Interaction between Genotype and Environment in Sire Evaluation for Milk Production

Abstract

A study was undertaken to estimate the extent of genotype-environment interaction in Swedish dairy cattle. The material used consisted of 1st-lactation records of Swedish Red and White cows calving during the years 1966-1978. In total, there were 478, 789 records and 2329 sires. The data were divided into 3 groups according to average level of production in the herd. Breeding values were estimated for each sire on each production level, low, medium and high. Phenotypic and genetic variances and heritabilities were estimated on each level using records from unproven sires. Genetic variance increased with increasing level of production. The heritabilities for milk yield were 0.21, 0.25 and 0.28 on low, medium and high levels, respectively. Product-moment correlations were calculated between the breeding values estimated on different levels of production. The expected and calculated correlations were compared and used to estimate the genetic correlations. Between low and medium levels, the correlation was about 0.93; between low and high, 0.90; and between medium and high, the correlation was 0.98. The estimated correlations were high and, according to present knowledge, genotype-environment interaction does not need to be taken into account in Swedish dairy cattle breeding. The present system, with progeny testing of sires across all herds, will ensure a selection for general adaptability where no particular environment is favored.