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Environmental Correlations in Pedigree Estimates of Breeding Value¹

Department of Animal Science, Iowa State University, Ames 50010

ABSTRACT

Effects of environmental correlations among the records of ancestors of bulls in artificial breeding were evaluated with data from the Holstein-Friesian Association of America. Formulas developed for the variances and covariances of means of records and progeny group means included the effects of distribution of records in both herds and year-seasons. Selection index procedures were used to estimate the breeding value of bulls from ancestor information.

Estimates of heritability were 0.338 and 0.358 for first-lactation mature-equivalent milk and records deviated from their adjusted herdmate average. Repeatabilities were 0.622 for mature-equivalent milk and 0.501 for deviation milk. The environmental correlations among records of cows calving in the same herd and year-season, in the same herd but different year-seasons, and in the same year-season but different herds were 0.328, 0.226, and 0.028 for mature-equivalent records. Similar estimates for deviation records were 0.0, 0.0, and 0.003. Additional environmental correlations for half-sisters in the same herd were 0.0005 and 0.102 for mature-equivalent and deviation records.

Correlations between computed indexes and the "predicted difference" of the bulls in artificial breeding were near zero for mature-equivalent records and near 0.25 for indexes of deviation records.

¹ Journal Paper no. J-6433 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Project 1053. This research was part of the North Central Regional Project NC-2.