“Part of NZAEL’s role is reflecting the fertility of animals as accurately as possible for farmers,” NZAEL manager Andrew Fear says. “Fertility is an important trait for New Zealand dairy herds, given our seasonal pasture-based farm systems. The change is important to farmers, as it means we aren’t unintentionally selecting for gestation length.”
The change separating gestation length from fertility is expected to be permanent.
“This is an example of the continuous improvements NZAEL is making,” Andrew says. “It’s important for farmers to make use of this change now, so they can confidently make good breeding decisions.”
The next fertility trait change is being developed. This will see NZAEL move to a conception-based fertility trait, which means GL won’t influence conception dates to the same degree as the current fertility trait, which is based on calving dates.
“Shorter GL is economically beneficial for farmers,” Andrew says. “For example, it allows more days-in-milk and more time to recover between calving and the start of mating, but its value is lower than that of early conception date. Therefore, both traits should be valued independently when considering an animal’s breeding worth (BW).”