Livestock Research for Rural Development 16 (6) 2004

Citation of this paper

Chemical composition and in vitro gas production characteristics of several tannin containing tree leaves

A Kamalak, O Canbolat*, Y Gurbuz, O Ozay, C O Ozkan and M Sakarya

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


Abstract

The aim of the present work was to determine the chemical composition including condensed tannin contents of leaves of some trees used for small ruminant animals in Turkey, and examine their relationships with in vitro gas production parameters.

Crude protein content ranged from 5.62 to 14.1 %, with Morus alba having the highest content. The content of neutral (NDF) and acid detergent fiber (ADF) ranged from 42.3 to 56.9% and 28.3 to 34.2 % respectively. The NDF content of Juniperus communis was significantly higher than the others. The ash content ranged from 4.99 to 15.8 % with Morus alba having highest ash. Total condensed tannin (TCT) content of tree leaves ranged from 1.42 to 21.3% with Juniperus communis having the highest TCT, most of which was in the soluble form. Gas production at 96 h incubation for leaves of Quercus libari was significantly higher than the others. The rank order in terms of potential gas production was Quercus libariPopulus nigraMorus alba > Juniperus communis. There was no significant difference among tree leaves in terms of the rate of gas production from insoluble but fermentable fraction. The gas volume of Quercus libari obtained from soluble fraction was significantly higher than the other tree species. The gas production from the insoluble but degradable fraction was significantly higher for Quercus libari than the other tree leaves whereas the potential gas production of Quercus libari was significantly higher than those of Morus alba and Juniperus communis. Total and soluble condensed tannins, NDF and ADF were negatively correlated with estimated parameters of gas production.

Key Words:Tree leaves, chemical composition, condensed tannin, in vitro gas production


Introduction

Tree and shrub leaves have the potential for alleviating some of the feed shortages and nutritional deficiencies experienced in the dry season on smallholder farms. Tree leaves are an important component of goats and sheep diets (Holecheck 1984; Papachristou and Nastis 1996) and play an important role in the nutrition of grazing animals in areas where few or no alternatives are available (Meuret et al 1990). However the use of tree and shrub leaves by herbivores is restricted by defending or deterring mechanisms related to high tannin content (Provenza 1995).

Although tree and shrub leaves are important sources of forage for small ruminants in most parts of Turkey during the critical periods of year when quality and quantity of pasture herbages are limited, there is little information on the nutritive value of tree and shrub leaves.

In vitro estimations of feed degradation are important tools for ruminant nutritionists. These methods measure either substrate disappearance or fermentation products (Blümmel et al 1997). It has been suggested that the gas production technique is more reliable than the nylon bag method for determining nutritive value of feeds containing anti-nutritive factors (Khazaal et al 1993). Gas production is associated with volatile fatty acid production following fermentation of substrate (Blummel and Ørskov 1993). In addition, the application of models permits the fermentation kinetics of the soluble and readily degradable fraction of the feeds, and more slowly degradable fraction to be described (Gatechew et al 1998). Moreover the gas production parameters of trees might demonstrate differences in their nutritional value that may be closely related to their chemical composition (Cerrillo and Juarez 2004).

The aim of the present work was to determine the chemical composition including condensed tannin contents of leaves of some trees used for small ruminant animals in some part of Turkey, and examine their relationships with in vitro gas production parameters.


Materials and methods

Forage samples

Leaves from four trees were harvested in 2003 from the city called Kahramanmaras, in the South of Turkey. The area is located at altitude of 630 m above sea level. The mean annual rainfall and temperature are 857 mm and 16.2 °C respectively. Leaves were hand harvested from at least 10 different trees, then pooled and oven-dried at 60 °C for 48 h (Abdulrazak et al 2000). The samples were ground to pass a 1 mm sieve for later analysis and determination.

Chemical analysis

Dry matter was determined by drying the samples at 105 °C overnight and ash by igniting the samples in muffle furnace at 525 °C for 8 h. Content of nitrogen (N) was measured by the Kheldal method (AOAC 1990). The crude protein (CP) was calculated as N x 6.25. Contents of neutral detergent fiber (NDF) of leave samples were determined by the method of Van Soest et al (1991). Acid detergent fibre (ADF) of leave samples were determined following the method of Van Soest (1963). Total condensed tannin (TCT), soluble condensed tannin (SCT) and bound condensed tannin (BCT) were determined by the butanol-HCL method (Makkar et al 1995). Mimosa tannin (MT; Hodgson, England) was used as an external standard.

In vitro gas production

Rumen fluid was obtained from two fistulated sheep fed twice daily with a diet containing alfalfa hay (60%) and concentrate mixture (40%). The samples were incubated using calibrated glass syringes following the procedures of Menke and Steingass (1988). Approximately 200 mg of OM sample was weighed in triplicate into glass syringes. The syringes were pre-warmed at 39 °C before the injection of 30 ml rumen fluid-buffer mixture into each syringe followed by incubation in a water bath at 39 ºC. The syringes were gently shaken at 30 min after the start of incubation and every hour for the first 10 h of incubation. Gas production was recorded before incubation (0) and 3, 6, 12, 24, 48, 72 and 96 h after incubation. Total gas values were corrected for blank and hay standards with known gas production. Cumulative gas production data were fitted to the model of Ørskov and McDonald, (1979) using the Fig P program.

p = a + b (1-exp -c t)

Where:
             p represents gas volume (ml) at time t,
            a
the gas produced from soluble fraction (ml),
            b
the gas produced from insoluble but fermentable fraction (ml),
            (a+b) the potential gas production (ml), and
            c
the rate constant of gas production during incubation (ml h-1).

Statistical analysis

One-way analysis of variance (ANOVA) was carried out to compare the chemical composition and in vitro gas production with species as the main factor using the General Linear Model (GLM) (Stastica 1993). Significance between individual means was identified using Tukey's multiple 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. A simple correlation analysis was used to establish the relationship between chemical composition and in vitro gas production parameters.


Results and discussion

There were significant differences in the chemical composition among tree leaves. The CP content in DM ranged from 5.62 to 14.1 % with Morus alba having the highest content. The CP content of Morus alba was significantly lower than that reported by Liu et al (2001) and Phiny et al (2003), who found the CP of 18.5 and 23.0 % of DM.

The NDF and ADF content ranged from 42.3 to 56.9% and 28.3 to 34.2% respectively. The NDF content of Juniperus communis was significantly higher than the others. The ash content ranged from 4.99 to 15.8 % with Morus alba having highest content. The TCT content of tree leaves ranged from 1.42 to 21.3% with Juniperus communis having the highest TCT, most of which was in the soluble form. Chemical composition is influenced by seasonal, environmental, soil and other factors (Khanal and Subba 2001).

Table 1. The chemical composition of four different tree leaves

(%)

Morus alba

Populus nigra

Juniperus communis

Quercus libari

SEM

Sig.

DM

93.17 a

93.26 a

95.61 b

93.91 a

0.118

***

CP

14.00 b

14.11 b

5.62 a

8.65 a

0.170

***

NDF

42.33 a

43.11 a

56.98 b

46.13 a

1.006

**

ADF

25.35 a

24.92 a

34.22 b

28.30 a

0.862

**

EE

6.58 ab

5.34ab

9.31 c

8.54bc

0.465

**

Ash

15.88 c

9.17 b

5.67 a

4.99 a

0.163

***

TCT

1.42 a

4.99 a

21.31 b

4.87 a

0.779

***

BCT

0.59 a

2.19 c

3.37 c

3.15 c

0.212

**

SCT

0.83 a

2.79 a

17.94 b

0.375 c

0.211

***

abc Means within the same row without superscript in common are different. SEM: Standard error of mean. ***P<0.001**P<0.01

TCT: Total condensed tannin, SCT: soluble condensed tannin, BST: bound condensed tannin

Gas production of tree leaves increased with increasing incubation time (Figure 1). There were significant differences among the four tree leaves in gas production at all incubation times. Gas production of leaves of Quercus libari was significantly (P<0.001) higher than the others at 96 h incubation.


Figure 1. Cumulative gas production of four tree leaves

Fermentation parameters for leaves from the four different trees are presented in Table 2. There was no significant difference among tree leaves in the rate (c) of gas production. The gas volumes from soluble fraction (a) and fraction (b) were significantly higher in Quercus libari than in the other tree species. The rank order in terms of potential gas production performance was Quercus libariPopulus nigraMorus alba > Juniperus communis.

Table 2. Fermentation parameters of leaves from 4 different leaves (defined by the equation: p = a + b (1-exp –c t)

 

Morus alba

Populus nigra

Juniperus communis

Quercus libari

SEM

Sig.

c 1

6.70

6.80

8.40

6.70

0.409

NS

a 2

4.09b

4.64bc

1.78a

5.37c

0.392

***

b 3

58.65 b

59.85 bc

53.26 a

61.66 c

0.400

***

a+b 4

62.66 b

64.50 bc

55.04 a

67.03 c

0.448

***

1 = rate constant of gas production during incubation (ml h-1)
2 = gas produced from soluble fraction (ml)
3 = gas produced from insoluble but fermentable fraction (ml)
4 = potential gas production (ml)
abcMeans within the same row without superscript in common are different.
SEM: Standard error of mean.
***P<0.001, NS = Non significant

The intake of a feed is mostly explained by the rate of gas production (c) which affects the passage rate of feed through the rumen, whereas the potential gas production (a +b), is associated with degradability of feed (Khazaal et al 1995). Therefore the higher values obtained for the potential gas production in the Quercus libari and Populus nigra might indicate a better nutrient availability for rumen microorganisms.

There were significant correlations between estimated parameters and the chemical composition of tree leaves from four different species (Table 3). Contents of NDF and ADF were negatively correlated with most of the estimated parameters. This result is in agreement with findings of Abdulrazak et al (2000), and Ndlovu and Nherera (1997). Rate of gas production was not related to TCT, BCT and SCT. The lack of correlation between these parameters has been observed in previous studies (Khazaal et al 1994). Rate of gas production did not correlate with NDF and ADF content. This result is not in agreement with findings of Ndlovu and Nherera (1997). There is no obvious explanation for these anomalies.

Table 3. The correlation coefficients (r) between the chemical composition and estimated parameters of tree leaves incubated with rumen fluid

 

CP

NDF

ADF

TCT

BCT

SCT

c 1

0.348NS

 0.415 NS

 0.372 NS

 0.476 NS

 0.038 NS

 0.483 NS

a 2

0.504 NS

- 0.737**

- 0.698**

-0.796***

0.330

-0.865***

b 3

0.543 NS

- 0.775**

- 0.740**

-0.845***

0.334

-0.930***

a+b 4

0.544 NS

- 0.783**

- 0.745**

-0.851***

0.341

-0.933***

1 = rate constant of gas production during incubation (% h-1)
2 = gas produced from soluble fraction (ml/0.200 g OM)
3 = gas produced from insoluble but fermentable fraction (ml/0.200 g OM)
4 = potential gas production (ml /0.200 g OM)
***P<0.001, NS = Non significant

TCT and SCT were also negatively correlated with most of the estimated parameters. This result is consistent with findings of Frutos et al (2002). On the other hand, Larbi et al (1998) reported a weak relationship between TCT and gas production parameters of tree leaves during wet and dry season in West Africa. A possible reason could be differences in the nature of tannins between browse species (Jackson et al 1996). The negative correlation between potential gas production and NDF, ADF, TCT, or SCT may be a result of the reduction of microbial activity from increasingly adverse environmental conditions as incubation time progress (Abreu et.al 1998; Wood and Plumb 1995).

The tree leaves had low contents of CT (less than 6.51 g / kg DM) which would generally be considered unlikely to significantly affect digestion of nutrients in ruminants (Frutos et al 2002). There was, however, one exception to this in tree leaves collected from Juniperus communis, which showed high TCT contents.

NDF and ADF explained 61.1 and 55.5 % of the variation of cumulative gas production respectively whereas the TCT and SCT content explained 72.4 and 87.0 % of variation of cumulative gas production. Cerrillo and Juarez (2004) reported that 81 % of the variation in potential gas production could be explained by the changes in ADF content. The low predictive values in the current experiment could be due to species variation in quantity and quality of fibre content as well as variation in complexation of fibre with polyphenolics (Ndlovu and Nherera 1997).


Conclusion


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Received 31 March 2004; Accepted 9 May 2004

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