| Livestock Research for Rural Development 17 (1) 2005 | Guidelines to authors | LRRD News | Citation of this paper |
A study on grazing pattern and sustainability of feed resources was conducted in selected pastoral areas of eastern zone of Tanzania from 1999 to 2003. Discussion with pastoralists indicated that pastoralists traditionally identify different soil types and relate to presence of dominant pasture species. Grazing pattern is established such that animals graze near homesteads with short grazing duration during rainy and cold seasons. Animals are transferred to distant grazing areas during the dry seasons. Quality of forage is normally related to animal performance as well as height and colour of dominant grass species available in grazing areas.
The study indicated that there are hierarchical steps that are followed in decision making before shifting herds of cattle to distant grazing areas. Further studies indicated that native multipurpose trees namely, Dichrostachyscinerea, Acacia tortilis and Acacia nilotica thrive well in pastoral areas. These multipurpose trees reported by pastoralists as useful feed resources during the dry season. However, these multipurpose trees have multiple uses that sometimes result in resource user conflicts. The conflicts were reported to occur between pastoralists and charcoal producers because the trees are also valued for good quality charcoal. Other pasture species valued by pastoralists for dry season feeding were Commelina benghalensis, which is considered as water supplier to ruminants, and Enteropogon macrostachyus which is valued as potential feed for weaned calves. The carrying capacity in the study areas was concluded as 0.3 TLU/ha/yr.
Key words: Carrying capacity, grazing pattern, pastoralists, pastoralism, sustainability of feed resources.
More than 90% of 494733 cattle kept in the eastern zone of Tanzania belong to the traditional livestock sector (National Statistical Bureau 2001). This sector is characterized by ownership of large stock numbers, uncontrolled livestock movement, communal grazing, traditional husbandry practices, absence of animal records, undeveloped identification methods, estimation of cattle numbers and continuous breeding (Issae and Lugenja 2001). Improvement of this sector to enhance better living standards of pastoralists, requires a thorough understanding of the existing situation.
Pastoralists have been keeping animals for many years. Definitely, they possess some valuable knowledge that enables them to sustain their animals for centuries. There is evidence to the complementarities of modern scientific knowledge and traditional natural resource management for sustainable livestock productivity (Mwilawa et al 1998). The authors described that traditional knowledge of natural resource management and utilization has been recognized as an important tool in the improvement and development of land use system in the world. One of the traditional practices has been the reserve grazing areas. Agro-pastoralists and pastoralists in arid and semi-arid lands of Tanzania usually set aside a portion of their grazing land during the period of forage scarcity. Reserve grazing areas have been in use for long time but their importance in terms of nutritive value and as source of emergency feed has not been studied.
It is argued that grazing animals are powerful tool for a rangeland manager to use to either retain or alter the species composition of grassland (Whalley 2000). Different grasses have different leaf: stem ratios (Lodge and Whalley 1983) and, at least for some species, those with lower ratios have slower growth rates than more valuable, leafy species (Gardener 1998). There is increasing evidence that grazing at high stock densities for short periods of time followed by long periods of rest in appropriate seasons will swing the competitive balance in the direction of the leafier, faster-growing species and so produce a change in species composition (Earl and Jones 1996; Whalley et al 1999). Furthermore, determination of the ability of pasture to support livestock production in grazing lands is important because the number of animals has an effect on the quantity of forage available to the grazing animals, thereby affecting intake and animal performance. Overgrazing reduces the ability of pasture to produce and can lead to changes in botanical composition (Morris et al 2000). Normally, these changes constitute a reduction in the palatable and productive plant species that are replaced by unpalatable and less productive grasses and forbs. Pastures in eastern zone of Tanzania are subjected to seasonal variations within and between years. Periods of scanty rainfall have profound effects on quantity and quality of grass pastures available in grazing lands.
Kakengi et al (1999) reported low quantity and quality of grass pastures in communal grazing lands such that minimum nutrient requirements for maintenance and production of cows could not be met. The authors described that farmers in Shinyanga try to cope with the situation by reserving certain portions of pasture during the wet season for grazing during the dry season. However, forages from these portions have low nutritive values especially crude protein. Supplementation with commercial concentrate is often advocated to meet the nutrient requirements for maintenance and production of cattle as recommended by ARC (1990). Nevertheless, the prices for commercial feeds are extremely high and often such feeds do not reach distant rural villagers because of transport problems.
In an endeavour to supplement cattle in distant villages, studies have been conducted to improve the quality and productivity of pastures by introducing high quality fodder species such as Leucaena leucocephala (Otyisinaet al 1995; Shem 1996). Pastoralists in eastern zone of Tanzania traditionally supplement grazing animals during the dry season by supplying pods from 'Olkiloriti' (Acacia nilotica), 'Endundulu' (Dichrostachys cinerea) and 'Oldepesi' (Acacia tortilis) trees. Pastoralists use long hooked sticks to shake branches so as to drop pods on the ground while animals eat the pods under shade during the mid-day when temperatures are high. Pastoralists raised their concern about resource use conflict between them and charcoal producers because the same trees are used by charcoal producers that poses a threat to decline of trees population.
The objectives of the study were to understand grazing pattern and feed resources that exist in pastoral areas of eastern zone of Tanzania as well as determination of carrying capacity of grazing areas.
The study was conducted in Handeni District which covers an area of 13,975 km2. The main ethnic groups are Zigua, Nguu and Ilparakuyo Maasai. The Zigua and Nguu are predominantly agricultural while Ilparakuyo Maasai are predominantly pastoral. Rainfall is unevenly distributed. Areas with altitude between 600 to 800 metres above sea level receive about 800mm of rain per annum. The slopes of the mountain with an altitude up to 1400 metres above seas level receive 800 to 1000 mm of rain per annum. The areas west of Nguu mountain bordering Maasailand with an altitude of 1200 m above sea level receive an average rainfall of 600 mm per annum. This area is semi-arid and more suitable for pastoralism.
Field visits and group discussions with pastoralists were conducted in order to understand the grazing pattern and their perception with respect to livestock husbandry. Random sampling of forage in grazing areas was done four times per year to assess range productivity for estimation of carrying capacity. This was done purposely to account for seasonal variations. Animal unit requirement was calculated according to Maule (1990). Carrying capacity was calculated by considering proper use factor of 50% while animal's forage dry matter requirement was regarded as 3% of animal's body weight.
Population of tree species was estimated by demarcating 50m x 50m square plots in grazing areas and then a transect walk was done along the diagonal. Points of 10m apart were established along the transect line where distance from the point to the closest tree among the tree species under consideration was measured. The average area (m²) occupied by one plant was calculated using the following formula:
a = 2d2
Where,
d
= Mean distance in m
a = Average area occupied
by one plant (m²)
Population of tree species per hectare was calculated as 10,000/a
Pastoralists consider that soil type influences the type of dominant pasture that exist in a certain location.
Table 1. Different soil types known by pastoralists in Eastern zone of Tanzania |
|
Soil type |
Vernacular name (Maasai) |
|
Sandy soil |
Osonyai/Ngulukoko Osanyai |
|
Clay soil |
Oloipurudi |
|
Loam soil |
Soito |
|
Red soil |
Olukuonyoli |
|
Black soil |
Engurukinarok |
|
Montmorillonite soil |
Ngulukoni narok |
Pastoralists mentioned that Dactyloctenium aegyptica prefer sandy soil while Cynodon dactylon (Emurua) flourish on clay soil and Enteropogon macrostachyus (Arakojeraonyoke) prefers black soil. Red and black soils are regarded as the most fertile soils. It was mentioned that grasses that establish on clay soil are very good in terms of quality during the rainy season; however, they dry soon after onset of the dry season. This can be explained scientifically as water molecules are held tenaciously on clay soil particles such that large force is required to dissociate water molecules from the soil to grass roots. Pastoralists explained that grasses that establish on sandy soil sprout soon after showers as compared to grasses that grow on clay soil. The reason for that could be easy water percolation of sandy soil that enables activation of growth promotion hormones in plant roots that stimulate shoot formation while poor percolation in clay soil affects rapid sprouting of grasses after showers.
Unlike conventional range science, where range suitability for grazing is based on plant indicators and soil condition, the pastoralists in Eastern zone of Tanzania regard body condition and milk yield as the perfect reflection of suitable range for grazing. Rumen fill and milk yield determine the need to shift from one grazing area to another. It is perceived that if the grasses are sparsely established and cow-dung dominates the area then the place is not suitable for grazing, as the animals could not be satisfied. Decision to shift from one village to distant grazing areas is based upon forage and animal factors. A grazing area could be abandoned if forage colour turns yellow from greenish together with too much trampling. Decision to shift animals from a particular grazing area occurs when animals lose body condition, become weak and succumb to diseases easily, together with deprived appetite while on grazing grounds.
During the rainy season (January - April), animals leave the kraals at 10.00 am and come back at 5.00 p.m. During this period, forage is abundant and grazing area is near the homestead.
During the cold season (May - July), animals leave the kraals at 8.00 a.m. and come back at 5.00 p.m. Animals are not allowed to leave early in the morning and come back late because of cold weather. Normally animals are crowded in kraals to reduce heat loss during the cold season.
During the dry season (August - December), animals leave the kraals at 5.00 a.m. and come back at 7.00 p.m. During this period, pastures are inadequate and grazing grounds are far from homesteads. The animals require long grazing time to meet their requirements for body maintenance.
The quality of forage at a particular period is assessed by level of milk production and libido of the bulls. It is said that when animals graze good quality forage, milk production is high as well as libido of bulls. Pastoralists consider good quality grass during the rainy season as that whose height is less than the animals' height. It is perceived that grasses with height of 30 - 60 cm are suitable for grazing. The most valued grass species include Panicum species (enjokononoi), Bothriochloa species (enimbulyashi), Brachiaria deflexa (embalakai), Hyparrhenia species (olgor-oing'oki), Chloris roxburghiana (ngaidosi) and Cynodon species (emurua). Some grass species are associated with performance of the herd in the season. For example existence of armyworms in Cynodon species is associated with high mortality of animals in that year. It was mentioned that animals become weak and could not withstand long distance trekking if they persistently graze on an area dominated with Digitariaspecies (erube). Herbaceous plants of the genus Commelina are valued for provision of water to ruminants during the dry season due to their succulent nature. Suitable leguminous species for goats were described as Acacia tortilis (Oldepesi) and Piliostigma thonningii (Os sangararam).
Selection of breeding herd was based on the following:
Females - ancestry performance records in terms of milk production, large body size, and big mammary vein during pregnancy, big dewlap and long tail.
Bulls - large body size, big and pendulous testicles, docile, strong and good body conformation. Generally, healthy animal is considered as active with smooth and glittering hair coat.
Decision of the welfare of the herd is based upon observations by the head of the household. Normally the head of household observes the animals when they are leaving the kraal in the morning and when they are coming back in the evening. It was explained that if the animals grazed satisfactorily their rumens protrude and the animals go back straight to the kraal in the evening. However, they become astray if they are not satisfied and exhibit frequent bellowing. As a routine, herd-boys report to the head of household about the condition of the grazing areas. If the condition is critical i.e., animals appear weak and emaciated then the head of household orders the young-men (morani) to shift the animals to distant places where water and pasture are available.
The water sources in pastoral areas include rivers, ponds and wells. The pastoralists mentioned that presence of Erythrina abyssinica (Olng'aboli), Acrocerus macrum, Acrocerus ziznoides (Oleperyai), Cyperus species (Elng'onom) and Kigelia africana (Oldarboi) indicate presence of underground water.
Good quality water for livestock is perceived as that which contains some salts and with moderate colour. Clear and tasteless water is considered as not ideal for livestock because it does not provide minerals required by animals for better performance in rangeland. Water is assessed based on the following features.
Colour - slightly coloured water is acceptable but milky coloured water is not preferred
Taste - Salty taste is considered good for livestock as compared to tasteless water
Turbidity - muddy water is considered not suitable for livestock and blamed as source of diseases
Odour - muddy smell water is not acceptable
Wild animals - presence of healthy wild animals around water source indicates availability of suitable water for livestock
Parasites - presence of large number of swimming insects lead to rejection of water source
Algae - presence of floating algae indicates unsuitable water for livestock
Drinking water in a pond is quantified by marking the level of water on the animals' body when they enter the pond during watering session. Usually water level above hock joint is most preferred. The rate at which wells refill after adrinking session determines the persistence of the particular water source during the dry season. Water shortage in pastoral areas of eastern zone of Tanzania is experienced between July and December such that animals periodically get access to water. During this period animals drink water once in two days. This system of provision of water to animals is termed in vernacular as 'NGARONI'.
Discussion with pastoralists at the beginning of the study indicated that there are potential native multipurpose trees of the acacia family that provide edible pods to livestock during the dry season. However, the same trees are preferred by charcoal producers thus they reduce plant population very rapidly and that consequently affects dry season feed supply to livestock. Based on the pastoralists' concern, a study on population density of the tree species was conducted.
|
Table 2. Population density of native multipurpose trees in study area |
||
|
Plant species |
Density (plants/ha) |
|
|
Scientific name |
Vernacular name |
|
|
Acacia tortilis |
Oldepesi |
318 |
|
Acacia nilotica |
Olkiloriti |
586 |
|
Dichrostachys cinerea |
Endundulu |
1126 |
The population of Dichrostachyscinerea was the highest (Table 2), while cutting of trees for charcoal making could have more effect on Acacia tortilis that had the lowest population density. Differences in population density between species could be attributed to human and livestock interferences as well as the differences in seed germination ability. Germination of Dichrostachyscinerea is very good and the trees are prolific when established in open land (Mbuya et al 1994). This could be one of the reasons that enabled Dichrostachyscinerea to be dominant in pastoral areas of the eastern zone of Tanzania.
Table 3. The year effect on carrying capacity of grazing lands in pastoral areas |
|
Year |
Carrying capacity, TLU/ha/yr |
|
1999 |
0.4a |
|
2000 |
0.5a |
|
2001 |
0.3a |
|
2002 |
0.4a |
|
2003 |
0.1b |
|
SEM |
0.04 |
|
TLU=Tropical livestock unit, ha=hector, yr=year, a, Values with different subscripts within a column are significantly different (P<0.05) |
|
Carrying capacity is the maximum number of individuals, or population size, a particular environment can support. Results shown in Table 3 indicated that there was significant difference (P<0.01) between years in terms of carrying capacity. This could be caused by the influence of rainfall on vegetation growth within a year. The overall carrying capacity established as a result of a study carried for five years was 0.3 TLU/ha/yr.
Pastoralists as farm managers are able to relate environment with performance of their animals. More endeavours are required to improve their knowledge to suit rapid social and environmental changes that occur within their locations so as to ensure sustainability of pastoralism.
From this study, it has been established that the carrying capacity of grazing areas in pastoral communities of eastern zone of Tanzania is 0.3 TLU/ha/year.
The authors wish to acknowledge financial support from Government of Tanzania through Tanzania Agricultural Research Project II (TARP II) that enabled execution of this study. Special thanks to District Agricultural Offices and all field officers involved in this study for their tireless support during the entire period of study.
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Received 22 November 2004; Accepted 28 December 2004