How were the all AB herds performing before going all AB?
In the year before switching to all AB, these herds were higher performing, larger, and already doing around 8 weeks of AB.
What happens to their results when they switch to all AB?
The year that herds switch to all AB, there is a slight drop in reproductive performance, but in the second and third years of being all AB, performance lifts to be similar or better than it was before the switch to all AB.
In addition, we seem to be getting better at switching to all AB. When we look at the results for the herds that go all AB on an individual season basis (e.g. just looking at herds that went all AB in 2015 vs those who went all AB in 2016), we see that any detrimental impact of switching to all AB has been reducing.
Do farmers who go all AB stay with it?
The results indicate that just over half of the herds that go all AB continue to do all AB for a second season, but only around a third go on to do a third or fourth all AB season. In light of M. bovis and the drive to be more self-contained, the rate of farmers sticking with all AB may increase.
What happens to the results of the herds that don’t stick with all AB?
The year that the herds changed back to AB + Bull, their 6-week in-calf rate and not-in-calf rates returned to, or were better than, the performance they had before going all AB.
Herds that changed back to AB + Bull tended to have a greater drop in performance in their first year of all AB than those who stayed with it.
Together, these two results highlight the fact that going all AB is not for everyone.
The results indicate that in general herds that are all AB have a very similar repro performance to AB + Bull herds, but there is a journey that all AB herds tend go through over a couple seasons when switching to all AB.
In other words, going all AB may not be for everyone, but sticking with all AB can produce similar or slightly better repro performance than AB + Bull herds.
For more information, check out this National Reproductive Strategy Group article - Biosecurity focus at mating.
*Herds included in the analysis for this article were spring calving seasonal herds that had a Detailed InCalf Fertility Focus Report. The seasons analysed were the 2014 to 2017 spring matings. The reproduction measures analysed were generated from data and information entered by herd owners and collected by LIC and DairyNZ. Accuracy of the results reported here is subject to the accuracy of the data entered.