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.
_Incubator Cellar._ It is necessary to provide some room in which the
incubators can be installed and operated. This may take the form of a
cellar, or the incubators may be operated in rooms above the ground.
Many of the incubator cellars on duck farms are only partially under
ground and not a few of them are built entirely out of ground. The
particular size and shape of the cellar or incubator room will, of
course, depend upon the number of incubators to be installed and upon
their make and shape. Usually these buildings are constructed with
rather thick walls so that the temperature of the room will fluctuate
less with changes in outside temperature. Provision is also necessary by
means of windows or other ventilating devices to provide for good
ventilation in the room. The cellars are usually constructed with cement
floors as moisture is used freely and wooden floors would rot out
quickly.
_Incubator Capacity Required._ The aim on commercial duck farms is to
hatch all of the eggs produced which are suitable for the purpose.
Practically no eggs are sold except the cracked eggs or those which
would not give good results in the incubator such as too large or too
small eggs