Bull Management
/‘Rule of thumb’ is to have 1 sound bull to 30 non-pregnant cows. Ideally there should be two teams of bulls and these should be changed every second day.
A bull is capable of mating up to 3 cows a day before semen quality drops. The daily work rate in most herds will be the same after the 3rd week as it is in the 5th week as the number of cows coming on heat on a daily basis will be similar. Like-wise the work rate will be similar between the 6th week and the 8th week.
Therefore in a 700 cow herd which is doing 4 weeks of AI, they will need (based on 3 weeks of mating):
700 cows x 82% submission rate x 52% conception rate = 300 pregnant,
this leaves 400 non-pregnant, which requires 13 sound bulls in the herd at all times
In a 700 cow herd which is doing 6 weeks of AI, they will need:
700 cows with 65% 6 week-in-calf rate = 455 pregnant
This leaves 245 non-pregnant, which requires 8 sound bulls in the herd at all times.
Bull numbers in general can be reduced by about 40% at the end of each cycle. Remember to ensure that bulls have been both vaccinated and tested clear for BVD.
