RESUMO
Inadequate feed quality and quantity are the major constraints to dairy cow productivity in the southern Ethiopian Rift Valley. Dairy cows thrives predominantly on high-fibre feeds, with a reduced capacity for microbial fermentation in the rumen. Although variations in free-ranging dairy cow rations of the Ethiopian Rift Valley are assumed to depend on season and altitude alias agro-ecological zone, their potential impact on milk production is undocumented. This study evaluated seasonal changes of ranging dairy cow rations and milk production at different altitude regions within the Southern Ethiopian Rift Valley. A cross-sectional field survey using a structured questionnaire was used to collect data from 430 households with distinctive agro-ecology using a structured questionnaire and observation from a total of 340 households. Eighteen major feed types used by dairy farms were identified in the area and categorized into five classes: grazing pasture, cultivated pasture, crop residues, crop aftermath, agro-industrial by-products, and non-conventional feeds. All farmers indicated the continuous use of natural pasture. The daily milk yield was higher during the rainy season than during the dry season. It was also highest in midlands, followed by the highlands and then the lowlands. A significant (P < 0.001) association was found between season and agro-ecological zone and season and milk yield. In the dry season, milk yield had the strongest positive association with access to crop aftermath. This association turned negative in the rainy season, when the use of hay and agro-industrial by-products was most positively associated with milk yield. The higher availability of hay in the midlands agreed with the higher milk production in this zone, especially during the rainy season. Therefore, ranging dairy cows in tropical regions might respond differently to dietary interventions not only because of seasonal changes, but also because of interactions with the agro-ecological zone.
