Comparative Study of Curcumin and Garlic Extracts as Antioxidants in Growing Rabbit Diets on Productive Performance and Antioxidant Status

Feed additives are an important component of poultry feeds that help them perform better and produce more (Abd-Elsamee et al., 2012; Mohamed et al., 2016; Hassan et al., 2016; Khan and Iqbal, 2016; Elsherif et al., 2021). In terms of weight increase, feed efficiency, and reduced mortality in chicken, natural feed additives (phytogenic) have shown promising results (Jahan et al., 2008). Phytogenic are supposed to boost poultry performance by encouraging the release of digestive enzymes, which leads to better digestion and absorption (Recoquillay, 2006; Elsherif et al., 2021). Phytochemicals or their extracts have a positive impact on bird performance, immunity, and blood parameters. Phytogenic and their extracts are effective feed additions in poultry nutrition because of their favorable effects and safety (Hassan et al., 2015; Elsherif et al., 2021). Many studies were conducted on natural feed additives such as garlic, ginger, fenugreek, curcumin, castor, propolis and other plant extracts as an alternative to antibiotic to enhance performance and gut function of broiler chicks (Schepetkin et al., 2019; Oluwafemi et al., 2021; Elsherif et al., 2021). Alliin, allicin, ajoenesn, vinyldithiins, and flavonoids are among the sulfur-containing phyto constituents found in garlic. Allicin is the principal active component in garlic (Allium sativum L.) extract (Gaber et al., 2020). Garlic extract could be beneficial in broiler feed as a natural feed additive. Garlic’s antibacterial properties are related to the presence of organosulfur compounds such allicin and diallyl sulphide. Organosulfur compounds may also be able to impact gut fermentation patterns by increasing propionate and butyrate and decreasing acetate levels (Mbiriri et al., 2016). Supplementing garlic to the rabbit diet increased live body weight and improved feed efficiency (Ahmed et al., 2002). Garlic in the diet of rabbits enhanced body weight and feed efficiency (Gebreyohannes and Gebreyohannes, 2013). Also, Broilers with garlic extract supplemented diet had superior growth performance (Khan et al., 2017). Garlic promotes nutrient digestion by reducing peptic and stomach ulcers, boosting the growth of helpful microbes digesting fibrous feed, and therefore increasing the number of nutrients accessible for assimilation (Chen et al., 2019). Garlic contains Polyphenols and flavonoids, which protect cell membranes and DNA from oxidative damage (Shahidi and Hossain, 2018; Rodrigues and Percival, 2019). In addition to, Garlic includes various antioxidant actions, such as organosulfur, flavonoids like quercetin, which may contribute to a healthier animal and improved nutrient utilization and performance (Schepetkin et al., 2019). Oluwafemi et al. (2021) found that adding 0.4% of ginger and garlic oil mixture to broiler feed significantly increased growth performance. Shiyou et al. (2011) reported that turmeric (Curcuma longa) is a rich source of phenolic chemicals, terpenoids, and curcuminoids. Curcumin is the primary bioactive component of turmeric, and it has antioxidant, antiviral, and antibacterial properties (Mehdipour Biregani and Gharachorloo, 2020). Curcumin’s improved the excretion of lipase, trypsin, chymotrypsin, and amylase, which may be responsible for curcumin’s beneficial effects on broiler growth performance (Olukosi and Dono, 2014). Al-Sultan (2003) concluded that using turmeric at 5.0 g/kg in broiler diets improved the growth performance. Al-Jaleel (2012) observed that introducing 0.50% turmeric in broiler diets increased body weight compared to the control and other dietary treatments (0.25, 1, 1.5 % turmeric). Curcumin significantly reduced total cholesterol, probably by inhibiting the hepatic enzyme 3-hydroxyl-3-methyglutaryl Co-A reductase, that is responsible for the synthesis of cholesterol in the liver (Al-Kassie et al., 2011). Therefore, the goal of this study was to investigate the influence of the addition curcumin or garlic extract in rabbit diets on productive performance, digestibility, carcass characteristics, thyroid hormones, and antioxidant enzyme activities.

This study was conducted at Egypt’s Kafr Elsheikh Governorate’s Ministry of Agriculture’s Sakha Research Station. The laboratory work was carried out at department of Animal Production, National Research Centre, Egypt and department of by Products Research, Animal Production Research Institute, Agricultural Research Center. The goal of this study was to investigate the influence of curcumin and garlic extracts in growing rabbit diets on performance and antioxidants status.

Curcumin and garlic were extracted using dried turmeric rhizomes and fresh garlic which acquired from a local Egyptian market. All of the chemicals and solvents were acquired from Merck and were of analytical grade.

Curcumin extract (CE) is obtained by extracting curcumin from dried turmeric rhizomes. To obtain a curcuminoid-rich extract, use Soxhlet extraction by Percolation (boiler and reflux) with acetone as solvent (Zieliska et al., 2020; Yadav et al., 2017).

Garlic extract (GE) was extracted using a heat reflux extraction process including 70% ethanol and continuous stirring for three hours, following by separation of the extract using a rotary evaporator at 40°C (Loghmanifar et al., 2020; Elsherif et al., 2021).

Finally, calcium carbonate was used as a carrier material to load the extracts separately so that they could be easily used and mixed with feed ingredients.

According to Agriculture Ministry Decree (1996) instructions, the control diet was formulated to meet the nutritional requirements of growing rabbits. Five diets containing the same proportions of all nutrients were made. The first control diet (without any additives); curcumin (CE) or garlic extract (GE) at concentrations of 200 or 400 ppm were added to the other diets. The experiment period lasted from 6 - 14 week of age. Components and chemical analysis of a control diet are presented in Table 1.

Sixty growing rabbits (APRI strain) were randomly distributed into five groups, 12 rabbits of each, the average start body weight was closely to 635 g. The rabbits were housed in battery cages measuring 60 x 50 x 40 inches with separate feeders. Water and feed were freely available. The rabbits were housed in the same sanitary and management conditions. Weekly feed intake and live body weights data were used to calculate feed conversion ratio (FCR) and body weight gain (BWG).

Table 1: Components and chemical analysis of a control diet.

* Each 3 kg of mineral and vitamin premix contains the following: Vit. A (12000000 IU), Vit. D3 (200000 g), Vit. E (10 g), Vit. K3 (2.5 g), Vit. B1 (1.0 g), Vit. B2 (5.0 g), Vit. B6 (1.5 g), Vit. B12 (10 g), Pantothenic acid (10 g), Niacin (30 g), Choline chloride (500 g), Folic acid (1.0 g), Biotin (50 mg), Fe (30 mg), Mn (40 mg), Zn (45 mg), Cu (3 g), Co (100 mg), I (300 mg), Se (100 mg). 2DE was estimated using values from the N R C (1977).

Five rabbits from each group were used in a digestibility trial at the end of the study. According to AOAC (2000) feces were daily collected and dried at 50-60 oC for 24-48 hours for constant weight before being finely powdered and were kept till chemical analysis. The digestibility coefficients of nutrients and nutritive values of the dietary treatments were determined using data from quantities and chemical analyses of feed and feces, according to Cheeke et al. (1982).

At the end of the experiment, 5 rabbits per feeding treatment were starved for 24 hours and slaughtered for carcass and internal organs measures. Live weight, carcass weight (g), carcass percentage, gastrointestinal tract weight percent (GIT percent), organs represented as percentages of live weights, giblet (heart, liver, and kidney) percentage, and abdominal fat percentage were calculated. The meat composition of breast muscle was determined using the AOAC (2000). The blood samples were taken with the rabbits slaughtering.

Blood serum samples were separated by centrifugation at 4000 rpm for 10 minutes, and then stored at -20 oC until chemical analysis. Total antioxidant capacity (TAC) and malondialdehyde (MDA) concentrations were assessed in blood serum.

Furthermore, the livers were collected for the analysis of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH) antioxidant enzymes using commercial kits (biodiagnostic, Cairo, Egypt) in an automatic calibration spectrophotometer with high-performance readings (FlexorEL200 Biochemical Analyzer).

Commercial ELISA kits were used to measure total T3 and T4 concentrations in the blood (MyBioSource, Inc., San Diego, CA). The T4/T3 ratio was obtained by dividing the value of T4 by the value of T3.

SAS’s (2001) General Linear Models technique was used to examine the data. The statistical data of 95 percent reliability was analyzed using one-way analyses of variance. The differences among means were compared using Duncan’s multiple rang test (Duncan, 1955) at significance level (P<0.05).

The effects of curcumin or garlic extract on live body weight (LBW), daily weight gain (DWG), daily feed intake (DFI), and feed conversion ratio (FCR) of growing rabbits are shown in Table 2. The results showed that adding 200 ppm (CE1, GE1) or 400 ppm (CE2, GE2) of curcumin or garlic extract had a significant (P<0.05) favorable effect on LBW during the experimental period. The greatest significant (P<0.05) LBW values were obtained when curcumin or garlic extract were used at 400 ppm. At 14 weeks of age, the inclusion of CE2 and GE2 resulted in the greatest LBW and DWG values (2230 and 2249g) and (28.35 and 28.82g), respectively compared to the control group that had the lowest LBW (1899g) and DWG (22.83g) values. At all ages, the daily feed consumption of rabbits fed diets containing various doses of curcumin or garlic extract remained were no significantly affected. Curcumin and garlic extract supplementation had a significant (P<0.05) effect on the FCR of growing rabbits during the experimental period. In comparison to 200 ppm levels and the control group, inclusion of curcumin or garlic extract at 400 ppm resulted in considerably (P<0.05) enhanced FCR values during the experimental period. The results of the performance index (PI) and growth rate (GR) showed significant (P<0.05) differences in PI and GR among the dietary treatments at overall ages of the rabbits, with the best values of PI and GR for rabbits fed diets containing CE2 (81.88 and 110.54) and GE2 (82.61 and 111.93), respectively and the worst values recorded for rabbits fed control diet (56.93 and 101.51), respectively.

The improvement in body weight and feed conversion ratio could be attributed to optimum antioxidant activity of curcumin and garlic extracts, which stimulate protein synthesis via the enzymatic system, based on the findings of this and prior investigations. Furthermore, curcumin and garlic extracts can inhibit or limit the growth and colonization of a wide range of pathogenic and non-pathogenic bacteria in the gut, resulting in a more balanced microbial ecosystem and improved nutrient digestion and absorption, as well as improved growth performance and physiological status.

These findings are consistent with those of numerous researches, including Kafi et al. (2017), who found that adding 0.75 percent turmeric (Curcuma longa) to broiler diets were significantly enhanced growth rate. Hussein (2012) also found that using curcumin in the broiler diet significantly (P<0.05) improved growth performance. Growing rabbits fed a diet supplemented with Curcuma longa showed a slight increase in body weight at all ages (Abd El-Latif et al., 2019). Al-Sultan (2003) found that adding 5 g/kg turmeric to the diet of broilers was boosted body weight. Similarly, Al-Jaleel (2012) investigated the effect of feeding broiler chicks dietary Curcuma longa at 0, 0.25, 0.50, 1, 1.5 percent on performance and found that including 0.50 percent curcumin enhanced body weight compared to the other groups. El-Rawi et al. (2020) found that adding 4 and 8 g/kg of turmeric powder (Curcuma longa) to rabbit diet had a significant impact on final weight, weight gain, feed intake, feed conversion ratio, and relative growth ratio when compared to the control group. Garlic supplementation to broiler chicks improved growth performance and feed conversion ratio by increasing villus height, digestive enzyme activity, and nutrient absorption in the intestine (Tollba and Hassan, 2003). Garlic supplementation significantly improved (P<0.05) rabbit weight gain, feed conversion ratio, and hematological parameters, according to Onu and Aja (2011). Garlic supplementation improved body weight gain and feed conversion ratio in broilers, according to (Makwana et al., 2018; Chimbaka and Walubita, 2020; Gaber et al., 2020). This could be due to the action of allicin, which has antibacterial, antiviral, antiprotozoal, antifungal, antioxidant, anticancer, and anti-inflammatory properties in garlic and its extract.

Table 3 are showings the influence of curcumin and garlic extracts on digestibility coefficients and nutritive values. The addition of CE or GE had no significant effect on the digestibility coefficients of DM, OM, or NFE. While the digestibility coefficients of CP, CF, and EE were significantly (P<0.05) affected. The addition of CE or GE were substantially raised the digestibility coefficient of CP (P<0.05), with the inclusion of 200 ppm GE yielding the highest value (78.60%). The digestibility coefficients of CF and EE were significantly (P<0.05) different where, the best digestibility coefficient of CF value (38.13%) was achieved, with no significant differences with the addition of 200 ppm GE or CE. The addition of 400 ppm CE considerably (P<0.05) enhanced the digestibility coefficient of EE, with the addition of 400 ppm CE recording the highest value (76.33%). The addition of CE or GE were significantly (P<0.05) improved total digestible nutrients (TDN), digestible energy (DE), and digestible crude protein (DCP), where 400 ppm CE had the best DE (2876.06 Kcal/Kg) compared to control group. There were no significant differences in DE among 200 ppm CE, 200 ppm GE, and 400 ppm GE. The group supplemented with 400 ppm CE had the highest TDN value (64.92%) on record, while no significant differences in TDN percent with 200ppm CE, 200ppm GE, and 400ppm GE addition.

The beneficial effects of herbal plants and their extracts in animal nutrition include improving digestive enzyme secretion, stimulation of appetite, activation of the immune response, and antibacterial, antiviral, and antioxidant actions that may affect the digestive tract’s physiological and chemical function (Rahimi and Ardekani, 2013). Turmeric extract (curcumin) is an antioxidant that can help the gallbladder secrete bile and boost the secretion of pancreatic juice, which contains enzymes like amylase, lipase, and protease that help with carbohydrate, fat, and protein digestion (Utami et al., 2020). These findings are consistent with those of Astawa et al. (2016), who found that turmeric extract (curcumin) had the best CP and OM digestibility coefficients of body weight when compared to the control group. The bile synthesis and secretion into the small intestine may be linked to improve fat and protein digestion when CE was added by 0.04 ml/Kg to diets (Al-Sultan and Gameel, 2004).

Table 4 is showing the effects of dietary treatments on carcass characteristics. The effects of dietary treatments on carcass weight, carcass percent, gastrointestinal tract percent (GIT), and abdominal fat percent were significant (P<0.05) compared to the control group. The highest carcass weight and carcass precentage values were recorded with the groups supplemented with 400 ppm CE (1312g, 65.63) and 400 ppm GE (1304 g, 64.53), respectively. Different additions had no effect on the liver, heart, kidney, giblets, and spleen percentage. All dietary treatments significantly (P<0.05) decreased GIT percent compared to the control which had the largest GIT percent (20.08%), while dietary supplementation with CE or GE at 400 ppm having a lowest value 16.47% and 17.88%, respectively.

Table 2: Effect of curcumin and garlic extracts on growth performance of rabbits.

a,b,c Means in the same row with different superscript are significantly different (P< 0.05). LBW: live body weight, DWG: daily weight gain, FI: feed intake, FCR: feed conversion ratio. Performance index % (PI)= final live body weight (Kg)/feed conversion ratio x 100. Growth rate% (GR)= (W2-W1)/(1/2(W2+W1))x100. Whereas: W1= initial bodyweight, W2= Final body weight (g)

Table 3: Effect of curcumin and garlic extracts on nutrients digestibility of rabbits

a,b Means in the same row with different superscript are significantly different (P< 0.05). *DE = TDN X 44.3 (Schneider and Flatt, 1975).

Table 4: Effect of curcumin and garlic extracts on carcass characteristics of rabbits.

These findings were in line with those of Sarica et al. (2005), who discovered that thyme and garlic extracts had no influence on the weight of broiler chickens’ hearts, livers, gizzards, or spleens. In addition, Alçiçek et al. (2003) discovered that using herb extract improved carcass weight but had no effect on belly fat percentage. According to Raghdad and Al-Kassie (2012), adding turmeric powder to broiler chicken feeds dramatically enhanced the dressing percentage as the quantity of inclusion increased. According to Okanlawon et al. (2020), rabbits fed a diet supplemented with 10 g and 15 g turmeric/kg feed had the highest dressing percentage.

Table 5 is showing the impact of curcumin and garlic extracts on rabbit meat composition. The addition of CE or GE to the diet of growing rabbits had a significant (P<0.05) impact on the meat moisture, protein, and ether extract content. While the addition of curcumin or garlic extract had no effect on the meat content of ash, there was no significant effect on the meat content of ash. Curcumin or garlic extract were significantly (P<0.05) boosted crude protein while decreasing moisture and fat levels in meat. With the addition of 200 ppm GE, the highest value of crude protein (25.77%) was observed. While, control had the greatest moisture and ether extract values (70.88% and 2.31%), respectively.

Meat moisture content reduced in response to CE or GE, implying that CE and GE may impact meat’s water retaining ability. These findings are consistent with Rajput et al. (2013), who found that adding turmeric powder curcumin (150-200 mg/kg of feed) to the diet significantly reduced belly fat relative to the control group. This reduction in abdominal fat could be attributed to better fat digestion and metabolism (Sugiharto et al., 2011). Dzinic et al. (2013), on the other hand, found that adding 2% garlic to the feed of broiler chicks had no influence on the protein level of the meat. Similarly, Kanani et al. (2017) found that adding 0.5 percent turmeric powder to broiler chicks had no influence on meat protein content.

Figures 1 and 2 are showing the effects of different treatments on antioxidant enzymes in rabbits. The addition of 200 or 400 ppm CE or GE significantly (P<0.05) enhanced TAC, SOD, CAT, and GSH compared to the control group. The inclusion of curcumin and garlic extract, resulted in a slight (P>0.05) reduction in MDA. Total antioxidant capacity is an important metric that takes into account all antioxidants in the blood (Ghiselli et al., 2000). Total antioxidant capacity, SOD, CAT, and GSH all increased in response to dietary CE or GE supplementation in this investigation, demonstrating that CE or GE treatment may improve the total antioxidant status of rabbits. Total antioxidant capacity changes in blood plasma after supplementation with antioxidant-rich feeds offer information on the absorption and bioavailability of ingested antioxidants (Ghiselli et al., 2000). The present findings tie with prior research on the antioxidant properties of CE or GE, which were also demonstrated in this study. Allicin, alliin, allyl disulfide, and allyl cysteine are antioxidant chemicals found in garlic (Elkelawy et al., 2017). These findings are in line with those of other research (Durak et al., 2002), which found that garlic extract lowered MDA levels in blood samples, indicating fewer oxidation reactions in the body.

Table 6 is showing the effects of dietary treatments on thyroid hormones. The addition of 200 or 400 ppm CE or GE to the growing rabbit diets had no influence on T3, T4, or T4/T3 in any of the groups. Hassan et al. (2015) confirmed these findings and reported that phytogenic and their extracts are good feed additives and safe in poultry nutrition.

Table 5: Effect of curcumin and garlic extract on meat composition of rabbits

Table 6: Effect of curcumin and garlic extracts on thyroid hormones of rabbits

a,b Means in the same row with different superscript are significantly different at (P< 0.05). T3: Triiodothyronine, T4: Thyroxin.

It could be stated that adding up to 400 ppm of curcumin and garlic extracts to growing rabbit diets can improve growth performance, carcass weight, and antioxidant status without any negative effect.

Using a simple method to extract both curcumin and garlic to obtain phenolic compounds and flavonoids, which considered as natural antioxidants that have been used as important alternatives to antibiotics in feeding rabbits, and the results led to an improvement in body weight gain, nutritional efficiency and the state of the antioxidants in the body without any harmful effect on the rabbits.

All authors contributed equally to the manuscript.

The authors have declared no conflict of interest.