Learn How ERTs Can Increase Your Profits!
In selecting for improved performance, breeders have concentrated on those traits that have been easy to measure. These include individual weights at varying ages from birthweight to finishing. They have been used as indirect measures of the economically relevant traits that commercial producers benefit from or are directly paid for.
In New Zealand such traits have been birthweight (Indicator trait for calving ease or calf survival) and growth traits (Indicator traits for weaning weights or slaughter weights). From these data, Estimated Breeding Values (EBV) have been calculated. Such EBV are a means to select for animals within the limited framework that EBV provides.
Although selection using such EBV is normally more useful than selecting by eye or actual liveweights, the number of EBV now being produced can confuse the selection process and lead to inefficiencies in achieving a breeding objective.
Because of this the NZCCS in co-operation with Colorado State University has used new techniques that combine a number of related “Indicator traits” to make an ERT.
Calving Ease ERT
This is made up of a combination of the calving ease score of heifers and the birthweight information from all dams.
Calving Ease Score
For a bull with a direct calving ease ERT of +4.0, we expect his progeny, on average, to have a 2% (half of his breeding value) greater likelihood of calving ease than the progeny of a bull with an ERT of 0.
Do NOT use both EBV and ERT when selecting. Use only one or the other but ERT will provide the better selection system.