Modelling of long term pasture production and estimation of carrying capacity of Ankole pastoral production system in South Western Uganda

Abstract

The Ankole pastoral production system in South Western Uganda is based on grazing without supplementary feeding. A stochastic simulation model was developed to determine the dynamics of pastures grazed by Ankole cattle and their Holstein Friesian crosses and the carrying capacity (CC) of the livestock grazing system. The model used the concept of rain use efficiency which relates pasture production to rainfall. A cross sectional study was carried out on 16 selected farms and data on number of animals, sex, age group and size of available grazing land was collected. The similarity between the results of the simulation rainfall runs and field data are considered to be satisfactory. The overall annual forage production is 3905 ± 72kg/ha. The lowest CC (5.65 ± 0.75) occurs in long dry season (June to August) while the highest CC (1.41 ± 0.06 ha/TLU) occurs in short rain season (September to November). Annual carrying capacity ranges between 1.88 and 2.08 ha/TLU with an overall mean of 1.95 ± 0.04 ha/TLU. Sixty three (63%) percent of the surveyed farms have stocking rates that are higher than the CC throughout the year while the rest are overstocked in the dry seasons of the year. The results indicate that CC is dynamic and its variability is more pronounced within the year than between years. In response to seasonal CC, the major point of intervention in regard to reduction of actual stocking rates could be done in May shortly before the start of the long dry season. For Ankole pastoral system to be sustainable, the stocking rate should not go below 1.41 ha/TLU.