Published online by Cambridge University Press: 02 September 2010
1. Performance tests were made on 221 bulls of eight breeds or crosses from 90 days of age (weaning) up to 400 kg live weight. Feeding was in individual pens on a high-energy complete diet.
2. Pre-weaning gain was not significantly related to gain on test (r = 0·11) nor was 90-day weight to gain on test (r = 0·26) or feed conversion (r = −0·15). Weight for age at 200 and 300 kg was highly correlated with final weight for age (r = 0·72 and 0·89 respectively) while gain on test and final weight for age had a pooled correlation (across breeds) of r = 0·95. The correlation of feed conversion with gain on test was highly significant in all breeds. The range of values (−0·72 to −0·86) is higher than any previously reported estimates possibly due to an absence of initial weight effects, a reduction in the proportion of feed used for maintainenance and the use of complete diets.
3. It is suggested that with this testing system at least 50% of bulls could be culled at 300 kg without affecting selection of the best 20% of all bulls starting the test.