Synergistic Impact of Dietary Black Cumin (Nigella sativa L.) Powder and Probiotic Supplementation on Growth Performance, Feed Efficiency, and Economic Viability in Caged Broiler Chickens

Introduction

Modern intensive poultry production demands high feed conversion efficiency, rapid growth kinetics, and optimal physiological health to yield high-quality animal protein. Feed accounts for approximately 65-70% of overall operational expenditure in broiler operations, making nutrient optimization and gut microflora management critical drivers of enterprise profitability. Historically, synthetic sub-therapeutic antibiotic growth promoters (AGPs) were incorporated into poultry rations to reduce pathogen loads and promote growth. However, growing concerns over antimicrobial resistance (AMR), tissue antibiotic residues, and consumer safety have led to strict global restrictions and outright bans on prophylactic AGP use. Consequently, research focused on safe, eco-friendly phytogenics and direct-fed microbials (probiotics) as antibiotic alternatives has expanded. Phytogenic feed additives (PFAs) derived from medicinal herbs possess rich bioactive profiles capable of stimulating digestive secretions, enhancing mucosal absorption, exerting antimicrobial effects, and mitigating oxidative stress. Black cumin (Nigella sativa L., family Ranunculaceae) is an aromatic medicinal spice recognized for its therapeutic and nutritional properties. The proximate matrix of N. sativa seeds comprises 20-25% crude protein, 30-40% fixed lipids, 25-30% carbohydrates, 8-10% crude fiber, and essential micronutrients. The principal bioactive monoterpene in black cumin, thymoquinone, along with secondary alkaloids, saponins, and flavonoids, drives its pharmacological benefits. These constituents stimulate endogenous enzyme secretion (e.g., amylase, lipase, and trypsin), enhance villus morphology, reduce pathogen colonization, and improve systemic antioxidant status. Combining phytogenics with probiotics (synbiotic-like interaction) offers synergistic benefits. Phytogenic compounds optimize gut environmental condition by controlling pathogenic bacterial loads and oxidative stress, enabling probiotic strains to colonize, stabilize mucosal barrier integrity, and improve digestion. While individual benefits of black cumin and probiotics are recognized, data evaluating their combined effect at graded dietary levels in caged broiler production systems remain sparse. This investigation evaluated the effect of graded dietary inclusion levels of Nigella sativa powder (0.5%, 1.0%, and 1.5%) co-supplemented with a fixed level of multi-strain probiotics (0.1%) on weekly live weight kinetics, cumulative body weight gain, feed intake, and overall feed conversion ratio (FCR) in caged broiler chickens over a 35-day production cycle.

Materials and Methods

Environmental Management

The feeding trial was carried out at the Poultry Research Unit, Department of Animal Husbandry and Dairying, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology and Sciences (SHUATS), Prayagraj, Uttar Pradesh, India. The facility is located in a subtropical Agro-climatic zone. Prior to chick placement, the experimental house was thoroughly disinfected, flamesanitized, and subjected to a 14-day resting period. Experimental battery cages (60 × 45 × 45 cm) equipped with individual trough feeders and drinking systems were used. Temperature, ventilation, and lighting schedules were managed in accordance with standard broiler husbandry recommendations. Brooding temperature was initially set at 33°C during Week 1 and reduced by 2.5°C weekly until reaching an ambient room temperature of 24°C.

Experimental Design and Dietary Formulations

Forty-eight (n = 48), day-old commercial broiler chicks were weighed upon arrival to establish baseline weights. The chicks were randomly distributed in a Completely Randomized Design (CRD) across four dietary treatments (T₀, T₁, T₂, and T₃), with four replicate cages per treatment and three birds per cage. High-quality black cumin seeds were pulverized into a fine powder (particle size < 0.5 mm) prior to diet compounding.

The probiotic additive consisted of a viable commercial powder blend containing Lactobacillus spp. and Bacillus spp. Diets and fresh water were provided ad libitum throughout the 35-day period.

Performance Data Collection

Individual bird live weights were recorded on Day 0 and subsequently at weekly intervals (Days 7, 14, 21, 28, and 35) using a digital balance.

• Body Weight Gain (BWG): Computed weekly using where and represent live weights at the end and beginning of week , respectively.

• Feed Intake (FI): Monitored per replicate cage by quantifying the difference between weekly feed offered and unconsumed residue: .

• Feed Conversion Ratio (FCR): Calculated weekly and cumulatively on a cage-unit basis as.

Mortality was monitored daily.

Statistical Analysis

Data were compiled and analyzed using One-Way Analysis of Variance (ANOVA) in accordance with standard linear model procedures for Completely Randomized Designs. The statistical model utilized was , where is the dependent parameter observation, is the overall mean, is the fixed effect of dietary supplementation ( ), and is the random experimental error term. Treatment means were compared using Duncan's Multiple Range Test (DMRT) at a significance threshold of P ≤ 0.05.

Results

Live Body Weight Kinetics

Initial chick weights on Day 0 averaged 46.43 g (T₀), 46.20 g (T₁), 45.75 g (T₂), and 47.18 g (T₃), showing no statistically significant differences (P = 0.789), confirming balanced baseline randomization.

Body Weight Gain (BWG) Trajectories

Weekly and cumulative body weight gains mirrored the live weight patterns. Total cumulative weight gain was 1758.58 g (T₀), 1858.80 g (T₁), 1959.25 g (T₂), and 2035.33 g (T₃). Growth rates accelerated during the finisher phase (Weeks 4-5), with T₃ birds gaining 617.50 g during Week 5 compared to 517.50 g in T₀ controls.

Feed Intake and Feed Conversion Efficiency

Cumulative feed consumption showed a controlled increase with higher inclusion of phytogenic and probiotic supplements (P< 0.05). Total feed intake over the 35-day trial was 3150.00 g (T₀), 3275.00 g (T₁), 3338.75 g (T₂), and 3400.75 g (T₃). Despite higher feed intake, feed efficiency improved significantly. Cumulative FCR decreased linearly from 1.65 (T₀) to 1.50 (T₃). Treatment T₃ achieved a 9.09% improvement in overall feed conversion efficiency relative to the un supplemented control.

Discussion

The results demonstrate that co-supplementing black cumin seed powder with multi-strain probiotics enhances broiler performance. The combined treatment (T₃: 1.5% black cumin + 0.1% probiotics) produced a clear synergistic effect. Black cumin reduces gut oxidative stress and pathogen loads, establishing a stable microenvironment that enables probiotic strains to colonize and synthesize beneficial short-chain fatty acids (e.g., butyrate). This synergistic action supports mucosal microcirculation and absorptive surface area, facilitating systemic nutrient utilization. The higher feed intake observed in supplemented groups can be attributed to the palatable aromatic constituents of black cumin seeds, which stimulate appetite. Importantly, the concurrent decrease in FCR (improving from 1.65 in T₀ to 1.50 in T₃) confirms that consumed nutrients were efficiently directed toward skeletal muscle synthesis rather than metabolic maintenance.

Conclusion

Dietary supplementation with black cumin (Nigella sativa L.) seed powder combined with a multi-strain probiotic improves growth kinetics, feed intake, and feed conversion efficiency in caged broiler chickens. Among tested regimens, the inclusion of 1.5% black cumin powder co-supplemented with 0.1% probiotics (T₃) produced the best results, yielding a final live weight of 2082.50 g, cumulative weight gain of 2035.33 g, and a low FCR of 1.50 over 35 days. This natural supplementation strategy offers an effective alternative to antibiotic growth promoters in sustainable, residue-free broiler production.

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