Avian Reproduction Flashcards
1
Q
photoperiod
A
- time when a bird receives illumination = daylength
- most birds are seasonal long day breedrs
- spring - warmer climate and adequate food supply
neonatal survival - synchronizes flock and improve and maintain reproduction
- controls sexual maturity
2
Q
path of light into bird
A
eye
hypothalamus
pituitary gland
reproduction and body function
or
skull
pineal gland
hypothalamus
3
Q
light perception
A
- photoreceptors in the pineal gland, hypothalamus and eye
- photoreceptors transduce energy contained in photons into biological signal
- endocrine effects of photostimulation
4
Q
melatonin
A
- source: pineal gland and eye
- function: time to signal body, regulates circadian rythms of biological functions, antioxidants and immune system
- synthesis inhibited by light
- studies have shown that melatonin is NOT required for birds to respond to photoperiod
5
Q
circadian rhythms and light perception
A
- internal circadian rithms occur at 24 hour time frame - distinguish between long and short daylength
- light is the primary zeitgeber ( time giver)
- critical day length in chickens 11-12 hours
- period of photosensivities starts
rapid stimulation of hormones release - commercial photoperiod: 14-16 hours
6
Q
photorefractoriness
A
- failure to maintain gonadotropin secretion during long days
- can occur after extended exposures to long days
- to be photosensitive again, hens must be exposed to short days ( must experience short days for 10-12 weeks to start reproduction)
- birds are photorefractoriness at hatch - hatching during a long day - but not stimulation sexual maturity
7
Q
commercial practices for layers
A
Duration of day length:
- growing pullets are exposed to decreasing and short days ( 8L :16D)
- increasing daylength is used for photo stimulation
- using photoperiod to control age at sexual maturity 17 weeks ( 16L:8D)
- induction of sexual maturity - increase photoperiod beyond critical photoperiod
- critical daylength 12L:12D
- never decrease photolength period
8
Q
what happens when egg production declines
A
- economics of >80 week old flock poor
2 choices: - depopulation
- moulting (complete or partial feed reduction loose about 50% body weight
- stimulates reproductive tract regression
- force moulting is banned in north america, European Union and UK
- low nutrient diets lighting - meets maintenance requirements
- animal welfare concerns
9
Q
forced moulting
A
- moulting is a natural physiological process in birds: shed their old feathers and replace them with new one’s followed by reproductive inactivities = reduced egg production
- different birds undergo moulting at different points in their life:
- seasonal or end or breeding cycle
- commercial farms analysis the cost to benefit ratio to decide the time and method to adopt for molting
- commercial layer farms adopt different practices to force birds out of moult and restart the production cycle
10
Q
oviduct development
A
- develops from genital ridges in developing embryo
- right duct regresses at day 11
- very rapid development as approaching lay
11
Q
ovary
A
- left ovary is functional
- right ovary is rudimentary (produce androgens and estrogen)
- if left ovary is destroyed or damaged right ovarywill develop ovotestes ( prepping just in case)
- at sexual maturity some of the oocytes (ova) begin to develop
12
Q
chick oocyte development
A
- embryonic - dormant primordial follicles develop in functioning left ovaries
- as birds becomes sexually mature incorporation of protein rich white yolk leads ti formation of small white follicles
- some SWF continue to develop and eventually start lipid rish yellow yolk incorporation to form small yellow follicles
- most of the SWF/LWF undergo atresia, an important adoptotic process that keeps numbers of rapidly growing follicles fairly small
- selected SYF enter the follicular hierarchy, 1 per day
- much of the yolk mass is imported as very low density lipoprotiens and vitellogenins synthesized and secreted by the liver
- large amount of material to be incorporated into the follicle
- follicle are 30-40mm in diameter at ovulation
13
Q
follicle selection
A
- selection process unknown but follicle become responsiveness to FSH
- increased transcription for steroidogenesis
- switch from FSH and LH receptors in hierarchy
14
Q
defected follicle
A
- hierarchy in overweight broiler breeder hens
- double yolked eggs - f2 will be developed and sent
- if they are fertilized one will be a chick and the other will be a yolk, chick dies because there is not enough room
15
Q
endocrine effects
A
- development of characteristics essential for reproduction
- testosterone: stimulate comb growth and female specific plumage
- estrogen: stimulate separation of pubic bones, development of medullary bone
16
Q
steroidogenesis
A
- depositon of calcium in medullary bone
- secondary bone found only in laying hens
- egg shell formation when gastrointestinal tract empty
- not enough calcium - osteoporosis
17
Q
ovarian follicles
A
- small ovarian follicles produce oestrogens and androgens
- development of female specific plumage
- deposition of calcium inmedullary bone
- production of yolk precursors by the liver
- development of reproductive tract
- development of other sexual characteristics
- female pubic bone develops, combs and wattles grow from testosterone
18
Q
as the follicles grow
A
- production of oestrogen declines
- androgen secretion ( increases to f2 and is terminated within 16h of F1, reduction of androgens and increase of progesterone = releases f2)
- progesterone secretion increases with follicular development
- from granulosa cells, reaches a peak = ovulations
- can be alot on the birds = see visible personality change
19
Q
ovulation
A
- induced by LH serge ( there is a threshold that has to be met for the serge)
- coordination of open period (LH peak) and follicle maturation
- LH and progesterone interact to cause peak in LH sufficient to promote ovulation
- follicle ruptures at the stigma
20
Q
post ovulatory follicle
A
- P1 and P2 will secrete prostoglandins to promote:
- SYF into follicular heirarchy
- oviposition : smooth muscle contractions for egg laying
- nesting behaviour
21
Q
what do hens not have for ovulation
A
corpus luteum
22
Q
what are the portions of the oviduct
A
infundibulum
magnum
isthmus
shell gland
23
Q
infundibulum
A
- actively recieves ovum from ovary pocket within 15 minutes of ovulation
- internal laying ( yolk is not taken into the oviduct, but layed in the abdomen, this can fill the whole abdomen with eggs)
- sit of fertilization and sperm storage tubules
- secrete outer layer of the yolk ( keeps is from breaking (vitelline) membrane
- ovum spend 15 to 30 minutes in the infundibulum
- 10cm in length
24
Q
magnum
A
- developing egg spends 3 hours here
- 37.5cm in length
- most of the egg albumne ( egg white is deposited)
- chalaziferous or inner thick ( forms chalazae chord = this keeps the yolk centered in the egg so embryo doesnt get stuck to the shell)
- inner thin albumen
- outer thick or firm layer( ovomucin fibres)
- outer thin – derived from shell gland
25
Q
isthmus
A
- egg spends 1.4 hours in this region
- 10 cm in length
- deposition of the two shell memebranes
- air cells forms at large end of the egg
26
Q
shell gland
A
- most comparable to the uterus (not the uterus = no placenta)
- egg spends 19-20 hours in this region
- 10cm in length
- outer thin albumen
27
Q
shell
A
- is 12% of the egg weight
- 98% calcium carbonate ( occurs at night when there is no feed in the GI tract)
- two layers:
mammillary knob like structures
palisade or spongy layer - column like formation
-pores - for gas exchage
28
Q
shell pigment
A
- heritable trait = BXB = B BXW= B BXBr = green
BXDBr= olive green - porphyrins (protopotphyrin) derived from haemoglobin metabolism responsible for brown pigment
- oocyanin, which is a product of bile formation, responsible for blue/green eggs
29
Q
shell cuticle or bloom
A
- just before oviposition
- partially blocks shell pores ( drys and seals to prevent bacteria from going in)
- outer layer of the egg
- proteins carbs and lipids
- usually signals termination of eggshell formation in shell gland
- mediates UV exposure
- physical barrior ( plugs shell pores, pathway for gas diffusion)
- chemical barrier ( proteins with antimicrobial factors)
- effectiveness is variable
- important for food safety
30
Q
washing eggs
A
- table eggs in many countries are washed
- may increase bacterial penetration if done incorrectly
- temp and pH critical ( 10 or higher)
- will not improve hatchability
- in the countries that dont wash - they dont need to refridgerate because the cutical offers protection
31
Q
shell gland vagina
A
- sphincter like muscle
- area f major sperm storage tubules
- approximately 25 000 sperm storage tubules
- after insemmination, approximately 75% will contain an average of 400 sper per tubule
32
Q
vagina
A
- transport of egg through cloaca
- site of semen deposition ( after semon is deposited, vagina retracts)
- everted during natural copulation
- important for selection of healthy sperm
- 10cm in length
33
Q
oviposition
A
- oviposition time is linked to ovulation ( 25 hours after ovulation, egg is layed)
- P1 and F1 both play a role ( if there is a disfunction oviposition can be delayed
- prostoglandin
- eggs are layed in morning or early afternoon
