Effect of Stylo 184 (Stylosanthes guianensis CIAT 184) and Gamba grass (Andropogon gayanus cv. Kent) in diets for growing goats

Phonepaseuth Phengsavanh and Inger Ledin^*

Livestock Research Center, National Agriculture and Forestry Research Institute,
Ministry of Agriculture and Forestry, PO Box 811, Vientiane, Lao PDR
p.phengsavanh@cgiar.org
* Department of Animal Nutrition and Management,
Swedish University of Agricultural Sciences, Box 7024, 75007 Uppsala, Sweden

Abstract

The effect of different levels of Stylo 184 in a diet based on Gamba grass was studied in an experiment with 36 male goats of local breed (12.4±0.22 kg) in Lao PDR. The goats were blocked according to weight into three groups and allocated to four treatments, consisting of 4 levels (0, 20, 30 and 40%) of Stylo 184 in the diet based on expected dry matter (DM) intake.

The crude protein (CP) content in Stylo 184 was higher and the neutral detergent fiber (NDF) and acid detergent fiber (ADF) lower than in Gamba grass. Increasing the amount of Stylo 184 resulted in increasing intake of total DM, CP, NDF and ADF. The highest total DM intake, approaching 3% of body weight, was obtained in the diets with 30 and 40% Stylo 184. The highest daily weight gain was 70 g/day with 40%  Stylo 184, but was not significantly different from the diet with 30% of Stylo 184 (64 g/day).

The inclusion of Stylo 184 in a diet based on Gamba grass improved the quality of the diet, which resulted in higher intake and better growth rate.

Keywords: Gamba, goats, growth, intake,  Stylo 184,

Introduction

Smallholder goat raising systems in Southeast Asia are mostly based on traditional methods. Goats have the advantage over other ruminants that they can walk for long distances in search of feed, and this behaviour assists them in meeting their nutrient requirements (Devendra and McLeroy 1982). Such a situation exists in many regions of the tropics, where goats raised in traditional systems mostly roam freely in fallow land, forest and grassland. The main feed resources for animals are native grasses, legumes that occur naturally in grassland, tree leaves and few if any crop residues. In Lao PDR, goat production is small compared to production from other ruminants, but goats still play an important role for smallholders in terms of income generation, function as a bank, and as a meat or protein source, and are also used in traditional ceremonies.

Recently, in addition to problems with parasites that seriously affect small ruminants, there is also a problem of feed shortage, which occurs especially in intensive crop production areas. The increasing human population and resultant change in the environment (lower soil fertility and deforestation) in the last few years have resulted in increasing crop areas. Fences are often constructed around the cropping area, thus affecting the grazing areas. Therefore feed resources that were plentiful in the past do not exist any longer on many farms. Farmers have to spend more time finding feed for their animals (Horne and Stür 1999).

The seasonal effect on native forages is another problem that leads to feed shortage since feeds are abundant only during the wet season and will dry out in the dry season. In the wet season, animals need to be confined or tethered in many areas to avoid damaging of the crops. This is usually the case where there is not enough feed for the goats. In this situation, farmers spend a lot of time and labour to find, cut and carry natural grasses for their animals (Phonepaseuth Phengsavanh  1997). Planting forages for use in cut and carry systems can be an alternative for farmers to overcome feed shortage during the heavy rain period.

According to Phonepaseuth Phengsavanh (1997) there are a few forage species that are well adapted to a wide range of relevant environmental conditions. These species are Andropogon gayanus, Brachiaria spp, Panicum maximum and Stylosanthes quianensis. Of these species, only Andropogon gayanus cv. Kent (Gamba grass) and Stylosanthes quianensis CIAT 184 (Stylo 184), grow reasonably well in both the wet season and long into the dry season, and are also suitable for goat feeding. Brachiaria spp (B. brizantha, B. decumbens and B. ruziziensis) can cause photosensitization and Panicum maximum (Purple guinea) can grow well only in the wet season and on quite fertile soils.

Gamba grass is a tall perennial grass that is readily eaten by livestock when young. It has soft leaves with fine hairs and seed heads on very tall stems up to 4 m with light and fluffy seeds. It grows well on infertile, acid soils in hot climates and in a wide range of climates, but is particularly useful in areas with a long dry season. Gamba grass stays green long into the dry season when most other grasses are already dry, is easy to cut and can tolerate grazing. It needs frequent cutting or it produces seed heads, which are stemmy and unpalatable. It can be easily planted from young rooted tillers but not old tillers. Establishment from seed is often difficult because of poor seed quality (Horne and Stür 1999).

Gamba provides a palatable forage when young but feeding value declines rapidly with age and decreasing leaf/stem ratio. Nitrogen (N) concentrations range from 0.5 to 2% in dry matter, and in vitro dry matter (DM) digestibilities from 40 to 55%. Mineral content is low (0.08 to 0.14% P and 0.27 to 0.39% Ca in DM) (Mannetje and Jones 1992). The main use of Gamba grass is as a forage in permanent pastures grazed by ruminants (Mannetje and Jones 1992). It is also suitable for cut and carry systems.

Stylo 184 is a short-lived perennial legume (2 to 3 years) that grows into a small shrub with some woody stems. It is adapted to a wide range of soils and climates but is one of the few herbaceous legumes which will grow well on infertile, acid soils. It will not grow on very alkaline soils (pH>8). Unlike earlier varieties of S. guianensis (eg. cv. Schofield, Cook and Graham) Stylo 184 has shown good resistance to the fungal disease anthracnose in Southeast Asia. It is usually grown as a cover crop, which is cut every 2 to 3 months. It effectively suppresses weeds and is a good feed supplement for most animals, including chickens, pigs and fish. Stylo 184 can be fed fresh or dried for hay and leaf meal. It does not tolerate being cut close to the ground since there are few buds on the lower stem for regrowth. This can be improved by making the first cut at 10 to 20 cm to encourage branching close to the ground. Subsequent cuts must be made higher (>25 cm) to ensure good regrowth (Horne and Stür 1999). N concentrations of Stylosanthes guianensis range from 1.5 to 3 % in DM. DM digestibility of young plant material lies between 60 to 70%, but with increasing age and lignification this may be reduced to below 40% (Mannetje and Jones 1992).

The aim of this experiment was to study the effect of supplementation with Stylo 184 to a basal diet of Gamba grass on the growth of stall-fed goats in the period of heavy rains. The hypothesis was that feeding improved forages (Gamba and Stylo 184) to goats will increase productivity of the goats in the critical time of the year.

Materials and methods

Location and climate of the study area

The experiment was conducted in the Livestock Research Center, which is located about 40 km from Vientiane, Lao PDR, at an altitude of 150 m above sea level. The climate in this area is divided into two main seasons: dry and wet. The wet season lasts 6 months from May to October. Annual rainfall averages about 1600 mm and the peak rainfall occurs in the period July to August. The dry season lasts from November to April. Only about 1 to 2% of the annual rainfall occurs during the dry season. The average minimum and maximum temperatures are about 15^oC and 32^oC, respectively. The experiment was carried out during the months August to October 2002.

Experimental feeds

Two species of improved forage (Gamba grass and Stylo 184) were used in the experiment. The feeds were collected from existing pastures of the Livestock Research Center or were planted about 40 to 50 days before the start of the experiment. The forages were cut in the beginning of the wet season and fertilizer (N for grass and P for legume) was applied at the same time. The fertilizer was applied again after each cutting. The amount of fertilizer used was 80 kg urea/ha and 60 kg phosphate/ha on each occasion. The forages were harvested at the age of 40 to 45 days. At this stage, the forages produced many soft and green leaves. The height of Stylo 184 and Gamba was about 25 to 30 cm and 30 to 40 cm, respectively. The pasture was divided into 10 plots and each plot provided enough feed for 4 days and was rotated. The feed was manually harvested twice per day in the morning (06.00 h) and afternoon (15.00 h).

Animals and management

Thirty-six male goats weighing on average 12.4±0.22 kg were used in the experiment. The goats were bought from Savannakhet province in the central part of Lao PDR and about 500 km from the Center. The goats had an approximate average age of 7 months and were of a local breed, which has a mature weight of 35 to 50 kg for males.

The goats were de-wormed by using Ivomectin (against internal and external parasites) and were vaccinated against foot and mouth disease before the experiment started. The animals were adapted to the pens and the experimental feed for 21 days before the start of the experiment. The goats were individually housed and fed. The feeding troughs were divided into sections in order to offer the two feeds separately. The animals were fed twice per day at 08:00 h and 14:00 h. Water, mineral blocks and salt were available at all times. The mineral lick block weighed 2 kg and contained 145 g Ca, 375 g Cl, 242 g Na, 320 mg Fe, 295 mg Cu, 185 mg Mn, 80 mg Co, 280 mg Zn, 20 mg Se, 300 mg I and 2400 mg Mg. The remaining part of the block was not accounted for.

Experimental design

A randomised complete block design was used in the experiment. The 36 goats were blocked into 3 groups according to weight. Three animals from each group were allocated to each of the 4 treatments. Each treatment consisted of 9 animals. The treatments were based on the amount of Stylo 184 in the diet: 0, 20, 30 and 40% of expected daily DM intake. The amount of Stylo 184 offered to the animals in each treatment was calculated on an individual basis according to body weight (BW) and an expected daily intake of 3.0% of BW expressed as DM. The grass was fed ad libitum in the amount of 130% of the grass consumed in the previous week. This intake did not cover the nutrient requirements for goats of 10 kg live weight (LW) with a weight gain of 50 g/day according to Peacock 1996). At 15 kg and 20 kg LW the control animals (not fed Stylo) were not able to cover the CP requirements, while for the other treatments CP as well as energy requirements were covered.

The animals were weighed at the start of the experiment and then once every week and always at 07:00 h before feeding. The experiment lasted for 90 days.

Data collection and analysis

Samples of feed were taken once every week and were pooled for two weeks. The feeds offered and refused were recorded daily for individual animals. DM content of the feeds offered was checked using a microwave oven in order to be able to feed the correct amount of DM. The DM of the refusals was checked in the same way, so as to be able to calculate DM intake. In the beginning the feeds and the refusals from individual animals were checked daily. If the variations in DM content were low, DM was checked on the feeds twice per week and on pooled samples of refusals. The dried feed refusals were pooled for one week and for one treatment group and a sample was taken for chemical analysis. The recordings of feed consumption and refusals were done every morning before feeding.

The samples were analysed for DM and ash according to standard methods of AOAC (1980). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were determined by the methods of Van Soest and Robertson (1985). N was analysed by the Kjeldahl method and CP was calculated as Nx6.25; ash was calculated after incineration in a muffle furnace at 550^oC for 3 hours. All analyses were made in the Animal Nutrition Research Center, Pakchong, Nakornrachasima, Thailand.

The data from the experiment were analysed statistically by a variance analysis using the General Linear Model (GLM) of Minitab Software version 12.21 (Minitab 1998). Treatment means showing significant differences at the probability level of P<0.05 were compared using Tukey's pair-wise comparison procedures. The following model was used in the experiment:

Y_ij = μ + A_i +Bj +e_ij

whereY_ij = growth or feed consumption, μ = overall mean, A_i = effect of diet, Bj = block, e_ij = random error.

The results were also analysed by using a regression analysis to determine the relationship between intake of Stylo 184 as percent of total DM intake and live weight gain. The model used was Y_ij = a+bX_i+e_ij where Y is the live weight gain, a is the intercept, b is slope of Y_i against the corresponding value of X_i, X_i is the intake of Stylo 184 as percent of total DM intake, e_ij is the random error effect.

Results

The DM content of Gamba grass was slightly higher than in Stylo 184 (Table 1). There was only a low variation in DM content for Stylo 184, but there was a higher variation for Gamba grass during the experiment. The DM content of Gamba grass was especially low in the seventh week.  NDF of Gamba grass was higher in comparison with Stylo 184, but ADF was similar.  The chemical composition of the feed consumed was different from the composition of the feed offered which indicated the occurrence of feed selection among the goats.

There were significant differences in DM intake among treatments (Table 2; Figure 1). Animals fed 20, 30 and 40% of Stylo 184 had significantly higher intakes than those offered only Gamba grass. However, there was no difference in feed intake of animals fed 30% or 40% of Stylo 184. Intake of CP was significantly higher for the diets including Stylo 184.

Figure 1: DM intake of goats fed Gamba grass supplemented with 0, 20, 30 or 40% of DM intake as Stylo 184

There were no significant differences in live weight gain between goats fed 30% or 40% of Stylo 184 but the growth rates on these two diets were significantly higher than on the other two diets (0% and 20% of Stylo 184) (Table 3). There was a strong relationship between Stylo 184  intake (X) and live weight gain (Y) (Figure 3).

Figure 2.  Effect of supplementation with Stylo 184 (0, 20, 30 or 40% of diet DM)
on changes in live weight of goats

 

Figure 3.  Relationship between intake of Stylo and live weight gain of goats
 fed a basal diet of Gamba grass

Discussion

Goats have the ability to select and consume a wide range of forages, tree leaves and crop residues. When they are left to browse freely, they will select the best diet, that includes more fresh tender shoots and other more nutritious parts of  the vegetation (Chate 2001). However, in many areas, especially where there is intensive cropping, goats are tethered or confined in limited grazing lands. Several improved forages can be brought into the systems, and two common species are Gamba and Stylo 184, which are mostly used in cut and carry systems.

The present results concerning the chemical composition of Gamba and Stylo 184 are in agreement with those from Le Khac Huy et al (2000) and Southirat et al (1991), who reported values of  DM of Stylo 184 and Gamba of 21% and 22%; and CP of 19 to 21 and 9 to 12 %, respectively. NDF content of both species was slightly higher than the value obtained by Khemsavat et al (1986) and Said and Tolera (1993), but slightly lower than what was reported by Getachew et al (1994).

Inclusion of Stylo 184 to diets based on Gamba did not result in any changes in intake of Gamba, which was not significantly different between treatments. There was, however, a tendency for higher Gamba intake at higher Stylo 184 levels and when looking at total feed intake the animals fed the highest levels of Stylo 184 had the highest DM intake. This was probably an effect of the higher CP intake, which would create a better rumen environment for the digestion of feed. When ruminants are fed crop residues, supplementation with small amounts of green forage improves the rumen ecosystem (Preston and Leng 1987). Said and Tolera (1993) and Tolera and Said (1997) supplemented different levels of legumes to a basal diet of maize stover and found that supplementation with S. guianensis resulted in significantly higher DM intake. Similar results were also reported by Navas-Camacho et al (1993) who supplemented tree legume forage to a basal diet of hay in different amounts and Ngwa and Tawah (1990) who supplemented a protein source to a basal diet of rice straw for sheep. The highest intakes in the present study, approaching 3% of body weight, were obtained by animals in the groups with inclusion of Stylo 184 at 30% and 40%. These findings are in contrast with those of Phimphachanhvonsod (2001), who showed that supplementation with Gliricidia sepium as a protein source to Guinea grass at different levels to goats resulted in a reduction of Guinea grass intake when the amount of Gliricidia sepium was increased and there was no significant effect on total DM intake. Mpairwe et al (1998) also reported that when the goats were fed Elephant grass and supplemented with legumes as a protein source the effect of supplementation on DM intake was not significant. Generally, if the basal feed is of good quality the supplement will function as a substitute, while if the basal diet is of low quality the supplement will increase the intake of the basal feed. An important point when supplementing with a legume crop is that the ideal supplement should maintain or increase the intake of the basal diet rather than substitute it (Moran et al 1983). The supplementation should aim at contributing fermentable energy and protein to the rumen to stimulate fiber digestion (Silva and Ørskov 1985).

It is important to also note that the intake of Stylo 184 in each group did not meet the expected target. The actual intakes for the groups 20%, 30% and 40% were 15.5%, 26.5% and 34.1%, respectively.

The goats fed Stylo 184 had a higher daily weight gain than the goats without Stylo 184. There was a relatively strong relationship between Stylo 184 intake and daily weight gain. This was probably a result of the fact that the CP intake was higher for those diets than for the diet of Gamba grass only. The highest weight gain was obtained for the goats fed 40% of Stylo184 (71 g/day), which shows that the growth capacity in this breed is higher than the estimated 50 g/day.  Njwe and Kona (1994) also reported that the daily weight gain of goats fed Elephant grass with supplementation of Stylo hay was significantly higher than for those fed only Elephant grass. A similar result was also obtained by Sukkasem et al (2002) that goats fed signal grass hay with supplementation with Stylo 184 hay had significantly higher weight gain than for those fed only signal grass hay. This is in contrast with the result from the study of Getachew et al (1994), which indicated a weight loss and low feed intake of sheep fed maize stover supplemented with Stylo hay.

The daily live weight gain increased as the level of inclusion of Stylo 184 increased up to about 30%, but there was no further significant increase in growth rate when the inclusion of Stylo was increased to 40%. The results in the present study basically agree with the recent findings of Mpairwe et al (1998), Hao and Ledin (2001) and Phimphachanhvonsod (2001), who supplemented legume diets in different amounts (up to 50%) and found that diets with 30% of legume gave the best intake and the highest growth rate.

It can be seen from Figure 1 that the effect of supplementation with Stylo 184 was manifested after the third week. The intake and live weight gain then became significantly different from the fifth week, which might be a result of compensatory growth, as the animals were brought from different areas and conditions.

Conclusion

Providing Stylo 184 as a supplement to a medium quality grass diet  resulted in significant increases in feed intake and weight gain of local goats, with the optimum level being from 26 to 30 of the diet DM.

Acknowledgements

The authors would like to acknowledge the Swedish International Development Authority (Sida/SAREC) for financial support of this research. We are also grateful to the Swedish University of Agricultural Sciences, and staff members of the Livestock Research Center, National Agriculture and Forestry Research Institute of Lao PDR. This research was submitted in partial requirement of the MSc degree in the Swedish University of Agricultural Sciences, Uppsala.

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Received 2 May 2003; Accepted 13 August 2003