Abstract
M.Sc.
This study aims to assess the potential impacts of intense feedlot activity on the aquatic
freshwater environment, with reference to three feedlots, ranging in production size and all
situated in the upper Vaal catchment area. Field assessments were done over a high flow
and low flow period, while controlled exposures were also done to quantify a potential stress
reaction to growth hormone exposure (using Clarias gariepinus as test organism). It was
ascertained that water quality variables contributing towards differences between upstream
and downstream environmental conditions are NH4 concentrations pH and conductivity. Lead
concentrations were also periodically higher downstream from feedlot activity, in comparison
with upstream. Taking the sediment assimilation potential of growth hormones into
consideration, it was determined that Feedlot C showed the highest assimilation potential,
while Feedlot A reflected the lowest. Alterations on family level invertebrate community
structures indicated a categorical decline in abundances and species richness at sites
situated downstream from feedlots. However, some clear seasonal influences were also
observed. Further community and diversity analyses reflected alterations in invertebrate
community structures that were not reflected in SASS 5 scores. With regards to the
biomarkers applied in this study, it was noted that there was a significant (p<0.05) difference
in the cellular energy allocation (CEA) between control and hormone exposed groups. The
total amount of energy available (Ea) increased significantly for test organisms exposed to
Diethylstilbestrol (DES), while there was a significant increase in energy consumption (Ec) of
test organisms exposed to Trenbolone acetate (TBA). In addition to CEA, metabolic profiling
of blood plasma was also performed, which indicated a definite ordination in metabolic
constituents after fifteen days of exposure. This was established by subjecting the data to
principle component analysis (PCA), which accounted for 83 % variance observed. The
impacts and biotic responses identified in this study were contextualised with known
literature on the effects of feedlot activity and growth hormone exposure on the aquatic
environment. Finally, conclusions were drawn and recommendations made with regard to
improving feedlot operational activities. The results obtained in this study contribute towards
an integrated framework for the environmental management of feedlot activities.