Duration of performance tests for growth rate, feed intake and feed efficiency in four biological types of beef cattle

Data from the centralised performance tests for young beef bulls in South Africa were used to determine the minimum test duration required to obtain an accurate measure of feed intake, growth rate and two measures of feed efficiency: feed conversion ratio and residual feed intake. Five breeds from four different biological types were used to investigate whether different duration tests are required for different types of cattle. The results indicated that a test of between 42 and 56 days is sufficient for measurement of growth rate when a linear regression equation is used to model weight vs. time. Feed intake required approximately 56-70 days to measure accurately, while feed conversion ratio and residual feed intake both required around 70-84 days. There was little evidence of consistent breed differences in the time required to measure the traits, and it was concluded that the duration of performance tests could be shortened from 112 days to between 70 and 84 days for all breeds with no loss in accuracy of the test. (C) 2000 Elsevier Science B.V. All rights reserved.