AVAILABILITY OF FEED RESOURCES, UTILIZATION, BIOMASS YIELD, SEASONAL AND AGROECOLOGICAL DYNAMICS IN NUTRITIONAL CHARACTERISTICS OF INDIGENOUS BROWSE SPECIES FOR RUMINANTS IN EASTERN ZONE OF TIGRAY, NORTHERN ETHIOPIA

Abstract

The study was conducted to assess the availability of feed resources, major constraints of ruminant production, identify the major indigenous browse species (IBS) in the area, characterizing their local utilization, chemical composition, degradability and biomass yield in two agro-ecologies (Midland and highland)in the eastern zone of Tigray in northern Ethiopia. A semi structured questionnaire was used at community and household levels and a total of 270 respondents (180 from highland 90 from midland) participated in the study. A total of 20 IBS foliage (10 from highland and 10 from Midland) were collected during the wet and dry seasons for chemical composition, in vitro organic matter digestibility (IVOMD) and (top 5 from highland and top 5 from midland) separately for in sacco dry matter digestibility studies during both seasons. The availability, abundance, distribution and habitats of the IBS varied between the two agro- ecologies. Significant (P < 0.001) variations were observed for chemical composition, Degradability, minerals and biomass yield for main effects, two way and three way interactions. Significant (P < 0.001) variations were noted for IBS biomass yield. Leaf collected from Ficus vasta gave the highest biomass yield (10640.7 kg/plant) than the other IBS from the midland where as Ficus thonninghii was highest (392.9Kg/plant) from highland. Significant (P<0.001) two way species*season interactions were detected for chemical composition and digestibility parameters. In the highland Abutilon sandwicense had significantly (P < 0.001) highest CP content (24.64 %) than the other IBS while in midland Faidherbia albida had significantly (P < 0.001) highest CP content (23.41%). In both agroecologies significantly (P < 0.001) higher NDF, ADF and ADL contents were recorded in the dry season than in the wet season while CP and ash contents showed the reverse trend. In the highland Abutilon mauritianum had significantly (P < 0.001) highest IVOMD (51.55%) while in the midland Psydrax schimperiana had significantly (P< 0.001) highest IVOMD (57.07%) than the other IBS. Macro minerals were also significantly affected (P<0.001) by species*season interaction in both agro- ecologies. The P and K contents of the sampled IBS was higher as the dry season advances while Ca content increased during the dry season. Significant (P < 0.001) species*season interactions in both agro- ecologies was observed for degradation parameters Rapidly degradable fraction(a) , slowly degradable fraction (b), xx Potential degradability (PD), Effective degradability( ED )and Rate of degradation (c ) of DM. In the highland Boscia angustifolia harvested in wet season had significantly (P < 0.001) higher DM (89.60%) degradability than the other IBS. Similarly in the midland Psydrax schimperiana exhibited the highest degradability (84.33%). Likewise a, b, ED and c values of DM were higher in wet season than in the dry season. There was a strong correlation between farmers’ feed value score and laboratory results especially with CP and ash. There was also great variation with respect to their chemical composition and digestibility parameters among the IBS, season and agro ecology. Therefore, these variations need to be considered carefully when incorporating IBS into the ration of ruminant animals for appropriate utilization. It is concluded that indigenous browse species has a high potential as ruminant feed in northern Ethiopia because of its high level of CP content and degradability characteristics. In highland, the best quality species in terms of their CP content and digestibility which are prioritized for further consideration were Abutilon sandwicense > Abutilon mauritianum >Rumex vernosus > Ficus thonninghii > Acacia etbaica > Rhus vulgaris, where as in midland agro ecology Faidherbia albida > Cordia africana >Acacia etbaica > Dodonaea angustifolia > Ekebergia capensis.