REGRESSIONS OF PROGENY PROOFS FOR CALVING EASE AND GROWTH ON TEST STATION PERFORMANCE OF CHAROLAIS AND HEREFORD BEEF BULLS

Abstract

Performance records of 32 Charolais and 52 Hereford beef bulls tested at the Manitoba Bull Test Station for which progeny proofs were available (1984 Canadian Beef Sire Monitoring Program) were analyzed to determine if performance-tested bulls with progeny proofs were representative of the selected group of bulls which were eligible for sale (i.e, had station indexes of 95 or more) and to determine the regressions of progeny proofs on bull performance. The bull performance information included start and end of test weights, interim weights and gains, all expressed as deviations from their respective year-breed contemporary group means. This group of 84 bulls was not significantly different in test gains from the group of all bulls tested over the years 1976–1984 with station indexes of 95 or more. Regressions of progeny proofs for calving ease (CE, in score point units), preweaning gain (WG), yearling gain (YG) and postweaning growth (YG–WG) on bull weights and gains were estimated within breeds, weighting proofs by their prediction error variance. The only significant (P < 0.05) regressions of CE proof on bull performance were for bull weights in the Charolais group. Regression coefficients of WG and YG proofs on bull weights and gains were similar in magnitude with the coefficients for the Hereford breed being significantly different from zero more often than those for the Charolais breed. Effective heritabilities and genetic correlations between bull performance traits and progeny traits were estimated and, for traits defined similarly on parent and progeny, the estimates were similar to literature values. Test station procedures seemed to be effective in that bull performance was an indicator of subsequent progeny performance. Key words: Beef cattle, performance test, progeny test, heritability