This section is from the book "The Dogs Of Great Britain, America, And Other Countries. Their Breeding, Training, and Management in Health and Disease", by John Henry Walsh (Stonehenge). Also available from Amazon: The Dogs Of Great Britain, America And Other Countries.
The foster nurse need not be of the same breed as the puppies which she is to suckle; a smooth-skinned bitch is superior for the purpose to one with a rough coat, which is apt to harbor fleas, and in other ways conduces to the increase of dirt. For all large breeds the bull-terrier (which is most commonly kept among the class who alone are likely to sell the services of a nurse) answers as well as any other, and her milk is generally plentiful and good. For small breeds any little house dog will suffice, taking care that the skin is healthy, and that the constitution is not impaired by confinement or gross feeding. Greyhound puppies are very commonly reared by bull-bitches without any disadvantage, clearly proving the propriety of the plan. It may generally be reckoned, in fixing the number which a bitch can suckle with advantage, that, of greyhound or pointer puppies, for every seven pounds in her own weight the bitch can nurse one; so that an average bull-terrier will rear three, her weight being about twenty one pounds, and smaller dogs in proportion.
When the substitution is to be made, the plan is to proceed as follows: - (Jet a warm basket, put in it some of the litter in which the bitch and her whelps have been lying, then take away all her own progeny, and put all in the basket, together with the whelps to be fostered, mixing them so that the skins of the fresh ones shall be in contact with the bitch's own pups, and also with the litter. Let them remain in this way for three hours, during which time the bitch should be taken out for an hour's walk, when her teats will have become painfully distended with milk. Then put all the pups in her nest, and, carefully watching her, let her go back to them. In ninety-nine cases out of a hundred, she will at once allow them all to suck quietly, and if she licks all alike, she may be left with them safely enough; but if she passes the fresh ones over, pushing them one side, she should be muzzled for twelve hours, leaving all with her, and keeping the muzzle on excepting while she is fed, or watched until she is observed to lick all alike. On the next day, all but one of her own puppies may be withdrawn, with an interval of one hour or two between each two, taking care that she does not see what is done.
After two days the last may also be taken away, and then she acts to her foster-puppies in every way the same as to her own. Some people squeeze a little of the bitch's milk out of her teats, and rub this over the puppies, but I have never seen any advantage in the plan, and, as I have never had any difficulty in getting puppies adopted, I do not recommend any other than that I have described. In most cases the foster-bitch is strange to those about her, having been brought from her own home, and in that case a muzzle is often required for the safety of the servants watching her as well as for the whelps; but if she seems quiet and good tempered, it may be dispensed with.