Breed profile
ISA Brown
The production hybrid, plain and simple. ISA Brown is a sex-linked cross developed in 1978 by France's Institut de Sélection Animale for egg production as a battery hen, and in a backyard setting the same genetics mean roughly 300 eggs per hen in the first laying year. The official numbers run higher on longer horizons: the breeder's own table averages 476 eggs hen housed over a lay period to 100 weeks, with a headline of up to 500 first quality eggs, at a 62.5-gram average egg. Hens run about 4 to 4.4 pounds, so that output arrives on a small frame and a modest feed bill. What you don't get is heritage: this is a proprietary commercial cross, not a standardized breed, and hatcheries sell the same genetics under other names — the Golden Buff and Red Star listings both say so on their own pages.
The egg numbers
| Eggs per year (first laying year) | 300 |
|---|---|
| In-lay rate | ≈6 a week |
| Egg weight | 62.5 g |
| Strain note | About 300 eggs per hen in the first laying year. The Golden Buff line (sold as an ISA Brown): an estimated 395 eggs in 72 weeks of lay. The breeder's official 18-100-week table: 476 eggs hen housed, with a headline of 'up to 500 first quality eggs'. |
| Egg color | brown |
| Egg size | large |
| Starts laying | 17–20 weeks |
| Persistence | The breeder's cage-housing table: 50% production at 145 days, a 97% peak, and 'excellent persistency in egg production' across a lay period measured to 100 weeks. |
Body and climate
| Form | standard |
|---|---|
| Strain | hybrid cross |
| Comb | single |
| Leg feathering | clean |
| Leg color | yellow |
| Distinguishing features | sex-linked coloration: day-old pullets and cockerels hatch in different colors |
| Bird size | large |
| Skin color | yellow |
| Weeks to maturity | 18 |
| Mature hen weight | 4.4 lb |
| Mature rooster weight | 5.5 lb |
| Weight note | No standard exists for a hybrid. Hens: 2 kg (4.4 lb) on the reference listing, the breeder's table 1,950 g (4.3 lb) in lay, the Golden Buff line 4.0 lb. Roosters: the Golden Buff averages 5.5 lb while the Red Star — the same cross under another name — averages 8 lb; both figures are published rather than averaged. |
| Cold hardiness | excellent |
| Heat tolerance | good |
| Climate note | The Red Star spec table grades cold tolerance excellent and heat tolerance better, the Golden Buff page reads 'Hardy in all climates', and the breeder states the hens adapt well to different climates and housing systems. |
Character
| Temperament | Developed as a battery hen; docile around people in small flocks. The Golden Buff listing reads Active, Dominant with a quiet temperament. |
|---|---|
| Disposition | excellent |
| Free range | good |
| Meat production | better |
| Broodiness | low |
| Broody note | Both hatcheries rate the cross as a non-sitter: the Red Star listing says 'not at all likely', and the Golden Buff page lists Broody: No. |
| Good first breed | Yes |
What this means for your setup
The honest trade-offs live in years two and beyond: hybrid production lines are bred to spend everything early, and the long-horizon figures above come from commercial housing, not a backyard coop. Rooster weight isn't standardized either — the Golden Buff line averages 5.5-pound males while Red Star flocks average 8 — and most backyard orders are hens only. Broodiness is a non-issue (both hatcheries grade the cross as a non-sitter), and the climate ratings are the quiet surprise: hardy in all climates per the hatchery page, adaptable to different climates per the breeder. Feed math is where the breed shines: a 4-pound hen laying at this rate converts feed about as efficiently as a backyard keeper will ever see.
Gear that fits this breed
Coop Size Calculator
turn 4.4-lb hens into coop, run and roost numbers
Egg Calculator
turn the 300 egg-a-year range into a hen count
Best Coops for Cold Climates
a cold-excellent breed earns the winter-spec picks
ISA Brown FAQ
How many eggs do ISA Browns lay a year?
About 300 eggs per hen in the first year of laying. The Golden Buff line estimates 395 eggs in 72 weeks of lay, and the breeder's official table averages 476 eggs hen housed to 100 weeks with a headline of up to 500. The longer the horizon, the bigger the number.
Are ISA Browns a breed?
They're a sex-linked crossbreed, not a standardized breed: the cross was developed by France's Institut de Sélection Animale in 1978 for battery production.
How big do ISA Browns get?
Hens run about 4 pounds: the Golden Buff line averages 4.0 lb, the breeder's table lists 1,950 g (4.3 lb) in lay, and the reference listing 2 kg (4.4 lb). Rooster figures split: 5.5 lb per the Golden Buff page, 8 lb per the Red Star table — the hybrid has no standard male weight.
Are ISA Browns cold-hardy?
The hatchery tables say yes: the Red Star listing grades cold tolerance excellent and heat tolerance better, and the Golden Buff is listed as hardy in all climates. The breeder adds that the hens adapt well to different climates and housing systems.