Short communication: Validation of estimates of genetic trend in the Norwegian cattle population

Abstract

We examined alternative definitions of herd × year effects in models used to estimate genetic trends for clinical mastitis in Norwegian Cattle. The model with random herd × year effects showed significant bias and clearly overestimated genetic trend. To obtain unbiased estimates of genetic trend for clinical mastitis with this data, herd × year should be defined as fixed. Our results emphasized the importance of validating estimates of genetic trend.