Tom Allan, Daniel Barlaser, Dan Langley, Kell Watts and Jack Young are all eligible to play in remaining Premier League fixtures should the need rise and with nine games in the Premier League plus the FA Cup quarter-final up and coming, there could strain on Bruce's roster.
First team coach Steve Harper, speaking to club TV, said: "We brought in five of the young lads just because of the sheer volume of games.
"It's just to pad out the numbers in the training squad really. I have worked with four of them in the Under-23s last season.
"Dan Barlaser has come in on a high.
"It's important they keep moving forward."