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Title: THE EFFECT OF GENOTYPE X ENVIRONMENT INTERACTION ON THE WEANING WEIGHT OF NELLORE CALVES RAISED IN FOUR DIFFERENT REGIONS OF BRAZIL

Author
item SOUZA, J. - ANDRADINA, S.P. BRAZIL
item RAMOS, A. - ANDRADINA, SP, BRAZIL
item SILVA, L. - EEZRP, SP, BRAZIL
item EUCLIDES FILHO, K. - EMBRAPA-CNPGC, BRAZIL
item ALENCAR, M. - EMBRAPA, CPPSE, BRAZIL
item WECHSLER, F. - EEZRP, SP, BRAZIL
item GADINI, C. - EEZRP, SP, BRAZIL
item Van Vleck, Lloyd

Submitted to: World Congress of Genetics Applied in Livestock Production
Publication Type: Proceedings
Publication Acceptance Date: 8/21/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: An important question for cattle breeders is whether a bull that has superior progeny in one region of the country would also have superior progeny in another region. If the ranking of bulls change with the region of the country, a genotype (bull) by environment (region) interaction exists. This study of 56,039 weaning weights of Nelore calves raised in four regions of Brazil provided evidence of bull by region interaction. The rule of thumb is that a correlation between genotypes (sire's genes) in different environments less than .80 indicates a potentially important genotype by environment interaction. All genetic correlations were below 0.80 (ranging from -.06 to .63). The intensity of this interaction varied substantially according to region pairs, depending on the similaries of environments. The presence of genotype x environment interaction indicates the need to choose sires specifically for each region, because not always will the best sires for a specific region maintain their superiority in another region.

Technical Abstract: The objective of this study was to evaluate the effect of genotype x environment interaction and estimate the genetic parameters of 205-day adjusted weaning weight observed in four different regions of Brazil. The data consisted of 56039 weight records of Nellore calves raised on pasture and born from 1977 to 1994. The genetic parameters and expected progeny differences (EPD) were obtained using a sire model simultaneously for the four regions, having as random effects sires and cows (uncorrelated), and as fixed effects sex, month and year of birth, farm and age of dam as covariate. The EPD estimates having been obtained, Spearman correlations between EPD's of different regions were calculated to verify whether the sire ranks were different among regions. The proportion of total pheno- typic variance due to permanent environment effects of dam ranged from 0.16 to 0.23. The heritability coefficients were 0.27, 0.33, 0.39 and 0.25 5for regions 2, 5, 6, and 8, respectively. The genetic correlations were 0.37, -0.06, 0.12, 0.36, 0.63 and 0.60, the Spearman correlations being 0.60, 0.02, 0.40, 0.55, 0.87, and 0.78 for region pairs 2-5, 2-6, 2-8, 5-6 and 6-8, respectively. These correlations indicate important genotype by environment interactions with all genetic correlations less than .65. The presence of genotype x environment interaction indicates the need to choose sires specifically for each region, because not always will the best sires for a specific region maintain their superiority in another region.