Identification: Need help identifying cactus, and help with discoloration?

Hi! I'm new here, super glad to find this place as I'm having some issues with a cactus. Although from reading other posts, I think it may be some type of euphorbia...

I bought this cactus about 2 years ago and it's been doing great. It's about 5 feet tall, and pretty top heavy. I water it once a month, and like I said, there haven't been any issues. However today I noticed that one branch is leaning pretty bad, much thinner than it used to be, hard, and discoloured. I'll attach some pics. The branch actually has some new growth closer to the top that looks pretty healthy. I'm just hoping it can be saved.

If anyone can provide some advice on how to help or ideas on what may be going on, it would be much appreciated.

Thank you!

 

Welcome to the forums!

Your plant is actually a Euphorbia, not a cactus at all. Maybe Euphorbia abyssinica, but several other species are similar.

I'd prune out the dead/dying branch; when you do, watch out, the white sap is caustic, can cause severe skin burns - best to wear gloves.

 

How do you suggest I prune the branch? And what do you think caused it to die?

 

My inclination would be to see if you can snap it out by hand (but remember the gloves!), as low as possible. But see what others say too.

Sorry, no idea what might have caused it.