| dc.description.abstract | The primary energy pathways, energy intake, habitat exploitation patterns and feeding
interaction of free ranging agropastoral herds (cattle, goats and sheep) in Kibwezi, a
semiarid environment were investigated in two cycles of four consecutive grazing
periods. The bites count and herd locations per area methods were used. The water
balance and soil loss associated with key perennial grasses subjected to different levels of
utilization were assessed using simulated rainfall. Using energy intake-digestibility
constraint curves and a growth-consumption rate model, the optimal grass biomass at
which energy intake and digestibility equilibrate were derived and the stability properties
of the agropastoral system described, respectively. Also, the nature and extent of use of
secondary land rights to access grazing resources and the factors affecting their
application were analyzed by use of questionnaire and econometric techniques. These
analyses aimed at contributing to enhanced livestock productivity in the agropastoral
system.
The animals exploited a wide array of plant species. Forage energy for cattle and sheep
came primarily from herbaceous plants, while goats largely exploited woody plants.
Enteropogon macrostachyus was the single largest energy pathway and accounted for
over 30% of the total energy intake of cattle. The other important grass resources were
Panicum maximum (9.9%) followed by Eragrostis superba (7.3%). Combretum exalatum
and Duosperma kilimandscharica were the primary energy pathways that accounted for
over 10% of total energy intake of goats with seasonal peaks of 18.5 and 17.2%,
respectively. Sheep were largely mixed feeders, but Enteropogon macrostachyus (16.6%)
and Blepharis integrifolia (10.3%) were the primary energy pathways. Energy constraint
curves revealed that energy intake by cattle was optimized at 460,420,470 and 480 gm-2
of sward biomass, corresponding to 60.6, 64.3, 62 and 55.5 organic matter digestibility
percentage for Enteropogon macrostachyus, Panicum maximum, Eragrostis superba and Chloris roxyburghiana, respectively. The animals had significantly different energy intake within and between seasons. All the
animal species had a lower and higher energy intake in the dry and wet seasons,
respectively. Energy intake more than doubled and tripled from the late dry to the late
wet season, for sheep and goats, and cattle, respectively. All animal species recorded a
negative energy balance only in the second late dry season. During this period, 100%,
100% and 67% of the cattle, sheep and goats in the ranch lost weight, respectively. While
50%, 67% and 33% of the cattle, sheep and goats in the agropastoral areas lost weight,
respectively. Based on energy balance, goats maintained a superior position and thus
were relatively hardier, followed by sheep and cattle. This was further evident given that
78%, 44% and 33% of the goats, sheep and cattle kidded, lambed and calved,
respecti vel y.
During the dry season, areas of concentrated drainage, river valleys, bottomlands and
ephemeral drainage ways absorbed a greater feeding load, taking 57.1 to 60% of the
grazing time by the animals. In contrast, areas of limited moisture concentration, the open
sandy/clay plains, were mainly exploited in the wet season, and accounted for 52.6 to
55.6% of the grazing time. The trophic interaction patterns indicated that goats and cattle
had a seasonal mean diet overlap index of less than 0.5 for all forage classes. Sheep and cattle, and sheep and goats had a seasonal mean diet overlap index of greater than 0.5 on grass and forbs, and browse and forbs, respectively. This suggested that during periods of
resource scarcity, sheep and cattle or sheep and goats could become competitive feeders
for same resources.
Infiltration capacity for sites dominated by perennial grasses increased with increasing
stubble height before levelling off towards the highest stubble height. A 50% removal of
current growth was the upper limit above which runoffs and sediment loss from the grass
stands increased rapidly. Aggregate stability, organic carbon and ground plant cover
percentage were the most significant attributes that influenced infiltration capacity.
Panicum maximum and Enteropogon macrostachyus stood out as the most suitable
perennial grasses with favourable soil physical properties and infiltration capacity in the
study area. From a growth-consumption rate model, a stocking rate of 7 TLUha-1 appears
to be the upper limit in this agropastoral system, above which the system is destabilized
during the growing period.
Seventy percent of the households used secondary rights to secure pasture for their
animals, particularly short term loans (64%) and exchange of bulls for ploughing (38%).
Use of secondary land rights was positively and significantly influenced by increasing
livestock per adult, smallstock to cow ratio, and small farm size per household. The
amount of crop residue available and increasing grazing area per adult had a negative
effect. Secondary rights gave households flexibility in dealing with pasture shortages
during critical periods. Grazing management strategies that enhance a broadly stabilized
energy extraction pattern and complementary trophic interactions, augmented by flexible
secondary land rights, could be central to sustainable livestock production in such
environments. | en |
