The objective of any livestock breeder is the identification of stock of superior genetic merit with respect to some goal for the production of future generations; their objective is the estimation of genetic merit. Traditional breeders achieve this simply by visual appraisal. Some breeders have realised the value of collection of performance records to make the assessment more objective. The animal’s performance record however results not only from the animal’s genetic make-up but also from the management and other non-genetic factors (age of dam, age of measurements) that it has experienced. Best Linear Unbiased Prediction (BLUP) is a method to estimate genetic merit (or breeding values) of animals. BLUP is universally regarded as the best method available to us to predict genetic merit of animals when performance records have been collected In a variety of herd, year, season and management environments. Considerable investment of time and money Is made in the organisation of unique animal identification and collection of records. It is therefore appropriate that maximum use is made of those records in the accurate prediction of genetic merit of individual animals.