The breeders should be turned off to market whenever their egg production drops off so decidedly that it no longer pays to hold them. In most cases this will be about the 1st of July but it may range considerably earlier than this, especially with pens of ducks that have started laying early. When the ducks finish laying their eggs they begin to moult and it is at this time that they should be marketed. If marketing is delayed, the ducks will lose condition as the moulting progresses and will therefore be held at a loss. Diseases and Pests _Disease._ Old ducks, that is, mature ducks, are practically free from disease. Of course, there will be a certain amount of loss in the breeding stock from various causes but this should not run for the entire season more than 10% of the flock. Ducks do not become egg bound, but sometimes, especially during heavy laying, they become ruptured. _Insect Pests._ Ducks are remarkably free from lice and other insect pests and those which they do have do not trouble them much. It is unnecessary therefore to take any precautions in the way of treating the ducks to keep them free of insects. _Dogs._ Occasionally trouble may be experienced from dogs. If these animals get into the yards with the breeders or the fattening ducks, they may kill a good many and in addition will seriously injure the rest by chasing them and by the fright which the ducks are given. CHAPTER V Commercial Duck Farming--Incubation The Pekin duck is essentially a non-broody breed. It, therefore, becomes necessary to resort to incubators for the purpose of hatching the eggs. Occasional ducks will sit if allowed to do so but it is not the practice on commercial duck farms to allow them to sit and hatch their young. No special means are taken to break them of broodiness other than not to allow them eggs to sit on. _Kinds of Incubators Used._ Both the smaller kerosene lamp heated incubators and the large or mammoth hot water heated incubators are used for hatching duck eggs. At the present time the mammoth hot water machines are those which are in principal use due largely to the lessened labor required to operate them.