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Oxytocin is frequently used after delivery to increase uterine contractions and encourage milk letdown. If she has produced milk but it has not become available to the babies yet--this may be something that would work for her, although you'd need to see a veterinarian to have an injection administered. If she has not produced any milk at all (ie she's had her kittens but she shows no signs of mammary swelling) the chances that she's going to produce any milk is very low and you will need to plan to hand rear the babies. KMR is a good choice for young felines.
Also, if this is the second time she has produced a litter and has not been capable of feeding them--it would be wise to spay her unless you prefer to hand feed the kittens each time she produces a litter. She likely won't be a mother that produces milk if this is her second time not doing so.
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