Lecture 8

What is the average chicken meat consumption per person in Australia?

Approximately 50 kg per person per year.

What are the main driving factors for chicken consumption?

Price and the carbon footprint, as chicken production has a lower carbon footprint compared to other farm animals.

What are the basic reproductive features of avian reproduction 

• No oestrous cycle or pregnancy

• Often lay eggs in batches (clutch)

• Oviparous

• Photoperiodic

• A single ovary and oviduct (most bird species)

  • Usually the left

• Female is heterozygous (ZW), male is homozygous (ZZ)

• Internal testes

• No prostate gland, seminal vesicles or penis

What stage do laying hens reach sexual maturity?

At approximately 18 weeks of age.

What factors affect avian reproduction?

Light duration, moisture availability, nutrition (especially calcium), and environmental conditions.

Describe the female reproductive system anatomy

The female reproductive system anatomy in birds consists of a single ovary, usually the left, and an oviduct where eggs are produced and transported.

Where does an immature ovary usually sit in the abdomen

Immature ovary sits caudal to the lung and sits on top of the cranial lobe of the left kidney

Where is yolk made ?

In the liver 

What is the hormonal control of avian ovarian maturation

Breeding cues → positive stimulus on hypothalamus → release GnRH → targets pituitary gland to produce FSH and LH → FSHH increases ovarian and oviduct growth and LH produces oestrogen

What role does oestrogen have

• Follicular growth

• Oviduct growth

• Calcium metabolism

• Vitellogenesis (egg embryo development)

What is the site where the rupture of follicular membranes occurs

Stigma

Where does fertilisation occur in aviary species

In the infundibulum of the oviduct

What are the hormonal changes resulting in follicular rupture 

Large follicles start producing progesterone which acts on the pituitary gland to produce an LH surge which induces prostaglandin production in the follicles which causes them to rupture

Describe oviposition

1. 24 hours after ovulation → egg forms in oviduct and ends up in uterus

2. PGF2 alpha induces muscular contractions in uterus

3. PGE causes uterovaginal sphincter to relax

4. Uterine contractions stimulate arginine vasotocin release form the pituitary gland

5. AVT stimulates uterine prostaglanding release

6. Oviposition

What is broodiness in hens?

A natural behaviour involving laying hens, where they sit on their eggs resulting from a drop in oestrogen levels and increases serum prolactin

considered negative in commercial poultry but common in backyard conditions.

What other changes do you see with broodiness

• Loose breast feathers and develop a bare patch of skin

• Exhibit aggressive behaviour

• Won’t leave the nest

• Stop laying

How might you stop or prevent broodiness

• Once started, requires time (~21 d) to revert

• Remove eggs

• Remove nesting materials

• Replace litter with grills

• Eliminate access to nesting box

• Place the hens in cooler environment

• Hormone therapy (not very effective)

What is the significance of the infundibulum in the reproductive process?

It is where the ovum is picked up after ovulation and fertilization occurs.

What is the role of the oviduct

Transfers fertilised ovum to the cloaca

Provides nutrients and protection to the growing embryo

What occurs within the magnum of the oviduct

Produces egg white, albumen and chalazae

What occurs within the isthmus of the oviduct

Produces the shell membranes

What occurs within the uterus

Egg shell is deposited and pigments and cuticles are produced

What stage requires the longest time in the oviduct

The uterus = 15 hours

What region has potential sperm storage capacity 

Uterovaginal junction

Describe the anatomy of an egg

The yolk is lined by a perivitelline membrane

The yolk is mainly made of fat and is lighter than albumen

The chalazae are twisted cords made of albumen

The shell has 2 membranes

The shell itself can be pigmented an contains cuticle which covers the outside of the shell

What is significant about the chalazae

joins the yolk to the ends of egg and is important the yolk in staying in the middle

What does the papilla of the ductus deferens do

Eject sperm through the grove between the phallic bodies into the female cloaca

What acts as the copulatory organs in the male

The phallic bodies (lateral and medial) and lymphatic fold

What is he role of the lymphatic fold

Expand due to engorgement with lymphatic fluids → these transfer sperm to the cloaca during tumescence

What role do the male reproductive hormones FSH and LH play in birds?

FSH stimulates spermatogenesis while LH promotes the development of leydig cells that produce testosterone.

How does insemination occur in aviary species if there is no external male copulatory organ

Insemination occurs through the cloacal contact, where the male and female align their cloacas