Wk13avian repro Flashcards
Sex determination of avians: chromosomes
How does this differ to mammals?
- Chromosomes
- Male: ZZ (homogametous)
- Female: ZW (heterogametous)
- Primary oocyte divides by meiosis, extruding a polar body and leaving the secondary oocyte (ZW)
The secondary oocyte then undergoes mitosis, extruding the second polar body and leaving an ovum which carries either the Z or W chromosome
Differentiating the gonads: development of testes and ovaries in avians depending on ZW or ZZ chromosomes
- ZW = ovary (left mainly developed, right less)
- ZZ = testes L and R
Gonads then produce hormones testosterone or oestrogen
Dimorphic and monomorphic, and delayed dimorphism
- Dimorphic = different colours(e.g. Female green trying to hide, males red/purple stand out)
- Delayed dimorphism: can be months or years before can show e.g. Rings around males neck when about 3 years turns purple.
Monomorphic = the same/identical (no differentiation between male and female)
- Delayed dimorphism: can be months or years before can show e.g. Rings around males neck when about 3 years turns purple.
Identifying the sex of monomorphic birds approaches
- Surgical sexing - incised LHS (ovaries for females, and can see testes of males)
- DNA sexing (much cheaper, but not as accurate..)
- ‘wait and see’
Vent sexing in ratites and poultry - lots of mistakes can be made with this
Female anatomy: location and blood supplies
- Ovary
- Location: LHS of body, on dorsal body wall, between kidney, adrenal gland and the lung
- Blood supply: arterial supply is branch of cranial renal artery and caudal vena cava
- Very risky for surgical procedures..
Oviduct and formation of an egg: 5 sections it goes through and what occurs
- Infundibulum
- Magnum –> egg white
- Isthmus –> shell membrane
- Uterus –> where hard egg shell is formed
Vagina –> seal pores, sperm storage
Ovulation process:
- Oocyte reduction
- Hormonal input (FSH and LH)
- Stigma rupture from the follicle wall and release of follicle
- Fertilisation
Follicle regression
Calcium metabolism of egg laying
- Every 15minutes a weight of calcium equalling the total amount circulating at any one moment is withdrawn from the blood
- So if calcium is not replenished every 15 minutes you will get hypocalcaemia
- Calcium used for: eggs, bone structure, heart function**
Calcium will be pulled out of the bones to put into egg shells if required…
Egg laying in the hen; what does this do to blood calcium levels and how do they increase again
Egg laying –> drop in blood calcium –> mobilise medullary bone, increases vit D3, decrease Ca excretion, increase PO excretion —> Increase blood calcium
Male anatomy: location, development, blood supply
- Blood supply same as the female, cranial medial artery
- Much easier to remove teste in male than ovary in female due to the blood supply being in a suspensory stalk (not as risky)
Between kidney, lung and adrenal grand as well
- Much easier to remove teste in male than ovary in female due to the blood supply being in a suspensory stalk (not as risky)
Male anatomy avians
- Testicle sitting between kidneys
- Ductus deferens runs down towards cloaca
- Semen stored in seminal, off from the ductus deferens
- Epididymis: has ducts running into the adrenal glands
May still get reproductive activity in a desexed male
Testicle: histology
- Seminiferous tubules
- Sertoli cells
Interstitial cells
Spermatogenesis avians
- Mitosis, meiosis I and meiosis II and then differentiation
Pre-nuptial acceleration
- Before the breeding season (spring)
- Increase in warm, gonads get larger leading up to breeding season
- ## No bird has a penis, it is called a phallus*
What do birds without a phallus do? What do birds with phallus do
- Copulation: cloacal ‘kissing’
- Semen pushed into the female cloaca
- Phallus:
Into the cloaca of female
Fertilisation process: where does it occur
- Fertilisation occurs in the infundibulum
- Spermatozoa have 15 minute window
- Source of spermatozoa
- Mating at time of ovulation - less than 1% of semen reach the vagina
Release of the spermatocytes from the vaginal glands (line the vagina wall) will store semen ready to move it up into the infundibulum after ovulation
- Mating at time of ovulation - less than 1% of semen reach the vagina
Puberty in birds
- Endocrine and physical sexual maturity
- Proportional to body size
- Males earlier than females
- Male is ready but female is not = aggression of male to hen
Captive earlier than wild birds
- Male is ready but female is not = aggression of male to hen
Reproductive success of birds: what is this determined by
- When they breed
- Level of investment made during
- Egg laying and chick rearing
Female thus plays predominant role
- Egg laying and chick rearing
Timing of egg laying; are birds seasonal breeders?
- Yes birds are seasonal breeders (spring)
- Dependent on female-specific physiological processes
- Environmental cues: longer days, warmer air, some rainfall
- Suggesting to hens that breeding time is coming
- Development of chick at hatching
Extent of parental care
Endogenous and exogenous factors that regulate reproductive effects
- Captive birds show seasonality and so do tropical birds
- Why? Poorly understood
- Exogenous factors: understand these more
- External to the bird
- Genetic selection for birds that breed with best chance of success
- Explains why birds breed when they do
- Environment cues for birds to predict onset of breeding season
Varies year to year
Initial predictive factors, essential supplementary factors, synchronising and integrating factors and modifying factors required for reproduction in birds
Seasonal development; what phases occur during different seasons of the year
- late winter - early spring: prenuptial acceleration and gonads, reproductive tract enlarge
- spring-early summer: culmination phase, ovulation and spermatogenesis, & egg laying
- late sumer-autumn: refractory phase, atresia of remaining follicles, tract reduces in size
Endocrine cycle in birds: process from hypothalamus to testosterone and oestrogen
- Hypothalamus in brain, received auditory input (rainfall, sun, increase temperature etc.) –> produced GnRH goes to pituitary gland –> FSH and LH –> go to the gonads –> produce oestrogen (calcium, follicle growth) and testosterone (behaviour)
Egg laying in relation to the endocrine cycle in birds: what hormone is produced by the ovary / increased for egg laying?
Clutch size in birds: what is it determined by?
- Egg laying date (Early or late)
- Chick-rearing ability
- Nest predation (predators or people)
- Ambient temperature
Genetic selection
Clutch size in birds: what is it determined by?
- Egg laying date (Early or late)
- Chick-rearing ability
- Nest predation (predators or people)
- Ambient temperature
Genetic selection
Indeterminate verse determinate layers
- Indeterminate layers lay additional eggs if eggs are removed from the nest during laying –> egg quality may decrease
- Determinate layers: do not respond to egg removal by laying additional eggs
Possibly linked to unknown tactile stimulation from eggs in nest - don’t really know
Indeterminate verse determinate layers
- Indeterminate layers lay additional eggs if eggs are removed from the nest during laying –> egg quality may decrease
- Determinate layers: do not respond to egg removal by laying additional eggs
Possibly linked to unknown tactile stimulation from eggs in nest - don’t really know
Avian follicles - what is their role and what is the stigma of the follicle? what can happen if yolk spills into the body
- Follicles:
- Full of fat from the liver; under influence of oestrogen, forms source of nutrition for the developing embryo / chick that hatches
- Stigma: this is where follicle splits when ovulating to release the follicle into the body, infundibulum wraps around it then
Yolk can spill into the body when infundibulum doesn’t do its job, and will be noticed as foreign body part stimulating immune response/inflammatory fluid = yolk peritonitis.
function of the infundibulum
- capture the ovulating follicle off the ovary and fertilisation of ovum
- 15 mins
function of the magnum
albumen added to the follicle
3hrs
function of the isthmus
- small amount of protein added to albumen inner and outer shell membranes are laid down and shell calcification begins
- 75 mins
function of the uterus in the oviduct
plumping - addition of watery solutions to the egg for 8 hours doubling the weight of the albumen
- shell is formed
- 20hours
function of the vagina in the oviduct
passage to the cloaca and oviposition
sperm storage and spermatic fossulae
1-5seconds in length
