Abstract: Two experiments were conducted to evaluate the potential use of jackbean (Canavalia ensiformis) forage as a feed supplement for West African dwarf goats in the derived savannah zone of Nigeria. In experiment 1, the forage production potential and quality of Canavalia ensiformis was investigated at three different spacing in a randomized complete block experiment. In the second experiment, the supplementary feeding value of the herbage in goats was investigated in a completely randomized experiment. Results showed that plant components (leaves, stem and whole) decreased (p<0.05) with increasing spacing. Leaf yield were 0.223, 0.209 and 0.109 t ha-1 for spacing 50x50, 75x75 and 100x100 cm, respectively. Crude protein contents of the leaves were similar (p>0.05) and were; 14.88 15.09 and 15.00% at 50x50, 75x75 and 100x100 cm spacing, respectively. In the second experiment, the total dry matter intake increased with increasing levels of supplementation (p<0.05). The total crude protein intake followed a similar trend. Average daily weight gain differed among the treatment groups with 0.18 g day-1 gain at the control group. It can be concluded based on herbage dry matter yield, nutrient composition and the animal performance that Canavalia ensiformis forage can be usefully incorporated into the dry season feed strategy of WAD goats in the derived savannah zone of Nigeria.
INTRODUCTION
The livestock industry in Nigeria have contributed substantially to the national wealth and for supplying the populace with essential animal protein required for good health and body maintenance (Upton, 1985). The WAD goats can subsist on household leftovers, resistant to trypanosomiasis and are prolific. Thus with little nutritional intervention, high productivity from WAD goats are inevitable.
Carnavalia ensiformis (Jack bean) is high yielding and produces nutritious pods. It is a food in marginal areas where other pulse had failed and is a high green manure forage (NAS, 1979) and aids in soil erosion control (Smartt, 1990). Jack bean tolerates a wide range of soil texture and fertility (Akpapunam and Sefa-Dedah, 1997). It can grow well on leached and nutrient depleted soil. Once established its deep root system allows the plant to utilize stored soil moisture and thus could survive dry season. The plant produces a large bulk of green fodder (Puseglove, 1974) and the leaf contains adequate level of crude protein (Sridhar and Seena, 2006).
The seeds of Jack bean are endowed with a multiplicity of protein and other cyanogenic glucosides and tannins (Swain, 1979) and when oven dried or boiled, it has been fed up to 30% in the diet of finisher broilers (Udedibe et al., 2002) and up to 20% in the diet of rabbits. The plant could produce a large quantity of green fodder 1-10 t ha-1 (Kessler, 1990). The herbage contains 13-16% CP (Diaz et al., 1998). The pant is not threaten by insect as it posses secondary metabolite (Swain, 1979) that deter insects.
Omokanye et al. (2004) reported that spacing influence herbage yield and quality. However information is scanty on the use of forage from Carnavalia ensiformis as supplement in the diet of ruminant animals. The objective of this study was to investigate the influence of three spacing on Canavalia forage yield and nutritional quality for West African dwarf goats.
MATERIALS AND METHODS
Site
The trial was conducted at the Teaching and Research Farm of Ladoke Akintola
University of Technology, Ogbomoso, located in the derived Savannah zone of
Nigeria.
The site is on Latitude 8°26' and longitude 4°29'E. Average annual rainfall is 1173 mm and usually occurs between June and October. The top soil (0-15 cm) is sandy loam with a pH of 6.7 (H2O), 0.69% organic carbon and 2.94% total nitrogen and 37 ppm available phosphorus.
Land Preparation/Planting
Canavalia ensiformis seeds were procured from International Institute
of Tropical Agriculture (IITA), Ibadan, Nigeria. About 1.5 t ha-1
land space was designated for the agronomic study. The soil was plough and harrowed
before the seedbeds were prepared. The seeds were planted by drilling the seeds
at the rate of 2 seeds per hole. The 3 different spacing were: 100x100, 75x75
and 50x50 cm. Each spacing was replicated thrice. No inoculums or fertilizer
was applied. Weeding was done thrice before harvesting to prevent weeds from
competing with the Jack bean for nutrients and to also prevent predators from
entering the plots.
Herbage yield was estimated when 50% of the plants had flowered (12 weeks after planting) from each spacings. Total plant harvest of each plots under each spacings were carried out. The harvested plant was separated into different components (whole plant, leave and stem) and weighed. Sub samples of the herbage were taken and oven dried at 60°C for 48 h to calculate the dry matter contents. Herbage dry matter yields at each spacings were estimated using the respective DM levels. The leaves were later dried, bagged and stored in a dry place until required for further studies.
Feeding Trial
A feeding trial involving 12 WAD goats was carried out. Animals balanced
for age, weight (8.5±1.2) and sex were randomly divided into 3 treatments
of four animals per treatment. Animals were housed in individual pens. Herbage
from all the spacings were pooled together since there were no difference crude
protein contents among the herbage harvested from the three spacings. Canavalia
ensiformis forage meal was offered as supplement at 0, 10 and 20% of the
daily dry matter allowance of individual animal. The basal diet was Panicum
maximum. Diet was constituted as 3% of body mass. The animals were allowed
an adjustment period of seven days to enable the animals to acclimatize to the
feed and pen. Mineral salt lick and clean water was provided ad libitum.
In vivo Nutrient Digestibility
Three bucks of comparable weight (10.3±0.67) and age were randomly
selected and put in separate metabolic cages. The cages were equipped with facilities
that allowed for separate collection of faeces and urine. A 4x4 Latin square
experiment was conducted to determine in vivo nutrient digestibility.
Animals were allowed 7 days of adjustment period and 5 days of data collection
per period Canavalia herbage from all spacings pooled together was fed at 0,
10 and 20% levels to a basal diet of P. maximum. Diet was constituted as 0.3
of body weight of individual animals. Feed intake and faecal production was
monitored daily. Sub samples of daily faecal production were taken and oven
dried at 60°C for 48 h to determine the dry matter level.
Chemical Analysis
Forage samples was analyzed for crude protein, crude fibre, ether extract
and ash, Ca, Na, K, Mg, Zn, Cu and Pb. Crude protein analysis was by the micro
Kjeldahl method according to AOAC (1990). Mineral analyses were carried out
by the use of dry ashing procedure. Mineral elements in the forage were read
using an atomic absorption spectrophotometer at appropriate wavelengths.
Statistical Analysis
Data on feed intake was analyzed as a completely randomized design, data
on nutrient digestibility as a Latin square while data on agronomic studies
was laid out in a randomized complete block design. Both data were then subjected
to the General Linear Model (GLM) procedure (SAS, 1985).
RESULTS AND DISCUSSION
Spacing had a significant effect (p<0.05) on the forage yield of Canavalia ensiformis (Table 1). The 50x50 cm spacing was observed to produce the highest herbage yield which was in the order of 50x50 cm > 75x75 cm > 1x1 m. The jack beans used gave increasing yield with density probably because it is an erect and determinate type and more importantly it produces few branches. A plant with such morphology would be less affected by intraspecific competition, as shading is minimal even when densely populated. It is obvious from this study that with more plants per unit area at high density with a plant type that is low branched, there is more leaf area for photosynthesis and more rapid accumulation of dry matter in all plant parts (Remison et al., 1983; Omokanye et al., 2004). The result of the proximate composition of biomass is shown in Table 2. There were no differences (p>0.05) in CP of the herbage across the treatments. The CP values were 14.9, 15.1 and 15.0 for 5x5, 75x75 and 100x100 cm spacings, respectively. The lack of significant difference in the CP content may be attributed to the high soil fertility. Thus the nutrient (N) available in the soil far exceeded the amount required by plants in the respective spacings. The leaf across all spacings had crude protein concentration greater than 80 g kg-1 DM, the level below which voluntary feed intake of tropical forage is limited (Minson, 1980).
| Table 1: | Effect of spacing on forage yield of Carnavalia ensiformis (1 kg ha-1) |
| Means on the same row with different superscript are significantly (p<0.05) different | |
| Table 2: | Effect of spacing on mineral composition of (Canavalia ensiformis) leaves in the derived savanna zone of Nigeria |
The higher CP level of jack bean suggests that it could effectively provide supplemental N when browsed with native pasture or when offered to stall fed animals on low N cereal crop residues diets. However, the availability of the crude protein may depends on the concentration of anti nutritive factors such as condensed tannin (Onwuka, 1992).
Result of mineral composition of the herbage leaf is shown in Table 3. Spacing had no effect (p>0.05) on mineral composition of Canavalia ensiformis leaf. The overall value of sodium (Na) in the leaf was lower than the critical level (0.18) required by ruminant animals for optimum performance. Average zinc (Zn) value was less than the critical level required for efficient production of the ruminant animals. The calcium level across the spacings was below (0.3%) recommended. However, the value obtained for K in this study fell within the recommended range (0.2-0.6%) for ruminant. The lead (Pb) content of (0.23%) was within the tolerance level of 200 ppm recommended for ruminant animals (NRC, 1985). The implication of these generally low minerals content of the leaf is that an additional mineral supplement may have to be provided when C. ensiformis is being used as feed supplement to West African Dwarf goats. The total dry matter and crude protein intakes increased (p<0.05) with increased level of supplementation (Table 4). The differential in feed intakes may be accounted for by increased CP intake with increased supplementation level. Higher intake of CP encourages higher proliferation of microbes in the rumen. Higher proliferation of microbes in the rumen normally enhances efficient degradation, high passage rate and thus more feed intake (Crampton et al., 1960). Both the weight gains and dry matter digestibility were affected with levels of supplementation (Table 5). The improved dry matter intake and weight gains may be attributed to increased feed intake with advanced level of supplementation.
| Table 3: | Effect of spacing on proximate composition of Canavalia ensiformis forage |
| Means in a row with different superscripts differed (p<0.05) | |
| Table 4: | Feed intake, in vivo digestibility and weight gain of goats supplemented with fresh Canavalia ensiformis leaf at three levels of supplementation |
| Means in a row with different superscripts differed p<0.05 | |
| Table 5: | In vivo digestibility and weight gains of goats fed Canavalia ensiformis as supplement |
| Means in a row with different superscripts differed p<0.05 | |
It can be concluded that based on data from biomass yield, feed intake, in vivo digestibility and daily weight gains that Canivalia ensiformis has a potential role in the dry season feeding strategy for goats in the derived savannah zone of Nigeria. However, further studies needs to be carried out especially on the concentration of anti nutrients in the leaf of the supplement.