How do I redirect an RSS feed to the root feed of my site?

I recently purchased an expired domain in my same subject category which I'm mapping to my existing site. I'm finding out the new domain has a good bit of residual traffic pointing to various "now non-existant" RSS feeds. I would like to somehow divert the requests to those feeds to my main RSS feed on the original site. Although the subject mater of the new domain was the same as mine the previous choice of categories is to varied for my use so I don't want to try to recreate feeds for each of them.

Examples of such are as follows:
newdomain/category1/feed
newdomain/category2/feed
newdomain/category3/feed (etc., etc.)

should all direct to:
myoldsite.com/feed

I've been trying to do this with .htaccess but I can't get my mind around the concept of redirecting a feed as opposed to a page. Can someone advise me of the best way to make this happen?

Thanks,
Larry