Topic 97 - Reproduction of birds

Question 1

Words to include

Answer 1

Male birds

• Internal organs
  
  • Testis
    
    • Abdominal cavity (location)
    • Spermatozoa production
    • Lead to ductus deferens
  • Epididymis
    
    • Sperm maturation
  • Ductus deferens
    
    • Inactive spermatozoa storage
  • Ø accessory reproductive gland
    
    • Dense semen
• External organs
  
  • Phallus
    
    • Copulatory organ / ejaculatory papillae
    • Wall of cloaca (location)

Spermatogenesis

• Spermiocytogenesis & spermiomorphogenesis
  
  • Thickening seminiferous tubules (location)
  • Sertoil cells
• ​Cockerels
  
  • Sexual maturity 3-5 months

Hormones of the male bird

• Male basic gender in birds
• Leydig cells
  
  • Androgen secretion
    
    • Sexual dimorphism role
  • LH-receptor
• Testosterone
  
  • 5-α-DHT (metabolite)
  • Testosterone → 5 ß-DHT-t (inactive)
    
    • CNS
• Testis produce:
  
  • P4
  • Estrogen
• GnRH secretion
  
  • Hypothalamus
  • Season influenced
  • Negative feedback of teststerone
    
    • Works only if 5 ß-reductase reduces 5 ß-DHT
• Adenohypophysis
  
  • LH
    
    • Influencing leydig cells
  • FSH
    
    • Influencing sertolis cells
• Leydig cells
• Sertoli cells
• Androgens
• Testosterone
  
  • 5-α-DHT
  • 5 ß-DHT-t (inactive)
• P4
• Estrogen
• GnRH
• LH
• FSH

Female bird

• Three stage development
  
  • Prepuberty (1-12 weeks)
    
    • Small white follicles
  • Intermediate phase before sexual maturation
    
    • Small, medium & large follicles
  • At maturation
    
    • Small, medium & large follicles
    • Granulosa and thecal layer thickening
      
      • For hormone production
    • FSH
      
      • Follicular growth stimulation
    • LH
      
      • Ovulation stimulation

Hormones of the female bird

• Estrogens
  
  • E1
  • E2
  • Morphofunctional preparation of oviduct
  • Preparation of calcium-metabolism
  • Depostion of abdomial fat ↑
  • Secondary sexual characteristics
  • Creation of adequate behavior
• Progesterone
  
  • P4 level ↑ → second phase of follicle maturation ↑
  • Interovulation period
    
    • Plasma P4 low
    • Preovulatory peak (4-7 hours before ovulation)
• LH-FSH
  
  • Preovulatory peaks
    
    • Sensitizing phase
      
      • Hypothalamic P4-receptors ↑
        
        • Hig estrogen and P4
        • High P4 → GnRH production
    • Inductive phase
      
      • Hypothalamo-hypophyseal axis
• Ovary
  
  • Androgen production
    
    • Testosterone
    • Androsterone

Formation of egg

• Infundibulum
  
  • 30 min
  • Engulf preovulatory follicle
  • Spermium storing glands
  • Fertilization
  • Membrane extravitellina (gland of infundibulum covering egg)
• Magnum
  
  • 3 hours
  • Secretion regulation by:
    
    • ​E1
    • E2
    • P4
    • Androgens
  • Albumen production
  • Egg-shell production
• Isthmus
  
  • 1-2 hours
  • Cell membrane formation
• Uterus
  
  • 19-20 hours
  • Mamillary knobs from mamillary core
    
    • Calcification formation
  • Albumen layers develop
  • Plumping → shell formation
  • Soft shell-membrane stretching
  • Calcification begins
• Uterovaginal sphicter
  
  • 1 min
  • Egg transport to outside

Brooding patch

• PRL influence in synergism with estrogen → brooding patch development
• Abdominal skin bare
• Epidermis thickens
• Underlying connective tissue swells
• Good blood supply (venous network)
• Thyroid hormones
  
  • Basal metabolism ↑
  • PRL secretion ↑
  • Gonad function inhibited

Bird embryo

• Egg shell
• Shell membrane
• Air sac
• Egg white
• Yolk balancer
• Vitelline membrane
• Blastoderm (embryo)
• Yolk

Question 2

Topics to include in the essay

Answer 2

1. Male birds
   
   • Internal organs
     
     • Testis
     • Epididymis
     • Ductus deferens
   • External organs
     
     • Phallus
   • Hormones of male birds
2. Female birds
   
   • Development
   • Hormones of female bird
     
     • Estrogens
     • Progesterone
     • LH-FSH
   • Formation of egg
   • Brooding patch

Question 3

Male birds

Name the male reproductive organs, and their function

Answer 3

• Internal organs:
  
  • ​Testis
    
    • ​In abdominal cavity
    • Produces spermatozoa
    • Lead to ductus deferens
  • Epididymis
    
    • _​_Sperm maturation
  • Ductus deferens
    
    • ​Storage of inactive spermatozoa
• External organs:
  
  • ​Phallus
    
    • ​Two papilla coming together from each side
    • Copulatory organ /ejaculatory papillae
• Ø accessory reproductive organs

Question 4

Male birds

Spermatogenesis

Answer 4

Spermiocytogenesis and spermiomorphogenesis

• ​During puberty, they take place in the thickening of seminiferous tubules, with contribution from setoli cells

Cockerels

• Sexual maturity around 3-5 months
• Mature spermiums are appearing
• Leydig cells are activated
  
  • Androgen secretion

Spermatogenesis

• Copulation: 20-40 times mating a day
• Vitality: 30 days

Question 5

Male birds

Male sexual hormones

Answer 5

• The basic gender in birds is the male
• Leydig cells:
  
  • ​Synthesize androgens
  • LH-receptors on the surface
    
    • ​LH influences leydig cells
• Sertoli cells:
  
  • ​Androgen production
  • FSH influences sertoli cells
• Testosterone:
  
  • ​Effective metabolite of testosterone is 5-α-DHT
  • Converted to 5 ß-DHT-t in CNS (inactive)
• GnRH:
  
  • Hypothalamus
  • ​GnRH secretion is influenced by:
    
    • Season
    • Amount of daily light
    • Negative feedback-effect of testosterone
      
      • ​Works only if 5 ß-reductase reduces the amount of 5 ß-DHT
• Lutenizing hormone (LH)​:
  
  • ​Produced in adenohypophysis
  • Influences leydig cells
• Follicle stimulating hormone (FSH):
  
  • ​Produced in adenohypophysis
  • ​Influences sertoli cells
• Progesterone
  
  • ​Produced in testis
• Estrogens
  
  • ​Produced in testis
• Androgens
  
  • ​Important in forming sexual dimorphism
  • Leydig cells synthesize androgens
  • Sertoli cells have androgen production

Question 6

Female birds

Development of ovary and ovum

Answer 6

Three-staged development

1. At the beginning of prepuberty (1-12 weeks):
   
   • Small white follicles
2. Intermediate phase just before sexual maturation
   
   • Small follicles
   • Medium follicles
   • Large follicles
3. At maturation
   
   • ​Small yellow follicles
   • Medium yellow follicles
   • Large follicles

Question 7

Female birds

Female sexual hormones

Answer 7

• Estrogens
  
  • ​E1andE2
  • Role:
    
    • Morphological preparation of the oviduct
    • Preparation of calcium metabolism form egg production
    • Deposition of abdominal fat ↑
    • Creation of secondary sexual characteristics
    • Ceration of adequate behavior in the successive reproductive periods
• Progesterone
  
  • _​_P4 level in the plasma increases in the second phase of the follicle maturation (together with LH ↑)
  • Just before maturation, P4 & LH decreases
  • Interovulation period
    
    • ​Plasma P4 low
    • Preovulatory peak
      
      • ​4-7 hours before ovulation
• LH-FSH
  
  • LH: ovulation and progesterone production
  • FSH: follicluar growth and estrogen/androgen production
  • _​_Preovulatory peak takes place:
    
    • Sensitizing phase
      
      • Hypothalamic P4-receptors are increased by high estrogen and P4
      • High P4 stimulates GnRH production​
    • Inductive phase
      
      • ​Constant rise of preovulatory P4 peak is enough to stimulate LH secretion by the hypothalamo-hypophyseal axis

Question 8

Female brids

Formation of egg

Answer 8

Infundibulum

• 25-30 minutes
• Engulf the preovulatory follicle
• Spermium storting glands
• Fertilization site

Magnum

• 3 hours
• Longest part of ovuduct
• Role:
  
  • Albumen production
  • Egg-shell production
• Secretion regulated by:
  
  • E1
  • E2
  • P4
  • Androgens

Isthmus

• 1-2 hours
• Forms two fibrous cell membranes

Uterus

• 19-20 hours
• Mamillary knobs developed from mamillary cor
• Albumin layers develop
• Soften shell membrane will stretch
• Calcification begins
• Plumping is followed by shell formation

Uterovaginal sphincter

• 1 minute
• Transport of egg to the outside

Question 9

Female birds

Brooding patch

Answer 9

• Brooding patch: Featherless skin that is visible on the underside of birds during the nesting season, with well supplied blood vessels at the surface making it possible for the birds to transfer heat to their eggs when incubating
• Brooding patch developes due to PRL influence in synergis with estrogens
• Physical signs:
  
  • Abdominal skin becomes bare
  • Epidermis thickens
  • Underlying connective tissue swells
  • Abundent venous network
• Thyroid hormones:
  
  • ​Increase the basal metabolism
  • Stimulates PRL-secretion
  • Inhibit function of gonads