Correlated responses in linear type traits of nelore bulls of lines selected for post-weaning weights

Abstract

The present study utilized the data from 364 nelore bulls born within three herd lines of the Estação Experimental de Zootecnia de Sertãozinho, São Paulo, Brazil and tested in the 1986, 1987 and 1988 performance tests. The herd lines were: selection line, NeS (high selection intensities for post-weaning weights); control line NeC (zero selection intensities) and traditional line NeT (intermediate selection intensities). The objectives were to evaluate the effects of selection on final weight on test (PPF); hip height (ALTPPF), and on several traits of a linear type appraisal scores. The type appraisal system considered the following traits, some of them considered important for racial standards: distance beetween horns (MA), bridge of nose (CHA); lenght of ears (ORE); lenght of neck (PES); size of hump (CUP); hair ands skin color (PEL); chest width (PEI), lenght of back and loin (DOR); body depth (PROF); lenght of sheath (UMB); pelvic angle (GINC); rump lenght (GCOM); pelvic width (GTRÃS), size of sacrum (SA), position of tail attachment (INS); angle of hind legs (POST) and lenght of shank (CAN). The line effect was significant for all the traits considered of economic importance like: PPF, ALTPPF, PEI, DOR, PROF, GCOM and GTRÃS and also for SA and INS. The higher least square means were those for NeS line, whose sires and dams were selected based on higher selection pressure (higher selection differentials). This was an evidence of a positive correlated response on body and rear quarter dimensions. The lowest means were those of NeC line (zero differentials for post weaning weights). The linear appraisal traits considered important for racial standards, like MA, CHA, ORE, PES, CUP and PEL and also POST and CAN were not affected by selection for growth rate.