Selection for lower or negative days to calving has a very strong relationship with pregnancy rates. Females with negative days to calving EBVs are generally those which achieve puberty at a younger age, and are more likely to be cycling when joined as maidens.
In turn this should result in both an earlier calving, and a longer opportunity to recover and regain condition ahead of rejoining.
Age and particularly weight have a major influence on puberty ahead of joining. However, including the selection for females that genetically are more likely to be pubertal at joining can make a significant difference for breeding success.
BEEF CENTRAL Genetics Editor Alastair Rayner, March 16, 2021