Assessment of determinants for reducing HCN content in Sorghum used for ruminant in Gujarat, India

R K Pandey, Dharmendra Kumar* and K M Jadhav

Department of Veterinary Medicine, College of Veterinary Science and Animal Husbandry,
Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar - 385 506 (Gujarat)
* Animal Nutrition Research Department, Anand Agricultural University, Anand - 388110 (Gujarat).
drdharmendravet@yahoo.co.in

Abstract

An investigation was undertaken to determine the relationship of HCN content in Sorghum with soil nitrogen and phosphorus, plant age at harvest, varieties of Sorghum and find out determinants of reducing HCN content in Sorghum. Data regarding the N and P level of soil of different villages were collected from the soil research station, Deesa, Gujarat. Green Sorghum fodder sample of different varieties at different stages of plant growth were collected on five occasions at 10 days interval from randomly selected ten villages of Banaskantha district.

Out of 250 green Sorghum fodder samples, 8 were negative, 92 showed dark brick red colour and remaining samples showed orange to brick red colour in picrate paper test, which were harvested at 10-20 days after sowing. It indicated presence of comparatively higher HCN content in the immature plants. Significantly (P<0.01) decreasing trend in HCN content was observed with the advancement in the plant growth. Sorghum fodder grown on soil high in N and P had higher HCN content. It was higher in hybrid varieties like duchuniyo, CSH-17 and GJ-39 as compared to local sorghum variety like malavan, also grown as fodder. The HCN content of green (fresh) Sorghum fodder before and after sun drying was almost same, however it was reduced  significantly (P<0.01) to non toxic level on oven drying at different time interval under the study. HCN content is reduced to non-toxic level after 45-50 days of sowing in most of the varieties of Sorghum fodder except ; GJ-39 and CSH-17. It was concluded that Green Sorghum fodder can be fed safely after 45-50 days of sowing or at any stage of growth after oven drying.

Key words: hybrid variety, nitrogen, phosphorus

Introduction

Sorghum is extensively grown as a major source of fodder as it is preferred over Maize (Zea maize L.) because of its high tolerance to various stresses (Reddy et al 2004). Among all Sorghum growing countries, India rank first in the geographic area and third in the production. The total area under cultivation and production of Sorghum during 2008 was estimated to be 7.76 million hectare (21.5% of world) and 7.90 million tonnes (12.6% of world), respectively with the average grain yield of 798 kg/ha (FAO 2009), therefore Sorghum plays a vital role in providing fodder to dairy animals.

Sorghum fodders contain cyanogenic glucoside which liberates HCN in the rumen and may be fatal to ruminants (Holmes 1966). Srinivasa et al (2006) and AL-Sultan (2003) reported high HCN content in the sorghum plant in early growth stage, which decreased with plant maturity. ELObeid et al (2006) and Mohanraj et al (2006) reported greater variability of HCN among sorghum genotypes. Aziz and Abdel- Gwad (2008) and Gladis et al (1999) reported that higher levels of nitrogen application increased the HCN in sorghum, however, information regarding determinants of reducing HCN content in Sorghum is scanty. The present work aimed to determine the relationship of sorghum HCN content with soil nitrogen and phosphorus, plant age at harvest, varieties of sorghum and find out determinants of reducing HCN content in Sorghum.

Materials and Methods

The present investigation was conducted in randomly selected ten villages from five talukas (two villages/taluka) viz. Palanpur, Vadgam, Dantiwada,  Deesa and Dhanera of Banaskantha district. The climate of the area is tropical and semi arid. Information on package of practices followed for cultivation of Sorghum in these villages was collected from individual farmer with the fair degree of precision based on a questionnaire developed. Data regarding the N, P and K level of soil of different villages were collected from the soil research station, Deesa, Gujarat.

Sample preparation

The green fodder samples of different Sorghum varieties ( hybrid viz. duchiniyo, GJ-39, CSH-14, CSH-17 grown at SRS, Deesa and local (malavan) being cultivated at villages) were collected on five occasions at 10 days interval. Samples collected were separately chopped into small pieces using knife and 100 gram of samples were placed in aluminum dish and kept under direct sunlight for 24 hours, another set of  100 gram of sample placed in aluminum dish was kept in hot air oven at 100^oC for 24 hours for moisture estimation. The HCN content was determined in green as well as sundried  and oven dried samples.

Analytical methods

Qualitative analysis

Qualitative and Quantitative analysis of hydrocyanic acid in the sample was carried out as suggested by Hogg and Ahlgren (1942). Qualitative analysis (picrate paper test):

(i)         Two gram of chopped green or dry sorghum fodder was taken into the test tube.
(ii)        Sample was moistened by adding few drop of distilled water.
(iii)       Then few drops of  chloroform were added.
(iv)       The freshly prepared sodium picrate strips (dipping whatmann no. 1 filter paper strip into 1% picric acid and 10% sodium carbonate solution) were inserted in the test tube immediately in hanging position without touching sides or sample. The test tubes were rubber corked tightly.
(v)        Colour development of strips were began after 5 minutes.
(vi)       The tube with the content were then kept at room temperature for minimum six hours, paper changes from yellow to brick red according to level of hydrocyanic acid.

Quantitative analysis:

(i)         Dried picrate paper strips used in the qualitative test were removed and chopped using scissor into the test tube containing 10 ml distilled water.
(ii)        The samples were thoroughly mixed by cyclomixture and centrifuged at 5000 rpm for 10 minutes.
(iii)       The supernatant was examined for colour intensity using spectronic 20 at 520 nm and compared with the standard.

Statistical analysis

The data were analyzed statistically as per Snedecor and Cochran (1994).

Results and Discussion

Agro climatic conditions and package of practices

In Gujarat, Sorghum is grown throughout the year either for the grain or fodder production. Sorghum is the most widely grown forage crop in summer season due to its better productivity, palatability, high dry matter digestibility and greater adaptability. While preparing the land, the farmers mix farm yard manure thoroughly with the soil. About 80 kg (N) and 40 kg (P₂O₅)/ hectare was added as chemical fertilizer. However, these practices slightly varied between the villages and individual farmers. Soil of the Banaskantha district is sandy and loamy, low in nitrogen (1-1.47%), low (1-1.65%) or medium (1.9-2.0%) in phosphorous in Vagdha, Narasan and Sikariya, while high in potassium (3%), but in some villages like Narasan, high nitrogen percentage (2.7%) was recorded. Higher nitrogen level may be associated with continuous use of urea as preferred fertilizer. The farmers of the area under study practiced more or less similar pattern of cultivation of Sorghum fodder. The farmers in these areas sowed the Sorghum mainly by broadcasting but some uses drilling methods (for fodder purpose).

HCN content

Out of 250 green Sorghum fodder samples, 8 were negative, 92 showed dark brick red colour (Table-1) and remaining samples showed orange to brick red colour in picrate paper test, which were harvested at 10-20 days after sowing. It indicates presence of comparatively higher HCN content in the immature plants. Samples collected towards the maturity of plant revealed either absence or reduced intensity of reaction. This is in agreement with work on picrate paper expressing intensity of colour development (Joshi and Lalwani 1977).

Variation due to soil nitrogen and phosphorus  

The HCN content of the green Sorghum fodder samples within the villages  at different period of collection are presented in Table-2. In Palanpur taluka the lower HCN contents in Vagdha village compared to Khumbhasan may be attributed to higher P content of soil (Shaikh and Zende 1971). In Vadgam taluka HCN content in  samples collected from Narasan village revealed significantly (P<0.01) higher HCN content than the Magarwada village at the same stage of growth. This may be attributed to higher level of nitrogen in the soil of this village. These  observation are in agreement with Aziz and Abdel- Gowd (2008) who reported that higher levels of nitrogen application increased the HCN in sorghum. The HCN content of samples from Sorghum Research Station (SRS), Deesa revealed consistently significantly (P<0.05) higher HCN content than the contemporary samples collected from village Sikariya at different stages of growth. This might be due to variation in the Sorghum varieties grown as fodder.

Variation between the plant age

The district average of HCN content of Sorghum fodder (Table-2)  was 146 ± 12.4, 91.0 ± 7.62, 50.2 ± 4.33, 24.2 ± 2.33 and 13.2 ± 1.31 mg %, respectively in fodder samples when harvested at  10, 20, 30, 40 and 50 days after sowing. The decreasing trend in HCN content was observed with the advancement in the fodder growth. The difference for the same were highly significant (P<0.01). Similar observations have been recorded by Kumar and Devendra (2010) who reported that mean HCN content declined with plant maturity.

Variation between different varieties of Sorghum

There is variation in HCN content (Table-3) at the same stage in different varieties. Duchiniyo, GJ-39 and CSH-17 had higher HCN content (464-15.3 mg%) as compared to malavan (175-8.79 mg%) in which CSH-17 had consistently higher HCN content from the first sampling onward i.e. 464, 261, 146, 72.9 and 35.7 mg% at 10, 20, 30, 40 and 50 days, respectively while Malavan variety showed the lowest HCN content for the similar periodic sampling. HCN content is reduced to non toxic level (< 20mg%) after 45-50 days of sowing in most of the varieties of Sorghum fodder except; Gj-39 and CSH-17. Similar variation have also been reported by Patel et al (1984) that high variation in the HCN content in the range of 5.28 (S-1049) to 75.36 (JS-3) mg % in different varieties of Sorghum at one month post sowing.

Higher HCN content was recorded in hybrid varieties as compared to local variety viz. malavan, which is also grown for fodder purpose. This might be due to difference in cultivation practices like rate of fertilizer application, and Managemental practices (drilling method of seeding at distance of 20-30 cm used at SRS, Deesa but broadcasting method in Sikariya) adopted in order to obtain higher yield of green Sorghum fodder. These differences could be attributed to wider spacing during sowing. Similar findings of  genotypic differences for HCN in sorghum were also reported earlier by EL Obeid et al (2006) and Mohanraj et al (2006). Blood and Henderson (1963) reported that the hybrid of Johnson grass (S.halpense), Sudan grass (S.sudanse) and Sorghum (Sorghum bicolor) were more toxic than the pure species.

Variation in HCN as green (fresh), sun dried and oven dried Sorghum sample 

The HCN content of green Sorghum fodder showed no difference between sun dried and green (fresh) samples but highly significant differences (P<0.01) with oven dried sample in all the collections studied (Table-4). It was observed that in samples collected after 10 days and oven dried, the HCN content was reduced to non toxic level. This is in agreement with the findings of Leather (1906), Swanson (1921) and Acharya (1933) who reported only partial decrease in HCN content after 24 hours sun drying and significant difference could only be achieved when samples were oven dried.

Conclusions

• The Sorghum fodder grown on soil high in N and P had higher HCN content and hybrid varieties have higher HCN content than the local variety.

• The HCN content of the green Sorghum fodder showed decreasing trend with the advancement of age of the fodder from 10 days onward after sowing.

• Sun drying of Sorghum fodder for 24 hours did not show any effect on its HCN content; however, it was reduced to non toxic level on oven drying.

• The farmers are advised to harvest green sorghum fodder not earlier than 45 days after sowing however, in scarcity condition Sorghum fodder can be harvested during early stage  and  fed safely to animals after oven drying.

Acknowledgement

Authors are thankful to Director of research Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar, Gujarat, India for providing necessary facilities to carry this work. Part of MVSc. (Veterinary Medicine) Thesis approved by Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar –385 506 (Gujarat)

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Received 10 October 2010; Accepted 26 November 2010; Published 6 March 2011

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