Maximum Likelihood Estimates of Parameters of First and Second Lactation Milk Records

Abstract
Variance and covariance components, heritabilities and genetic and phenotypic correlations between 1st and 2nd lactation milk records were estimated by Maximum Likelihood procedures. Data consisted of 423,314 1st records and 339,182 selected 2nd records completed in over 160,000 herd yr seasons from daughters of 1873 Holstein sires. Heritabilities of 1st and 2nd milk records were 0.41 and 0.35. Genetic and phenotypic correlations were 0.91 and 0.56. Computational practicality and bias in estimation by Maximum Likelihood were discussed.