Selenium (Se) is an essential mineral in the animal body for effective metabolism and health reasons. It can also have toxic effects if ingested in amounts exceeding the body’s metabolic requirements for extended periods (Underwood and Suttle, 1999). Its processes are not fully understood due to its intricate metabolism and its variable responses in the presence of other heavy metals (Rosenfeld, and Beath, 1964; Diplock, 1970: and Georgievskii, et al., 1982). Arthur and Beckett (1989) and Echevarria, et al. (1986) noticed that both the deficiency and toxicity of Se affects a wide range of enzymes and metabolic processes. It may thus affect many pathways due to the changes in hormonal concentrations. Se has been observed in the groundwater of livestock across different regions of South Africa at concentrations exceeding the recommended guideline ranges (Casey and Meyer, 2001: Casey et al., 1998; Department of Water Affairs and Forestry, 1996). The respective water was classified as potentially hazardous in some instances and unacceptable in others. It may help cause several health and reproduction problems in livestock and wildlife (Elsenbroek et al., 2003). The marginal difference between adequacy and toxicity of Se in the animal body led to investigations into the effect of the total dissolved solids (TDS) content of the water on the selenium status and its effect on production parameters of mutton sheep over a ten-week period. The guideline limit for Se in drinking water is 0,05 mg / L (DWAF, 1996) with a target water quality range of 0,02mg / L (WRC, 2004). Se was supplemented at 0,7 mg / L during the trial and TDS was given at 3000 mg / L. Animals not receiving Se were less productive than those that received Se. Those that received both Se and TDS grew as well as those supplemented only with Se, but were more efficient. They seemed to accumulate less Se in the blood. Their excretory mechanisms and the functioning of their homeostatic controls against both Se deficiency, at first, and at a later stage against chronic selenosis, were more suitable. Further research exposing the animals for a longer time period and in an extensive production system would assist in quantifying these results.
Dissertation (MInst.Agrar (Animal Production))--University of Pretoria, 2007.