Introduction
Plant products have been used for centuries by humans as food and to treat ailments. Natural medicinal products originating from herbs and spices have also been used as feed additives for farm animals (Guo, Reference GUO2003). Compared with synthetic antibiotics or inorganic chemicals, these plant-derived products have proven to be natural, less toxic, residue free and are thought to be ideal feed additives in food animal production (Wang et al., Reference WANG, LI and BOURNE1998).
Advances in chemistry and identification of plant compounds which are effective in the treatment of certain diseases have renewed the interest in herbal medicines. Black cumin (Nigella sativa) is an annual spicy herb native to Mediterranean regions and is now cultivated in other parts of the world including Middle East, North Africa and Asia. It has been used for medicinal purposes for centuries, both as a herb and pressed into oil. It has been traditionally used for a variety of conditions and treatments related to respiratory health, stomach and intestinal health, kidney and liver functions, circulatory and immune system support and for general wellbeing (New International Encyclopaedia).
Chemical analysis of black cumin
Proximate analysis of whole mature black cumin showed that the moisture content ranged from 5.52-8.50%, crude protein from 20-26.7%, ash from 3.77-4.86%, total carbohydrates from 23.5-33.2% and ether-extractable lipids from 34.49-38.72% (Takruri and Dameh, Reference TAKRURI and DAMEH1998; Salma et al., Reference SALMA, SOUHAIL, BASMA, CHRISTOPHE, CLOUDE and HAMADI2007). Chemical analysis showed that black cumin is a significant source of essential fatty acids, proteins, carbohydrates and other vitamins and minerals (Takruri and Dameh, Reference TAKRURI and DAMEH1998; Salma et al., Reference SALMA, SOUHAIL, BASMA, CHRISTOPHE, CLOUDE and HAMADI2007; Durrani et al., Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007). It contains the essential fatty acid linoleic acid which is important for obtaining maximum body weight in animals (Saleh-al-Jassir, Reference SALEH-AL-JASSIR1992). Most properties of black cumin are mainly attributed to quinine constituent compound. Quinonic alkaloids are likely to be involved in pharmaceutical properties (AL-Beitawi and El-Ghousein, Reference AL-BEITAWI and EL-GHOUSEIN2008).
Antimicrobial effect of black cumin
Black cumin have been reported to have an antimicrobial effect (Rathee et al., Reference RATHEE, MISHRA and KAUSHAL1982; Hanafy and Hatem, Reference HANAFY and HATEM1991; Ferdous et al., Reference FERDOUS, ISLAM, ASHAN, HASAN and AHMED1992; El-Kamali et al., Reference EL-KAMALI, AHMED and MOHAMMED1998; Mouhajir et al., Reference MOUHAJIR, PEDERSEN, REJDALI and TOWERS1999; Salem, Reference SALEM2005) as well as an antibacterial activity against Listeria monocytogenes (Nair et al., Reference NAIR, VASUDEVAN and VENKITANARAYANAN2005). Takruri and Dameh (Reference TAKRURI and DAMEH1998), Salma et al. (Reference SALMA, SOUHAIL, BASMA, CHRISTOPHE, CLOUDE and HAMADI2007) and Durrani et al. (Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007) reported that black cumin protects normal cells against the destructive effects of viruses. Salman et al. (Reference SALMAN, KHAN and SHUKLA2005) demonstrated that black cumin oil is active against sensitive as well as multi-drug resistant strains of Staphylococcus aureus and Pseudomonas aerugenosa. Black cumin has been reported to have fairly good antimicrobial properties against most of gram-positive bacteria and some of gram-negative ones. The highest activity was found with methicillin-sensitive S. aureus, S. epidermidis, Beta and Alpha-haemolytic Streptococci, the pathogenic Neisseriae, Haemophilus influenzae, Brucella melitensis and Streptococcus faecalis (Bilal et al., Reference BILAL, BATOUK, ABU-ESHY, AL-GHAMDI and AL-WABEL1996). Maraqa et al. (Reference MARAQA, AL-SHAROA, FARAH, ELBJEIRAMI, SHAKYA and SALLAL2007) reported that both black cumin extract and oil inhibited the production of aflatoxins from fungal contaminated material.
Toxicity effects of black cumin
The seeds of the plant are characterised by a very low degree of toxicity in mice and rats (Badary et al., Reference BADARY, AL-SHABANAH, NAGI, AL-BEKAIRI and AL-MAZAR1998; Ali and Blunden, Reference ALI and BLUNDEN2003). This suggests that therapeutic doses of the fixed oil of the seed have a wide margin of safety. Two cases of contact dermatitis in two rats have been reported following topical use up to 12 weeks. Administration of either the seed extract or its oil has been shown not to induce significant adverse effects on liver or kidney functions (Ali and Blunden, Reference ALI and BLUNDEN2003). Supplementation of broilers diet with 20 and 100 g/Kg black cumin seeds did not adversely affect growth (Al-Homidan et al., Reference AL-HOMIDAN, AL-QARAWI, AL-WAILY and ADAM2002). The acute toxicity of thymoquinone is very low. The maximum non-fatal dose was 500 mg/Kg (Ozbek, et al., 2004).
Effects of black cumin on laying hens performance
It was noticed that, supplementation of layers ration with black cumin increased egg production, egg mass and feed efficiency (El-Ghammry et al., 1997; El-Sheikh et al., Reference EL-SHEIKH, AMIN and ABDELATI1998; Akhtar et al., Reference AKHTAR, NASIR and ABID2003). Rahim Aydin et al. (Reference RAHIM AYDIN, OZUGUR, TOPRAK, KAMALAK and KARAMAN2006) reported that offering of 3% black cumin to the laying hens diet significantly (P<0.05) affected egg weight, but had no effect on egg production, feed consumption and feed efficiency. This opposite results may be due to different levels of supplementation of black cumin.
Effects of black cumin on eggshell thickness, egg constituents and mortality rate
Akhtar et al. (Reference AKHTAR, NASIR and ABID2003) showed that the addition of black cumin to layers diets significantly (P<0.05) increases eggshell thickness and Haugh unit. Also, the author reported that black cumin decreases yolk-cholesterol, serum triglycerides and total cholesterol. Furthermore, black cumin decreases mortality rate (El-Ghammry et al., 1997; El-Sheikh et al., Reference EL-SHEIKH, AMIN and ABDELATI1998; Akhtar et al., Reference AKHTAR, NASIR and ABID2003).
Effect of black cumin on broiler performance
AL-Beitawi and El-Ghousein (Reference AL-BEITAWI and EL-GHOUSEIN2008) reported that broiler chicks fed 1.5% crushed black cumin had higher (P<0.05) live body weight, body weight gain and the better feed conversion ratios. Similar findings were obtained by Abu-Dieyeh and Abu-Darwish (Reference ABU-DIEYEH and ABU-DARWISH2008). The authors found that supplementation of broiler diet with 1.5% black cumin increased (P<0.05) body weight gain and enhanced (P<0.05) feed conversion ratio. Addition of black cumin to the broilers ration at the rate of 40 g/kg resulted in the highest weight gain (Osman and Barody, Reference OSMAN and BARODY1999; Halle et al., Reference HALLE, THOMANN and FLACHOWSKY1999; Siddig and Abdelati, Reference SIDDIG and ABDELATI2001; Al-Homidan et al., Reference AL-HOMIDAN, AL-QARAWI, AL-WAILY and ADAM2002; El-Bagir et al., Reference EL-BAGIR, HAMA, HAMED, RAHIM and BEYENEN2006; Durrani et al., Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007) and improved feed conversion ratio (Osman and Barody, Reference OSMAN and BARODY1999; Halle et al., Reference HALLE, THOMANN and FLACHOWSKY1999; Soliman et al., Reference SOLIMAN, GHAZALAH, EL-SAMRA, ATTA and ABDO1999; Al-Homidan et al., Reference AL-HOMIDAN, AL-QARAWI, AL-WAILY and ADAM2002; Durrani et al., Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007). In addition, Tollba and Hassan (Reference TOLLBA and HASSAN2003) mentioned that using of black cumin in broiler diets under normal or high temperature conditions significantly (P<0.05) increased live body weight and weight gain and improved feed conversion ratio. Furthermore, Osman (Reference OSMAN2002) found that supplementation of broiler chicks diet with black cumin oil significantly (P<0.05) enhanced live body weight, body weight gain and feed conversion ratio, and decreased feed consumption. These results disagreed with those obtained by Abbas and Ahmed (Reference ABBAS and AHMED2010) who reported that birds offered a diet supplemented with 1 or 2% black cumin showed significantly (P<0.05) lower live body weight, weight gain, and feed conversion ratio was not affected. This disagreement may be due to the different levels of supplementation, or to the method of preparation of black cumin powder. In some trials the black cumin was prepared freshly every day, and in others it was prepared only one or two times during the experiments.
The lack of agreement between studies may be due to variations in chemical composition, cultivated regions, environmental and rearing conditions or different ages of birds used in the studies. Durrani et al. (Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007) noticed that significantly (P<0.05) lower feed consumption occurred as the result of offering black cumin to broilers at the rate of 40 g/kg. In spite of this, the same group of birds had significantly (P<0.05) higher weight gain, which in turn reflects a more efficient feed conversion ratio. A similar result was obtained by Halle et al. (Reference HALLE, THOMANN and FLACHOWSKY1999) who explained that the addition of essential oil from black cumin affected feed consumption in broilers. This finding was supported by Afifi (Reference AFIFI2001), who reported that, broilers fed a ration free of black cumin exhibited higher feed consumption compared to those fed ration supplemented with 2 or 3% black cumin. Furthermore, Abbas and Ahmed (Reference ABBAS and AHMED2010) mentioned that, addition of 1or 2% ground black cumin to the broiler diet significantly (P< 0.05) decreased feed consumption.
Effect of black cumin on the carcass quality of broilers
Many researchers found that the addition of 40 g/kg black cumin to broiler ration resulted in increased weight of thigh and breast (Osman and Barody, Reference OSMAN and BARODY1999; Halle et al., Reference HALLE, THOMANN and FLACHOWSKY1999; Siddig and Abdelati, Reference SIDDIG and ABDELATI2001; Al-Homidan et al., Reference AL-HOMIDAN, AL-QARAWI, AL-WAILY and ADAM2002; El-Bagir et al., Reference EL-BAGIR, HAMA, HAMED, RAHIM and BEYENEN2006; Durrani et al., Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007), increased dressing percentage and liver weight (Durrani et al., Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007). Osman (Reference OSMAN2002) mentioned that the addition of 1 g/kg feed of black cumin oil to a broiler diet significantly increased dressing percentage. Abdel-Malak et al. (Reference ABDEL-MALAK, ABDEL-MALAK, EL-GENDI and NAGUIB1995) reported that inclusion of different levels of black cumin seeds had a significant effect on the relative weight of liver and heart. Durrani et al. (Reference DURRANI, CHAND, ZAKA, SULTAN, KHATTAK and DURRANI2007) noticed that birds fed on rations supplemented with black cumin revealed no significant (P> 0.05) effect on weight of gizzard, intestine and abdominal fat. In contrast to the above findings, AL-Beitawi and El-Ghousein (Reference AL-BEITAWI and EL-GHOUSEIN2008) mentioned that the supplementation of different levels of crushed or uncrushed black cumin did not affect any of the carcass characteristics parameters. Also, El-Ghammry et al. (Reference EL-GHAMMRY, EL-MALLAH and EL-YAMNY2002) found that broiler chicks fed rations contain low levels (0.2 and 0.4%) of crushed black cumin seeds revealed significant decrease in dressing percentage. In addition, Afifi (Reference AFIFI2001) found that feeding broiler chicks freshly crushed black cumin had no significant (P>0.05) effect on the relative weight of liver, heart, spleen and bursa of fabricious. Furthermore, Abbas and Ahmed (Reference ABBAS and AHMED2010) reported that birds fed on diet supplemented with 1% whole crushed black cumin seeds had a significant (P<0.05) reduction in dressing percentage when compared to those fed on control or 2% supplemented diets. Addition of ground black seeds had no significant effect on liver, gizzard, heart and abdominal fat %.
Effect of black cumin on Japanese quail
Abou-Egla et al. (Reference ABOU-EGLA, GENEDY, ABOU-ZEID and ZEWEIL2000) studied the effect of replacing soybean meal (SBM) by Nigella seed oil meal (NSOM) in Japanese quail diet on the performance. The results showed that replacement of 5% soyabean meal (SBM) by NSOM increased live body weight, weight gain and improved feed efficiency. Replacement of 10% SBM by NSOM will also improve feed efficiency. Replacing up to 20% SBM by NSOM had no significant effect on feed consumption. Offering Japanese quail NSOM instead of 40% SBM reduced live body weight and weight gain. Other researcher examined the effect of feeding Japanese quail whole crushed Nigella sativa seeds (WCNSS) and Nigella sativa oil (NSO) on the performance. Abou El-Soud (Reference ABOU EL-SOUD2000) found using of 2% WCNSS increased final body weight, total weight gain, daily weight gain, total feed consumption, and improved feed conversion ratio. These findings agreed with those obtained by Abd El-Latif et al. (Reference ABD EL-LATIF, FATEN and EL-KAIATY2002). The researchers reported that supplementation of 0.1% black cumin to Japanese quail diets improved live body weight, weight gain and feed conversion ratio. Abou-El-Soud (2000) found that the addition of 2% WCNSS increased antibody titre and the addition of 1% NSO enhanced relative weight of liver, spleen and bursa of fabricius at 35 day of age.
Conclusions
Black cumin (Nigella sativa) can be used as a natural growth promoter in the poultry diet, due to its pharmacological properties and wide margin of safety, in addition to its positive effects on broilers, layers and Japanese quail performance and health. Further research is required to determine it mode of action and to clarify the more efficacious form to use for certain performance benefits.
