The direct effect of Red Angus (<img width=32 height=32 id="_x0000_i1034" src="../../../../img/revistas/rbz/v28n3/a10s1.gif" align=absbottom>), computed as deviation from the direct effect of Nellore (<img width=32 height=32 id="_x0000_i1035" src="../../../../img/revistas/rbz/v28n3/a10s2.gif" align=absbottom>), and the effects of individual (<img width=32 height=32 id="_x0000_i1036" src="../../../../img/revistas/rbz/v28n3/a10s6.gif">) and maternal (<img width=32 height=32 id="_x0000_i1037" src="../../../../img/revistas/rbz/v28n3/a10s4.gif" align=absbottom>) heterozygosity, resulting from crossing these breeds were estimated. The multiple regression method was used to analyze birth weight (PNT), weaning weight (PDS), yearling weight (P12M), and for the daily weight gain from birth to weaning time (GMD_ND) and from weaning to 12 months (GMD_DA). A total of 410 calves from the groups of Nellore, 1/2 Red Angus+1/2 Nellore, 3/4 Nellore+1/4 Red Angus and 3/4 Red Angus+1/4 Nellore, raised at Estação Experimental Paranavaí, in the North-West of Paraná State-Brazil, from 1985 to 1995, supplied the data for the study. Weaning weight and GMD_ND were corrected for 205 days of age and P12M and GMD_ DA were corrected for 365 days of age. The direct effect of the Angus breed (<img width=32 height=32 id="_x0000_i1038" src="../../../../img/revistas/rbz/v28n3/a10s1.gif" align=absbottom>) did not show significance for any of the studied traits. The individual heterozygosity effect (<img width=32 height=32 id="_x0000_i1039" src="../../../../img/revistas/rbz/v28n3/a10s6.gif" align=absbottom>) was significant for all traits, except for PNT. The partial regression coefficients of PDS, GMD_ND, P12M and GMD_DA upon the expected fraction of heterozygous loci in the genotypes of the calves were 31±6 kg, .143 ± .028 kg, 55±7 kg and .126± .032 kg. The maternal heterozygosity effect (<img width=32 height=32 id="_x0000_i1040" src="../../../../img/revistas/rbz/v28n3/a10s7.gif" align=absbottom>) was significant for PNT, PDS, GMD_ND and P12M. The corresponding partial regression coefficients were 2.8±0.7 kg, 27±4 kg, .117±.019kg and19±4 kg.
additive effects; heterozygosity; Nellore; Red Angus
