The Brooks Cambium saddle line is a direct result of Brooks not wanting to lose the ever-growing "vegan" marketplace where mostly young people refuse to purchase any animal based products for food or clothing. Or bike saddles. It's a gimmick. A nicely thought out and well made gimmick, but nonetheless, I firmly believe that in a world with fewer "tender sensibilities" regarding animal products / by-products that the Cambium line would not exist. Unless Brooks is running low on those special cows.
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A good thing to keep in mind is that 99% of EVERYTHING is made from animals or petroleum. Even vegetables (if they were ever fertilized). So before you go through needless suffering, realize that the alternative to animals is likely petroleum made.

If you must get a Brooks, get one (or more) of the leather ones. Seriously.

(Disclosure: I rode Brooks saddles exclusively for 30 years. Then IMO synthetic materials far outpaced the comfort level of my best Brooks saddles. Back in the day Brooks leather saddles were hands down the best, longest lasting, most comfortable (after break-in) saddle you could buy. Past 20 years I've gone with modern (Space Age) materials, research, and manufacturing. Only so much you can do with a slab of leather, or rubber covered in cotton)

^^That said, the Cambium saddles do not feel comfortable to me. Your results may vary.