Ecological implications of bush encroachment on foraging behavior of dairy cows and goats at SUA farm, Morogoro, Tanzania

Abstract

The study was carried out at SUA Magadu Farm to investigate the influence of bush encroachment in a native rangeland on foraging behavior and grazing distribution of dairy cows and goats. Characterization of bush in terms of woody density was done using the PCQ method. A mixture of animals (150 cows and 60 goats) were rotationally grazed on areas with 3 different levels of bush encroachment (dense - 60%; moderate - 35%; and open grassland - ≤5%) and grazing behavior of 3 cows and 3 goats was monitored. Six trained observers recorded behavior of these animals for 2 hours in the morning and 2 hours in the afternoon for 9 days on a rotational basis. There were significant interactions between animal species in terms of grazing behavior and level of bush encroachment. Both species spent similar amounts of time grazing on open grassland (>75% of total feeding time) but on treatments with moderate and dense bush encroachment levels goats spent at least 70% of their time browsing, while grazing time of cows did not change. Goats took many more bites than cows on all treatments and as a result spent more time walking than cows. The implications of these findings for management of bush encroachment are discussed. Further studies on nutritive values and chemical composition of key forage species in the study area are recommended as well as the changes in behavior with different seasons and the impacts on animal production.