenced by reduced carcass weight and dressing yield and increased intestinal weight in the challenged control pared with medicated or NC groups. Our findings are consistent with those of Moryani et al. (2021) and Qaid et al. (2022), who reported that oral challenge with Eimeria-infected oocysts adversely affected growth performance indices and carcass yield. Intestinal enlargement likely reflecting inflammation and tissue damage associated with coccidiosis, which can impair nutrient utilization and growth. These findings are consistent with previous reports showing that cecal coccidiosis impairs nutrient utilization and promotes intestinal inflammation, ultimately reducing carcass yield (Qaid et al., 2021b, 2022; Youssef et al., 2021).

Dietary supplementation with prebiotic, probiotic, and synbiotic partially alleviated these effects, improving carcass weight and dressing percentage. Similar improvements have been reported in broilers supplemented with probiotics or synbiotics under coccidial challenge, where enhanced gut health and nutrient absorption translated into better carcass performance (Cha et al., 2020; Qaid et al., 2022). The greater responses observed with probiotic treatment in the current study agree with earlier findings indicating that live beneficial microbes, alone or in combination with fermentable substrates, exert stronger effects on growth and carcass yield than prebiotics alone (Atuahene et al., 2025).

The reduction in intestinal weight in supplemented groups further supports improved gut integrity and reduced inflammatory response, which has been consistently observed in studies where biotic additives mitigated intestinal damage caused by Eimeria spp. Infection (Galamatis et al., 2025; Madlala et al., 2021). Overall, these findings corroborate previous evidence that dietary biotics, particularly probiotics and synbiotics, can partially restore carcass performance in coccidia-challenged broilers by improving intestinal health, reducing inflammation, and enhancing nutrient utilization (Javanmiri et al., 2024). Javanmiri et al. (2024) also concluded that the efficacy of feed additives in preventing coccidiosis varies according to their type and source, as well as the duration and dosage of application, the level of oocyst challenge, and the Eimeria species involved.

The present findings on meat pH and color in broilers challenged with E. tenella are consistent with previous reports indicating that dietary biotics exert limited and variable effects on early postmortem pH, but more pronounced effects on meat color stability (Cha et al., 2020; Pandey et al., 2026; Qaid et al., 2022). In the current study, pH differed among treatments, with synbiotic supplementation promoting a lower pH and the anticoccidial group showing higher values or slower acidification, reflecting differences in postmortem glycolysis. The significant difference between CONP and CONN highlights the effect of challenge status on glycogen depletion, while the lack of differences between CONP and supplemented groups suggests limited pH recovery. However, biotic treatments did not consistently restore pH relative to the challenged control, supporting earlier observations that pH responses depend on physiological and experimental conditions (Pandey et al., 2026).

In contrast, meat color traits were more responsive to dietary supplementation. Probiotic treatment improved lightness and reduced color difference (ΔE), indicating enhanced color stability. These effects are likely associated with improved antioxidant status, which preserves muscle pigments and delays discoloration, as previously reported. Redness (a*) and yellowness (b*) were not affected, consistent with earlier studies showing that these parameters are relatively stable and less sensitive to dietary interventions (Cha et al., 2020; Qaid et al., 2022; Suryadi et al., 2019). Overall, these results support the view that dietary biotics, particularly probiotics and synbiotics, have modest effects on pH but contribute to improved meat color stability primarily through antioxidant mechanisms.

Conclusion

In conclusion, dietary supplementation with biotic additives alleviated the adverse effects of Eimeria tenella challenge in broiler chickens. Biotic supplementation improved growth performance, anticoccidial efficacy, antioxidant status, intestinal morphology, and selected carcass and meat quality traits compared with the challenged control group. In particular, supplemented birds exhibited reduced oocyst shedding and lesion severity, improved villus architecture and feed efficiency, and lower oxidative stress, indicating enhanced intestinal integrity and physiological resilience during coccidial infection.

Among the evaluated treatments, probiotic and synbiotic supplementation generally produced the most consistent beneficial responses, restoring several parameters to levels comparable with the non-challenged control group. These findings suggest that dietary biotics, especially probiotic and synbiotic formulations, may represent effective nutritional strategies for supporting intestinal health and productivity in broilers under coccidial challenge conditions and could serve as sustainable alternatives or complementary approaches to conventional anticoccidial programs.

Nevertheless, the study was conducted under controlled experimental conditions using a single Eimeria tenella challenge model, which may limit extrapolation to commercial production systems. Future studies should evaluate the efficacy of dietary biotics under commercial farming conditions and further investigate their mechanisms of action through gut microbiota, immune response, and molecular analyses.

Funding

This project is supported by the Ongoing Research Funding Program (ORF-2026-1500), King Saud University, Riyadh, Saudi Arabia.

CRediT authorship contribution statement

Hani H. Al-Baadani: Writing – review & editing, Visualization, Validation, Software, Methodology, Investigation, Funding acquisition, Data curation, Conceptualization. Mohammed M. Qaid: Writing – review & editing, Writing – original draft, Visualization, Validation, Formal analysis, Conceptualization. Abdulrahman S. Alharthi: Writing – review & editing, Visualization, Validation, Supervision, Project administration, Funding acquisition. Ibrahim A Alhidary: Writing – review & editing, Supervision, Resources, Project administration, Investigation.

Disclosures

The authors declare no conflict of interest.

Data availability

The data that support the findings of this study are available on request from the corresponding author upon reasonable request.