Genotype and Environment in Sire Evaluation

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Abstract
First (45,876) and second (39,261) lactation records of New York AI Holstein daughters were divided into 4 groups depending on the level of their adjusted stable-mate averages relative to the DHIA season average. The high level was greater than 1000 lb of milk above the season average, whereas the low level was more than 1000 lb of milk below season average. Components of variance for sires and within sires were then estimated for each level from deviations of daughter records from their adjusted stable-mate averages. Genetic correlations between the genotypes in different environments were estimated. Results indicate that although there is little, if any, genotype-environmental interaction in the usual sense (ranking of sires in different environments), there is another form of genotype-environmental interaction: genetic variability is evidently different from one environmental level to another[long dash]the higher the level, the more genetic variability. The fraction of the total variability which is genetic is also lower in the lower levels of environment than in the higher levels.