Rangeland condition and feed resources in Metema District, North ...

than in P. spheslatum and C. ciliaris. Mean OM, CP and IVDMD contents in P. lucens
were significantly (P < 0.05) higher than the other two species. The differences in nutrient
content between species could be associated with their inherent nature, i.e. fodder trees
contain more protein than grass species. As reported by Mathur et al. (1991) most grasses
and tree leaves in arid environments are low in nutritive value because of high contents
of lignin and relatively indigestible (compared with starch) cellulose and hemicelluloses.
The effects of season on chemical composition
Data on the effect of season on chemical composition of dominantly growing two
grass and one fodder species are given in Table 16. The DM, OM, NDF, ADF and ADL
contents of feeds were significantly (P < 0.05) higher in October than in August. Whereas,
the percentages of ash, CP, IVDMD of the feeds were significantly (P < 0.05) lower
in October than in August. This may be associated with the temperature, the stages of
growth and the plant species that influenced the quality of feeds. This finding agrees with
earlier reports (Alemayehu 2006; Sisay 2006), that the structural constituents of plant
materials (lignin, cellulose and hemicelluloses) increase with maturity. During the growth
stage, plants are most nutritious. Once mature, plants are subject to leaching and dilution
of nutrients and reduction in nutritive value. Declines in nutrient composition and
leaching are especially serious in the case of herbaceous plants. As the plant matures,
the contents of crude protein, the more readily digestible carbohydrates and phosphorus
decrease and that of fibre, lignin and cellulose increase. The decline in nutritive value
of these feeds in October indicates that feed conservation practised by the communities
between mid October and November is not appropriate time and should be done earlier
than in mid October.
Table 16. Effect of season on chemical composition (Mean ± SE) of composite samples of dominant
feed species in Metema
Chemical composition, %
Season
Wet (August) Dry (October)
DM 88.9 ± 0.11 b 90.5 ± 0.11 a
ASH 18.2 ± 2.07 a 10.5 ± 2.07 b
OM 81.8 ± 2.07 b 89.5 ± 2.07 a
CP 10.8 ± 0.35 a 8.2 ± 0.35 b
NDF 60.8 ± 0.52 b 73.9 ± 0.52 a
ADF 40.3 ± 0. 45 a 49.6 ± 0.45 a
ADL 10.1 ± 0.60 b 13.5 ± 0.60 a
IVDMD 50.7 ± 0.96 a 37.9 ± 0.96 b
Means with different superscripts in a row differ significantly (P