Effects of Stylosanthes guianensis and Aeschynomene histrix on the yield, proximate composition and in-situ dry matter and crude protein degradation of Panicum maximum (Ntchisi)

F T Ajayi, O J Babayemi* and A A Taiwo

Institute of Agricultural Research and Training, Obafemi Awolowo University, P.M.B 5029, Moor Plantation, Ibadan, Nigeria
*Department of Animal Science, University of Ibadan, Ibadan, Nigeria
ajayiajay@yahoo.com

Abstract

Dry matter yield, chemical composition and mineral content and nitrogen degradability of four weekly cut grass / legume mixtures were evaluated using fistulated N'dama cattle. Forages evaluated were combinations of Panicum maximum (PM) intercropped with Stylosanthes guianensis (stylo), PM intercropped with Aeschynomene histrix (histrix), PM / stylo mixture, PM / histrix mixture , sole PM, Stylo and histrix. The forages were cultivated in a randomized complete block design with three replicates.

Dry matter yield (Kg / ha) among treatments were significant (P < 0.05), the mean value ranged between 1573 kg / ha in sole PM and 2345 kg / ha in PM intercropped with stylo. The crude protein was between 7.63 and 8.85 g /100g DM. Phosphorus, calcium, sodium and iron content of PM increased when intercropped with histrix and stylo. Dry matter and protein degradability characteristics of forage were evaluated at 0, 6, 12, 24, 48, 72 and 96 hours using the equation P = a + b (1- e ^-ct). The insoluble but fermentable fraction, b ranged from 40.79 in sole PM diet to 42.25 g /100g DM in PM / histrix mixture (P > 0.05). Rate of degradation, c of 2.9 % h^-1 was obtained in sole PM diet, better results were obtained for the PM / legume mixtures and the sole legumes. Potential degradability of substrates ranged from 66.03 in PM only to 66.63 g /100g DM in PM / histrix mixture. Protein degradability of b was better in PM / legume mixtures (P < 0.05) than the PM only. The mean values of c ranged from 4.0 % h^-1 in PM only to 7.0 % h^-1 in PM / stylo mixture . The potential degradability, a + b ranged from 47.62 in PM only to 60.39 g / 100g DM in PM / stylo mixture. Significant correlation (P < 0.05) existed between b value of dry matter (DM) and N- degradation as well as the DM and CP content of the diets. The potential degradability values of N- degradation and the DM and CP content of the proximate composition of the diets were significantly correlated (P < 0.05). The effective degradation values of DM and N- degradability of the ether extracts and Nitrogen Free Extract (NFE) were highly correlated (P < 0.01).

This result showed that intercropping Panicum maximum with Aeschynomene histrix or Stylosanthes guianensis would result in increase in the nutritional status of the Panicum maximum and enhances better degradability.

Keywords: Aeschynomene histrix, composition, degradability, grass / legume mixed pastures, Panicum maximum, Stylosanthes guianensis

Introduction

Pastures deteriorate very fast due to continuous grazing by ruminants especially when there is no improvement. This leads to poor nutritional intake by ruminants and hence poor performance in terms of slow growth and low reproductive potential. One of the logical approaches to alleviating these problems is pasture improvement vis-a-vis incorporation of forage legumes into native grass swards or grass / legume mixed pasture cultivation.

Herbaceous forage legumes have been identified as potential protein supplements for ruminants since they contain high crude protein (150 -300 g/kg DM), minerals and vitamins needed for the growth of ruminal microbes (Norton and Poppi 1995). Protein supplementation of grass diets containing 70 g CP / kg DM or less has been reported to increase dry matter intake, dry matter digestibility and animal performance (Osuji et al 1993; Umuna et al 1995).

An assessment of the performance of goats raised on grass improved by nitrogen fertilization and grass incorporated with forage legumes have been reported (Bamikole et al 2001). The authors observed that high nitrogen content of N-fertilized grass could not be efficiently utilized in the rumen of goats. Thus leading to high total nitrogen excretion by the animals fed the grass.

The use of N-fertilizer to improve grassland is undesirable because it is uneconomical and could increase environmentally related problems (Bamikole et al 2001) due to excessive release of nitrogenous compounds. The use of herbaceous or tree legumes have been reported (Ezenwa and Aken'ova 1988; Bamikole and Ezenwa 1999). Compatibility studies involving Panicum maximum with Pueraria phaseoloides, vigna species, Calogoponia mucoides and Centrosema pubescens have been carried out and reported (Kavana et al 2005). Pennisetum purpureum (Napier grass) have also been combined with Macroptilium atropurpureum (sitratro) (Kavana et al 2005)

Panicum maximum is the most outstanding grass for hay making due to its high biomass and dry matter yield and is well cherished by ruminants (Ademosun 1992). One of the major reasons for its low nutritive value most times is the soil condition on which it is grown. This is because herbaceous legumes are not usually found in grazing areas to improve the grass. Therefore, the objective of this study was to evaluate the effects of Stylosanthes guianensis and Aeschynomene histrix on the yield, proximate composition, dry matter and crude protein degradability of Panicum maximum.
 

Materials and methods

Pasture cultivation

The experiment was conducted at the Dairy Unit of the Institute of Agricultural Research and Training, Ibadan, Nigeria (Latitude 7^o15¹-7^o30¹ N and Longitude 3^o 45¹ - 4^o E) between March and October in 2004 and 2005. The area has a humid climate, the mean annual rainfall during the experimental period being 805 mm and 1350 mm for 2004 and 2005 respectively. The mean monthly temperature was 31 ^oC for each year.

After land preparation, the land was divided into fifteen plots each measuring 15 m x 6 m. Panicum maximum was cultivated in all plots at 1m x 1m using the crown split. The seeds of forage legumes were scarified to break dormancy and to enhance germination. Seeds of Aeschynomene histrix were immersed in hot water at 80 ^oC for 5 minutes while seeds of stylo were rubbed on sandpaper until seed coats were broken. Seeds were air-dried before planting and were intercropped in the sown Panicum maximum plots at 1m x 1m spacing and in the following treatments and proportions

1. Panicum maximum and Aeschynomene histrix 50: 50

2. Panicum maximum and Stylosanthes guianensis 50: 50

3. Panicum maximum 100: 0

4. Aeschynomene histrix 100: 0

5. Stylosanthes guianensis 100: 0

The legume seeds were drilled at 1cm depth soil a month after the establishment of Panicum maximum. Each treatment was replicated thrice in a completely randomized block design.

Pasture harvest

The sole Panicum maximum and legumes as well as the Panicum maximum intercropped with legume were harvested at four week interval for six months. Sub-sample of each harvest was oven dried at 105 ^oC. The dried sub-samples were pooled together and milled with Thompson hammer mill. One part was milled using 1 mm sieve for proximate analysis. The second part of the dried samples was milled with 2 mm sieve for rumen degradation study.

Animal management

An N'dama steer fitted with permanent rumen cannula was used to evaluate the nutritional status of the Panicum maximum intercropped with legume. The steer was allowed an adjustment period of two weeks during which prophylactic treatments of long acting antibiotics and vitamin injections were administered at 1 ml / 10 kg body weight. Levamisole injections at 1 ml / 10 kg body weight was administered against ectoparasites. The steer was fed daily 1 kg of Panicum maximum and 0.2 kg concentrate consisting of maize 15 %, corn bran 25 %, wheat bran 30 %, palm kernel cake 25 %, Oyster shell 4.5 % and salt 0.5 % as supplement. Clean water was given every morning. The pen was cleaned every morning and wood shavings spread on the floor as bedding.

Rumen degradation

2.5 g of the dried samples (n = 3) of Panicum maximum and legume mixed pastures were incubated together at ratio 60:40 in the nylon bags. Conversely, 2.5 g sample of the sole Panicum maximum, stylo and histrix were weighed into the nylon bags (Ørskov et al 1983; Ørskov et al 1988) . The bag measured 5.5 cm x 13.0 cm in size with pore size of 41μ. The bags were incubated in duplicate in the rumen of the steer for 6, 12, 24, 36, 48, 72 and 96 h. The experiment was conducted three times because of the constraint in the use of the fistulated animal. There were six replicates per treatment. Bags were withdrawn by method of sequential addition (Osuji et al 1993). The bags were then washed in cold running water until the rinsed water became clear. The samples obtained were dried in oven at 105 ^oC. The experiment lasted forty days because of the single steer that was used for the study. Washing losses were determined by weighing 2.5 g of each sample in the nylon bags in triplicate and soaked in warm water in a water bath at 37 ^oC for one hour. The samples were washed and dried at 105 ^oC. The exponential equation, PD = a + b (1- e ^-ct) (Ørskov and McDonald 1979 ) was used to describe the samples. PD is the potential degradation, a + b of the substrate, a represents immediate soluble fraction of nutrient, b is insoluble but rumen degradable fraction, c is the rate of degradation of b at time t. ED is effective degradation calculated from the Ørskov curve (Ørskov et al 1980) and considering a rate of passage of 3 % h^-1 .

Chemical analysis

Dried samples were analysed for crude protein using the Kjeldahl procedure (AOAC 1990) method. Dry matter, crude fiber, ether extract and ash were determined according to the Official Methods of Analysis (AOAC 1990). After ashing of samples in a muffle furnace at 550 ^oC, mineral analysis of iron and calcium were read with atomic absorption spectrophotometer. Sodium was read with flame photometer and phosphorus was read with spectrophotometer (AOAC 1990).

Statistical analysis

Data obtained were subjected to the Analysis of Variance procedure of SAS (1987). Treatment means were compared using the Duncan (Duncan 1955) option of the same software.
 

Results

The mean values of treatments differed significantly (P < 0.05) for all parameters considered (Table 1). The highest mean value obtained for dry matter, crude protein and ether extract were for Aeschynomene histrix while the least values were recorded for Panicum maximum.

The dry matter yield (kg / ha) differed significantly (P < 0.05) among the treatment means (Figure 1). The highest yield observed was in Stylosanthes guianensis. Panicum maximum in stylo and histrix intercrop had values of 2345 and 2215 kg / ha respectively and were better than the sole Panicum maximum.

The mean values of the mineral composition of forages differed among the treatments (Table 2).

The mean values of obtained for the Panicum maximum intercropped with legumes were better than the values obtained for the sole Panicum maximum. Phosphorus, and sodium contents of the legumes were not significant (P >0.05). The Iron contents of the Panicum and legume intercrops were higher than values obtained for sole grass and the mixtures.

The mean values of dry matter degradation characteristics for the mixtures and sole Panicum maximum were not significantly different (P > 0.05). However, higher values were obtained for the mixtures than the sole Panicum maximum (Table 3) .

Similarly, the insoluble but degradable fraction and the effective degradability of the feedstuffs were similar (P > 0.05) in the two legumes. Higher values were obtained in the Stylosanthes guianensis.

The mean values of protein degradation characteristics in all the treatments differed (P< 0.05). The values obtained for the mixtures differed significantly (P < 0.05) except in the b, c and PD values (Table 4).

Higher rate of degradation was observed in the legumes than the mixtures and Panicum maximum only.
 

Discussion

The study revealed that intercropping Panicum maximum with Stylosanthes guianensis or Aeschynomene histrix would improve the proximate composition of the Panicum maximum over the sole Panicum maximum.

The values obtained for the proximate composition agreed with earlier report (Ezenwa and Aken'ova 1988) that the effect of the legume component in a grass / legume mixture would increase the quality of the mixture. The value of the crude protein reported for the sole Panicum maximum was higher than value reported elsewhere (Onyimonyi and Ene 2003). Higher values of crude protein were obtained when the Panicum maximum was intercropped with either Stylosanthes guianensis or A. histrix. The values of crude protein and crude fiber obtained for A. histrix agreed with earlier report (Nworgu and Ajayi 2005). The crude protein values obtained were within the requirement of ruminant animals (ARC 1980). The mineral values of A. histrix for calcium, phosphorus and sodium obtained in this study were closer to values reported (Nworgu and Ajayi 2005). The values of the soluble fraction, a (22.34 - 29.07 %) for DM degradation was higher than a value of 20.2 % reported elsewhere (Sibanda et al 1993) for dry matter of cotton seed cake and a value of 19.6 % obtained when cotton seed cake was incubated in combination with maize. The b fraction represent the diet that potentially may escape rumen degradation but absorbed in the rumen (NRC 1985). The b values obtained in this study (40.79 - 44.43 %) were lower than value cited by Sibanda et al (1993). This value compared with 7.12 - 11.5 % reported for dry matter degradation of some tropical seeds reported elsewhere (Odeyinka et al 2004) The lower b values obtained is an indication of the fibrous nature of the feedstuffs incubated. (9.14 - 17.64 %) The c value of 2.9 - 10.2 % h^-1 obtained was higher than 5.3 % h^-1 (Sibanda et al 1993) and 3.5 % h^-1 reported (Tona et al 2003) when combinations of cottonseed cake, dried brewer's grain and Lablab purpureus hay were incubated in N'dama steers. The Potential degradation (PD) of 66.03 - 71.59 g/100 g DM obtained in this study was in line with the range of 48.5 - 87.0 g/100 g DM reported for tropical legumes and grasses (Kimambo et al 1994). The effective degradation (ED) of 33.0 - 44.5 g/100 g DM obtained was also within 39.2 - 59.1 g/100 g DM reported for some tropical grasses (Mgheni et al 1996). The value for ED obtained for Stylosanthes guianensis and A. histrix, 44.5 and 42.0 g/100 g DM respectively agreed with the values of ED for tropical legumes which is 32.3 - 56.2 g /100 g DM (Mgheni et al 1996).

The value of a obtained for CP degradation, 7.79 - 13.47 g/100 g DM was higher than the value of 9.8 % (Sibanda et al 1993) and 6.49 - 11.11 g/100 g DM reported elsewhere (Tona et al 2003). The b values of 39.86 - 49.52 g/100 g DM were lesser than value of 72.90 % reported (Sibanda et al 1993) when cotton seed cake alone was incubated. This may be as a result of the fibrous nature of the test diets in this study. Similar trend was observed in the PD values, lesser values of 47.62 - 62.99 g/100g DM was obtained when compared with value of 82.7 % (Sibanda et al 1993) and 88.36 - 94.30 g/100 g DM reported (Tona et al 2003). The c mean values of 4.0 - 18.4 % h^-1 obtained was higher than 2.0 - 3.3 % h^-1 reported (Tona et al 2003) and lower limit was close to 5.0 % h^-1 (Sibanda et al 1993). This observation may be as a result of the fiber level of the Panicum maximum, Panicum maximum intercropped with Stylosanthes guianensis and Aeschynomene histrix. The higher rate of degradation observed in the legumes was due to the lower fiber contents and high digestible nature of the legumes. The PD mean values of 47.62 - 62.99 g/100 g DM was lesser than 82.7 g/100 g DM cited by Sibanda et al (1993) and 76.8 - 82.4 g/100 g DM (Bamikole et al 2004). However, the values were within the range 48.5 - 87.0 g/100 g DM reported for tropical legumes and grasses (Kimambo et al 1994). The ED of the protein is an estimate of the total amount of nitrogen captured and utilized by the rumen microbiota for growth and synthesis of microbial protein (AFRC 1993). The ED value of 36.0 to 49.5 g/100 g DM obtained in this study was within the range 39.2 - 59.1 g/100 g DM reported for tropical legumes and grasses (Mgheni et al 1996). The values obtained were close to the range of 38.5 - 48.8 g/100 g DM reported (Bamikole et al 2004).
 

Conclusion

• The observed variations in the chemical composition for crude protein and mineral composition of Panicum maximum / legume intercropped suggests that the nutrient composition of guinea grass (Panicum maximum) could be better improved by intercropping legumes into the grass pasture. Better dry matter yield and degradability obtained in Panicum maximum intercropped with legumes showed that pasture improvement through incorporation of legumes in native pasture is a panacea to ruminant livestock production.
   

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Received 12 December 2006; Accepted 13 January 2007; Published 1 March 2007

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