Ask the Expert: ISA Browns
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Life Span of an ISA Brown Hen
I’d like to know how long an ISA Brown hen lives. I know that it is less than a pure-bred chicken, but why does that happen? I used to have 40 ISA Brown hens but when they reached two years old, they started to die. I’m losing one hen per month. Is there something I can do to prolong their lives? They are free range and we’re in a tropical country (Brazil) so we have long photoperiods throughout the year. I thought about keeping them locked into their coop for some extra periods of the day so they can rest their laying activities for some time. (I read that hybrids live less because they lay so much.) That makes sense? Do you have some other ideas?
Renata Carvalho, Sete Lagoas, Brazil
That’s an interesting question. There isn’t a lot of research on lifespans of different breeds or lines. There are lots of anecdotal statements on the internet saying that purebreds live longer. There isn’t anything about the chickens being hybrids that would affect their longevity, though their rate of production might. It’s interesting that the opposite claim is made for dogs – purebreds are short-lived and hybrids (i.e., mutts) live longer.
There has been research using laying hens as a model organism for ovarian cancer since ovarian tumors spontaneously develop in quite a few hens as they get older. These researchers suggest that a high ovulation rate increases the incidence of ovarian cancer in hens. So, since commercial hybrids generally lay more eggs, there is a good chance that they will have a higher incidence of ovarian tumors. This may be what you are seeing in your ISA Brown hens. It’s not clear that it would be different from hens from high-producing purebred lines. Indeed, most of the research has been done in White Leghorn hens, though some would argue that the commercial strains aren’t “purebred,” as they are crosses of different strains or lines.
As you mentioned, some of the research has shown that decreasing the number of ovulations can help prevent this, so taking the hens out of production for a while could help. This likely won’t be easy to do unless you have completely blacked-out facilities, where no light can leak in.
You might try to find an avian veterinarian or conduct a necropsy yourself (if you don’t mind doing that!) on one of the dead hens. You may be able to see what is causing their deaths if there are visible signs internally. It is possible that something else is going on with the flock.
Good luck with them!
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