Is a drop in mating length to blame for the rise in NICR?
Inductions were fully phased out in 2015. To try and maintain a good calving pattern,
many made the choice a season or two before 2015 to reduce how long they mated
for. This resulted in the national
average mating length dropping from a little over 12 weeks (85 days) in 2012 to
just under 11 weeks (75 days) in 2017 (Table 1). Since 6-week in-calf rate stayed pretty much
the same over that time, we’d have expected a 2% increase in NICR due to the
shorter mating (based on Table 3).
It looks like two thirds of the reason for the 3% increase
in NICR over the last 6 seasons is due to us shortening mating length by 10
days (without lifting our 6-week in-calf rate).
Using the rule of thumb that a 2% change in 6-week in-calf
rate generally results in a 1% change in NICR, to compensate for the expected
2% increase in NICR, we’d have needed to lift our average 6-week in-calf rate
by around 4%.
If you’re thinking about shortening your herds mating length
in the future, make sure you have a plan to get more cows in calf in the first
6 weeks to help minimise the impact of reducing mating length.
To find out more about lifting your herd’s 6-week in-calf
rate, check out the reproduction
resources on our website.
1 Herds included in this
analysis were 4,032 spring calving seasonal herds that had a 2017 Spring Detailed
InCalf Fertility Focus Report.
2 Not-in-calf rate is the percent of the herd that have
not been recorded as ‘pregnant’. As well
as cows recorded as empty, the not-in-calf rate includes cows without a
pregnancy test result recorded and those still recorded as ‘doubtful’. The ‘herd’ is the number of cows that calved
that season and were still there at mating start.
3 Herds were included in the analysis of a seasons
results (e.g. the spring 2012 season) if they were a spring calving seasonal
herd that had a Detailed InCalf Fertility Focus Report. The number of herds included ranged from 2543
herds for the 2012 season to 4032 herds for the 2017 season.
4 These figures are from the analysis of the 2016 spring
mating results for 3,852 herds. Herds
were included in the analysis if they were spring calving seasonal herds that
had a Detailed InCalf Fertility Focus Report.
The reproduction measures analysed were calculated from data and information
entered by herd owners and collected by LIC & DairyNZ. Accuracy of
the results reported here is subject to the accuracy of the data entered.