Swallowing kibble without chewing is more common in puppies, especially if they come from a large litter where they had to eat their food quickly before a brother or sister got hold of it. 

How to slow down your dog?

• Make sure that his eating environment is relaxing and does not feel like a hostile place to eat. Make sure your dog does not hear or see another dog while eating.
• Moistening the food with water or switching to wet food. 
• Get larger kibbles.
• Get a larger bowl with a single layer of food in it. A small bowl with multiple layers of food will encourage your dog to eat more pieces whole at a faster rate. 
• Swap out the metal or glass bowl for a plastic bowl instead. This will cut down on the noise. Not only that, it is recommended to heighten the bowl off the ground in order to have it closer to the dog's mouth. This will help your dog feel like his food is safer and as if he does not have to protect it as much.

What is this does not help?

It is not bad that the dog swallows the kibble all at once, as long as he/she does not get a stomach ache or vomit.