Since you do have boars, i have heard people say boars generally smell worse than sows. I'm not sure if that is true as I have never had a sow to compare Alfie with but it might just be that. Like Eviolus said, you could try to litter train them. You could get a rabbit or gp litter box and some specially made small pet litter or cat litter wood pellets. You would be best putting the litter tray under or in front of the hay rack. As gps spend most of their time eating hay, they would be sitting in the litter box while eating hay and most of the poo and pee will remain in the litter box, preventing the smell from being all over. You could litter train them by putting the litter box under or infront of the hay rack and put small pet safe litter or cat litter wood chips in the litter tray, put most of their existing poos in the litter box so they know what its for. Although actually “training” them might not be nessesesary as if you put the litter box infront or under the hay rack, they will be forced to poo and pee in the box because they spend most of their day eating hay. I would reccomend changing the cat wood pellets or small pet safe litter every three days. More often than you clean the actual cage. Also whenever you clean the cage before you put the new fleece in if you arent already i would reccomend getting some small pet cage wipes or depderizer to wipe down the cage with.