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Articles by M. John King
Total Records ( 3 ) for M. John King
  G. Maria Nassuna-Musoke , J.D. Kabasa and M. John King
  In order to know whether heat stress associated with the warm tropical environment in Central Uganda has a direct effect on the physiology of imported temperate Friesian cows, physiological responses of 81 Friesian animals grouped into Zero Grazed (ZG), n = 28 and Open Grazed (OG), n = 53 cows to heat stress were measured. The responses examined included Hair Coat Temperature (HCT), Breathing Rate (BR) and Rectal Temperature (RT). Cow responses were measured repeatedly every 7-9 days during 4 seasons, between 1200 and 1700 h, simultaneously with spot measurement of microclimatic parameters, i.e. ambient Temperature (TA), Relative Humidity (RH), Solar Radiation (SR), Wind Speed (WS) and black globe Temperature (TBG). Statistical analyses of physiological responses were done using the SAS 6.12 statistical package and included FREQ procedure, TTEST and GLM. Results indicated that animals responded to changes in the microclimate and temperature, relative humidity and solar radiation were directly causing heat stress to a proportion of cows at the smallholder farms. These climatic parameters had stronger effects on animal responses in OG than ZG cows accounting for up to 24 and 36% of variation in physiological the parameters, respectively. Wind movements were important in reducing hyperthermia in both systems.
  G. Maria Nassuna-Musoke , J.D. Kabasa and M. John King
  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
  The hypothesis that environmental constraints in the warm tropical Central Uganda depress milk production of Friesians on smallholdings was tested using records from 85 small farms around Kampala. Daily Milk Yield (DMY), Lactation Milk Yield (LMY) and the shape of the lactation curve were compared with those of a typical Friesian cow in the temperate zones. Differences yields of shaded/Zero Grazed (ZG) and non-shaded/Open Grazed (OG) cows demonstrated the microenvironment effect on performance. Nutrition effects were evaluated by comparing the variation of monthly DMY with that variation in monthly total rainfall. Lactation curves were generated by plotting mean DMY against time in months after calving. The overall mean DMY and LMY/cow/day of lactation were 60 and 65%, respectively of those of a Friesian in the temperate zone. The lactation curve of Friesians in Central Uganda was characterised by a transient peak followed by a consistent drop in daily yield compared to the typical lactation curve of a temperate dairy cow that is characterised by a peak at 5-6 weeks followed by a gradual decline. ZG cows had longer lactation lengths, higher LMY and higher DMY than OG cows. Least squares mean DMY was 12.8±0.1L and 10.6±0.1L litres for ZG and OG cows respectively. So, environmental constraints depress production of Friesians on small farms in Central Uganda and although cows may benefit from shading, production is generally below the genetic potential of the Friesian genotype.
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