Mating time key to empty rates
On many farms the bulls have now been removed and the empty cows are becoming quite evident. As a result the timely question of what is your herd's "empty rate" has come up at recent discussion groups. For some, overall mating appears to have gone well with empty rates of 4-8pc. For others, even with favourable weather, empty rates of greater than 15pc have been reported.
If you fall into this latter category you may be questioning where it has gone so wrong? What is Mr 4pc doing so right? Before you go picking his brains for a cure to your infertility issues, just remember to quantify that empty rate with one important question -- how many weeks did you mate for? This is more important than you think as illustrated for five herds (A-E) of 100 cows in the table right.
So is the empty rate of 6pc so good? The in-calf rates above follow a bell shape curve. But is an empty rate of 10pc after 10 weeks of mating (nine cows in calf per week) any better than a herd that achieved an empty rate of only 6pc after weeks (only five cows in-calf per week). Clearly empty rate is not a good measure of a herd's fertility by itself, and should be tempered with mating weeks.
Ideally, as farmers we would all quote empty rates to no later than week 12, as any animal calving after week 12 is essentially calving after the start of mating. As we all know this late calving animal is one of the hardest to get back in-calf, and if she does, she's still likely to be calving late, and also has a reduced milk production due to shorter lactation length.
So if your empty rate is causing you concern the next step is actually to take some time to analyse your herd's recent mating and calving data. This requires a good set of records. Herd Plus can help you with this. A herd's reproductive performance is farm specific and there is generally no one silver bullet that will fix all problems.
This may seem an odd time to be looking at calving and mating performance because it's all done and dusted.
But it makes sense because it gives you a chance to do some investigatory work if required, and come up with a reproduction management plan for next year.