I have found that the 12 x 25 MHP is too small for 25 chicks. I have brooded 17 - 22 chicks under MHP, and find that around 2 weeks old, they get too big to all fit under MHP at the same time. So, in view of the flock mentality, they ditch the pad before they are really ready. Several nights ago, in a storm, I went out to check on them, and they were in a screaming panic. At 3 weeks old, they were smushed into the corner, trampling each other. They had stopped using the pad several days ago (at 2.5 weeks old, because they all wouldn't fit under it, so NONE of them used it), but that night, it got down to 30*, and they DID need the heat, but even more than that, they needed the sense of safety it provided. Had I not intervened, I'm sure that there would have been quite a few dead chicks in the morning. I moved MHP, and propped up one end, so that while it wasn't low enough to satisfy their heat "wants" it did allow them all to get under at the same time. I also had to give them a new towel, b/c they'd trampled the old one into the litter. Part of the reason they weren't happy with MHP was b/c the draping of the towel was missing, and they felt more vulnerable without it. Even so, I had to spend a few minutes stuffing chicks under the pad, till one bright little chick decided it was a good place to be (amazing that they can squirt out faster than you can stuff them in). That little one started trilling, and almost immediately, they went under and stayed.
Ralph tried 2 MHP in his brooder, and found that, again... due to the flock mentality, they ignored one HP, and all smooshed under the second one, resulting in some dead chicks.
So... This is my recommendation. Your frame NEEDS to have opening at front and back. I'd ditch the rigid wire in favor of something more flexible that can be bent as the chicks grow. I set my frame up so it is arched in the middle, with same height at front and back. I sew a pillow case to fit frame and HP. If you don't sew, you can wrap it in a sheet, tuck the cut ends in so they won't unravel, and securely tape it so it won't come un-done. Painters tape, duct tape or masking tape will work ok. Just be sure you don't have any areas where the fabric pulls away from the tape, as chicks will find a way to tape themselves to the frame! I went down one morning to find that one little hatchling had done so. Newly sprouted flight feathers were stuck to the tape, on both wings, with the chick hanging with wings up over his back! That was hard to peel him free, cause every time I'd get one spot of wing free, he'd start flapping, and get stuck all over again. Finally, he was freed, and no worse for the wear. However, it could have ended with a broken wing or a dead chick. Chicks are notorious for finding new and ever more ingenious ways to commit suicide.
Got 2 pads? If so, you might attach them together and make one giant MHP. Or set them up very close together, after the chicks outgrow the first one. Leave a space about 2" between the 2 pads, with an opening at either end between the pads, as well as the towel draped down a bit over the openings on the long ends of the cave. I'd opt for a single towel covering both pads, allowing the middle openings, and the openings under the draping on the long ends (4 openings) If you only have one pad (12 x 24) you could extend the frame, allowing the towel to cover more area. That way, as they grow, they can still have the cover and security of MHP, even though they are not all directly under the heat. The towel draping will help hold the heat in.
What are your night time low temps??? That will make a difference in how safely they can ditch the MHP at night? Also, larger brood size = more heat from those warm little bodies to share!
Edited by lazy gardener - 5/10/16 at 5:47am