Browsing by Author "Zemicael, Mulugeta Berhe."
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Item Liver abscesses and performance in feedlot cattle as influenced by dietary roughage level and tylosin inclusion.(2003) Zemicael, Mulugeta Berhe.; Nsahlai, Ignatius Verla.The focal interest of this study was the problem of liver abscesses that occurs in intensively fed beef cattle. The literature on metabolic disorders and diseases associated with feeding high concentrate diets to beef cattle was reviewed, with special emphasis on liver abscesses (Chapter 1). The antibiotic tylosin is generally included as a feed additive to curb liver abscesses, but has recently been banned as a feed additive in Europe. Whilst tylosin use is still permitted in South Africa, a long-term alternative to its use as a liver abscess control agent is needed . Previous research has shown a linear decline in liver abscesses as the roughage portion of high-concentrate finishing diets increases at the expense of concentrates. Unfortunately, animal performance and profits decline with such an increase in roughage inclusion, apparently due to the lower nutritive value of roughages relative to concentrates. However, if the nutritive value of roughages can be improved sufficiently, for instance by chemical treatment methods such as urea ammoniation, the detrimental effects of concentrate replacement may be at least partially alleviated. This will allow beef cattle finishing operations to use higher dietary roughage levels to reduce the incidence of liver abscesses, without severely compromising animal performance and economic returns. Hence, this study was undertaken to examine: (i) the incidence of liver abscesses in feedlot cattle originating from three feedlots in Kwazulu-Natal province, South Africa (Chapter 2); (ii) the effect of dietary roughage level (20% or 40%), with or without tylosin (10 mg/kg feed) inclusion, on biological and economic performance of feedlot cattle, and the incidence of liver abscesses (Chapter 3); and (iii) the effect of dietary roughage level, with or without tylosin inclusion, on in situ degradation characteristics of dry matter (DM) and crude protein (CP) in dietary concentrates and roughage (either urea ammoniated or untreated), when incubated in the rumen (Chapter 4; dietary roughage levels and tylosin level as for Chapter 3). In the last chapter (Chapter 5), a general discussion of the outcomes of this study is presented. The results of the survey show that the incidence and severity of liver abscesses in the feedlot beef cattle was high (25.4%), and there was a difference among the feedlots studied concerning the incidence of liver abscesses. The results of the feedlot experiment show that tylosin inclusion did not affect the performance and carcass characteristics of the steers. Roughage level had an adverse effect (P