Intraherd prediction of beef cattle genetic values using linear model techniques

An adjustment factor for herd genetic merit is algebraically derived from mixed-model national sire evaluation procedures, and the application of this factor to intraherd mixed-model evaluations is discussed. The behavior of the adjustment is then explored using a simulated data set. The merit of the adjustment is investigated in comparison with the true genetic levels of the simulated herds and in terms of the ability of the adjustment to reflect the true differences between herds. The relationship between the error of adjustment, years of accumulated data, and measures of the strength of the ties among herds are also studied;The error of adjustment appears to be unaffected by herd size or the connectedness of the herds within the ranges simulated. The error actually increases over time because the slope of the sire genetic trend is steeper than that for the dam population. The correlation between herd ranks based on the true and estimated adjustments increases over time despite the increase in error, indicating that the proposed adjustment factor accurately represents the genetic differences among herds