The aim of this study was to compare the growth performance and incidences of health disorders of the Drakensberger breed to the collective total of all other beef breeds in feedlots. The objective was to conduct a meta-analysis on the performance, health and centralised growth data (Phase C) of all cattle breeds from different regions in South Africa. The intention was not to compare different breeds with each other but only the Drakensberger breed to other breeds and crossbreeds generally found in feedlots. Results from Phase C performance tests at the centres, as well as historical growth and health data were gathered from a number of feedlots. Data from feedlots were only accepted when individual animal records were kept; classification was according to breed type; and when Drakensbergers were present in the particular feedlot. The aim was to utilise historical records of up to ten years per feedlot. After initial processing and elimination of outliers, a meta-analysis was performed on the growth data. Each feedlot was analysed separately, followed by a final meta-analysis, which incorporated results from all the feedlots. It included 497 798 head of cattle from 5 feedlots, with a separate analysis on Phase C performance test data, comprising of 6139 animals from 4 Agricultural Research Council (ARC) test centres. Health data from 2 feedlots, comprising of 24 819 animals, along with Phase C performance test data from 2 ARC test centres, including 1746 head of cattle, were analysed. The variables included in the analysis were: average daily gain (ADG), feed conversion ratio (FCR), mortality and morbidity ratios and type of disease or disorder. In addition to determining the individual effects of breed, sex, season, year, region and diseases, possible interactions amongst these factors were investigated. The meta-analysis on the feedlot performance and Phase C performance tests revealed that other breeds had a higher (P < 0.01) ADG than Drakensbergers. No difference was observed between Drakensbergers and other breeds within gender and within season. The meta-analysis on Phase C performance test data showed no significant difference in FCR between Drakensbergers and other breeds. A feedlot study, including 23 554 head of cattle, has shown that Drakensbergers have a higher rate (P < 0.01) of respiratory disease occurrence during the winter season than other breeds. Likewise, results from the ARC test centre in Irene, consisting of 1553 animals, reveal that the occurrence of respiratory diseases was less (P < 0.01) in other breeds than in Drakensbergers. However, there seem to be no significant differences in the occurrence of metabolic disturbances and other diseases between Drakensbergers and other breeds. Although a statistical difference of only 20 grams per day (P < 0.01) in ADG were found between Drakensbergers and other breeds in feedlots and test centres, the biological and economical effect would most probably be insignificant. The large dataset of close to 500 000 cattle also contributed to such a small weight difference being significant. The majority of the contributing feedlots stated that their record keeping lack accuracy and do not comprise of a complete set of health data. Readers are therefore advised to interpret the health data analyses with caution as the analyses are not representative of the actual health status of cattle in the feedlot industry, simply because accurate data does not exist.
Dissertation (MSc(Agric))--University of Pretoria, 2013.