Wastes from citrus processing

Citrus is a genus of bushes, shrubs or trees from the Rutaceae family. The expansion of citrus cultivation area around the world has led to more conversion industries, such as factories for juice production. In juice factories, in addition to the main product, a relatively large amounts of pulp, peel, seed and flesh are produced, which are considered waste and account for about 25% of the original product (Sadighi and Nobakht, Reference SADIGHI and NOBAKHT2015). Research on citrus peel and pulp showed that these by-products contain a good amount of crude protein, metabolisable energy, phenolic compounds, ascorbic acid, pectin, coumarin, flavonoids, and the peel is a rich source of antioxidants that are used in the food, cosmetics and pharmaceutical industries (De Peters et al., Reference DE PETERS, FADEL and AROSENA1997; Bampidis and Robinson, Reference BAMPIDIS and ROBINSON2006).

Studies on these products have shown that citrus wastes (pulp, extract and peel, seeds and fibres of dried fruit) can be successfully used in poultry diets (Mourao et al., Reference MOURAO, PINHEIRO, PRATES, BESSA, FERREIRA, FONTES and PONTER2008; Nazok et al., Reference NAZOK, REZAEI and SAYYAHZADEH2010; Ebrahimi et al., Reference EBRAHIMI, ALAW QOTBI and SEIDAVI2013a; Reference EBRAHIMI, ALAW QOTBI, SEIDAVI, LAUDADIO and TUFARELLI2013b). In a recent study, Ebrahimi et al. (Reference EBRAHIMI, ALAW QOTBI and SEIDAVI2013a) found that dried orange peel can be used as a growth stimulant as well as an alternative to antibiotics in broiler diets. In their trial, the highest carcass weight was achieved by chickens fed 1.5% dried orange peel over the entire growing period (1-42 days). Moreover, in this experiment, feeding 3% dried orange peel in the starter period (1-21 days) gave the highest breast and thigh weight and pancreas weight compared to the control-fed birds. The lowest abdominal fat was found in chickens fed 3% dried orange peel during the starter period. In another trial, Ebrahimi et al. (Reference EBRAHIMI, ALAW QOTBI, SEIDAVI, LAUDADIO and TUFARELLI2013b) investigated the effects of different levels of dried sweet orange peel on growth and performance of broiler chickens. Dried peel at either 1.5 and 3% were used in the diet. Chickens fed 1.5% peel had higher feed intakes during the starter period. More recently, Seidavi et al. (Reference SEIDAVI, EBRAHIMI, ALAW QOTBI and GÓMEZ NIETO2015) investigated the effects of different levels of sweet orange peel extract on performance, blood parameters and immune responses in broiler chickens. In their study, the levels of 1000 and 1250 mg/l of orange peel extract were fed for 42 days. The results showed that adding different levels of this extract to drinking water for broiler chickens improved weight gain and feed conversion ratio. Furthermore, the number of red blood cells increased for both levels of the orange peel extracts. Since the addition of the extract improved blood properties, it has been recommended for use as a cheap and supplement in broiler diets.

Ebrahimi et al. (Reference EBRAHIMI, ALAW QOTBI, SEIDAVI and BAHAR2014) investigated the effects of citrus peel extract on the growth traits and meat quality of broiler chickens; the results of this experiment showed that citrus peel extract could be used as an effective nutritional supplement in improving the productivity and carcass quality of broiler chickens. In fact, the highest carcass weight belonged to chickens fed 1000 mg/l of orange peel extract in drinking water during the starter period and the lowest abdominal fat belonged to chickens fed 1250 mg/l of orange peel extract over the entire growing period (1-42 days).

Dried orange peel was found to improve digestive traits and immune response in broiler chickens by Abbasi et al. (Reference ABBASI, SEIDAVI, LIU and ASADPOUR2015) and Ebrahimi et al. (Reference EBRAHIMI, SANTINI, ALISE, POURHOSSEIN, MIRAALAMI and SEIDAVI2015). Supplementation with dried orange pulp resulted a nutritious and a natural source of antioxidants for chicken feed. Feeding 2% dried citrus pulp in feed significantly increased feed intake and weight gain during the grower period; and a significant decrease in liver weight, abdominal fat and a reduction of triglyceride levels were observed in broiler chickens compared to untreated groups. Pourhossein et al. (Reference POURHOSSEIN, QOTBI, SEIDAVI, LAUDADIO, CENTODUCATI and TUFARELLI2015) examined the effects of different levels of sweet orange extract in drinking water (0, 1000, 1250 and 2000 mg/l) on the immune system of Ross-308 broiler chickens. The results showed that the highest number of red blood cells (RBC), immunoglobulin G (IgG) and immunoglobulin M (IgM) belonged to the treatment containing 1250 mg/l extract of dried orange peel. Application of orange extract in the diet of broiler chickens increased WBC concentration and lymphocytes and reduced heterophile percentage and heterophil to lymphocyte (H:L) ratio. Chickens fed dried orange peel extract had a higher immune response to SRBC than those fed control diets. The IgG and IgM titres were significantly increased in these chickens. Moreover, flavonoids in the dried orange extract stimulated the body immune system by increasing IgG and IgM antibodies and improved the humoral immune system of chickens.

Alefzadeh et al. (Reference ALEFZADEH, BOUYEH, VAN DEN HOVEN, SEIDAVI, LAUDADIO and TUFARELLI2016) examined the effect of dried orange peel powder (0, 0.1 and 0.4%) and a multi-enzyme complex (Natuzyme-P50^®, containing phytase 1000,000 U/g, β glucanase 700 U/g, α-amylase 700 U/g, cellulase 6,000 U/g, pectinase 700 U/g, xylanase 10,000 U/g, lipase 30 U/g, protease 3,000U/g, amylo-glucosidase, hemicellulase, pentosonase, acid phytase, and acid phosphatase) at 0, 350 and 700 mg/kg in diets for broiler chickens and demonstrated that the application of a multi-enzyme improved the chickens performance, but the supplement of dried orange peel powder did not have a positive effect on birds growth and productive performance.

Pourhossein et al. (Reference POURHOSSEIN, QOTBI and SEIDAVI2012) examined the effect of 1.5 and 3.0% of dried orange peel in the diet of broilers and its effect on the microbial population in the gastrointestinal tract. Results showed no significant difference among the treatments in regard to mean ileum Lactobacillus spp. at the age of 42 days. However, the highest and lowest rates of this trait belonged to the treatments with 3.0 and 1.5% dried orange peel until the end of the rearing period, respectively. The results from the mean of Lactobacilli spp. in the caecum until the end of the experiment showed that there was no difference and the highest amount belonged to the treatment with 3% dried orange peel.

Ebrahimi et al. (Reference EBRAHIMI, ALAW QOTBI, SEIDAVI, EDENS, LAUDADIO and TUFARELLI2016) investigated the effect of a diet containing different levels of dried orange peel (0, 1.5 and 3%) on the plasma constituents of broiler chickens during starter and grower periods and reported that the peel caused a reduction of cholesterol, low density lipoprotein (LDL), and triglycerides (TGL) levels, but had no significant effect on high density lipoprotein (HDL). Plasma glucose significantly decreased during 42 days by feeding 3% dried orange peel, whereas there was no significant change in the ALP activity and uric acid with the application of orange dried peel. The authors concluded that the application of dried orange peel in broiler diet did not have a negative effect on plasma components. Thus, based on the research, in general, broilers can be fed up to 3% of citrus as powder in feed or up to 1250 mg/l as extract in drinking water of the same waste.

Grape waste

Many studies have shown that the waste from grape-processing contains a wide range of polyphenols (Bonilla et al., Reference BONILLA, MAYEN, ME´RIDA and MEDINA1999; Alonso et al., Reference ALONSO, GUILLEN, BARROSO, PUERTAS and GARCIA2002; Torres et al., Reference TORRES, VARELA, GARCIA, CARILLA, MATITO, CENTELLES, CASCANTE, SORT and BOBET2002). Peel and seed of grapes are rich sources of flavonoids with potent antioxidant ability, and so they can be useful in removing free radicals and reducing oxidative reactions (Gonzalez-Paramás et al., Reference GONZALEZ-PARAMÁS, ESTEBAN-RUANO, SANTOS-BUELGA, PASCUAL-TERESA and RIVAS-GONZALO2004; Yilmaz and Toledo, Reference YILMAZ and TOLEDO2004; Ruberto et al., Reference RUBERTO, RENDA, DAQUINO, AMICO, SPATAFORA, TRINGALI and TOMMASI2007). Goñi et al. (Reference GOÑI, BRENES, CENTENO, VIVEROS, SAURA-CALIXTO, REBOLÉ, ARIJA and ESTEVEZ2007) found that the use of grape seed (3% in the diet) and grape seed extract (0.36% in the diet) as phenolic compounds sources in chickens’ diet improved feed conversion ratio. However, when applying 6% of grape seed the high amount of tannins reduced feed intake and negatively influenced feed efficiency. Brenes et al. (Reference BRENES, VIVEROS, GOÑI, CENTENO, SÁYAGO-AYERDY, ARIJA and SAURA-CALIXTO2008) reported an increase of antioxidant activity in broiler chickens by using 6% concentrate and pulp of grape in the diet. Also, Wang et al. (Reference WANG, SUO, GU, ZHANG, FANG and WANG2008) demonstrated that the proanthocyanidins in grape seed extract, as a rich source of antioxidants, improved the performance of broiler chickens and reduced the effects of infection from the important coccidial pathogen E. tenella. Kara and Kocaoglu-Guclu (Reference KARA and KOCAOGLU-GUCLU2012) examined the effect of grape pomace in diet on performance, egg quality and some biochemical parameters of laying hens. The results of this study showed that there was a significant improvement in regard to performance, egg quality, total serum cholesterol, proteins and triglycerides when fed grape pomace. Further, plasma and yolk MDA as well as the serum level of glucose were decreased by using grape pomace.

Dorri et al. (Reference DORRI, TABEIDIAN, TOGHYANI, JAHANIAN and BEHNAMNEJAD2012) investigated the effect of different levels of grape pomace on the immune system and serum oxidative stability (as MDA level) responses of broiler chickens. In this experiment, levels of 3, 6, 9, 12 and 15% of dried grape pomace were used in the diet. Results indicated that grape pomace increased immune responses and reduced the concentration of serum MDA in chickens. In this study, feeding 3% pomace increased the rate production of washed SRBC antibodies on after 49 days. Serum MDA concentrations in broilers fed up to 15% grape pomace in their diets, significantly decreased compared to control-diet. In a previous study, Wang et al. (Reference WANG, SUO, GU, ZHANG, FANG and WANG2008) assessed the effects of grape pomace waste on diet digestibility, polyphenols and antioxidants levels in chickens. Levels of 15, 30 and 60% grape pomace and 200 mg vitamin E were used and found no significant effects of dietary grape pomace level on growth performance, relative abdomen fat or organ weight. However, the percentage of body fat decreased in chickens fed grape pomace. Antioxidant activity, ileal content and faecal excretion in birds fed grape pomace diets were higher than those in control treatment. Thus, the findings showed that grape pomace can be successfully used as a source of antioxidants in poultry nutrition.

Kara and Kocaoglu-Guclu (Reference KARA and KOCAOGLU-GUCLU2012) found that the inclusion of 2% grape pomace in diet of laying hens did not negatively affect eggshell thickness and weight, albumin index and egg specific gravity compared to those from hens fed the control. Accordingly, Ozgan (Reference OZGAN2008) reported that albumin content and index increased by adding 2% grape pomace in a laying hen diet. Lichovnikova et al. (Reference LICHOVNIKOVA, KALHOTKA, ADAM, KLEJDUS and ANDERLE2015) investigated the effect of red grape pomace in diet of broiler chickens. Their data showed that feeding of 1.5% diet of red grape pomace did not have adverse effects on growth traits, and that the use of this waste increased the apparent nutrient digestion and the metabolisable energy of diet. Grape pomace had a positive effect on the number of the considered beneficial bacterial Lactobacillus spp. in ileum and the antioxidant activity of the blood, demonstrating its potential as an antimicrobial agent.

In conclusion, the results presented showed that grape pomace supplementation in both broilers and laying hens diets did not impair productive performance, and an increased antioxidative activity in meat when grape products were combined with vitamin E was demonstrated.

Pomegranate wastes

Pomegranate (Ponica granatum) belongs to the Punicaceae family and it is native fruit of Iran and the Mediterranean. The fruit is used, in addition to fresh consumption, to prepare concentrates, juice or sauce. In pomegranate processing factories, a large amount of by-products are produced, including outer peel and pomegranate seed pulp, which contain good levels of fatty acids (i.e. oleic, palmitic, stearic, palmitoleic, arachidonic, lauric and caprylic) (Abbasi et al., Reference ABBASI, REZAEI and RASHIDI2008). Due to the high percentage of fatty acids in pomegranate waste, it can be successfully used as a valuable source of fat in poultry nutrition (Modarresi et al., Reference MODARRESI, FATHI, NASRI, DAYANI and RASHIDI2010; Hosseini-Vashan et al., Reference HOSSEINI-VASHAN, YAGHOBFAR and GOLIAN2016). Moreover, antioxidant properties (Dhar et al., Reference DHAR, BHATTACHARYYA, BHATTACHARYYA and GHOSH2006; Louba, Reference LOUBA2007), reduction of body fat (Koba et al., Reference KOBA, AKAHOSHI, YAMASAKI, TANAKA, YAMADA, IWATA, KAMEGAI, TSUTSUMI and SUGANO2002), anticancer activity (Igarashi and Miyasawa, Reference IGARASHI and MIYASAWA2000), decreased blood glucose (Chuang et al., Reference CHUANG, HSU, CHAO, WEIN, KUO and HUANG2006) and the improvement of the immune system (Yamasaki et al., Reference YAMASAKI, KITAGAWA, KOYANAGI, CHUJO, MAEDA, KOHNO-MURASE, IMAMURA, TACHIBANA and YAMADA2006) have been documented from using pomegranate peel and oil in diets.

Hosseini et al. (Reference HOSSEINI, AMOLI and MODARESI2014) investigated the effect of pomegranate pulp on the performance and blood parameters of broiler chickens. In this study, dietary levels of 0, 1, 2, 3, 4, 5 and 6% of pomegranate pulp were fed from 1 to 42 days of age, and this had a significant effect on birds feed intake, weight gain, feed conversion ratio, carcass traits and blood parameters. However, chickens fed 6% pomegranate pulp in diet had higher blood HDL level than control. Thus, the authors concluded that since pomegranate seed pulp had no adverse effect on performance of chickens, it could be used up to 6% in diets. Recently, Ahmed et al. (Reference AHMED, MANIRUL ISLAM, RUBAYET BOSTAMI, MUN, KIM and YANG2015) examined the influence of pomegranate waste (four dietary levels: 0.0, 0.5, 1.0 and 2.0%) on the meat quality of broiler chickens. The findings showed that pomegranate wastes increased protein and reduced cholesterol in breast meat. The total fatty acids in breast and thigh meat muscles were enhanced when birds fed 2% of pomegranate compared to the other treatments, and reduced meat lipid oxidation. Conversely, Rajani et al. (Reference RAJANI, KARIMI TORSHIZI and RAHIMI2011) showed that feeding broiler chickens with pomegranate peel had no effect on the performance and growth of chickens compared to the control.

Mirdehghan et al. (Reference MIRDEHGHAN, RAHEMI, MARTÍNEZ-ROMERO, GUILLÉN, VALVERDE, ZAPATA, SERRANO and VALERO2007) found that a significant amount of minerals such as iron, magnesium and sodium in pomegranate peel, and feeding chickens with this by-product may increase the minerals content in the breast and thigh meat. Kim et al. (Reference KIM, YUN, NA, PARK, CHOI, YANG and LEE2013) reported that the waste from pomegranate juice processing was a rich source of polyphenols and tannins. Saleh et al. (Reference SALEH, GOLIAN, KERMANSHAHI, FARHOOSH and TAHER MIRAKZEHI2015a; Reference SALEH, GOLIAN, KERMANSHAHI, TAHER MIRAKZEHI and AGAH2015b) examined pomegranate peel and extract as a source of natural antioxidants on immune response, antioxidant enzymes and blood indices in broiler chickens, and found an improvement in humoral immune response. In particular, using 200 and 300 mg of pomegranate peel extract in diet improved immune response and reduced oxidation and triglycerides levels in blood. In this same study, feeding pomegranate peel increased the relative weight of thymus and reduced the relative weight of Bursa of Fabricius. Thus, using pomegranate peel extract had better results compared to pomegranate peel.

Szymczyk and Szczurek (Reference SZYMCZYK and SZCZUREK2016) compared the effect of pomegranate seed oil and linseed oil on the performance and fatty acid composition in meat from broiler chickens. The results showed no significant difference between the oils regarding the chickens’ growth and meat lipid profile. However, the percentage of unsaturated fatty acids in breast muscle significantly decreased with feeding pomegranate oil. Other trials conducted by Bostami et al. (Reference BOSTAMI, AHMED, ISLAM, MUN, KO, KIM and YANG2015) evaluated the effect of waste from pomegranate processing (0.0, 0.5, 1.0 and 2.0% of inclusion level in diet) on broiler chickens productive traits and found that the use of pomegranate wastes increased weight gain during the grower period. However, feed intake and FCR were not significantly affected by treatments. However, faecal pH in chickens fed pomegranate waste was lower than for in control animals. In addition, feed cost to reach broiler weight was reduced when birds were fed pomegranate waste. At around the same time, Yaseen et al. (Reference YASEEN, EL-KHOLY, ABD EL-RAZIK and SOLIMAN2014) studied the influence of using pomegranate peel extract on blood lipids and immune system in broiler chickens. The findings showed there were no significant differences among treatments on body weight and gain, feed intake or FCR. Furthermore, lipid content in liver and heart was decreased by consumption of 0.05 and 0.1% of pomegranate extract in diet. Moreover, triglycerides, cholesterol and serum LDL concentrations were significantly reduced when birds were fed pomegranate waste and the amount of lysozyme in chickens fed 0.05 and 0.1% of pomegranate peel extract significantly increased compared to unsupplemented dietary groups.

Based on the available research, inclusion of pomegranate by-product to feed at levels that are not detrimental to performance may be a promising method to improve poultry meat quality.

Apple wastes

Apple production has increased considerably around the world in recent years. A significant portion of this product, which has mostly lost its fresh-use properties, is used to produce juices, flavours and concentrates (Lu et al., Reference LU, ZHANG, GE, WANG, ZHOU, YOU and ZHANG2016). During the production of these value-added products, a relatively large amount of solid residues is produced which do not have the necessary characteristics to be used for human nutrition, and contains mainly peel, seeds, or pulp, which has high nutritional value and can be used in poultry diets (Villas-Bôas et al., Reference VILLAS-BÔAS, ESPOSITO and MENDONC2003).

Ayhan et al. (Reference AYHAN, ARSLANDURU and OZKAYA2009) examined the use of apple pulp in the diets of broiler chickens at 0, 5, 10 and 15% inclusion level. The findings showed that using more than 5% apple pulp in broiler diets caused weight loss, but no fatalities were recorded. Moreover, there was no difference observed in the performance of broilers fed diets with different levels of apple pulp compared with an unsupplemented control. At the end of the trial, it was concluded that using apple pulp up to 5% can be used as feed source in broiler diet. Nobakht (Reference NOBAKHT2013a) used apple pulp (0.0, 2.5, 5.0 and 7.5%) in the diet of laying chickens, and the results showed that the best performance and the highest levels of lymphocytes belonged to the hens fed 5% apple pulp; however, all treatments resulted in a negative effect on egg quality.

Ahmad (Reference AHMAD2004) reported that the use of 15% apple pulp alongside sugar beet molasses could be used as an energy source in broilers. Other combinations may be useful, for example Matoo et al. (Reference MATOO, BEAT, BANDAY and GANAIE2001) reported that including 15 or 20% of apple pulp together with enzymes improved the growth performance of chickens. Zafar et al. (Reference ZAFAR, IDREES and AHMAD2005) found that using apple pulp instead of corn up to 20% in poultry feed had no negative effect on the meat yield of broiler chickens, increased weight gain and feed intake and improved FCR. Different responses have been reported in broilers, including a reduction of cholesterol and an overall improvement of health status (as bacterial populations) in gastrointestinal tract (Zafar et al., Reference ZAFAR, IDREES and AHMAD2005; Amer et al., Reference AMER, AL-HILFY and AL-TAIE2011). Joshi et al. (Reference JOSHI, GUPTA, DEVRAJAN, LAL and ARYA2010) investigated the effect of apple pulp on the performance of broiler chickens and indicated that the birds fed apple pulp had the best weight gain, and the mortality rate and liver and kidney disorders were reduced, suggesting apple pulp as a valid dietary by-product in broiler ration.

Ghaemi et al. (Reference GHAEMI, NOBAKHT and RAZZAGHZADEH2014) investigated the effects of apple pulp and a multi-enzyme on performance and blood parameters of laying hens. Four levels (0, 5, 10 and 15%) of apple pulp were used in this study. The results showed that apple pulp significantly improved the performance, egg traits, blood biochemical parameters and immunity cells of laying hens up to 10%. In fact, feeding 15% apple pulp in feed reduced egg weight and laying production. In treatments containing 10% apple pulp, the amounts of albumin, heterophile, lymphocyte and heterophile to lymphocyte ratio were increased. Overall, adding 10% apple pulp improved egg performance and blood parameters of laying hens without adverse effects.

Recently, Heidarisafar et al. (Reference HEIDARISAFAR, SADEGH, KARIMI and AZIZI2016) examined the effect of apple peel (0, 5 and 10% diet) on the performance of broiler chickens under heat stress conditions. The addition of 10% of apple peel in diets increased the weight of the gizzard and small intestine from chickens. Dietary treatments with 5 and 10% apple peel waste increased lipid and HDL and decreased LDL and malondialdehyde in blood serum. However, apparent ileal protein digestibility in chickens fed diets containing 5 and 10% of apple peel waste was reduced. Further, Nobakht (Reference NOBAKHT2013b) suggested that the presence of potassium in apple waste assisted electrolytic equilibrium, increased the digestibility and absorption of nutrients and, in general, improved the growth traits and health status of poultry.

The published literature showed that apple waste can be included successfully in poultry diets without any adverse effect on their productive performance, being also a valuable candidate as a natural antioxidant due to its ability to decrease serum MDA.