Abstract. Recent reports on estimating QTL positions and effects on milk production traits show several chromosomal regions, for example on BTA6, being putative QTL regions, for milk yield and traits of ingredients. The statistical methods and genetic models on which these results were based on, show different advantages and limits. Thus, it is sometimes difficult to compare and evaluate such results. Confirmation studies are inevitable, before drawing conclusions towards finemapping analyses or practical use of such results. We compared three published approaches, realizing up to five different genetic models of QTL estimation analysing the traits fat yield (kg) and fat content (%) based on a real data set of five granddaughter families from the German Holstein dairy cattle population. The marker map contained 16 microsatellite markers, distributed across chromosome BTA6. The focus was mainly on the most likely map positions of the putative QTL and on its character. The significant results obtained from using different methods and adapting several genetic models were conclusive and comparable to QTL positions reported elsewhere.