The average breeding farm has about 50-75 breeding tribbles, most of which are kept on a carefully balanced ratio that maintains the tribble without discomfort but leaves not room for reproduction.
When a litter is desired, the breeder selects the tribbles he wants to breed and places them in a breeding cage.
An exact measurement of food is given, as the breeder usually will want to get a litter only from the selected tribbles, and not an immediate litter from the youngsters, as well. This is done by making sure the parent tribbles get exactly enough food for one litter, and one litter only. There will not be enough nutrients for the youngsters to be born pregnant, as is the case in tribbles when the parent animals have been fed free choice.
When fed too much, the youngsters will be pregnant, even if the litters will be small if the over-feeding was little. When fed too little, the two planned litters will be small, yielding smaller offspring which is rarely show quality.
After 10 hours, the tribbles are fed on a normal ratio again, another measure to assure no more than one litter is obtained.
After 12-14 hours the litter can be expected. The average litter is about 10 youngsters. The youngsters are immediately rendered safe by genetically altering, or selected for further breeding and put on a growth -but not breeding- ratio.
It takes much practice to balance the feed ratios in such a manner as to not starve the tribbles, or interfere with their growth, while staying low enough as to prevent reproduction. The margins might be as small as 2 mg. per tribble per day in miniatures.
Less experienced tribble breeders, afraid to over-feed their tribbles, often underfeed their breeding stock, but his leads to smaller tribbles with dull hair and shabby coats.
Once the youngsters which have not been selected for further breeding have been genetically altered, they are separated from the breeding stock and are fed more freely on a special growth mixture of grain. They are registered and given an NTBC.