Nutritional value of raw and extruded chickpeas ( Cicer arietinum L . ) for growing chickens

The effects of the inclusion of different concentrations (0, 100, 200 and 300 g kg-1) of raw and extruded chickpeas on performance, digestive organ sizes, and protein and fat digestibilities were studied in one experiment with growing broiler chickens (0 to 21 days of age). Data were analyzed as a 3 x 2 factorial arrangement with three levels of chickpea with or without extrusion. A corn-soybean based diet was used as a positive control. Increasing chickpea content in the diet did not affect weight gain, feed consumption and feed to gain ratio. Relative pancreas and liver weights, and relative lengths of duodenum, jejunum and ceca were significantly (P<0.05) increased in response to increasing chickpea concentration in the diet. The inclusion of graded concentrations of chickpea increased (P<0.05) the apparent ileal digestibility (AID) of crude protein (CP) and apparent excreta digestibility (AED) of crude fat (CF) only in the case of the intermediate level of chickpea used (200 g kg-1). Extrusion improved weight gain and lowered relative pancreas weight (P< 0.05) respect to birds fed raw chickpea-based diets. AID of CP and AED of CF were improved (P<0.001) by extrusion. We concluded that the inclusion of up to 300 g kg-1 chickpea in chicken diets did not affect performance, and caused a negative effect on the relative weight of some digestive organs. Additional key words: chick, extrusion, legumes.


Introduction
Chickpea (Cicer arietinum L.) seeds are an important staple food in Southern Europe, North Africa, India and some other areas.It is cultivated mainly as a legume crop, since it is well adapted to semi-arid conditions.Although most chickpeas are currently produced for human consumption, as production increases more chickpeas will be feed grade and available as an alternative source of protein and energy for animal nutrition.
Like other legumes, chickpea seeds contain a variety of antinutritional factors such as protease and amylase inhibitors, lectins, polyphenols and oligosaccharides (Chavan et al., 1986;Cerioli et al., 1998).In comparison to soybean (Glycine max L.), peas (Pisum sativum L.) and common beans (Phaseolus vulgaris L.), chickpea offers less problems as far as these factors are concerned (Singh, 1988).Little research has been published on the nutritional value of chickpeas for growing chickens.Viveros et al. (2001) showed that the inclusion of up to 450 g kg -1 of kabuli and up to 150 g kg -1 of desi chickpea seed meal in the diet had a negative effect on the chicken performance.
Attempts to increase the utilization of legumes have employed a wide range of processing techniques such as soaking, autoclaving, pelleting, dry roasting, dehulling, germination, fermentation and recently extrusion cooking (Van der Poel, 1990;Mariscal-Landin et al., 2002;Abd El-Hady and Habiba, 2003).The nutritional advantages of extrusion have gained more attention due to its increased industrial use.Extrusion cooking is a technology classified as a high temperature/short time process to produce a wide variety of foods and ingredients.The exposure of feed material to high temperature for short times has the favourable effect of high rates of destruction of microorganisms and heat labile antinutrients.This technology offers numerous advantages including versatility, high productivity, low operating cost, energy efficiency, and high quality of resulting products.The high shear forces may also denature protein and disrupt the food matrix thereby improving the digestibility of nutrients (Milán et al., 2000).Modifications of physicochemical and nutritional properties of hard-to-cook beans by extrusion cook ing have been reported by Martin Cabrejas et al. (1999), and the nutritional quality of extruded kidney bean and its effects on growth and skeletal muscle nitrogen fractions in rats have been studied by Marzo et al. (2002).Similarly, the extrusion process counter -acts the negative effect produced by the addition of raw kidney bean by the removal of the antinutritional factors (ANF) and by improving the nutrient availability of the seed (Arija et al., 2006).The extrusion process also improved the physicochemical and nutritional characteristics of extruded flours from fresh and hardened chickpeas (Milán et al., 2000).
There is little information on the effectiveness of extrusion to remove ANF and the degree to which nutrient availability of legumes is affected in chickens diets.The objectives of this study were to study the productive response of growing broiler chicks under practical conditions to different and increasing concentrations of raw chickpea, and to study the extrusion effect on some nutritional parameters of chickpea in chicken diets.

Test product and extrusion
Chickpea seeds (var kabuli) cultivated in Navarra (Spain), were added to the diet in either a raw or extruded form.Prior to extrusion the seeds were ground through a hammer mill and sieved to a 0.5-mm diameter particle size.Extrusion of finely ground seeds was performed in a Clextral X-5 model BC 45 twin-screw extruder (F-42100 Firminy, France).The extruder was operated at 100 rpm and the feeder was set to deliver 350 g min -1 .Moisture content in the extruder barrel was constant at 250 g kg -1 and the extrusion temperature was 150ºC.Samples of raw and extruded chickpeas were analyzed for dry matter (DM), crude protein (CP), ether extract, crude fiber, ash and amino acids.

Birds and diets
One hundred sixty eight newly hatched Cobb 1-dold broiler chickens were used in a 21-d feeding trial.The chicks were housed in electrically heated batteries brooder placed in a temperature-controlled room with 23 h d -1 constant overhead fluorescent lighting.They were randomly distributed and allocated to 28 pens, each pen containing six chicks, to receive seven dietary treatments with four replicates of each treatment.The diets were given in mash form, and water was supplied ad libitum.Celite (Celite Corp., Lompoc, CA 93436), a source of acid insoluble ash (AIA), was added at 10 g kg -1 to all diets as an indigestible marker.All diets were formulated to meet or exceed the minimum National Research Council (1994) requirements for broiler chickens.At the end of the experimental period, birds were weighed and feed consumption was recorded for feed efficiency computation.All housing and handling procedures were approved by the University Complutense of Madrid Animal Care and Ethics Committee in compliance with the Ministry of Agriculture, Fishery and Food for the Care and Use of Animals for Scientific Purposes (OJ, 1990;BOE, 1996).

Collection of samples and measurements
At 21 days of age, 12 chicks selected at random per treatment were weighed and sacrificed by cervical dislocation.The pancreas, liver and spleen were removed and weighed.Likewise, small intestinal sections (duodenum, jejunum, ileum) and ceca were also removed and length recorded.Ileum was defined as the distance between the yolk stalk and the ileo-caecal junction.The ileum was quickly dissected out and the content expressed by gentle manipulation into a plastic pot in which it was stored at -20ºC.Digesta were pooled from two birds of each replicate within the same treatment.The ileal contents were freeze-dried and ground (1 mm screen) and subsequently analysed for N-Kjeldahl and celite.Clean stainless steel collection trays were placed under each cage and excreta from the birds were collected for 48 h.A sub-sample of excreta was collected in polyethylene bags, weighed, freeze-dried, and subsequently analysed for crude fat.

Chemical analyses
DM, CP, crude fiber, and ash were analysed according to the methods of the AOAC (1995).Ether extract was determined by extraction in petroleum ether following acidification with 4 N HCl solution (Wiseman et al., 1992).The AIA contents of diet, excreta and ileal digesta were measured after ashing the samples and treating the ash with boiling 4 M hydrochloric acid (Siriwan et al., 1993).Amino acids in the diets were analyzed following AOAC (1995) procedures and separated using a Beckman Model 6300 AA autoanalyzer.Three replicates of all analyses were performed.Tryptophan was not determined.

Calculations and statistical analyses
Apparent ileal digestibility (AID) of CP and apparent excreta digestibility (AED) of CF were calculated using the following formula: 100% -[100% x (AIA concentration in feed / AIA concentration in ileal or excreta content)] x (CP or CF concentrations in ileal or excreta content / CP or CF concentrations in feed).Data were analyzed as a 3 x 2 factorial arrangement with three levels of chickpea with and without extrusion.Data were subjected to ANOVA using the GLM procedures of SAS (SAS Institute, 2001) where Y ijk is the individual observation, µ is the experimental mean, C i is the chickpea effect, E j is the extrusion effect, CE ij is the interaction effect, R k is the replication effect, and e ijk is the error term.Significant differences among treatment means were determined at P<0.05 by Duncan's multiple-range test.

Results
The chemical composition of raw and extruded chickpeas is shown in Table 1.Moisture and ether extract con-tent of EC was lower than that of RC.Apparent metabolizable energy calculated value was higher in EC compared with RC.The concentrations of CP, ash, and crude fiber were similar in both seeds.Aspartic acid, glutamic acid, glycine, and phenylalanine concentrations were higher in EC compared with RC.Methionine and cysteine concentrations were higher in RC than EC.
The performance results of broilers fed graded concentrations of RC and EC are summarized in Table 3.Although values for raw chickpea diets were lower in some cases, the main effect data indicated that the inclusion of graded concentrations of chickpea did not affect the performance of the birds.Extrusion improved weight gain (7%; P<0.015).
Results of the relative organ weights and intestinal length are shown in pectively.Likewise, a significant interaction (P<0.001) between chickpea concentration and extrusion for AID of CP (P<0.001) and AED of CF was observed.

Discussion
The composition of raw and extruded chickpeas was similar to values presented by Khan et al. (1995) and Marzo et al. (2002).Extrusion cooking caused a significant decrease in moisture and ether extract contents.This could be due to the high temperature environment inside the screw channel that resulted in evaporation of water and volatile compounds.The release of water at die produced extrudates with lower moisture content than raw flours.These results are similar to those reported by Arija et al. (2006) using raw and extruded kidney bean.
The present study also demonstrated that the inclusion of graded concentrations of chickpea in chicken diets did not affect birds performance.These results are in agreement with those reported by Viveros et al. (2001) and Farrell et al. (1999), who found a negative tive pancreas (up to 10%; P<0.029) and liver weights (up to 3.6; P<0.045) and the relative duodenum (up to 5.6%; P<0.034), jejunum (up to 11.7; P<0.01) and ceca lengths (up to 6.7%; P<0.034).The extrusion of chickpea reduced the relative pancreas weight (17.9%;P<0.001), as compared to raw chickpea diets, to values which were not different from controls.Relative liver weight of birds fed extruded chickpea diets was higher (9%; P<0.05) than those fed control diet.A significant interaction concentration x processing was observed for relative pancreas (P<0.004) and spleen weights (P<0.013),indicating a greater response in the highest chickpea concentration.
The effect of inclusion of graded concentrations of RC diets in broilers on AID of CP and AED of crude fat are reported in Table 5.The main effect data indicated that the inclusion of 300 g kg -1 chickpea caused a reduction of the AID of CP (1.5%; P<0.05) and the AED of CF (1.4%; P<0.05) compared to the addition of 200 g kg -1 chickpea.Statistical analysis of the data also demonstrated that extrusion (P<0.001)improved the AID of CP and the AED of CF by 2.9 and 2.8 %, res- effect when chickpea was included up to 360 g kg -1 in the diet.However, Johnson and Eason (1990) did not observe differences in performance of birds fed with 200 g chickpea kg -1 .These discrepancies could be due to the presence of certain amounts of antinutritional factors in the seed, which can vary considerably among batches of the same legume.Saini et al. (1992) observed a large variation in concentrations of trypsin and chymotrypsin inhibitors of chickpea grown in Australia, which were influenced by the location and year of cultivation.Singh and Jambunathan (1981) also showed that trypsin inhibitor activity of two varieties of chickpea varied considerably among different genotypes.
Although the inclusion of graded concentration of chickpea did not cause growth depression, the relative pancreas weight was increased in the birds fed the higher concentration of chickpea.This result agree with previously reported data in rats (Cavallé de Moya et al., 2003) and chickens (Rubio et al., 1990;Viveros et al., 2001;Brenes et al., 2002;Arija et al., 2006) with the use of faba bean, chickpea, and lupin seed in the diets.The enlargement in the pancreas is usually linked to the presence of trypsin inhibitors and lectins in the legume seeds.This fact has frequently been observed in rats (Grant et al., 1995;Cavallé de Moya, 2003) fed kidney bean, and chicks (Huisman et al., 1990;Rubio et al., 1990) fed diets containing legumes.Miller et al. (1991) and Miller and Holmes (1992) demonstrated that birds fed on kabuli chickpea had greater pancreas weight.Farrell et al. (1999) also observed a linear increase (although not significant) in pancreas weight when the rate of chickpea was increased.Inactivation of free trypsin in the gut stimulates the release of cholecystokinin from neuroendocrine cells in the intestine, thereby initiating hypersecretion of pancreatic digestive enzymes and subsequent enlargement of the pancreas (Grant et al., 1999;Cavallé de Moya et al., 2003).In the case of the liver, the observed increase in the relative weight could be related to the nutritional status of the chickens fed chickpea.The mobilization of body reserves to meet Data also demonstrated a significant reduction in the AID of CP and AED of CF in birds fed the highest chickpea concentration.Similar results have been published in previous studies with faba beans, peas and chickpeas, suggesting that their lower nutritional value is due to the antinutritional factors present in the seed, particularly trypsin inhibitors (Huisman et al., 1990;Grosjean et al., 1992).The presence of trypsin and chymotrypsin inhibitors in chickpea seeds could be at least partially responsible, since they can inhibit digestive enzymes (Bressani and Elias, 1988;Viveros et al., 2001).Rubio et al. (1995) and Cavallé de Moya et al. (2003) also attributed this effect in rats to an excessive secretion of endogenous nitrogen by the use of legumes.
Extrusion improved significantly weight gain and relative pancreas weight.This beneficial effect could be attributed to the reduction or inactivation of the trypsin, chymotrypsin and α-amylase inhibitors by the extrusion process.Earlier experiments (Savage and Thompson, 1993;Savage et al., 1995) showed the possibility of reducing the effect of the ANF by various cooking and processing methods.Extrusion has been shown to be very effective in destroying lectins, protease inhibitors and α-amylase inhibiting enzymes (Marzo et al., 2002;Abd El-Hady and Habiba, 2003;Arija et al., 2006).Moreover, due to the presence of shear forces and high-energy input, proteins are more easily accessible for enzyme attack during the extrusion process (Camire, 1991).Extrusion is also known to gelatinize starch, which would improve the conditions for efficient digestion of protein in the small intestine of pigs (Bengala-Freire et al., 1991), chicks (Arija et al., 2006) and in in vitro conditions (Alonso et al., 2000).Martin-Cabrejas et al. (1999) also showed increased solubilization of insoluble fiber by the extrusion processing of common bean.
In conclusion, the use of chickpea in chicken diets up to 300 g kg -1 did not affect performance, and caused an increase in the size of some digestive organs.Extrusion improved weight gain, protein and fat digestibilities, and counteracted the negative effect of raw chickpea feeding on pancreas size.the needs of the rapidly growing tissues might increase the liver´s activity, thus causing hypertrophy.Viveros et al. (2001) and Arija et al. (2006) also observed an increase in the relative weight of the liver in birds fed chickpea and kidney bean, respectively.Changes in liver weight have also been observed in rats due to an increase in amino acid degrading enzymes and a decrease of protein synthesis (Rubio, 2000).
The increase in the relative duodenum, jejunum and ceca lengths of birds fed on chickpea could be attributed, at least to some extent, to the presence of high levels of complex carbohydrates, including resistant starch, oligosaccharides, and non-starch polysaccharides (NSP) present in this seed (Rossi et al., 1984;Champ et al., 1986;Garcia Alonso et al., 1998).Alonso et al. (2000) and Brenes et al. (2003) determined, by in vivo and in vitro procedures, low starch, oligosaccharides, and NSP digestibilities in several legume seeds (faba bean, kidney bean, and lupin seed).In experiments with rats, Ikegami et al. (1990) showed that the addition of indigesti- . Treatment 1 was 1 AME: apparent metabolisable energy.Calculated value; European table of energy values for poultry feedstuffs (WPSA, 1986).a,b Data are means of five determinations ± SD.Row values with different superscripts differ (P<0.05).Table 1.Composition (g kg -1 as fed) of raw and extruded chickpea seeds (Cicer arietinum L.) considered a positive control.The statistical model used was:

Table 3 .
Performance of broiler chicks (0 to 21 d) fed raw and extruded chickpea 1

Table 4 .
Relative organ weights and intestinal lengths of broiler chicks (0 to 21 d) fed raw and extruded chickpea 1

Table 5 .
Apparent digestibility of protein and fat in broiler chicks (0 to 21 d) fed raw and extruded chickpea 1