Custom services
text in 
English (pdf)
Article in xml format
Article references
Send this article by e-mail
Cited by SciELO 
Similars in
SciELO 
Permalink
Introduction
Livestock rearing and animal husbandry is on the increase globally. The need for high fodder yield and nutritious crops to meet the daily demands of several millions of cattle heads also increases accordingly. The major and cheapest sources of feed supply to livestock are forage crops and availability of forage crop with good quality is a panacea to successful livestock farming. For this purpose, pearl millet (Pennisetum glaucum L.) and Napier grass (Pennisetum purpureum Schumach.) which are the two most economically important members of the genus Pennisetum could be an excellent choice. Pearl millet is the most popular millet, it is grown mainly in arid and semi-arid zones primarily for human consumption and as forage crop. The crop is well adapted to environments characterized by drought, low soil fertility, and high salinity, thus, pearl millet can be grown in areas where other cereal such as maize, wheat or rice may not survive (FAO/ICRISAT 1996). Pearl millet is often used as hay, silage and green chop by livestock smallholder farmers and it is a preferred choice of forage due to low prussic acid and tannins content, which made it safe for the remnants (Newman et al. 2010).
On other hand, Napier grass (P. purpureum) also known as elephant grass, is of great importance to tropic agriculture. It is a robust, rhizomatous, invasive, perennial grass that can be grown under a wide range of environmental conditions and cropping systems (Farrell et al. 2002). Napier grass is a valuable “cut-and-carry” forage mainly used as feed in stalls, or made into silage and hay (Mannetje 1992 and FAO 2015). The annual productivity biomass yield is between 20 to 30 t DM/ha if grown under good agronomic and management practices (Skerman et al. 1990 and Farrell et al. 2002). Napier grass can be grazed at lush vegetative stage or cut as fodder for later use, its other uses are documented elsewhere (Burkill 1994 and EPA 2013). Based on chemical composition and dry matter digestibility, Napier grass is a high quality forage (Tessema 2005). The dry matter yield of Napier grass surpasses that of other tropical grasses (Skerman and Riveros 1990) and the grass can provide a continual supply of green forage throughout the year (Humphreys, 1994).
Inadequate or low quality feed is a major constraint to livestock production by smallholder farmers (Anindo and Potter 1994). The performance of forage species in term of yield and nutritional quality are important factors in choosing fodder for animal feed. Hence, it is imperative to evaluate and compare the forage yield and nutrient qualities of major forage crops so as to ascertain their nutritional potentials and to identify the best species or accession for utilization. Therefore, the present study comparatively evaluate the yield and nutrient content of pearl millet and Napier grass to determine the accession with highest potential agronomical and forage utilization.
Material and Methods
Plant materials. Eight accessions comprising of four pearl millet (NGB0055, IP17862, IP3122 and IP22269) and four Napier grass (Omuo-Green, Omuo-Purple, COM-CO3 and COM-CO4) were used for the study. NBG0055 was collected from National Centre for Genetic Resources and Biotechnology, Ibadan, Nigeria. IP17862, IP3122 and IP22269 were collected from International Crops Research Institute for the Semi-Arid Tropics, India. The Napier grass Omuo-Green, and Omuo-Purple were sourced from the wild population in Omuo-Ekit, Ekiti State, Nigeria while COM-CO3 and COM-CO4 were collected from University of Agriculture, Coimbatore, Tamil-Nadul, India.
Experimental field. The field experiment was conducted at C. G. Bhakta Institute of Biotechnology (CGBIBT), Uka Tarsadia University (UTU), Bardoli, Gujarat, India during the monsoon (July- Sept) 2015. UTU is located on latitude 21.04°N, longitude 073.03°E and at elevation of 39 feet above sea level. The local annual average maximum temperatures was 33 °C and the minimum was 22 °C. The mean rainfall for the year was 117.6 mm, the wettest month was July with an average of 441.96 mm and the driest month was March with 0.0 mm precipitation. The annual maximum and minimum average relative humidity were 77 % and 54 % respectively, the estimated average day-light was 12.5 hours (Indian Metrological Society 2016).
Soil characteristic and preparation. The field was basically sandy clay-loam soil. Prior to the commencement of the field experiment, soil samples were taken randomLy from eight points (0-30 cm depth) for physical and chemical analyses. The analyses were conducted using the methods described by Cottenie et al. (1982) and But (2004). The soil was fluvisol, clay-loam with pH 4.9 and electrical conductivity of 1.21 dS∙m−1. The percentage organic matter was 4.81 %, total nitrogen 0.36 % and available phosphorous of was 2.58 (ppm). The land was cleared, ploughed and made into ridges with 30 cm in-between rows.
Morphological and yield evaluation. Evaluation of morpho-agronomic traits and biomass yield of the pearl millet and Napier grass accessions was carried out in a randomized complete block design of plot size 2 m x 4 m in three replicates. Pearl millet seeds were sown in single row of 30 cm apart and in- between the rows using a seed rate of 15 kg∙ha-1. The Napier grass clones (stem cuttings) with two nodes were planted at a depth of 15-20 cm at an angle of 45º. The inter and intra spacing of the Napier grass was 0.5 x 1 m making a total of 25 stem cuttings per plot. Plants along the borders of plots were excluded from measurement. Only 10 stool per plot in three replicates were sampled for morphological character. Morphological characters evaluated at 10 weeks after planting include plant heights, leaf length and leaf breadth which were measured with tape rule, number of leaf and tiller per plant were counted while stem girth was measured using electronic vernier caliper (Titan 2378 Model) at 10 cm above the ground level.
Nutrient analysis. Shoot samples of each accession were analyzed for moisture (AOAC 1990). The amount of nitrogen was determined by Kjeldahl method from which crude protein was calculated as total N×4.43 (Yeoh and Wee 1994). Soluble sugar and total carbohydrate were estimated using the method of Nelson (1944). The ash, calcium, magnesium, potassium, zinc, iron and phosphorus contents were determined according to the procedures of AOAC (1990). Neutral (NDF) and acid detergent fibers (ADF) were estimated according to the method described by Van Soest et al. (1991).
Dry matter (DM) determination. Each of the 10 plants from a plot were clipped at 5 cm from ground level, then the weight of the bulked samples for each accession were determined. From the bulked sample, about 300 g were taken for each accession for dry matter analysis. The dry matter samples were oven- dried at 60 °C for 48 h and the percentage dry matter determined by weight.
Data analysis. Data from the vegetative yield and nutrient composition were subject to analysis of variance (ANOVA) using SPSS version 17. Duncan Multiple Range Test (DMRT) was used to test the differences between means and differences between means were considered significant if p-values were less than 0.05.
Results
Growth and vegetative characteristics of the pearl millet and Napier grass accessions at 10 weeks after planting (WAP) showed variation in the parameters evaluated as shown in table 1. Among the pearl millet accessions, plant height was statistically higher for NGB00551 and IP22269. In contrast, plant height was not significantly different for the Napier grass accessions with the exception of COM-CO4 which produced the least average plant height of 91.02 cm. Leaf formation per plant was significantly higher (29.00 - 17.00) for Napier grass than the pearl millet accessions (8.20-10.00). Meanwhile, significant intra an inter-specific variations were recorded for the accessions in term of leaf length. Generally, Napier grass accessions had longer and broader leaves than the pearl millet, nevertheless, pearl millet NGB00551 and IP17862 had most significantly narrow leaves. Stem girth was statistically higher in Napier grass than the millet accessions (table 1). The trend was similar for number of tiller per plant. While tiller per plant ranged from 0.48-0.89 among pearl millet, profuse tillering (18.21-31.55) were recorded for Napier grass accessions at 10 WAP.
Table 1 Vegetative characteristics of the pearl millet and Napier grass accessions at 10-weeks after planting
SEM = pooled standard error of the means. Means sharing the same case letter do not differ significantly at p < 0.05. PH =Plant height; NL = Number of leaves/plant; LL = Leaf length; LB = leaf breadth; SG= Stem girth; NTP = Number of tiller/plant
The degree of hairiness varied among the accessions, pearl millet accessions were scantly hairy; IP3132 had no visible trichomes (table 2). Napier grass accessions Omuo-Green and Omuo-Purple were densely pubescent, but COM-CO-3 and COM-CO4 were sparsely hairy around the leaf sheath.
Table 2 Hairiness pattern of accessions of pearl millet and Napier grass at different stages of growth
- No hair; + Scanty hairy; ++ Medium hairy; +++ Densely hairy
WAP = Weeks after planting
The total soluble sugar and carbohydrate content was higher in the pearl millet than the Napier grass accessions. Among the Napier grass, Omuo-Purple had the least total soluble sugar and carbohydrate (0.33 mg mL-1; 0.36 mg mL-1) (table 3). In term of calcium composition, pearl millet were higher than the Napier grass, however, among the Napier grass accession, COM-3 and COM-4 contained higher amount of calcium. This trend was similar for magnesium content of the accessions. Meanwhile, amount of potassium, phosphorous, iron and zinc constituents were higher for the millet accessions, although, Napier grass accessions COM-3 and COM-4 contained amount similar to the millets, the least of these elemental nutrients were found in the Omuo-Purple accession of Napier grass.
Table 3 Chemical composition of the leaf and stem of Napier grass and pearl millet accession
The table consists of the means and the standard error
Key: TSS = Total soluble sugar; TC = Total carbohydrate
The dry matter yield ranged from 11.67 to 8.67 t/ha and 6.28 to 4.16 t/ha for Napier grass and pearl millet accessions respectively (table 4). Accessions Omuo-Green and COM-CO3 had significantly highest dry matter while pearl millet IP17862 and IP3122 had the least performance in term of dry matter yield. The total crude protein composition of the accessions were statistically comparable with the least found on IP22269 millet accession. The acid detergent fibre (ADF) and neutral detergent fibre (NDF) were less in pearl millet than the Napier grass. While NGB00551 maintained the lead in these parameters among the pearl millet accession, Omuo-Purple had highest values among the Napier grass group. Contrary to variations obtained in dry matter, crude protein, acid and neutral detergent fibers of the accessions, their ash content were similar and not significantly different (table 4).
Table 4 Dry matter and nutrient composition of pearl millet and Napier grass for forage assessment
SEM = pooled standard error of the means. Means sharing the same case letter do not differ significantly at p < 0.05. DM = Dry matter; CP = Crude protein; ADF = Acid detergent fibre; NDF = Neutral detergent fibre; AS = Ash
Discussion
Pearl millet has high protein and energy with low fibre content and Napier grass is economically important for its quality feed for grazing, green chop, hay, or silage (Jennings et al. 2010). Comparative evaluation of yield performance and nutritional composition of the two most economic important forage grasses in the genus Pennisetum is very important for their preferential utilization in animal nutrition. Plant height, number of leaf and leaf dimensions are significant growth attributes which are directly linked with productivity and yield parameters of plant. The present results showed Napier grass attained height above 1 m at 10 WAP with high number of leaf per plant which indicated it high forage yielding capacity. The growth pattern observed in this study concurred with Orodho (2006) and Kebede et al. (2016) who reported plant height between 1.0-1.2 m in Napier grass at 3 months (12 weeks) after planting. Furthermore, the vegetative growth obtained for pearl millet in the present study was similar to earlier report (Amodu et al. 2007). The intra-specific variation in vegetative parameters in the accessions may be due to differential response to environment, disparity in genetic makeup or internal genetic control of the accessions (Animasaun et al. 2017). Since forage yield is directly proportional to vegetative growth, thus, Napier grass had higher green forage yield than the pearl millet. More vigorous vegetative growth which translated to bigger stem diameter, more number of leaves per plant and greater leaf area account for such higher biomass yield as previously noted by Ayub et al. (2012).
Glabrous nature or reduced trichome density in pearl millet accessions could confer better palatability and feeding preference by the ruminants. Napier grass Omuo-Green and Omuo-Purple accessions which were sourced from natural populations are densely hairy, this suggests a wild adaptive characters to prevent excessive browsing by the herbivores. However, if so, it becomes a limitation in its utilization as fodder and may require modification through breeding process.
Comparative shoot nutrient composition analysis of the pearl millet and Napier grass accessions showed that pearl millet is richer in soluble sugar, carbohydrate and elemental minerals viz: calcium, magnesium, potassium, iron and zinc. The presence of these important nutritional minerals in pearl millet gives credence to its preferential utilization as forage crop (Tabosa et al. 1999 and FAO, 2015). Moreover, according to Jennings et al. (2010), pearl millet does not produce hydrocyanic acids (unlike sorghums), hence, there is no risk of poisonous prussic acid, making it a safe fodder (Tabosa et al. 1999). Nevertheless, the nutritive elements in Napier grass significantly influence its usage as forage grass by small farm holders (Devasena et al. 1993). Since the two species have the capability to exchange alleles, their hybrid would carry desirable characteristics that enhance its forage utilization (Dowling et al. 2013).
Significant variation in amount of dry matter, crude protein, neutral detergent fibre (NDF), acid detergent fibre (ADF) and ash content have been reported in earlier studies (Ansah et al. 2010 and Rengsirikul et al. 2013). Phenotypically Napier grass has relatively wider, longer leaves and larger stem girth and cell wall fractions (NDF, ADF) compared to the pearl millet, but lesser crude protein percentage. This finding is in line with the report of Gwayumba et al. (2002) who demonstrated that Bana Napier grass with higher crude protein had lower ADF and NDF values than the French Cameroon Napier grass.
The nutritional quality of forage crop could be strongly influenced by a number of factors such as management practices, harvesting age, and frequency of harvest among others (Keba et al. 2013). Most grasses harvested during the early stage (usually between 10 to 12 weeks) would likely contain relatively higher crude protein content, meanwhile, plant structural components (NDF and ADF) may increase with the days of harvest (Mirza et al. 2002), and high content of NDF and ADF could reduce dry matter digestibility in ruminants (Keba et al. 2013). The nutritional quality of the grasses harvested at 10 WAP in the present study were believed to be of good quality and fall in range with those reported for Napier grass (Wangchuk et al. 2015) and pearl millet (Al- Suhaibani, 2011). The time of harvest (10 WAP), possibly accounted for the relatively low amount of NDF found in the studied Napier grass accessions and the values were lesser than the those obtained in overgrown Napier grass (Mukhtar et al. 2003). Considering the fact that pearl millet has relatively high crude protein but less amounts of NDF and ADF which implies higher digestibility, it is considered to be more suitable as a forage for dairy farming.
Conclusions
Two important forage grasses of the genus Pennisetum were compared for yield, dry matter and nutrient composition. Analysis of the data revealed pearl millet contained higher amount of carbohydrate and nutrient elements than the Napier grass accessions. Among the pearl millet accessions, NGB00551 had highest dry matter yield and nutritive values while COM-CO3 showed best performance among the Napier grass accessions. In general, pearl millet has relatively higher crude protein but less amounts of neutral and acid detergent fibers which implies higher digestibility and would therefore be more suitable as a forage than Napier grass. However, to improve the efficient utilization of both Napier grass and pearl millet varieties, hybridization would be necessary.
