You said: “Hard to believe that breathing through your anus will make you feel energized.”
You got it wrongly. It is not about “breathing through you anus.” It seems you did not read what I wrote “like horses do.” [Some sages in Himalayas developed this just by looking at what horses do—and we know horses are known for its power, even though they are purely vegetarians]
You only contract your anus muscles as shown in this link (http://theholisticcare.com/bandh-mudra-kriya/209-aswini-mudra-ahswini-gesture-horse.html) Tenth time when you breath out, you do it forcefully or blow it out through your mouth (not through anus).