Missing Mother,Abandoned Kittens

My cat had her second batch of kittens one week and two days ago.There's 5 of them.We let her outside last night and she hasn't come back.We've been letting her go out for the last couple of times she wanted out.She is an outside cat and by that I mean we let her come and go as she pleases and we figured her instincts would be strong enough to bring her back.The last few times we let her out at night and then let her back in she acted very strange.She was very cautious about everything,inspecting anything she crossed paths with and she didn't go over to her kittens until they cried.I am hoping she got disorientated or picked up by the animal shelter but we have to assume the worst so we got some milk replacement (the small pre-made carton) and an eye dropper.I've tried the bottle and the nipple seems to be to big for their comfort.
I've been feeding them every 2-3 hours.They each eat about 8-18 ml each feeding time.Is that enough?It takes about a solid hour and already today they've consumed about 1/3 of the carton.
Also,I have a heating pad which has settings low,medium,and high.When ever I set them on the pad when it was set on low they meowed and meowed.Since it's covered by layers of blankets/sheets I'm thinking it's not hurting them but to be on the safe side I turn it on while I'm feeding them and turn it off right before putting them in the basket so they'll have some warmth while they settle into a huddle.I'm also concerned about the chance of dehydration using the heating pad.
Any suggestions on dealing with the heating pad?
Oh,and should I take them to the vet?
They are very strong and wiggle around and have very loud voices when they want to.Two have pooped and all have peed and most of them have no problem just sucking a whole 8ml of replacement milk out of the eye dropper in one go.I'm also worried about over feeding.Can you do that?
I've been making sure that they each have a nice tight,round tummy before I put them back and watch how they act when it's not there turn to eat.If they start forming a pile(which they usually do after eating if I'm still feeding one) then I take it as a cue that they're full and sleepy.
Thank you for reading and sorry for the wall of text.

21 people have read this, and no one has commented? I am a little saddened with this. Obviously this person is new and is in dire need of our help.

Lets step up! Even with good vibes!

I am so sorry your momma cat has not returned. You are right, you can only hope for the best. Have you checked with the local shelters and posted signs? Post signs all over your neighborhood, and let them all know she is a momma with 3 day old babies at home. WHEN you find her, I wouldn't let her back out. And after she is done nursing, I would get her spayed. An inside/outside cat should not remain intact (unspayed) There are far too many kittens and cats that don't have homes already.

It sounds as if you are doing very well by the kittens. When bubbles start to form at their moths, they are done feeding. I am not sure about the heating pad. I have never had to use one.

It sounds as though you are being very careful and attentive. Thank goodness you are there to help them.

Sending lots of good vibes your way that momma returns soon. I am sure that someone who knows more about kitten care will comment soon, and others will be sending you the encouragement you need at least.

All my best,
Kristin

Thank you Kristin.
When we called the animal shelter they were closed.
Good News!Those vibes must have worked because she walked in this morning and went straight to her kittens.I'm so happy!Nothing can beat the warmth of a momma kitty.One of my main concerns was that I wasn't going to be able to provide the affection they need.
And I plan on getting her spayed asap. :]

I'm so happy she's back!

I also want to get the kittens spayed/neutered before I give them away.
Any idea as to what age that can be done?

Kittens can be altered when they are 8 weeks old and weigh at least 2 pounds. Some vets still wait until they are 6 months old, mine is one that does. You may have to call around to find one that will do the younger kittens. A shelter or rescue can probably give you the name of one that will alter the younger kittens.

YAY!!

I am so happy for you!!

Definitely call a shelter and ask around about the spay/neuter. They will probably know of a lowcost/nocost facility to refer you to. The organizations/programs who's sole purpose is to spay/neuter are usually willing to alter young. Our LB was very young. So much so they had to get vet approval on the day of. But his little peanuts where present so they were happy to do a snip-snip. He wasn't so happy though. Poor baby boy.

I am so glad she is home! Don't let her out again! No matter how much she carries on! Cats CAN and DO get preggo while they are nursing. That is what happened to the stray we are fostering right now. She had a litter of six when her owner turned her out on her first heat. She was nursing and went into her second heat, he turned her out again and she got preggo with this litter. We finally got her after he dumped her and 3 of her kittens because the kittens weren't using the litter box!!!!!

Sending out the best vibes to your kitty momma and kittens!

According to the breeder, my Angus was conceived when his mother gave birth unexpectedly to a litter and she hadn't isolated momma yet, she was around some of her other cats for just one night before it was discovered she had given birth. A few weeks later she took Angus' momma to the vet to check out the "tumor" that was growing in her abdomen and on xray they saw 3-4 kittens! Angus was born about a month later.

Your mom cat is once again pregnant-(bet on it) they go into heat 24 hours after the last kitten is born and they go off and on again in heat for a few weeks after. Please get her spayed, and her milk will drop 24 hours after surgery.

If you need this website in the future www.kitten-rescue.com it will help you through the tough stuff of raising kittens. Glad the queen is back, but please get her spayed. The kittens can be done when they are 2 pounds if your vet is willing (some are, some aren't)