Dietary inclusion of black cumin (Nigella sativa L.) seed meal in broiler chickens: Effects on growth performance, cecal microbiota, and cost efficiency

Highlights

• •Inclusion of BCSM up to 4.5% maintained broiler growth performance.
• •Improved feed conversion ratio observed at the highest level of inclusion.
• •Dietary inclusion of BCSM significantly reduced broiler mortality.
• •BCSM reduced cecal Escherichia coli and total coliforms, while increasing Lactobacillus.
• •BCSM treatment groups offered higher net income and marginal rate of return.

Abstract

The current study evaluated the effects of black cumin seed meal (BCSM) on growth performance, cecal microbiota, production efficiency, and cost efficiency in broiler chickens. A total of 144 one-day-old unsexed Cobb 500 broiler chicks were randomly assigned to four treatment groups, each with three replicates of 12 chicks using a completely randomized design. Broilers were fed isocaloric and isonitrogenous diets containing 0% (BCSM0, control), 1.5% (BCSM1.5), 3% (BCSM3), and 4.5% (BCSM4.5) BCSM over a 45-day feeding trial. The results showed no significant differences (P > 0.05) in feed intake, weight gain, or carcass characteristics among different treatments. However, feed conversion ratio (FCR) was significantly improved (P = 0.043 and P = 0.027) in BCSM4.5 during the finisher and entire periods, respectively compared with the control, which may be associated with slightly lower feed intake and the reported bioactive compounds in BCSM that may enhance digestion and feed utilization. Regarding the cecal microbiota, the inclusion of BCSM significantly reduced total coliform (P = 0.009) and Escherichia coli (P = 0.002) counts while significantly increased (P = 0.007) beneficial Lactobacillus populations, although the total bacterial load was not affected. Production efficiency factor and European broiler index were significantly better (P = 0.018 and P = 0.019, respectively) at the highest level of inclusion (4.5%) compared to the control. Partial budget analysis revealed that net income and the marginal rate of return were better for BCSM treatments groups. In conclusion, this study demonstrates that BCSM can be utilized as an alternative feed ingredient for broiler chickens. Inclusion of BCSM up to 4.5% beneficially modulated cecal microbiota, reduced mortality, and improved FCR, production efficiency, and cost efficiency, depending on the inclusion level, without adversely affecting growth performance.

1. Introduction

Poultry meat accounts about 40% of total global meat production, and feed expenses constitute >70% of the overall production cost (Bist et al., 2024). This has intensified interest in identifying cost-effective feed ingredients that can improve broiler performance and production efficiency. According to the Food and Agriculture Organization (FAO, 2023), poultry meat consumption in developing countries was predicted to rise by >16 million metric tons between 2015 and 2024. In a similar trend, broiler meat production in Ethiopia reached 13,000 tons by the year 2016, accounting for only 2% of the total production in East Africa (FAO, 2019).

Although commercial poultry production in Ethiopia is expected to grow due to its importance, level of consumption, and future prospects, it continues to face several challenges, including the inadequate availability and high cost of feed and feed ingredients, diseases, and shortages of other input supplies (Dugassa, 2022; Ayalew et al., 2023).

The cereal grains used in poultry feed formulation have direct food value for humans, creating competition between human and poultry nutrition; this competition, coupled with climate change–induced variability in grain yields, has increased demand and escalated the cost of these ingredients (Bediye et al., 2018; Katu et al., 2025). Consequently, poultry producers in Ethiopia consistently face challenges due to the high price and inconsistent quality of commercially available feeds. Thus, the future prospects of poultry production in Ethiopia may be constrained by the increasing price and decreasing supply of conventional feedstuffs (Asfaw & Etana, 2025). Therefore, identifying alternative, readily available feed resources could help to partially bridge the feed supply gap and improve profitability for poultry producers (Wagh et al., 2021).

Agro-industrial by-products have been widely highlighted as economically viable alternatives for poultry feed formulation (Sugiharto et al., 2018; Abd El-Hack et al., 2019; Sugiharto & Nuengjamnong, 2025), and black cumin seed meal (BCSM) may be considered among these alternative feed resources. BCSM is a by-product obtained after extracting the oil from black cumin (Nigella sativa L.) seeds through different methods, which can influence its nutrient composition. This meal has a potential as an alternative feed for poultry due to its high nutrient content including crude protein, all essential amino acids, fat, energy, and minerals (Obeidat, 2021; Fathi et al., 2023 and Zaazaa et al., 2023). Additionally, the cost of BCSM is currently low, as it remains a waste by-product which is either discarded into the environment or unknowingly used in animal feed due to limited scientific research and lack of awareness (Navidshad et al., 2024).

The meal constitutes 60–75% of the original seed weight (Tekeli, 2014; Barkah et al., 2021), making it an abundant by-product. The residual bioactive compounds such as thymoquinone, thymohydroquinone, and dithymoquinone are known to have antimicrobial, antioxidant, anti-inflammatory and immunomodulatory effects which can enhance the performance, health and sustainability of broilers (Bajagai et al., 2020; Aydin, 2021; Fathi et al., 2023). The physiological and therapeutic properties of BCSM align with the growing interest in evaluating alternative botanical products in animal nutrition. Gul et al. (2024) reported that supplementation with Urtica dioica improved carcass yield, enhanced immunity, and provided protection against various bacterial and viral diseases in birds and animals. Furthermore, Mba et al. (2025) demonstrated that Phyllanthus amarus leaf extract enhanced growth performance across distinct broiler strains (Arbor Acres, Marshall, and Ross 308) without causing deleterious effects on growth indices. Similarly, Ike et al. (2025) suggested that this botanical extract could serve as a viable alternative to synthetic antibiotics by reducing the risk of antibiotic resistance and lowering overall poultry production costs. In general, phytogenic feed additives have been recognized as effective alternatives for improving gut health and overall poultry performance through enhancement of immune responses, nutrient utilization, and gut microbial balance due to their diverse bioactive compounds, thereby reducing dependence on antibiotic growth promoters (Ntsongota et al., 2025; Oni & Oke, 2025).These bioactive compounds can positively modulate the gut ecosystem by inhibiting pathogenic bacteria and promoting beneficial microflora, which is a critical mechanism for enhancing nutrient absorption and the viability of broilers (Fathi et al., 2023).

Despite these advantages, limited previous studies on the use of BCSM as a feed ingredient have reported inconsistent effects and variable optimal inclusion levels in broiler diets, which may be attributed to differences in bird performance, environmental conditions, the nutrient composition of BCSM, and diet formulation methods, including its use as an inclusion or supplementation. In addition, there is a diversity in the composition of essential oils among Ethiopian black cumin seed genotypes (Degu et al., 2025), which may affect the performance of broiler chickens. Furthermore, while there are large and small-scale oil refining factories in different towns and cities of Ethiopia that extract oil from black cumin seed, the by-product is an underutilized and wasted resource which could become a source of environmental pollution in the long term.

Currently there is no documented study in Ethiopia that has evaluated the effects of BCSM as an alternative feed resource in animal feeding. Hence, the present study aims to evaluate BCSM at different levels to improve the performance, health and profitability of broilers, while also insuring the efficient utilization of available industrial by-products. Therefore, this study was conducted to evaluate the effects of dietary BCSM inclusion on growth performance, cecal microbiota, production efficiency and cost efficiency of broiler chickens.

2. Materials and methods

2.1. Description of the experimental site

The study was conducted in Haramaya University poultry farm, which is about 500 km from the capital city, Addis Ababa to the eastern part of the country. The area is situated at 9° 26′ North latitude and 42° 3′ East longitude with an altitude of 1980 m It receives average annual rainfall of 790 mm with an average minimum and maximum temperatures of 14 and 23 °C, respectively (Sahle, 2008).

2.2. Measurements of feed ingredients, diet formulation, and dietary treatments

The proportion of feed ingredients used to prepare the diets for each treatment group are presented in Table 1. The BCSM was obtained from Getfarms Private Limited Company (PLC), a large-scale black cumin seed oil processing factory located in Sebeta, Ethiopia. The oil was extracted through a cold-press method, and the resulting dry pelleted meal was used for this study. Prior to formulation of the treatment diets, representative samples of the feed ingredients were analyzed for their chemical composition. Iso-caloric and isonitrogenous diets were then formulated for the starter and finisher phases using FeedWin software by adjusting ingredient inclusion levels. The starter diets contained about 3140 kcal ME/kg DM and 21% crude protein, whereas the finisher diets contained about 3210 kcal ME/kg DM and 19% crude protein. The BCSM was incorporated into the diets at levels of 0% (BCSM0, control), 1.5% (BCSM1.5), 3.0% (BCSM3), and 4.5% (BCSM4.5), then the diet components were thoroughly mixed and ground together to ensure dietary uniformity. The inclusion levels (1.5%, 3.0%, and 4.5%) were selected based on previous literature and varying findings. Jahan et al. (2015) reported beneficial effects of 1.5% BCSM on FCR and cost efficiency, while Ghannam (2022) suggested further evaluation following assessment up to 3.5%. In addition, Fathi et al. (2023) reported favorable responses at 4% and 6% supplementation levels compared with 2%. The variation in responses among studies may be associated with differences in environmental conditions and the nutrient composition of the meal.

Table 1.

Proportion of feed ingredients used in broiler diets during starter and finisher phases.

Phase	Ingredients (%)	Treatments
		BCSM0	BCSM1.5	BCSM3	BCSM4.5
Starter	Maize	45	45	44	43.5
	Soybean meal	27	26.25	24	23
	Noug seed meal	16.5	16	17.25	17
	Wheat shorts	8.5	8.25	8.75	9
	BCSM	0	1.5	3	4.5
	Limestone	1.5	1.5	1.5	1.5
	Premix*	0.5	0.5	0.5	0.5
	L-Lysine HCl	0.15	0.15	0.15	0.15
	DL-methionine	0.25	0.25	0.25	0.25
	DCP	0.3	0.3	0.3	0.3
	Salt	0.3	0.3	0.3	0.3
Total (%)		100	100	100	100
Finisher	Maize	55	54.5	54.5	53
	Soybean meal	24	23.25	22	21
	Noug seed cake	12.5	11.75	12	11.5
	Wheat shorts	5.5	6	5.5	7
	BCSM	0	1.5	3	4.5
	Limestone	1.5	1.5	1.5	1.5
	Premix⁎	0.5	0.5	0.5	0.5
	L-Lysine HCl	0.15	0.15	0.15	0.15
	DL-methionine	0.25	0.25	0.25	0.25
	DCP	0.3	0.3	0.3	0.3
	Salt	0.3	0.3	0.3	0.3
Total (%)		100	100	100	100

BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively; BCSM = black cumin seed meal; DCP = dicalcium phosphate; ^⁎Premix = Each 2.5 kg contains: Vitamin A (10,000,000 IU), Vitamin D3 (2,000,000 IU), Vitamin E (15,000 mg), Vitamin C (1,000 mg), Vitamin K3 (2,000 mg), Vitamin B1 (2,000 mg), Vitamin B2 (5,000 mg), Vitamin B6 (2,000 mg), Vitamin B12 (15 mg), Biotin (260 mg), Folic acid (500 mg), Nicotinic acid (10,000 mg), Pantothenic acid (4,000 mg), Iron (70,000 mg), Zinc (62,000 mg), Manganese (90,000 mg), Copper (6,000 mg), Iodine (1,500 mg), Selenium (350 mg), Cobalt (350 mg), and Magnesium (20,000 mg).

2.3. Feed chemical composition

The feed ingredients used in this experiment were analyzed for proximate composition, including dry matter (DM), ash, crude fiber (CF), crude protein (CP), and ether extract (EE) following the standard procedure of (AOAC, 2000). The CP content was determined indirectly through the Kjeldahl method of Nitrogen (N) determination and calculated as N × 6.25. The equation described by Wiseman (1987), was used to calculate the metabolizable energy (ME) of the feeds as follows: ME (kcal/kg DM) = 3951 + (54.4 × EE) − (88.7 × CF) − (40.8 × Ash). The calcium and phosphorus contents of the experimental feeds and major feed ingredients were also analyzed according to AOAC (2000) methods. Feed samples were burned in a muffle furnace at 550 °C for 6 h, then the resulting ash was used to analyze these minerals. Calcium (Ca) content was determined using an atomic absorption spectrophotometer (AAS; Model SL-194, ELICO Ltd., Hyderabad, India), and total phosphorus (P) content was determined by the ammonium vanadate–molybdate colorimetric method using a UV–Vis spectrophotometer (Model UV-9000S, Shanghai Metash Instruments Co., Ltd., Shanghai, China).

2.4. Management of chicks and experimental design

A total of 144 one-day-old unsexed (straight-run or as-hatched) Cobb 500 broiler chicks were bought from Alema Farm, in Bishoftu, Ethiopia and transported to the experimental site. On arrival the chicks were randomly assigned to four treatment groups (36 birds per treatment) in three replicates of 12 chicks each, with an average initial body weight of 42.33 ± 0.19 g (mean ± SD), in a completely randomized design (CRD). The experimental design was consistent with standard practice in broiler nutrition trials, in which the pen, rather than the individual bird, is considered the experimental unit for performance variables, cecal microbial load, and economic evaluation (Kinati et al., 2022; Bhowmik et al., 2026). Chicks were vaccinated against Newcastle Disease at the hatchery and again within the LaSota booster vaccine at 21 days of age on the farm, which was administered through spray and drinking water, respectively. The experiment was conducted for 45 days, comprising 21 days for the starter phase and 24 days for the finisher phase. The experimental house and pens were cleaned, washed and sprayed before the arrival of the chicks. The floor of each pen was covered with Teff straw to a depth of approximately 7 cm as deep litter material, which was sprayed again with disinfectant before the placement of the chicks.

Each pen was heated with 250-watt infrared bulb, and the ambient temperature was maintained at about 32 °C for the first week and subsequently reduced by 2 °C weekly until reaching 22 °C, using a dimmer switch. The house was oriented in an east–west direction, and natural ventilation was provided through wire mesh openings at the upper sections of the walls, equipped with adjustable external coverings to regulate airflow and help in maintaining suitable relative humidity within the house. A lighting schedule of 24 h of light and 0 hour of darkness was applied on the first day, followed by a stepwise reduction in light duration with a corresponding increase in darkness toward the end of the starter phase. Thereafter, darkness was gradually reduced to 1 hour toward the end of the experimental period. Mash feed was given ad libitum and replenished twice a day in feeders, with clean and fresh tap water available at all times. Drinkers were washed every morning to maintain hygiene, and a footbath was placed at the entrance to the house for disinfection before entry. These management practices were followed throughout the experiment.

2.5. Measurements of feed intake, body weight gain and feed conversion ratio

The feed given and refusals in each pen were measured and recorded daily. Daily feed intake was determined as the difference between the amounts of feed given and the refusals collected the next morning. Mean daily feed intake was calculated as total feed intake divided by the number of experimental days. Body weight the broilers was measured weekly using a sensitive balance and pen average body weight was calculated in each pen. Body weight gain (BWG) was calculated as the difference between final body weight (FBW) and initial body weight (IBW). Average daily gain (ADG) was determined by dividing BWG by the number of experimental days. Feed conversion ratio (FCR) was calculated as the ratio of average feed intake to average body weight gain in each pen. Sanitary and hygienic measures, as well as the health status of the birds, were monitored throughout the experimental period. Mortality was recorded to determine the mortality rate and was expressed as a percentage for each treatment group at the end of the experiment.

2.6. Measurements of carcass characteristics

At the end of the experiment, three broilers per replicate were selected for carcass evaluation having a body weight close to the pen average. The broilers were fasted overnight, then weighed just before slaughter to determine slaughter weight. Killing cones were used to restrain and humanely exsanguinate the broilers by severing the jugular veins and carotid arteries using a sharp knife. The procedure was performed by a trained professional to ensure rapid and complete bleeding, following the methods described by Moran (1999).

The feathers were removed mechanically, then the carcass eviscerated and processed to separate and measure the carcass cuts, edible offal, and non-edible offal according to the procedure described by Kekeocha (1985). After the removal of blood and feathers, dressed weight was recorded, and dressing percentage was calculated as the ratio of dressed weight to slaughter weight. Eviscerated carcass weight was measured including edible offal (heart, liver, and gizzard). Eviscerated percentage was calculated as the proportion of eviscerated carcass weight to slaughter weight. Carcass cuts (breast, thigh, drumstick, back, neck, and wing), edible offal, and non-edible offal were weighed separately using a sensitive balance and expressed as a percentage of slaughter weight. The lengths of the small intestine, large intestine, and ceca were measured using a measuring tape.

2.7. Measurements of cecal microbiota

Cecal microbiota was analyzed using culture-based methods. Cecal contents were collected from the same slaughtered broilers used for carcass trait evaluation. The cecum was selected because it is the primary site of microbial fermentation and harbors the highest microbial density and diversity in the avian gastrointestinal tract. The paired ceca were identified, ligated, and gently squeezed to transfer the content aseptically into a sterile zipper plastic bag, then transported to the laboratory within an icebox. Ten grams of each cecal sample were aseptically weighed into a sterile container, in duplicate for each replicate of the treatments, and diluted in 90 mL of 1% phosphate-buffered saline (PBS). The mixture was thoroughly homogenized using a vortex mixer to prepare tenfold serial dilutions (10⁻² to 10⁻⁷). One milliliter of each serially diluted sample was transferred into a respective labeled petri dish to enumerate total bacterial count, E. coli, Lactobacillus, and total coliforms using respective selective media according to the method described by Ahsan et al. (2018). Briefly, Plate Count Agar (PCA; Micromaster Laboratories Pvt. Ltd., Thane, India) was used for total bacterial counts, MRS Agar (de Man, Rogosa, and Sharpe; HiMedia Laboratories Pvt. Ltd., Mumbai, India) for Lactobacillus, and MacConkey Agar (Sisco Research Laboratories Pvt. Ltd., New Mumbai, India; Ref: 76,875) for the enumeration of total coliforms and E. coli. The media were prepared according to the manufacturers’ instructions and used with the pour plate method, being poured into petri dishes containing serially diluted samples and allowed to solidify. The inoculated culture plates were incubated aerobically at 37 °C for 24 h for total bacteria, total coliforms, and E. coli, and anaerobically for 48 h for Lactobacillus (Ahsan et al., 2018; Abolfathi et al., 2019; Aziza et al., 2019). Plates showing well bacterial growth with 30–300 colonies were selected and counted using an automated colony counter to determine colony forming units per gram (CFU/g) of the cecal samples for each duplicate, which were then converted to log₁₀ for statistical analysis (Mahdavi et al., 2010; Manafi et al., 2017).

2.8. Production and cost efficiency of broilers

Production efficiency was evaluated by calculating the European Broiler Index (EBI) and Production Efficiency Factor (PEF) among treatment groups according to Marcu et al. (2013).

$$\text{EBI}=\frac{\text{Viability}(\%)\times \text{ADG}(\mathrm{g}/\text{chick}/\text{day})}{\text{FCR}(\text{kg}\text{of}\text{feed}/\text{kg}\text{of}\text{gain})\times 10}$$

$$\text{PEF}=\frac{\text{Viability}(\%)\times \text{BW}\left(\text{kg}\right)}{\text{Age}\left(\mathrm{d}\right)\times \text{FCR}(\text{kg}\text{of}\text{feed}/\text{kg}\text{of}\text{gain})}\times 100$$

Where; viability (%) = the percentage of chicks alive at the end of experimental period relative to the initial numbers; age (d) = the age of the chick at slaughter; d = day, BW = final body weight of the broilers in kilograms; ADG = average daily gain of the broilers in grams; FCR = feed conversion ratio.

Partial budget analysis was used to evaluate cost efficiency according to the method developed by Upton (1979) for each treatment group. The costs of day-old chicks, feed, labor, and veterinary services, were considered as total variable cost (TVC). Here the feed cost alone was used to represent TVC for cost-benefit comparison, as the costs of day-old chicks, labor, and veterinary services were constant across treatments. The revenue obtained from the sale of broiler carcasses was considered as total return (TR). Net income (NI) was calculated by subtracting total variable cost (TVC) from total return (TR). The change in net income (ΔNI) was determined as the difference between the change in total return (ΔTR) and the change in total variable cost (ΔTVC), i.e., ΔNI = ΔTR − ΔTVC. Marginal rate of return (MRR) measures the increase in net income (NI) per each extra unit of cost (ΔTVC) according to the following formula:$\text{MRR}=\frac{\Delta \text{NI}}{\Delta \text{TVC}}\times 100$.

2.9. Statistical analysis

The data were analyzed using one-way analysis of variance (ANOVA) test with the general linear models (GLM) procedure of JMP Pro, Version 16.0.0 (SAS Institute Inc., 2021). Tukey test was used to the separate the mean indicating significance difference at P < 0.05.

The following model was used for analysis of the data. ${\mathrm{Y}}_{\text{ij}}=\mu +{\mathrm{T}}_{\mathrm{i}}+{\mathrm{e}}_{\text{ij}}$.

Where Y_ij = an observation, µ= overall mean, T_i = Treatment effect, e_ij = error term.

3. Results

3.1. Chemical composition of feed ingredients and treatment diets

The chemical composition of the feed ingredients and treatment diets is presented in Table 2. The CP, EE, ME, Ca, and P contents of BCSM were within the ranges previously reported in the literature (Aydin, 2021; Obeidat, 2021; Ramdani et al., 2024). The energy content of BCSM was comparable to that of maize, whereas its protein content was comparable to noug seed meal. The chemical composition of the treatment diets was calculated from the analyzed composition and proportion of the feed ingredients used in formulation.

Table 2.

Chemical composition of feed ingredients (determined) and treatment diets (calculated).

Ingredients	Chemical composition (% on DM basis)
	DM	CP	EE	CF	Ash	Ca	P	ME (kcal/kg DM)
Maize	90.24	9.18	3.83	4.53	4.73	0.05	0.34	3565
SBM	92.09	38.97	4.37	8.19	6.23	0.38	0.65	3208
NSC	91.93	31.03	7.33	15.93	10.36	0.36	0.66	2514
WS	91.03	15.16	3.57	9.05	5.53	0.18	0.64	3117
BCSM	91.72	32.33	11.57	5.79	11.94	0.26	0.31	3580
Starter phase
BCSM0	91.15	21.06	4.33	8.58	6.87	1	0.56	3145
BCSM1.5	90.39	21.06	4.42	8.49	6.99	1	0.55	3153
BCSM3	91.62	21.04	4.56	8.68	7.07	0.99	0.54	3141
BCSM4.5	90.86	21.05	4.66	8.71	7.16	0.99	0.58	3140
Finisher phase
BCSM0	91.22	19.11	4.18	7.95	6.43	0.98	0.53	3211
BCSM1.5	90.21	19.1	4.26	7.92	6.57	0.97	0.51	3212
BCSM3	91.45	19.1	4.38	8.1	6.63	0.97	0.52	3209
BCSM4.5	90.69	19.13	4.47	8.04	6.76	0.96	0.57	3206

DM = dry matter; CP = crude protein; EE = ether extract; CF = crude fiber; Ca = calcium; P = phosphorous; ME = metabolizable energy; WS = wheat shorts; SBM = soybean meal; NSM = noug seed meal; BCSM = black cumin seed meal; BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively.

3.2. Growth performance

The feed intake, body weight gain, feed conversion ratio, and mortality rate of broilers across all production phases are presented in Table 3. No significant differences (P > 0.05) were observed in feed intake or body weight gain throughout the production phases among treatments. However, feed conversion ratio was significantly improved (P = 0.043 and P = 0.027) in BCSM4.5 compared with the control during the finisher phase and the entire experimental period, respectively. Mortality rate was significantly reduced (P = 0.006) in the BCSM treatment groups (BCSM1.5 and BCSM4.5) compared with the control during the entire experimental period. The BCSM treatment groups did not show significant differences (P > 0.05) in their FCR or mortality rates.

Table 3.

Effect of dietary BCSM inclusion on growth performance of Cobb 500 broilers during starter phase, finisher phase, and entire periods.

Production phases	Treatments
Starter Phase	BCSM0	BCSM1.5	BCSM3	BCSM4.5	SEM	P - value
Initial body weight (g/bird)	42.63	42.32	42.24	42.23	0.44	0.940
Feed intake (g/bird)	1024	1006	979	972	29.5	0.595
Average daily feed intake (g/bird/day)	48.76	47.90	46.60	46.29	1.41	0.595
Final body weight (g/bird)	486	482	484	485	4.78	0.939
Body weight gain (g/bird)	443.37	439.68	441.76	442.77	4.78	0.946
Average daily gain (g/bird/day)	21.11	20.94	21.04	21.08	0.23	0.946
Feed conversion ratio (intake/gain)	2.31	2.29	2.21	2.20	0.05	0.288
Mortality rate (%)	2.78	0.00	2.78	0.00	1.96	0.596
Finisher Phase (22–45 days)
Initial body weight (g/bird)	486	482	484	485	4.78	0.939
Feed intake (g/bird)	3166	3059	3046	3038	69.1	0.553
Average daily feed intake (g/bird/day)	131.92	127.46	126.92	126.58	2.88	0.553
Final body weight (g/bird)	1855	1831	1840	1851	27.2	0.919
Body weight gain (g/bird)	1369	1349	1356	1366	25.8	0.939
Average daily gain (g/bird/day)	57.00	56.20	56.50	56.90	1.07	0.939
Feed conversion ratio (intake/gain)	2.31a	2.27ab	2.25ab	2.22b	0.02	0.043
Mortality rate (%)	5.56	0.00	2.78	0.00	1.96	0.219
Entire period (1–45 days)
Initial body weight (g/bird)	42.63	42.32	42.24	42.23	0.44	0.940
Feed intake (g/bird)	4190	4065	4025	4010	77.1	0.397
Average daily feed intake (g/bird/day)	93.10	90.30	89.40	89.10	1.71	0.397
Final body weight (g/bird)	1855	1831	1840	1851	27.2	0.919
Body weight gain (g/bird)	1812	1788	1797	1809	27.2	0.920
Average daily gain (g/bird/day)	40.30	39.70	39.90	40.20	0.60	0.920
Feed conversion ratio (intake/gain)	2.31a	2.27ab	2.23ab	2.21b	0.02	0.027
Mortality rate (%)	8.33a	0.00b	5.56ab	0.00b	1.39	0.006

^{a, b} Means within a row bearing different superscripts are significantly different (P < 0.05); BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively; SEM = standard error of the mean.

3.3. Carcass characteristics

The carcass parts and internal organs, expressed in relative to their slaughter weight are shown in Table 4, Table 5. The weight and percentage of carcass and offal (edible and nonedible) did not differ significantly (P > 0.05) among treatments. The edible offal components included the gizzard, heart, and liver.

Table 4.

Carcass characteristics of Cobb 500 broilers fed different levels of BCSM at 45 days of age.

Parameters	Treatments
	BCSM0	BCSM1.5	BCSM3	BCSM4.5	SEM	P - value
Slaughter wt. (g)	1866	1873	1843	1887	56.2	0.954
Dressed wt. (g)	1683	1700	1678	1705	47.1	0.971
Dressed %	90.19	90.76	91.04	90.35	0.59	0.724
Eviscerated wt. (g)	1301	1305	1281	1326	36.7	0.861
Eviscerated %	69.72	69.67	69.51	70.27	0.49	0.719
Carcass wt. (g)	1222	1228	1204	1244	34.8	0.876
Carcass %	65.49	65.56	65.33	65.01	0.52	0.848
Drum stick %	9.40	9.59	9.40	9.51	0.12	0.580
Thigh %	10.53	10.42	10.58	10.57	0.18	0.912
Breast %	25.40	25.42	25.03	25.57	0.29	0.610
Wing %	3.80	3.70	3.81	3.82	0.07	0.985
Back %	7.71	7.62	7.73	7.64	0.21	0.993
Neck %	2.81	2.82	2.83	2.91	0.11	0.965
Gizzard %	1.50	1.51	1.60	1.61	0.05	0.339
Liver %	2.22	2.15	2.17	2.15	0.06	0.867
Heart %	0.49	0.48	0.49	0.47	0.02	0.801

SEM = Standard error of the mean; BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively; wt. = weight; g = gram.

Table 5.

Non-edible offal components of Cobb 500 broilers fed different levels of BCSM at 45 days of age.

Parameters	Treatments
	BCSM0	BCSM1.5	BCSM3	BCSM4.5	SEM	P - value
Slaughter weight (g)	1866	1873	1843	1887	56.2	0.954
Abdominal fat %	1.61	1.49	1.45	1.40	0.11	0.587
Kidney %	0.62	0.58	0.61	0.60	0.04	0.550
Spleen %	0.15	0.14	0.14	0.15	0.01	0.969
Large intestine %	0.16	0.17	0.16	0.17	0.01	0.858
Small intestine %	5.01	5.20	5.11	5.12	0.31	0.993
Ceca %	0.59	0.62	0.65	0.69	0.04	0.340
LI length (cm)	9.50	9.71	9.53	9.70	0.37	0.976
SI length (cm)	194	197	198	199	4.08	0.825
Ceca length (cm)	18	18	18	19	0.52	0.573

SI = Small intestine, LI = Large intestine, SEM = Standard error of the mean; BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively; g = gram; cm = centimeter.

3.4. Cecal microbial population

The effects of dietary inclusion of black cumin seed meal on selected cecal bacterial populations are presented in Table 6. No significant differences (P > 0.05) were observed in total bacterial counts among all treatment groups. The total bacterial count represents the aerobic portion of the bacterial populations. In contrary, BCSM inclusion significantly reduced (P = 0.009) the total coliform counts, which were lower in BCSM3 and BCSM4.5 compared to the control group. Similarly, E. coli counts were significantly decreased (P = 0.002) in all BCSM treatment groups relative to the control, whereas Lactobacillus counts were significantly higher (P = 0.007) in BCSM3 and BCSM4.5 compared to those of the control. However, the BCSM treatment groups did not show significant differences (P > 0.05) in counts of total coliform, E. coli and Lactobacillus among each other.

Table 6.

Cecal microbial populations of Cobb 500 broilers fed diets containing different levels of BCSM (log₁₀ CFU/g of cecal content) at 45 days of age.

Cecal microbiota	Treatments
	BCSM0	BCSM1.5	BCSM3	BCSM4.5	SEM	P - value
Total bacterial count	7.70	7.62	7.53	7.58	0.16	0.893
Total coliforms	6.70a	6.43ab	5.93b	5.67b	0.17	0.009
E. coli	5.54a	4.77b	4.75b	4.38b	0.13	0.002
Lactobacillus	6.25b	6.59ab	7.02a	7.28a	0.15	0.007

^{a, b} Means within a row bearing different superscripts are significantly different (P < 0.05); BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively; CFU = colony forming unit; g = gram; SEM = standard error of the mean.

3.5. Production and cost efficiency of broilers

Production efficiency factor (PEF), European broiler index (EBI), and viability percentage during the starter and finisher phases were similar (P > 0.05) among treatments (Table 7). However, all BCSM treatment groups were numerically higher than the control. During the entire period, EBI and PEF differed significantly (P = 0.019 and P = 0.018, respectively), with the better value was observed in BCSM4.5 compared to the control. Additionally, the viability percentage was significantly higher (P = 0.006) in the BCSM treatment groups (BCSM1.5 and BCSM4.5) during the entire period than in the control group.

Table 7.

Production efficiency of Cobb 500 broilers fed different levels of BCSM at 45 days of age.

Parameters	Treatments
Production Efficiency	BCSM0	BCSM1.5	BCSM3	BCSM4.5	SEM	P-value
Starter viability (%)	97.22	100	97.22	100	1.96	0.596
Starter EBI	88.74	91.3	92.62	95.87	2.56	0.327
Starter PEF	97.27	100.09	101.49	105.02	2.83	0.339
Finisher viability (%)	94.44	100	97.22	100	1.96	0.219
Finisher EBI	233.15	247.96	244.61	256.02	7.97	0.307
Finisher PEF	315.79	336.5	331.99	346.82	10.14	0.26
EP viability (%)	91.67b	100.00a	94.44ab	100.00a	1.39	0.006
Entire period EBI	159.93b	174.89ab	168.98ab	181.90a	3.74	0.019
Entire period PEF	163.59b	179.25ab	173.16ab	186.12a	3.81	0.018

^{a, b} Means within a row bearing different superscripts are significantly different (P < 0.05); BCSM0, BCSM1.5, BCSM3 and BCSM4.5 are treatment diets at 0, 1.5, 3.0 and 4.5% inclusion levels of black cumin seed meal, respectively; SEM = Standard error of the mean; EBI = European broiler index; PEF= Production efficiency factor; EP = Entire period.

Partial budget analysis (Table 8) showed that total feed cost decreased with increasing inclusion level of BCSM compared to those of the control, offering a reduction in total variable cost. As a result, net income and marginal rate of return (MRR) were highest in broilers fed the diet with the highest BCSM inclusion level (BCSM4.5), followed by BCSM1.5 and then BCSM3, while the lowest values were observed in the control group (BCSM0). In general, the production and cost efficiency analysis indicated that BCSM inclusion improved both production efficiency and profitability of broilers, providing research-based evidence for the sector to use the BSCSM as alternative and viable feed resource for sustainable broiler production.

Table 8.

Partial budget analysis of Cobb 500 broilers fed different levels of BCSM at 45 days of age.

Cost (ETB)	Treatments
	BCSM0	BCSM1.5	BCSM3	BCSM4.5
DOC price (ETB)	83.00	83.00	83.00	83.00
Feed Consumed (kg)	4.19	4.07	4.02	4.01
Cost of feed/kg (ETB)	42.12	41.78	41.32	40.86
Total Feed Cost (ETB)	176.50	169.80	166.30	163.80
Revenue
Carcass weight (kg)	1.22	1.23	1.20	1.24
Carcass Price (ETB/kg)	400	400	400	400
Total Return (ETB)	488	492	480	496
Net Return (ETB)	311.55	322.18	313.71	332.16
MRR (%)	176.56	189.71	188.64	202.73

DOC = Day old chick; ETB = Ethiopian birr; kg = kilogram, MRR = Marginal rate of return.

4. Discussion

4.1. Growth performance

Dietary inclusion of black cumin seed meal (BCSM) in broiler diets did not result in significant differences in feed intake or body weight gain compared to the control group across all production phases. This finding indicates that BCSM inclusion at both levels does not adversely affect growth performance and provide highlights its potential as an alternative protein and energy source in broiler diets. These results are consistent with previous studies reporting no significant effects on feed intake or growth performance at inclusion levels ranging from 0.5% to 10% (Jahan et al., 2015; Ghannam, 2022; Zaazaa et al., 2023). Similarly, El-Deek (2009) and Elgandy (2024) reported that substituting soybean meal with BCSM up to 50% in the diets of broilers did not affect growth performance of broilers. In contrast, Fathi et al. (2023) reported that body weight gain was significantly increased in broilers fed BCSM at 4% and 6% supplementation levels compared to the control. In addition, Mba et al. (2025) demonstrated that Phyllanthus amarus leaf extract enhanced growth performance across distinct broiler strains (Arbor Acres, Marshall, and Ross 308). On the contrary, Ershadi et al. (2022) observed a significant reduction in feed intake and body weight gain in broilers at inclusion levels of 7.5% and 15% BCSM.

Although no significant differences were observed in feed intake or body weight gain between the BCSM and control groups, feed conversion ratio (FCR) was significantly improved in BCSM4.5 during the finisher phase and over the entire experimental period compared with the control. This improvement may be attributed to the slightly lower feed intake observed with increasing BCSM inclusion levels while maintaining comparable weight gain to the control group, as well as to the bioactive constituents previously reported in BCSM, which enhance digestion and feed utilization (Fathi et al., 2023; Cakir & Cayan, 2026). This finding is very similar to Amad et al. (2011), who observed improved FCR due to the reduced feed intake and similar weight gain in broilers fed phytogenic feed additives with increasing level of test ingredients. Windisch et al. (2008) also reported that reduced feed intake, with negligible differences in body weight gain during poultry feeding trials, resulted in improved FCR. Improved feed digestion and nutrient absorption have been reported in broilers fed diets supplemented with Nigella sativa seed, ultimately improving FCR (Abdollahi et al., 2024; Khan et al., 2025), similarly BCSM enhance feed efficiency, likely due to its bioactive constituents which are retained in BCSM during extraction (Fathi et al., 2023). According to Kumar and Petra (2017) and Cakir and Cayan (2026), these bioactive constituents, such as thymoquinone, carvone, anethole, carvacrol, and 4-terpineol, stimulate the secretion of digestive enzymes from the intestinal mucosa and pancreas, thereby improving digestion, absorption, and feed utilization efficiency. Similar findings were reported by El-Kashef (2020) and Fathi et al. (2023), who observed improved FCR in broilers fed diets containing different levels of BCSM compared with the control group. Likewise, Sapsuha et al. (2025) reported improved feed conversion in broilers supplemented with Lactobacillus plantarum and Tomi-Tomi fruit extract synbiotics, which was attributed to better feed utilization efficiency relative to the control group. In contrast, Ghannam (2022), Zaazaa et al. (2023), and Elgandy (2024) reported no significant differences in FCR among broilers fed BCSM compared to the control. The inconsistency among studies may be attributed to variations in the nutritional composition of BCSM arising from differences in seed origin, oil extraction methods, genetic diversity of black cumin seed, experimental diet formulation, and management and environmental conditions.

In the current study a lower mortality percentage was also observed in broilers fed BCSM treatment diets compared to the control group. This finding suggests that the potential health benefits of BCSM may be due to the residual bioactive compounds and essential oils left in the meal after extraction. A significant level of bioactive compounds and essential oils were retained, which were not completely extracted from the seeds during the process (Fathi et al., 2023). Reduced mortality in broilers has also been associated with the antibacterial, antioxidant, and anti-inflammatory activities of these compounds (Ermumcu & Şanlier, 2017; Aydin, 2021). Similarly, Azeem et al. (2014) reported that Nigella sativa seeds have strong potential as alternatives to antibiotics and vaccines for improving immunity and reducing mortality in poultry due to their bioactive constituents. Phenolic compounds in aromatic medicinal plants are known to act against bacteria by targeting multiple cellular structures, leading to microbial destruction; in addition, their antioxidant properties help to reduce oxidative damage caused by reactive oxygen species in poultry (Aljohani, 2024). A recent study also identified diversity in the essential oil composition of Ethiopian black cumin seeds, which may contribute to beneficial pharmacological effects (Degu et al., 2025). Similarly, Ike et al. (2025) demonstrated that Phyllanthus amarus leaf extract could serve as an effective feed additive capable of supporting broiler health and reducing reliance on synthetic antibiotics in commercial poultry production.

4.2. Carcass characteristics

Dietary inclusion of BCSM in broiler diets did not have a significant effect on slaughter weight, dressing percentage, carcass weight, or the relative weights of carcass cuts and internal organs. Although not statistically significant, the relative weight of abdominal fat numerical reduced as the levels of BCSM inclusion increased, suggesting potential beneficial effects of residual contents in the meal, which may divert energy from fat deposition toward physiological functions (Abaza et al., 2008). The non-significant differences observed in body weight gain and slaughter weight among broilers across all dietary treatments may have contributed to the comparable carcass characteristics, as these parameters are closely associated with the final body weight. Similarly, Ghannam (2022) reported no significant effects on slaughter weight, dressing percentage, carcass weight, or the weights of carcass cuts, giblets, and offal in broilers fed diets containing BCSM. In addition, Sogut et al. (2012) reported no significant effects of black cumin seed inclusion in broiler diets on carcass characteristics. In contrast, Saleh (2014) and Kumar et al. (2018) reported significant improvements in slaughter weight, dressing percentage, carcass yield, and the weights of the thigh, breast, and edible internal organs in broilers fed black cumin seed, which could be due to variations in weight gain across treatments.

4.3. Cecal microbiota

Dietary inclusion of BCSM resulted in a significant effect on cecal microbiota, evidenced by lower total coliform counts at the 3% and 4.5% inclusion levels, and E. coli counts at all levels of BCSM inclusion. Concurrently, Lactobacillus counts increased significantly at the 3% and 4.5% inclusion levels compared to the control. However, no significant difference was observed in total bacterial count, which represents the aerobic bacterial population. This could be due to the selective modulation effects of BCSM rather than suppression of the overall bacterial population. These findings are in agreement with previous studies reporting reductions in coliform and E. coli counts in the ceca of broilers fed Nigella sativa seed, Nigella sativa oil, and BCSM (Khan et al., 2012; Saied et al., 2022; Fathi et al., 2023). Similarly, Arif et al. (2018) and Elbaz et al. (2025) reported significant reductions in coliform and E. coli counts in meat-type quail and rabbits fed diets supplemented with Nigella sativa seed and BCSM. Elbaz et al. (2025) and Talayi-Anbaran et al. (2025) also reported increased Lactobacillus populations in the ceca of broilers following dietary inclusion of Nigella sativa nanoparticles and Nigella sativa seed, respectively. However, Khan et al. (2012) and Fathi et al. (2023) observed no significant differences in Lactobacillus counts among treatment groups fed Nigella sativa seed and BCSM, respectively.

This modulation of cecal microbiota due to BCSM inclusion is likely the selective antibacterial activity of Nigella sativa constituents against pathogenic bacteria (Hassanien et al., 2014; Khan, 2018). Furthermore, BCSM promotes the proliferation of beneficial bacteria (Samy et al., 2023) by modifying the intestinal environment in favor of Lactobacilli (Abdollahi et al., 2024),which contributing to improved gut health and feed utilization efficiency (Stanley et al., 2013; Diaz Carrasco et al., 2019). Likewise, Ike et al. (2025) reported significantly higher counts of lactic acid bacteria and significantly lower counts of coliform bacteria in the ileum and cecum of broilers supplemented with Lactobacillus plantarum and Tomi-Tomi fruit extract synbiotics. A high population of lactic acid bacteria produces lactic acid, thereby reducing digesta pH, which may suppress or eliminate pathogenic bacteria in the digestive tract and help maintain a healthy balance of intestinal microflora that may support digestion and nutrient absorption, as similarly reported following supplementation with encapsulated coconut shell liquid smoke (Ardilla et al., 2021). Additionally, Li et al. (2022) reported that bioactive compounds in phytogenics, particularly essential oils, can disrupt the cell membranes of pathogenic bacteria by increasing membrane permeability and causing leakage of cellular contents, ultimately leading to cell death. Similar compounds have also been reported in black cumin seed (Degu et al., 2025) and were retained in BCSM following oil extraction (Fathi et al., 2023). These compounds promote gut health by reducing harmful bacteria and beneficially modulating microbial populations, ultimately enhancing immune responses, decreasing mortality, and improving nutrient absorption (Talebi et al., 2021; Fathi et al., 2023).

4.4. Production and cost efficiency

Production efficiency of broilers was assessed using the European broiler index (EBI) and production efficiency factor (PEF), which can be influenced by final body weight, average daily gain, feed conversion ratio, and viability percentage, as shown in their respective formulas. Higher value of PEF indicated that the farm was well managed and the body weight gain was uniform, whereas a higher value of EBI suggested better health status of the broilers (Venkatramana et al., 2020). In this study, EBI and PEF were significantly higher in broilers fed the highest level of BCSM inclusion (BCSM4.5) compared to the control group, while viability percentage was significantly higher in both BCSM1.5 and BCSM4.5 compared to control during the entire period. The increased EBI and PEF observed in MCSM4.5 could be attributed to the combination effects of equivalent final body weight and ADG, improved FCR, and reduced mortality. Particularly, the improvements in FCR and reduced mortality contributed to the increased production efficiency parameters, highlighting the role of BCSM in supporting both performance and health.

Partial budget analysis was used to assess the cost efficiency by considering total production costs and total returns. Feed costs decreased as the level of BCSM inclusion increased compared to the control diet, resulting lower costs of production as the other expenses were similar across treatments. Concurrently, net income and marginal rate of return were higher in broilers fed BCSM, with the highest values observed in birds receiving the diet containing 4.5% BCSM (BCSM4.5). These results were primarily attributed to reduced feed costs with increasing BCSM inclusion, efficient feed utilization, and negligible differences in body weight gain. The partial budget analysis indicates that dietary inclusion of BCSM is a cost-effective alternative feed ingredient. Its inclusion reduces overall production costs while increasing the number of marketable broilers at the end of the trial.

5. Conclusion

Dietary inclusion of black cumin seed meal (BCSM), particularly at 4.5%, improved feed conversion ratio and reduced mortality in broiler chickens, while beneficially modulating cecal microbiota across inclusion levels. These responses improved feed utilization efficiency, production efficiency, and economic return without adversely affecting growth performance or carcass characteristics. Overall, BCSM appears to be a promising dietary ingredient for improving gut health, flock viability, and production and cost efficiency in broiler production.

Ethical statement

All animal experiments were reviewed and approved by the Research and Ethics Committee of the School of Animal and Range Sciences, Haramaya University (Approval No SARS 053/24; May 25, 2024), and were conducted in accordance with institutional guidelines.

Funding

This study received small competitive based funding from Haramaya University Research Grant with budget code of HURG-2023–01–01–45 which has been completely utilized in this study.

CRediT authorship contribution statement

Muhammed Tilahun: Writing – review & editing, Writing – original draft, Visualization, Validation, Software, Resources, Project administration, Methodology, Investigation, Formal analysis, Data curation, Conceptualization. Mengistu Urge: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Methodology, Conceptualization. Meseret Girma: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Methodology, Conceptualization. Negassi Ameha: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Methodology, Conceptualization. Sileshi Gadissa: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Methodology, Conceptualization. Kiros Welay: Writing – review & editing, Visualization, Validation, Supervision, Software, Resources, Methodology, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

• The data supporting the finding of this study are available from corresponding author upon reasonable request.