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How to build a whelping crate for your mastiff or any other size of dog. You can determine what size whelping box you need by making sure your dog has enough room to walk around the whelping box. The purpose of the whelping box is to ensure that the mother does not trap one of the pups between herself and the box, and squeeze them to death.
The English mastiff, or any other large dog, can easily calm its young if they lie on top of it. The way I made my whelping box for my English Mastiff was I took a full sheet of 1/2 inch plywood and cut it in half. The floor was now a 4 x 4 piece, and I used 2 x 2 lumber to make a frame on the inside and along the edges for a nice look. I took 6 inch wide PVC pipe that you can buy at any hardware store, cut 6 inch pieces of the PVC and used it for the legs on the inside. I used plastic PVC elbows to connect them into a perfect 4 foot square that could go up and down fairly easily in the farrowing box.
When you have the PVC plastic tubing inside the crate, it makes it harder for the mommy to lie against the sides of the crate, when she’s feeding her puppies, and if one gets stuck behind her when she’s moving all the time, it gives the pup that added air vent underneath that keeps the mother off of the pup’s weight, and the pup can survive.