When we work with broiler breeders, we usually end the flock at 60 or 62 weeks of age, already for many years. Production and fertility by that time goes down, shell quality usually deteriorates and egg size is getting bigger, more difficult to incubate.

However, we can wonder if at this moment that is still an optimal age to kill a flock. Production at this moment is often exceeding 90% peak where 20 years ago we were often happy with 80% peak. Also hatchability has improved, from 80-82% 20 years ago to 85-86% nowadays. With a better performance it is logical to keep the birds for a longer period. If theoretically the production would never drop, one would never kill a flock. We see that very clearly in commercial egg layers, where we moved from an average age of 14 months to almost 2 years in production, due to better production numbers. However, in broiler breeders we do not see that trend.

For the first months after starting a flock, we only make costs. We have to buy the day old chicks, warm and ventilate the house, feed the birds, vaccinate them, put some labor in etc. Only when the first eggs start to come, we get some revenue to pay for the huge investments we made until that time.

When we do the calculation (which is different for every production result and for every price setting), we often see that it takes up to 50 weeks before we have enough profit to pay for all the initial costs, and we finally start to make some money. So only after roughly 50 weeks we get a positive margin on our birds. From that moment until the moment we process the birds the margin increases, and it increases until roughly the production drops so much that the running costs are not covered by the revenues in production value anymore. At that time, we should replace the flock for a fresh young flock with a good production. But that flock will also take until 50 weeks before the margins turn positive.  

Every farm and integration should make the calculation itself, but fact is that the economical optimal moment to kill a flock with the current results in production and hatchability is closer to 66 or 68 weeks than to 60 or 62 weeks. Until the moment the margin per hen houses starts stabilizing or even dropping, it is economically feasible to continue with the production.