Influence of Herbage/Browse allowance on nutritive intake of cattle grazing a commiphora savannah in Kenya.

This study was conducted in a commiphora savannah with two levels of bush canopy cover and two levels of herbage in august and December, respectively, in 1983 on the national range research station, kiboko, Kenya. Effects of season, available herbage, and bush level on dietary composition, preference, crude protein, digestible organic matter, and intake by cattle were determined. Diets were collected via oesophageally fistulated heifers while intake was estimated by the use of the external markers erbium and ytterbium orally administered daily to steers. Chloris roxburghiana, the most prevalent grass and sporobolus pellucidus produced more under high bush while cymbopogon pospochilii preferred open space. Availability of browse depended primarily on the shrub layer and was influenced by herbage level and precipitation. Treatment effects were influenced most by percent three-canopy cover. Cattle selected more grasses than browse of forbs in that order, regardless of bush level. More grass was selected in high herbage paddocks and during the dry season. Browse replaced grasses in all cases where grass consumption declined, particularly under low herbage level and during the wet season. Chloris roxburghiana, cymbopogon pospochilii and digitaria maeroblephana, and hermania alhiensis were the most dominate grasses and browse in the diets, respectively. Leaf fractions were the selected by cattle, especially in the high herbage paddocks and during the wet season. During the dry season under low herbage condition, cattle consumed recently shed dead browse leaves. Reduction of herbage mass led to selection of mopre dead and stemy material in the diets, and consumption of herbage relative to its availability, i.e., reduced preference. Selection of herbage relative to its availability, i.e. reduced preference. Selection of live material varied three fold between wet season and dry season trials. Season had a strong effect on dietary crude protein and energy intakes but had a strong effect on in vitro digestibility. Cattle had near or below maintenance level of crude protein and energy intake during the dry and beginning of the wet seasons, respectively. Digestibility was positively related to herbage level, the relationship being proportional. However, the influence of bush level on intake was inverse during the dry season. A drop in dietary digestibility required a similar drop in crude protein in order to effect a significant decline in intake

Arresting environmental degradation through accelerated on-site soil sedimentation and revegetation using microcatchments and reseeding

Degradation of arid and semi-arid lands (ASALs) through denudation has been found to result in lowered capacity to support livestock, particularly under extensive production systems. After a participatory rural appraisal (PRA) in Kajiado district, an opportunity was identified in the pastoral reserve grazing areas involving the combined use of microcatchments (specifically pitting) and reseeding with adapted forage species. Treatments were imposed before the 1996 short rainy season. Data were collected on soil sedimentation as well as herbaceous cover and standing crop. Much of the soil deposit comprised of fine silt/clay in the pits and sand on the up-slope. No soil deposit was observed on the down-slope of the pits. This increased in subsequent rainfall seasons. Although seeding was done by broadcasting to cover whole plots, establishment was only evident where it was pitted. Volunteer herbaceous vegetation expressed themselves and plant cover tended to also increase in freshly deposited soil form one wet season to another. Herbage was particularly dense on the crescents of the pits

Resilience of soils and vegetation subjected to different grazing intensities in a semi-arid rangeland of Kenya

The resilience of rangeland soils and vegetation to different levels of grazing is still poorly understood. A study was conducted to determine the recovery of a rangeland grazed at different intensities and allowed a two-year rest period. The following treatments were applied to 0.5 hectare plots: 0, 4, 8 and 16 heifers per hectare, hereafter referred to as CL, X, 2X and 4X respectively. At the end of the grazing period, the highest stocked treatments (2X and 4X) had lower herbage biomass, higher soil bulk density, lower soil moisture and lower herbaceous cover than the lower stocked treatments (CL and X). Drought in the rest period caused an increase in bulk density and decline in soil moisture in all the treatments. Even after the two-year rest period, the more heavily grazed treatments had higher bulk density and lower heavily grazed treatments had higher bulk density and lower soil moisture than the more lightly grazed treatments. Similarly, the herbaceous biomass in the 2X and 4X treatments did not recover after the two-year rest period and was lower (P<0.05) than the CL and X treatments. At the end of the recovery period a trend of declining herbaceous cover with stocking density was still evident. The relative cover of forbs in the 4X treatments increased more than in the other treatments, while the cover of perennial grasses did not recover in the 4X treatments after the rest period. Thus, stocking above 2X produced negative soil and vegetation responses which did not recover during the two-year rest period. This study also indicated that drought can cause vegetation and soil responses similar to those of overgrazing

Genetic variation between ecotypic populations of Chloris roxburghiana grass detected through RAPD analysis

Chloris roxburghiana is an important rangeland grass in Kenya. In some areas it has disappeared due to land degradation resulting from overgrazing and drought. Efforts to re-introduce the grass through re-seeding using seeds from research stations have had little success. One possible reason for low establishment is attributed to transplanting spatially separated populations that may represent genetically distinct ecotypes. To test this hypothesis, germplasm diversity within and among four populations of C. roxburghiana from four ecologically distinct sites was analysed using random amplified polymorphic DNA (RAPD) markers. A total of 131 polymorphic markers were identified using nine RAPD primers. There was significant variation among populations, with genetic diversity (H) ranging from 0.134 to 0.206. Analysis of molecular variance (AMOVA) revealed most variance within populations (76%). However, the variation among populations was also significant (24%). The UPGMA of the population frequency indicated that the four populations of C. roxburghiana were genetically distinct, probably as a result of variation in soil fertility, geographical isolation and socio-ecological history of the study sites. Although there are differences for neutral genetic markers between the populations, it is difficult to relate this directly to ecotype since correlation does not imply causality. The implication for optimising future seed collection is discussed and potential areas for further studies identified