As we enter a new era without inductions we now have to think longer about how we manage our calving spread.
It is important to have as many cows calving as possible in the first three weeks of calving every season to ensure that cows have plenty of time to resume cycling before the next mating. Getting this right should also maximise your 'days in milk' which is one of the biggest drivers of farm profit.
The above graph from a local herd clearly illustrates the impact that calving date has on subsequent reproductive performance. The blue cows are those that had calved in the first 3 weeks and shows that they were also the fastest group at getting back in calf. If you have too bigger percentage of a herd calving down in the 3rd or 4th cycle it will have a major impact on future herd performance. A standard recommendation is not to let your calving spread go beyond 10 weeks to ensure late calving cows do not impact too greatly in the following mating. 10 weeks after a PSM date of the 23rd of October is the 1st of January. This would be the date for bull removal if you did not wish to have any cows calving beyond the 10th of October.
In some herds restricting the mating period to 10 weeks may result in an unacceptably high level of empties so make sure you fully understand the economic consequences of bull removal date on your farm (discuss with your vet or consultant).
A new strategy of doing AI for a short burst of 10days after the 1st of January with LIC short gestation semen would allow you to mate for a further 10days but still have all cows calved by the 10th of October. This strategy will potentially limit cow wastage.