301 redirects via .htaccess or other way?

I have a multi-niche website and plan to start niche websites for each niche in a while when a niche has enough articles and traffic to justify a separate domain/hosting.

Example:
A "Health" blog (domain1) has the subcategory "Heart Disease". Now I have 30 articles in the "Heart Disease" subcategory and move all of these to domain2. This task is automated in my CMS.
What's the best way to redirect the incoming traffic from existing links to the new domain? It's important for me to see the original referrer on domain2.
Is it possible to automate this task (redirect/301/update .htaccess) too?

Thanks for suggestions.

Noone? Does it mean there is no way to do the redirect/update htaccess automatically/via script?