Poultry Biology - Raising Poultry - page 56

turkeys, where the testes during the breeding season increase upwards of three to four
times the size they are in the off-season.
The testes are made up of dense tubes, connective tissue, blood capillaries, and Ley-
dig cells . The Leydig cells produce the male steroid hormone testosterone . Testoster-
one causes sperm cells to mature and the development of secondary sex characteristics,
which include feather patterns and colors, crowing, and sexual behavior.
Other male sexual reproductive organs include the vasa efferentia, epididymis, ductus
deferens, ejaculatory groove, and the phallus (penis). The phallus of waterfowl is spiral
shaped with an ejaculatory groove that can protrude as much as an inch or so. Mating
chickens and turkeys, however, have no penis to convey the sperm to the female. In-
stead, the semen is transferred to the cloacal area near the phallus, where it makes con-
tact with the female's cloaca in an act called a cloacal kiss .
It is very important that there are no obstructions that prevent the cloacas from meet-
ing. For example, the lack of a tailbone in rumpless fowl makes feathers grow down
over the vent opening. If this characteristic occurs in both male and female birds, it acts
very much as a birth control device.
The average male chicken produces less than ¼ teaspoon (about 1 ml) of ejaculate
containing as many as 3.5 billion sperm. Because sperm can live within the body of the
hen for up to 20 days, the great volume is needed to maintain fertility for that period.
Other factors, including health of male and female, determine the amount of time the
hen remains fertile.
Light is a major factor in determining sexual maturity and sperm production in the
male. Hormones are released from the pituitary gland in response to increasing day
length and in turn stimulate the testes to produce sperm and testosterone.
In Females
The right ovary (female reproductive organ) and oviduct (tube that transports eggs from
ovary) are present in the embryo in all birds, but in poultry only the left ovary and ovi-
duct develop. If you were to dissect a young female bird, you would find a left ovary
containing roughly 2,000 visible small ova (reproductive cells). In a mature functioning
ovary, a hierarchy of developing yolks is found, with between four and six large yolk-
filled follicles seen at any one time. The largest one is the next one to be ovulated and
produce an egg.
The follicle (yolk) is covered by a membrane that is highly vascularized, except in
one section called the stigma . The follicular membrane ruptures along the stigma at ovu-
lation. If the follicular membrane ruptures anywhere else, a small amount of blood will
be released along with the follicle and a harmless blood spot will be on the egg.