| dc.description.abstract | The botanical composition of Machang'a Fiel~ Station, Mbee~e, in
Central- Eastern Kenya was inventoried by reconnaissance survey.
The relative abundance of the various plant species and ground
cover were then established for three seasons. Small East African
goats were allowed to graze freely on the range and their selective
grazing behavior used to identify the relative preference of plant
species. The preferred plant species were then sampled and their
nutritional value determined by analyzing their chemical
composition and digestibility.
Over one hundred and eighty plant species were identified at
Machang'a and recorded. The herbaceous ground cover varied with
season and was highest during the long rains study(40.8%) followed
by short rains(19.2%) and lowest for dry season(12.6%). Goats
showed strong preference for species which were relatively scarce
(r<-0.86). Browse species were more preferred than grass. Whereas
the mix of frequently eaten plants changed from season to season,
certain plants such as May tenus putterlickoides, Aspilia
mosambicensis, Combretum apiculatum, Acacia hockii, Grewia bicolor,
Barleria proxima, Combretum molle, Ocimum spp., Lantana camara and
Grass species were eaten in all the three seasons.
The relative density of the preferred forages were all less than 4%
except for Combretum molle and grass which were 30.5% and
approximately 14% respectively. Given the high frequency of grass
and C. molle at Machang'a, their sampling by goats could reflect
more of chance than choice. This is further indicated by the very
low preference indices(PI<-4.0) for all seasons. The general
scarcity of the preferred plant species was probably a reflection
of grazing pressure exerted on the plants by continued clipping by
herbivores. On the one hand some of the plants such as Lantana
camara, Combretum apiculatum and Aspilia mosambiscensis are
considered noxious bush problems in rangelands. Goats could be used
as agents of bush control to check their growth. On the other hand,
certain plant species such as Dalbergia melanoxylon is already
endangered by over-utilization for wood caving. The fact that it is
highly preferred and selected by goats(preference index of +9.8
during short rains) it will require propagation and protection
through legislative and agronomic interventions.
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Nylon bag dry matter digestibility (NBDMD) was significantly
affected by season (P<O.05). This was a reflection of different
phenological stages of the plants: vegetative during short rains,
reproductive during long rains and senescence during dry season.
During the short rains, the mean NBDMD was 43% while those of long
rains and dry season were 37.6% and 25.4% respectively.
Chemical composition of the preferred plant species especially
crude protein (CP%) varied significantly(p< 0.05) across seasons.
The mean CP content was 5.5% during dry season, 8.4% during long
rains and 10.5% during short rains. However, goats were able to
select feed with a high crude protein. The low CP content during
the dry season, was a reflection of effects of maturation and
lignification; the lowest CP content in selected forage was 3.1%.
Strategic feeding using conserved high CP feed during dry season
was recommended.
Certain indigenous plant species which could be exploited for
strategic goat feeding were identified based on their high nutrient
content, especially crude protein. These plants include May tenus
putterlicoides(CP=10.1%) , Acacia hockii(CP=10.7%) , Premna
hildebrandtii (CP=14. 5%) and Commiphora spp. fruit (CP=14. 7%) . It was
recommended that further research be conducted on such aspects as
dry matter yield potential, acceptability by other livestock
species I response to agronomic practices, possibility of
preservation and occurrence of any anti-nutritional factors and
toxicity of these plants for conclusive recommendations.
Mineral content of forage samples showed significant variation
across seasons(P<0.05) except for sodium and potassium. The
minerals were below the recommended dietary levels (NRC 1981) except
for potassium. Mineral supplementation of goats was therefore
recommended especially during the dry season when the forage
mineral contents were extremely low. Further research to monitor
the blood levels of various minerals was recommended to establish
the level of mineral supplementation. | en |
