 |
| Figure 1. Kinetics of the gas production from the three
substrates (BRS Barley straw, DPL Date palm leaves, ARPS Aristida pungens) and the blank |
| Livestock Research for Rural Development 23 (3) 2011 | Notes to Authors | LRRD Newsletter | Citation of this paper |
The main objective of this study is assessing the nutritive value of agricultural by-products dry palm leave, Aristida pungens in comparison to barley straw by chemical analysis, rumen fermentation characteristics and gas production technique in vitro. A quantitative analysis of gases produced from dry palm leaves was compared to that of Drin and barley straw which are common feeds in the semi arid and arid regions of Algeria.
The results obtained show that the activity of goats’ rumen microflora is very important on the studied substrate of the arid regions, which indicates very significant digestibility coefficient. This situation is certainly due to the high content of barley straw of total soluble sugars and thus more easily fermentable. For dry palm leaves, the value of in vitro gas digestibility is 49.8 ℅. It is close to that of Drinn, probably owing to the fact that these substrates present almost the same level of lignin and of cellular wall contents.
These results suggest a high potential of integrating dry palm leaves in ruminants’ feed in these areas leading to overcoming the problems of maintaining feed supply.
Key words: Drinn, goats, dry palm leaves, in vitro gas production, rumen microflora
Ruminant animals have evolved a unique system which involves a slow pre-gastric fermentation of plant fibre by bacteria, protozoa, and fungi that provide the host animal with nutrients (volatile fatty acids, microbial protein and B vitamin). High quality forages are crucial for proper feeding of ruminant animals since they provide energy, proteins and minerals (McSweeney et al 1999).
In the semi arid and arid regions of Algeria, the lowest production of forage is during dry season, which usually lasts for 6-7 months (from Mai to October) and leads to a rapid decline in the quantitative value of natural vegetation. Ruminants reared in those regions may have problems overcoming maintenance requirements on natural vegetation without any additional feed supply resulting in low performance.
Agricultural and agro-industrial by-products represent an important fodder reserve for livestock in harsh conditions that can be used by grazing ruminant in periods of feed scarcity. Dry palm leaves, the yearly maintenance of date palm trees let considerable quantities of green leaves, roughly 20 kg per tree (Bahman et al 1997; Pascual et al 2000; Arhab et al 2006). This date palm by-product is traditionally used as complementary feeding source for livestock by people who live in oases. Aristida Pungens (local name drinn), a spontaneous desert plant of the family of Graminaceous is currently harvested and fed to animals.
Knowledge about the potential feeding value of these plants is insufficient. The nutrient composition of feeds is commonly determined primarily by chemical analysis. However this does not provide sufficient information to determine the feed’s true nutritive value. The in vitro gas production system helps to better quantify nutrient utilization and its accuracy in describing digestibility in animals has been validated in numerous experiments. The in vitro gas production technique developed by (Menke et Steingass1988), has been used by (Blummel and Orskov 1993), to determine gas production at several incubation times and these values could describe the pattern of fermentation of feed, by using the equation of( McDonald 1981).
The main objective of this study is
assessing the nutritive value of agricultural by-products dry palm leave,
Aristida pungens in comparison to barley straw by chemical analysis, rumen
fermentation characteristics and gas production technique in vitro.
Three fibrous substrates were sampled from an arid region located in the south east of ALGERIA: Dry palm leaves (whole leaves: rachis plus leaflets) which represent a by-product of date palm trees (Phoenix dactylifera L.), Aristida pungens (local name Drinn) and barley straw.
The nutritive value of the three substrates was studied by measuring the volume of gas produced during the in vitro incubation of samples (200mg DM per syringe) according to the technique of Menke and Steingass (1988). Blanks and 200 mg of ground samples were incubated in triplicate into 60 ml calibrated propylene syringes with 30 ml of mixture of strained rumen fluid and buffer containing sodium hydrogen carbonate.
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 an electrically heated vessel equipped with a rotor runs continuously at 9 rpm. The syringes were gently shaken 30 minutes after the start of the incubation and every hour of the first 10 hour of incubation.
Rumen fluid was collected from the rumen of three male goats which were all fed a restricted amount of a commercial concentrate and wheat straw ad libitum. Immediately after slaughter, in the morning, samples of fresh digesta were collected from the rumen of the three goats. At the laboratory, rumen digesta was squeezed through four layers of cheesecloth to ensure liquors contained microbial population from both the liquid and solid phases. Rumen liquor was homogenized and kept at approximately 39 °C in a water bath, and flushed with CO2 before use. At the end of incubation (i.e. 96 h), the contents of each syringe were transferred to centrifuge tubes and centrifuged at 20.000 x g for 20 minutes at 4 °C. The residual pellet was lyophilized in the tubes over night. The residual moisture, if any was removed by drying the tubes overnight at 60°C, and then the tubes were weighed. IVDMD was calculated from differences between initial and residue weights, minus blank tubes.
Chemical analysis of the three substrates was carried out following AOAC (1990) procedures for determination of the dry matter (DM) and organic matter (OM). Nitrogen concentration was determined by a macro Kdjeldahl procedure. Acid detergent fibre (ADF) and neutral detergent fibre (NDF) were determined by the procedure of Van Soest et al (1991).
Cumulative
gas was expressed as ml of gas produced per 200mg of dry matter and corrected
for blanks. Cumulative gas production at time t was fitted to the
exponential model developed by Ørskov and
McDonald (1979) (Y = a
+ b (1 – exp-ct), where Y (ml) is gas production
at time t, a is the amount of gas or proportion corresponding to the rapidly
degradable fraction, b is the amount of gas corresponding to the slowly
degradable fraction, a+b is the potential gas production corresponding to
potential degradable DM, and c is gas production rate. The estimation of these
parameters was made by the Neway Excel software (Arhab et al 2006 ; Chen 1997).
Data were subject to analysis of variance (ANOVA) using STATITCF Version 5.
Crude protein content was low in all substrates (Table 1). The results agree with those reported in the literature (Ehag and Elkhangari 1992; Nicolic et al 1987). However, Pedraza (1998) announced a value of the higher NDF for the barley straw with 86.9% in DM.
Generally, the three substrates were high in cell wall content, related to the phenological role of each one. Because of their high content of cell walls and their crude protein deficit, these three feeds can be regarded as coarse substrates (Chermiti 1997).
|
Table 1: Chemical analyses of different substrates. |
||||||
|
|
DM, % |
Ash, % in DM |
CP, % in DM |
NDF, % in DM |
ADF, % in DM |
HC, % in DM |
Drinn |
92.4±0.24 |
8.7 ±0.51 a |
5.20±0.35a |
85.2±1.22 b |
60.9±1.71 b |
24.3±.3 a |
Barley Straw |
90.2±0.17 b |
6.25±0.10 b |
3.13±0.75c |
73.2±1.32 c |
55.9±1.39 c |
17.3±1.75c |
|
Dry palm leaves |
91.8±0.13 b |
8.25±0.64 a |
4.8±0.43b |
87.5±0.75 a |
65.5±1.45 a |
21.9±0.75b |
|
DM: Dry Matter, HC: Hemicellulose |
||||||
The dry palm leaves and the Drinn have almost the same curve of gas production (Figure 1), because of their closer structure and chemical composition compared to the barley straw which is characterized by a different curve indicating highe degradability at all times and a short latency time. This is due to their less fibrous chemical composition and their low lignin content. The latency time (time from incubation to start of gas production) is a very important digestibility parameter.
|
|
| Figure 1. Kinetics of the gas production from the three
substrates (BRS Barley straw, DPL Date palm leaves, ARPS Aristida pungens) and the blank |
The profile of fermentation of the three
substrates lengthens before becoming stable at 90 hours. This profile is
precisely a characteristic of the fibrous substrates which express a more or
less high latency time and spend a long period of stay in the rumen.
Therefore, in order to maximize the nutrient supply from the
leaves, longer residence time in the rumen may be required which may allow the
rumen microbes to attach and degrade the fibre that may otherwise be resistant
to intestinal enzymes (Salawu et al 1999).
Gas production from date palm leaves was comparable with that from Drinn but lower than from barley straw.
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Received 24 November 2009; Accepted 5 January 2011; Published 6 March 2011