...a.k.a. Hubbard ISA Browns, Hubbard Browns...
...are a line (or breed or whatever you want to call it) of sex-link layers, created by crossing certain Rhode Island Red roosters on certain Rhode Island White hens. I say "certain" because the strain is about 30 years old now and has been strongly selected for egg-laying characteristics the whole time. It was developed by the French company Institut de Selection Animale (hence the "ISA"), later bought out by Merck with the company name changed to Hubbard ISA (hence "Hubbard"), which is now part of Hendrix Genetics. The company produces other types of hybrid layers as well (www.hendrix-genetics.com).
Point being, this is a line (breed, strain, whatever) developed for industrial-agricultural use as a commercial brown layer.
They are average-sized, chestnut brown (I gather the roosters are white), with a single comb. They excel in the personality department. My 3 were extremely sweet, friendly, calm, and surprisingly intelligent birds. From what I've read, this is quite typical of the breed.
And as you'd expect, they were amazing egg producers -- many weeks we have got 21 eggs from our 3 chickens, and there was little or no seasonal drop in lay rate, despite being in southern Canada and not using any supplemental lighting. The eggs are large to extra-large and a nice toasty medium brown.
Unfortunately all three of our ISA Browns succumbed to complications from becoming eggbound and laying internally (a problem that occurs when eggs from the ovary do not go down the reproductive tract but instead get misdirected into the chicken's abdomen where they accumulate, causing discomfort, bloating and eventually death). One died at about 9 months old; another at about a year and a half; and the last one just before turning two years old. I do not know why. It is possible that this is more apt to happen in very high-performance industrial laying strains such as the ISA Brown. They were really great chickens and I miss them a lot.
That's our three year old son Harry having his shoe tasted there, shortly after we got the girls, they were probably about 16-18 wks old. Really pleasant and friendly hens!
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