Evaluation of carob, Ceratonia siliqua pods as a feed for sheep

A Karabulut, O Canbolat and A Kamalak^*

Bursa Uludag University, Faculty of Agriculture, Department of Animal Nutrition, Bursa, Turkey
Kahramanmaras Sutcu Imam University,
*Faculty of Agriculture, Department of Animal, Nutrition, Kahramanmaras, Turkey
akamalak@ksu.edu.tr

Abstract

The nutritive value of different fractions of naturally grown carob pods was evaluated by their chemical composition and in vitro gas production method. Gas production were calculated at 0, 3, 6, 12, 24, 48, 72 and 96 h and their kinetics were described using the equation p = a + b (1-e^-ct). There were significant differences among the fraction of carob pods in terms of chemical composition. Crude protein content ranged from 5.9 to 27.7 %. Crude protein content of carob seeds was significantly higher than that of whole carob pods and carob kibbles. The NDF, ADF and ADL contents ranged from 29.20 to 38.04 %, % 14.39 to 20.14%, 6.44 to 10.20% respectively. The NDF, ADF and ADL of seed were significantly higher than those of whole carob pods and kibbles. There was no significant difference in starch content among the fractions of carob pods whereas the sugar content of whole carob pod and kibbles were significantly higher than that of carob seed. After 24 h incubation times the in vitro gas production of whole pods and kibbles are significantly higher than that of seed. The gas production rate of carob seed was significantly higher than that of carob kibbles whereas the potential gas productions (a+b) of whole carob pods and carob kibbles were significantly higher than that of carob seed. On the other hand the estimated OMD and ME values of carob seed were significantly higher than that of whole carob pods.

It was concluded that whole carob pods contain high level of sugar but low protein and lipid. Apart from non-structural carbohydrates, the pods contain high amounts of dietary fibre. The carob seed is rich in cell wall content and CP whereas carob kibbles is rich in non-structural carbohydrate. Therefore whole carob pods have a potential energy source for sheep. Protein supplementation will be required when carob pods is included into ruminant diets.

Key words: Carob pod, Ceratonia siliqua, digestibility, metabolizable energy

Introduction

The productivity of ruminant animals in the most part of Turkey is limited by the low level energy and protein intake due to the lowest production of high quality forage in the summer season. Foliage and pods from trees and shrubs are used in ruminant diets to pass this critical summer period in the south of Turkey (Kamalak et al 2005). There is now significant move to look for new sources for ruminant animals from naturally grown plants to reduce cost of diets due to increases in feed prices (Kamalak et al 2005).

Carob, Ceratonia siliqua L is an evergreen tree cultivated or naturally grown mainly in the Mediterranean area and produces pods. Whole carob pods or its byproducts such as carob seed and carob kibbles which is the remaining pulp obtained after removal of the seeds can be were used as animal and human nutrition (Albanell et al 1991, Silanikove et al 2006). Although carob trees are found in great abundance in the South of Turkey there is considerably limited information about chemical composition, the in vitro organic matter digestibility, metabolizable energy and some in vitro gas production kinetics of naturally grown carob pods. Therefore the more information about the nutritive value of carob pods is required to prepare the balanced ration for ruminant animals.

The aim of this experiment was to evaluate the chemical composition, the in vitro organic matter digestibility, metabolizable energy and some in vitro gas production kinetics of naturally grown carob pods.

Materials and methods

Chemical analysis

Carob pods were hand harvested and oven dried at 60 ⁰C at 48 h. Dry matter (DM) was determined by drying the samples at 105 ⁰C overnight and ash by igniting the samples in muffle furnace at 525 ^OC for 8 h. Nitrogen (N) content was measured by the Kjeldahl method (AOAC 1990). Crude protein was calculated as N X 6.25. NDF, ADF and ADL contents were determined using the method described by Van Soest (1991). Starch content was determined by polarimetric method described by Karabulut and Canbolat (2005). Total sugar content was determined using the method described by Dubois et al (1956). Condensed tannin was determined by butanol-HCl method as described by Makkar et al (1995). All chemical analyses were carried out in triplicate.

In vitro gas production

Rumen fluid was obtained from two fistulated sheep fed twice daily with a diet containing alfalfa hay (60%) and concentrate (40%). Samples were incubated in vitro rumen fluid in calibrated glass syringes following the procedures of Menke and Steingass (1988). 0.200 g dry weight of the sample was weighed into calibrated glass syringes of 100 ml. The syringes were prewarmed at 39 ⁰C before the injection of 30 ml rumen fluid-buffer mixture into each syringe followed by incubation in a water bath at 39 ⁰C. The syringes were gently shaken 30 min after the start of incubation and every hour for the first 10 h of incubation. Readings of gas production recorded before incubation (0) and 3, 6, 12, 24, 48, 72 and 96 h after incubation. Cumulative gas production data were fitted to the exponential equation p = a + b (1-e^-ct) (Orskov and McDonald (1979), where p is the gas production at time t; a is the gas production from the immediately soluble fraction (ml), b is the gas production from the insoluble fraction (ml), c is the gas production rate constant, t = incubation time (h)

The metabolizable energy (MJ/kg DM) of silages was calculated using equations of Menke et al (1979) as follows:

ME (MJ/kg DM) = 2.20 + 0.136 GP + 0.057 CP + 0.0029CP²

Where,

GP is 24 h net gas production (ml/200 mg),
CP = Crude protein (%)

The OMD of silages was calculated using equations of Menke et al (1979) as follows:

OMD (%) = 14.88 + 0.889 GP + 0.45 CP + XA

Where,

GP is 24 h net gas production (ml / 200 mg),
CP = Crude protein (%)

Statistical analysis

Data of chemical composition and in vitro gas production were subjected to standard analysis of variance using general linear model (GLM) of statistica for windows (Statistica 1993). Significance between individual means was identified using the Tukey's multiply range test (Pearse and Hartley 1966). Mean differences were considered significant at P<0.05. Standard errors of means were calculated from the residual mean square in the analysis of variance.

Results and discussion

The chemical compositions of whole carob pods and its fractions are given in Table 1.

There were significant (P<0.001) differences among parts of carob pods in terms of chemical composition. Crude protein content ranged from 5.9 to 27.7 %. Crude protein content of carob seeds was significantly (P<0.001) higher than that of whole carob pods and carob kibbles. The NDF, ADF and ADL contents ranged from 29.20 to 38.04 %, % 14.39 to 20.14%, 6.44 to 10.20% respectively. The NDF, ADF and ADL of seed were significantly (P<0.001) higher than those of whole carob pods and kibbles.

Although there was no significant (P>0.05) difference in starch content among the fractions of carob pods the sugar content of whole carob pod and kibbles were significantly (P<0.001) higher than that of carob seed. The NDF of whole carob pods were in agreement with finding of Albanell et al (1991) who reported that NDF and total sugar contents ranged from 27.4 to 50.1% and 25.7 to 55% whereas the ADF and ADL contents of whole carob pods was considerably lower than that reported by Albanell et al (1991). The CP of whole carob pods is comparable with findings of Marakis (1996) who reported that the CP content of whole crop pods ranged from 3 to 4 %.

On the other hand there was no significant (P>0.05) different among the carob fraction in terms of CT which ranged from 1.6 to 1.8 %. In ruminants, dietary condensed tannins (2-3%) have been shown to impart beneficial effects because they reduce the wasteful protein degradation in the rumen by the formation of a protein-tannin complex (Barry 1987). However, it was reported that the presence of tannins in carob pods induced deleterious effects on digestion, growth, milk production and feed utilization (Volcani and Rodrig 1961, Alumot et al 1964, Priolo et al 2000, 2002).Tannins may form a less digestible complex with dietary proteins and may bind and inhibit the endogenous protein, such as digestive enzymes (Kumar and Singh 1984). Tannin can adversely affect the microbial and enzyme activities (Singleton 1981, Lohan et al 1983, Barry and Duncan 1984, and Makkar et al 1989).

In vitro gas production of whole carob pods, kibbles and seeds are presented in Figure 1. At early incubation times there was no considerable variation in terms of gas production among whole carob pods, kibbles and seeds.

However after 24 h incubation times the in vitro gas production of whole pods and kibbles are significantly (P<0.001) higher than that of seed. The reason why the in vitro gas production of seed was lower than those of whole pods and kibbles is possibly due to high cell wall and low sugar contents of carob seed. As can be seen from Table 1 whole carob pods, kibbles and seed had a considerable starch and sugar which are quickly available for microbial fermentation at early incubation times. After depletion of starch or sugar the less degradable cell wall fractions become available to micro-organism. As can be seen from Figure 1 after 24 h incubation time there was a significant (P<0.001) difference in gas production among different fraction of carob pods.

The gas production kinetics, OMD and ME contents of different fractions of carob pods are given in Table 2.

The gas production rate of carob seed was significantly (P<0.001) higher than that of carob kibbles whereas the potential gas productions (a+b) of whole carob pods and carob kibbles were significantly (P<0.001) higher than that of carob seed. On the other hand the estimated OMD and ME values of carob seed were significantly (P<0.001) higher than that of whole carob pods. The reason why the carob seed had the higher OMD and ME values is the method of calculation for OMD and ME. These parameters (OMD and ME) were calculated using the equations suggested by Menke et al (1979). As can be seen from these equations OMD and ME content were positively correlated with CP contents of samples. The high CP content of carob seed may have resulted in overestimation of OMD and ME.

Conclusions

• Whole carob pods contain high level of sugar but low protein and lipid.

• Apart from non-structural carbohydrates, the pods contain high amounts of dietary fibre.

• The carob seed is rich in cell wall content and CP whereas carob kibbles are rich in non-structural carbohydrate.

•  Therefore whole carob pods are a potential energy source for sheep.

• Protein supplementation will be required when carob pods are included into ruminant diets.

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Received 23 March 2006; Accepted 5 June 2006; Published 28 July 2006

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