SO.... First timer here and I think it may show in my tale i have to tell. We have bought Bantam Cochins to sit on our other birds eggs. Great move, I would suggest this breed to anyone wanting adoptive mothers for your main flock. They have been laying almost every day under a 12 hour light during this fall and winter, and now they are proving to be broody. Just about two weeks ago, one of the Bantam Cochin hens started to linger in the egg box a little longer each day until she wouldn't budge from her spot even when i came to collect. So I searched the forums of BYC to see if this behavior was indeed "broody-ness" and yes I got the thumbs up and dubbed her "Broody Mama". From my readings I gathered that I should let her fully go broody and then move her into a broody box and replace the eggs with the desired breed. Easy enough I thought. I had a small run ready to go, so about 4 days into her nest takeover I attempted to move at dusk to her to the new run I had set up for her with the new eggs... broody mama was having none of it. wouldn't sit or even settle down. Plan B. I made an alternative nesting box for the other ladies in the coup and moved Broody Mama's nest box off to corner setting up a half pallet to keep her head in the game and replaced her eggs with 6 Barred Leghorn's eggs and 1 of her own (call me gracious). I marked them all with pencil 1-6 and 1. Now the good stuff. All week I have been checking on her to remove new eggs and making sure she is not pooping in the nest (first time broody checklist from what I have read). All good, but i start to see some slight goo on the eggs which I attribute to the moisture from her body and condensation form the heat. Now comes candling weekend, day 9. I lift up broody mama and set her to the side and start to candle the eggs one by one, all fertile all moving!!! I am on cloud 9. all eggs accounted for 1-5 leghorns and 1 of her own because i have heart like that. I still notice the goo, and it has gotten worse and has solidified hay and feathers onto some eggs and matted some of the hay in the nest together. I remove the matted hay and scrape off some of the the grass and set off for the house to look up what this bum goo coming from broody mama is about. THANK YOU BYC FOR YOUR INFO!!! I find zero forum posts relating to bum goo but instead find plenty relating to exploded rotten eggs in the nest... hmmm, but all the eggs are there (1-5, and 1) and there is no egg shells in the nest. After reading about the pros and con's of cleaning hatching eggs I decide I need to clean this goo off the eggs, what ever it is. I get my warm water, paper towels, and a flashlight and head back out to the coop. I lift and move broody mama off the nest and set her aside while i wipe off every egg in the nest, recounting, re-candling, and re-confused. 1-5 and 1 all look healthy and not one missing. no broken shells from other eggs and no hen juice. I set broody mama back into the nest and see her tuck the eggs back under her when I notice she failed to tuck one leghorn egg under herself. I was just visible form under her wing so I decide to help her out by tucking it in for her... may hand recoils with goo in trail. I am more than confused, as i lift broody mama up too look at what caused the slime when i see the egg I had just tried to tuck in rise with her. WHAT!!!! I peel the egg off of her belly and sure enough #6 in pencil on the end with a hole in the middle dripping out goo. Really?!?!?! I set the rotten egg aside re-clean the eggs, clean broody mama's belly, all the while trying not to vomit on the whole production. First time brooding eggs... and I get this happening to me, hahahahaha. I am pretty annoyed with myself that I didn't catch this sooner, she must have had that egg stuck to her for 4 or more days slowly leaking out egg onto her clutch whenever she repositioned. Sorry broody mama. I has stupidly not written down the numbers and when #6 went missing I was none the wiser due to #1-#5 being intact. I also dropped her egg trough the toilet paper tube on to the flashlight i was using to candle the eggs (I hope it didn't kill the chick). All in a days work on the acreage right? That being told we have 6 chicks due on the 20th (Lord willing) and will learn from my mistakes to hopefully catch faults sooner and succesfuly brood and raise our marans, wyandottes, and leghorns through out cochins. The end.