So, it’s that time of year again when you’re selecting who is going on the cull list. Your favourite old girl is standing in the yard and you decide to give her another go. Why? Probably because she has given you a live calf each year, and otherwise doesn’t give you any trouble. However, have you ever thought about the negatives of keeping an old girl like her?
As a general rule, any cows over 8 years old will be less productive and less efficient than their younger peers and we see this in multiple ways.
Firstly, older cows will (on average) be less fertile. This is often reflected in failure to get in calf, or in longer calving to conception intervals. If you only breed 50 cows each year, do you really want 20 of those to be sub-fertile? Subfertility can lead to extended calving periods or an increased number of barren cows each year. Both of these can be costly.
Ok, but what if they do get in calf at the right time? Well, overall, calves weaned from older cows (>8yr) will have lower weaning weights. If the difference is 30kg average and you have 10 of them… that’s 300kg of lost profit.
What if these smaller calves grow OK and I keep the heifers as replacements? Well, there is data to demonstrate that heifers from older cows will not perform as well in their first 2 seasons, compared to those born from younger cows (4-8yrs).
On top of this, have you considered the genetic implications of keeping older stock? Beef farmers should be aiming to see noticeable genetic gain on the farm every 5-10 years. By maintaining an older herd, you slow down the introduction of new genetics, which may well be limiting your herd’s overall performance.
Finally, we know that once a cow reaches 10 years old, she is at a greater risk of suffering disease (anything from mastitis to milk fever). This is something I’m sure you have seen for yourselves and I bet you have told yourself ‘she should have gone last year’ more than once…
I do appreciate that rearing heifers is expensive, and this article doesn’t take into account other implications such as TB or other biosecurity concerns, but in the long run, you will be better off running a younger herd.
A good target to aim for is a 16% replacement rate. If you are hitting this each year, it is likely the herd is not too old. If you are unsure, please speak to your routine vet, as looking at the data is straightforward and very useful.
Written By Imogen Rogers, Veterinary Surgeon
