Authors : G. Maria Nassuna-Musoke , J.D. Kabasa and M. John King
Abstract: To examine the influence of farm management system of Open Grazing (OG) and Zero Grazing (ZG) on the microclimate ambience of the cow, spot measurements of ground and air temperatures, solar-radiation, Temperature Humidity Indices (THI) and wind speed were measured on three OG and three ZG farms over a 12 months period at weekly intervals in the afternoons. The spot-readings were backed up by continuous recording of on-farm ambient Temperature (TA) and humidity using a data-logger, plus standard weather recordings at a Met-station 12 km away at the Kawanda Agricultural Research Institute. Data was analysed using SAS general linear models. Results show that mean temperature maxima were > in OG than ZG farms (p = 0.0001), with AT of 30 and 28°C, respectively. Mean ground temperatures were 27.4°C for OG and 24.0°C for ZG (p = 0.018). Mean THIs were 77.9 for OG and 75.1 for ZG (p = 0.0001). Mean spot solar-radiation was 462 Watts m 2 and 12.2 Watt s m 2 (p = 0.0001) for OG and ZG, respectively. Climatic parameters and indices known to reduce heat stress were better in OG than ZG farms. Mean minimum AT was (OG 16.2°C, ZG 18.4°C, p = 0.0001), Diurnal Temperature Variation (DTV) was (OG 13.7°C, ZG 9.7°C, p = 0.0001), while spot wind speed was (OG 1.23 m s 1, ZG 0.23 m s 1, p = 0.0001). Thus, climatic heat stress was more on OG than ZG farms. However, cows under both management systems experience afternoon heat load above the comfort zone (THI< 72; TA 5�-21� C) throughout the year at levels that depress milk production of lactating Friesians. Although parameters known to reduce heat stress were better on OG than ZG farms, wind speed under both management systems was < 2.2 m s 1, the minimum required to reduce heat stress. Hence, microclimates under both systems were stressful and would contribute to depressed Friesian cow productivity.
G. Maria Nassuna-Musoke , J.D. Kabasa and M. John King , 2007. Microclimate Dynamics in Smallholder Friesian Dairies of the Tropical Warm-Humid Central Uganda. Journal of Animal and Veterinary Advances, 6: 907-911.