growth rate / efficiency question (broilers)


Flock Mistress
12 Years
Apr 20, 2007
Ontario, Canada
So all the "meatballs" are the same age, obviously, but some are smaller and some are larger. It is partly a cockerel/pullet thing but not entirely.

I will be processing them in small batches anyway, not all at once, so:

From the perspective of efficient feed conversion into meat, is it better to process the smallest ones first (if they're small b/c inefficient feed users), or is it better to process the largest ones first and leave the smaller ones to grow on more (if they're efficient enough but just small b/c eating and growing less)?

Which way is it, generally, with CornishX, does anyone know?


Do you want a standard sized bird? If you butcher the small ones first, you'll have small chickens in the freezer, and large chickens getting larger in the coop. And, once they reach a certain size, they start putting on fat rather than meat.

We did all 25 birds on the same day, because that was the day we had a few people to help. If I were to butcher them a few at a time, I'd start with the big ones and let the little ones grow a bit more.
I am taking and educated guess at this and saying that feed conversion is about
the same either way. The smaller birds just eat less.

I believe the maximum conversion is between 5 and 8 weeks so keeping them
around after that becomes more expensive.

I have a few friends who swear by using a finisher for 2 weeks before culling.
Well the FCR is a rate of conversion. So, I assume a FCR of 3.0 (which is conservative, but accounts for waste) in my crops.

So, if you have a 3 lb Cornish X next to a 6 lb Cornish X, all you can truly say is that the 3 lb bird had eaten 9 lbs of food while the 6 lb bird has eaten 18 lbs. They are converting at the same rate, but are eating at different rates.

So as far as economics go, the only really compelling thing is to eat the larger birds first, as the FCR actually starts down somewhere around 2.0 then increases upwards to 3.0 as the birds get over 6 lbs of live weight. This is also why commercial producers slaughter at 42 days, to stay in the really low FCR ranges, because they make pittance per bird and need all they help they can get.

As far as how FCR's are calculated, they are averaged over crops of hundreds (maybe even thousands) of birds. So, you may always have some birds in each crop which bucks the trend.

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