It is crucial to remember that the EBI/€uro-Star of your cows are not just affected by her performance and the progeny that she has produced in your herd. Her performance is included in her own EBI/€uro-Star evaluation, however the performances of all of her half-sisters and other relatives also has a large bearing on her figures.
Example: Your Holstein/Friesian cow at home, with tag ending ‘293’ is your best cow. She is doing everything that could be asked from a Cow in terms of her fertility and the kilograms of milk solids produced, however she is still only €8 EBI! The reason for this is due to the poor performance of all of her half-sisters in other herds, which you do not know about.
The EBI value that your cow receives is a reflection as to how that entire bloodline is performing. Overall, the daughters of your cow’s sire ‘XYZ’ have poor fertility and are producing poor quality cattle. This is reflected in his low EBI rating and his index of –€113. However, even if the majority of daughters of a bull have poor milk & fertility, they can still sire the odd great individual cow.
Your best cow ‘293’ is getting credit for her great performance as her index of €8 is higher than that of her 60 half-sisters who only have an average index of –€11. If her genomic information was included, her index may then go even higher. Genomics will allow a cow to break further away from what the majority of her bloodline has done and increase her EBI.
Reference Material: https://issuu.com/herdplus/docs/___uro-stars_explained