| Livestock Research for Rural Development 21 (12) 2009 | Guide for preparation of papers | LRRD News | Citation of this paper |
The research was undertaken from mid September 2006 to January 2007 at Dembia trial site of Gondar Agricultural Research Center. The aim of the study was to evaluate the β-ODAP content in forage, grain and straw of improved and local grass pea lines. The treatments were six grass pea accessions replicated three times and arranged in a randomized complete block design (RCBD). The four treatments of grass pea accessions (ILAT-LS-LS-B1, ILAT-LS-LS-B2, ILAT-LS-K-290 and ILAT-LS-610) were brought from Debre Zeit Agricultural Research Center (DZARC) and the two local lines Kok- Egir and Shanko were collected from the study area based on their seed coat color. Analysis of variance showed significant (P< 0.05) variation among grass pea accessions in β-ODAP content of straw, grain and forage DM with a mean of 0.15 %, 0.25 % and 0.23 %, respectively. Improved grass pea lines that where brought from DZARC showed low ODAP content compared to the locally available lines.
Therefore, improvement and dissemination of low β-ODAP grass pea varieties would be of great help to the resource-poor farmers in providing protein-rich food and nutritious fodder/feed for the livestock. Additional comprehensive study is required to evaluate the impact on meat and milk through feeding of grass pea grain and fodder for different class of animals.
Keywords: Accession, dry matter, grass pea and Lathyrism
Grass pea (Lathyrus sativus L.) could have an important role in human and livestock nutrition in the resource poor countries that have large area of semi-arid land. Grass pea is a very hardy crop, with tolerance to many of the diseases that affects other pulses and often grown on residual moisture (Chowdhury et al 2001).
In Ethiopia, grass pea is grown in cambisol and vertisols. It occupies 8.7 % of the total area and 7.6 % of the total production of food legumes in the country (Woldamlak and Alelign 1990).The area cultivated is increasing from time to time as a result of the increasing problem of growing other crops in many parts of the country due to shortage of moisture. Grass pea is grown both as feed for livestock and as a grain crop for humans. The crop is an excellent fodder crop with its reliable yield and high protein content. Grass pea also plays an important role in many farming systems by providing fertilizer (like all legumes it fixes nitrogen from the atmosphere) in different intercropping schemes.
In common with those of other grain legumes, grass pea seeds contain a variety of anti-nutritional factors. The presence of trypsin inhibitors, tannins and β-ODAP has also been established in selected Ethiopian grass pea germ plasm collections (Urga et al 2005). Beta-oxalyl-diamino-propionic acid (β-ODAP) is a neurotoxic secondary metabolite present in the legume Lathyrus sativus. The neurotoxic non-protein amino acid causes irreversible spastic paralysis of the legs known as neurolathyrism, when it is consumed as a major portion of the diet over a three-to-four month period (Urga et al 2005). Both ruminants and monogastric species are affected with monogastrics presumably affected more (Hanbury et al 2000).
The content of neuro-toxin in the seed of local varieties can be anywhere between 0.37 to 1.2 % (Tekele Haimanot et al 1993). Lathyrism is endemic to many parts of the world that have significant areas of Lathyrus sativus cultivation namely India, Bangladesh, Ethiopia and Nepal. Outbreaks were also reported in Afganistan, Algeria, China, France, Germany, Italy, Pakistan, Romania, Russia, Spain and Syria (Hugon et al 2000). In Ethiopia neurolathyrism is a widespread problem and occurs in recurrent epidemics in the north, north east and central parts following heavy consumption of grass pea seeds. Although sporadic cases of neurolathyrism also appear in normal years, the disease is highly prevalent in times of food shortages following flooding or famine (Getahun et al 1999).
Most studies on the Lathyrus sativus in Ethiopia have centered mainly on its agronomic characters, β-ODAP content in seed in selected germ plasm collections and prevalence of neurolathyrism. However, information of β-ODAP content from local grass pea forage dry matter (DM) and straw is scanty. The purpose of this investigation was, therefore, to evaluate the β-ODAP content in forage DM, grain and straw of improved lines and local grass pea land-races.
The study was conducted at Dembia trial site of Gondar Agricultural Research Center, Ethiopia located at an altitude of 1800 m.a.s.l. The average annual rainfall is 800 to 1200 mm and the average minimum and maximum temperatures range from 13 °C and 27 °C with a mean of 19 °C. The soil type of experimental site was black clay soil. The livestock population of the Dembia district is estimated to be 191,316 cattle, 10,370 sheep, 20,113 goats, 20,337 equines (ILDP 2006).
The research was undertaken from mid September 2006 to January 2007 and the treatments were six different grass pea accessions (ILAT-LS-LS-B1, ILAT-LS-LS-B2, ILAT-LS-K-290, and ILAT-LS-610, Kok-Egir and Shanko seed coat color). Each treatment was replicated three times and was arranged in a randomized complete block design (RCBD). The first four grass pea accessions brought from Debre Zeit Agricultural Research Center (DZARC). The last two namely, Shanko and Kok-Egir were local grass pea accessions with a black and grey seed coat color, respectively, were collected from the study area. The treatments were sown on September 2007 when field moisture is good at seeding rate of 40 kg/ha. The spacing between replications/blocks was 2 meters. Each replication had 6 plots (treatments). The plot size was 2 m x 4 m and the spacing between plots was 1.5 meter. The experiment was done on a total area of 10 m X 37m (370 m2).
Forage samples were taken from half part of the plot and seed and straw were harvested at maturing stage with sickle from the rest of the plot. The forge harvested from each plot was weighed, labeled and air dried and then dried with dry oven at a temperature of 60 oC until the sample weight becomes constant. β-ODAP content analysis on forage DM, straw and grain was done at Addis Ababa University, Department of Chemistry, using Rao (1978) method. Data were subjected to analyses of variance (ANOVA) using SAS statistical package for β-ODAP content of forage DM, grain and straw and subsequent comparison of means were carried out by the least significant (LSD) test.
Analysis of variance showed significant (P< 0.05) variation among grass pea accessions on β-ODAP content of forage DM, grain and straw (Table 1). The β-ODAP content of forage-DM ranged from 0.19 to 0.34 % with a mean value of 0.26 %.
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Table 1. Mean β-ODAP content of forage DM, grain and straw yield of grass pea |
|||
|
Treatments |
Parameters |
||
|
Forage DM, % |
Grain, % |
Straw, % |
|
|
ILT-LS-LS-B1 |
0.19d |
0.20b |
0.14bc |
|
ILT-LS-LS-B2 |
0.19d |
0.23b |
0.13c |
|
ILT-LS-K-290 |
0.24dc |
0.25b |
0.14bc |
|
ILT-LS-610 |
0.27bc |
0.25b |
0.18abc |
|
Kok-Egir |
0.33ab |
0.35ab |
0.21a |
|
Shanko |
0.34a |
0.45a |
0.20ab |
|
Mean |
0.26 |
0.29 |
0.16 |
|
SE (±) |
0.02 |
0.06 |
0.02 |
|
LSD (0.05) |
0.06 |
0.18 |
0.07 |
|
CV, % |
12.58 |
33.33 |
23.59 |
|
abc means with different superscripts within columns are significantly
different (P<
0.05); DM= dry matter, LSD= least significant difference, |
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The highest β-ODAP content of forage DM was found from grass pea accessions of Kok-Egir and Shanko with values 0.33 % and 0.34 %, respectively. The β-ODAP content of grain ranged from 0.20 to 0.45 % with a mean value of 0.29 %. The highest β-ODAP content of grain was found from grass pea accessions of Kok-Egir and Shanko with values of 0.35 % and 0.45 %, respectively. The β-ODAP content of straw ranged from 0.13 to 0.21 % with a mean value of 0.16 %.
The present study indicates a high variability in β-ODAP levels between different lines and parameters. Our results further evidence that the Lathyrus sativus are characterized as low to high neurotoxic lines which the level of β-ODAP is quite variable, between 0.19 to 0.34% for forage DM, 0.20 to 0.45% for grain and 0.13 to 0.21% for straw. The lines collected on the study area showed high β-ODAP concentration on grain and forage as compared to lines that brought from DZARC, while in the straw β-ODAP content compared to the forage and grain it showed low concentration. Similarly report from DZARC (2007) showed in the plant the β-ODAP concentrations vary widely in different organs with the highest occurring in the embryo, followed by cotyledon, seed coat, stem, leaf and root in decreasing levels. In addition, the report indicated that Ethiopia grass pea has β-ODAP content ranged between 0.20 to 0.55% of the seed fresh weight.
Furthermore, Wuletaw (1999) reported mean β-ODAP contents of grass pea were ranged from 0.31 to 0.62 % in seed of local land races. Such variability of the level of β-ODAP in seeds of Lathyrus sativus samples is also in agreement with similar previous reports (Urga et al 2005). Although the concentrations of β-ODAP reported in this paper are similar to the results previously reported, it must be emphasized that β-ODAP levels, even within the same species, may be influenced by environment and agronomic practices. Lines totally lacking in β-ODAP have not yet been identified in present breeding programmes, but there have been several reports of levels as low as 0.01% from Canada, ICARDA and Ethiopia (Campbell 1997).Thus development of safer cultivars of Lathyrus sativus will likely continue to be dependent in some degree on the development of genotypes that express low levels of β-ODAP in given environments.
Feeding trials conducted by Rotter et al (1991) using grass pea cultivars with much lower β-ODAP contents (0.27, 0.22 and 0.13%), they suggest maximum inclusion up to 40 % for low β-ODAP (0.13 %) and 20 % for the 0.27 % β-ODAP cultivars in poultry ration. While, higher value (0.495 %) by Alemu et al (2003) indicated that increased proportion of grass pea in the diet of young chicken decreased weight gain, feed intake and efficiencies of feed conversion. Similarly Hanbury et al (2000) reported that poultry show depressed performance when grass pea is included in the diet at level of 15 % or higher. Evidence exists indicating that sheep rumen micro flora adapt β-ODAP and break it down (Rasmussen et al 1992).
Like other legumes grass pea have high levels of protein, carbohydrates and minerals for humans and animals. The main limitation is the presence of various anti-nutritional factors, particularly the neurotoxin β-ODAP which could greatly undermine the potentials otherwise very tasty, nutritious, easily cultivated and hardy crop in Ethiopia and other countries. The present study also revealed that some cultivars from improved lines brought from DZARC have low toxin content, while high β-ODAP content from the local land-races in forage and seed. Therefore, improvement and dissemination of low β-ODAP grass pea varieties would be of great help to the resource-poor farmers in providing protein-rich food and nutritious fodder/feed for the livestock. Additional comprehensive study is required to evaluate the impact on meat and milk through feeding of grass pea grain and fodder for different class of animals.
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Received 8 September 2009; Accepted 6 October 2009; Published 3 December 2009