I don't think that mantids could even process the supplements you would add to the feeders. Your best bet would be to gutload your feeders a couple of hours before feeding the mantids. I say a couple hours because most mantids will not eat the food inside the feeders unless it is at least partially digested. I make my own, but there are a few sites that sell decent gutload. I would check out www.wildeyereptiles.com. I know the people there and they have excellent animals. I wouldn't doubt their gutload is top notch as well.

-----
Mantis Kingdom