Avian Theriogenology & Neonatology Flashcards
What is the most common reproductive strategy of passerine birds?
What other strategies exist?
Monogamy
Leks - birds or paradise, manakins, cock of the rocks - bright colors elaborate dances
Bower Birds - polygyny - males decorate nests
Parasitic Brooders - cowbirds, whydas
Describe the general reproductive pattern of passerine birds.
- Gonads of both males and females may undergo seasonal enlargement and regression.
- May lay from 1 to 12 eggs per clutch, depending on the species.
- Most eggs patterned or pigmented.
- Generally 1 egg laid per day.
- Pip to hatch usually 24h or less.
- Hatchlings are altricial and nidicolous but may grow rapidly.
Fowler 8
Describe the female reproductive anatomy of psittacine birds.
Which side has the active reproductive tract?
What are the five sections of the oviduct?
What is the typical oviduct transit time?
Where is sperm stored?
How long does it take to fully form an egg?
Where is most of that time spent?
- Reproductive tract of all female psittacines located on left side of coelom
- Right ovary and oviduct normally regress prior to hatching in psittacines
- In some species (raptors) these organs may be vestigial remnants or functional (rare)
- Oviduct takes up much of left coelom during breeding season
- Left ovary connected to urodeum via oviduct
- Ovary located cranial to left kidney and caudal to adrenal gland
- Oviduct - five sections: infundibulum, magnum, isthmus, uterus (shell gland), vagina
- Peristalsis transports ovum from cranial oviduct to uterus
- Oviduct transit time varies across species but generally 24 hours in chicken and most companion birds
- Ovary contains follicles that vary in size
- Smooth muscle contractions move ovum toward sperm
- Vaginal sphincter - located at junction between uterus and vagina
- Where sperm stored
- Uterus (shell gland) - site for formation of shell of egg
- 48 hours to fully form an egg – 80% time spent in uterus acquiring calcium to form shell
Describe avian male reproductive anatomy.
Are both testes present?
Where is sperm stored?
Do birds have accessory sex glands?
How does copulation occur?
Do any species have a phallus?
- Male reproductive organs
- Paired and located on both right and left sides of coelom
- Testes located ventral to cranial border of kidney
- Sperm formation occurs in seminiferous and straight tubules of testis
- Mature spermatozoa travel through rete testis, epididymis, epididymal duct, and ductus deferens
- Ductus deferens connects testes to urodeum – forms papilla at urodeum
- Where sperm stored
- No accessory sex glands
- Copulation involves eversion of cloacal wall to expose papilla to transfer semen to orifice of oviduct – most species
- Waterfowl - males have phallus comprised of erectile lymphatic tissue with an external groove (seminal groove) used to transport semen, purely reproductive function, may be amputated if necessary
Describe the reproductive cycle of psittacine birds.
Lengthening photoperiod stimulates release of what hormone?
What hormone is responsible for secondary sex characteristics and egg formation?
LH leads to production of what to hormones?
What triggers the preovulatory LH surge?
What hormone stimulates shell gland contractions?
What hormones cause ovulation?
What hormone increases blood flow to shell gland for egg calcification?
What hormone allows for relaxation of the uterovaginal sphincter and vagina?
- Reproductive cycle of psittacines
- Regulated by hypothalamus-pituitary-gonadal axis
- Environmental triggers and other internal factors cause hypothalamus to produce GnRH à stimulates pituitary gland to produce LH and FSH
- LH increases in concentration with lengthening photoperiod
- LH and FSH regulate gonadal function and production of androgens and estrogens
- FSH – role unclear
- Estrogens - responsible for secondary sex characteristics, stimulation of medullary bone production, and products used to form the egg
- Provide feedback regulation to hypothalamus, which controls GnRH
- LH stimulates progesterone production, both estrogens and progesterone must first prime pituitary and hypothalamus
- When progesterone increases à preovulatory LH surge
- Release of PGF2α coincides with shell gland contractions
- PGF2α and PGE2 increase smooth muscle contractions in connective tissue of follicle, cause follicle to rupture
- Eatio of PGF2α to PGE2 changes with transition of midsequence oviposition and terminal oviposition
- PGF2α most prominent at midsequence oviposition, PGE2 concentration higher at terminal oviposition
- PTHr protein concentration in shell gland increases, may increase blood flow to shell gland while egg present and membranes deposited on egg surface, signal Ca deposition
- PGF2α binds at shell gland receptor sites to cause mobilization of calcium, causes shell gland muscle contractions
- Binding sites for PGE2 predominate in vagina and may block binding of PGF2α and allow for relaxation of uterovaginal sphincter and vagina
- PGF2α has no ability to relax uterovaginal sphincter
What orders of birds produce crop milk?
What is unique about the esophageal mucosa of parent birds?
Label the sections of the avian oviduct and list their functions.
What avian species has two funcitonal ovaries but only one functional oviduct?
Infundibulum - funnels the yolk into the oviduct, fertilization takes place here
Magnum - albumen is added here
Isthmus - shell membranes are added here
Shell gland or uterus - shell is added here
List 6 environmental stimuli for laying in female birds.
Describe the normal hatching process of the avian egg.
What is the normal embryonic position of the embryo?
What triggers the internal pip?
What triggers the external pip?
How does the embryo enlarge the opening of the egg?
How do the following taxa have a different normal hatching process?
- Columbiformes?
- Ratites?
- Megapodes?
NORMAL HATCHING PROCESS
- Avian development highly conserved - thus can be applied across taxa with minimal variation
– All avian embryos assume the same hatching position
– Positioning: At 85% of incubation period: embryo has reached max size, consumed any remaining fluids within shell, and begins positioning for hatching
– Spine is roughly aligned with long axis of the egg
– Candling reveals “draw down” - inner and outer shell membranes start to separate around air cell making the air cell look larger (when it actually is not)
– Normal hatching position, with the head under the right wing and the egg tooth at the tip of the beak under the air cell membrane - can sometimes see egg tooth “pushing” under the air cell on candling
- Internal pip: When chorioallantoic membrane (CAM) no longer fully meets respiratory needs → causes slight hypoxia/hypercapnia → triggers hatching muscle (musculus complexus) along dorsal neck to engorge with lymph and contract → results in “internal pip” → egg tooth pierces inner shell membrane → pulmonary respiration initiated → hypoxia/hypercapnia resolves, internal pipping stops, embryo rests
- External pip: When embryo runs out of limited O2 supply in air cell → pipping contractions resume → egg tooth pierces outer shell membrane and shell → embryo breathes outside air → embryo rests for longer period of time than after internal pip
– Exposure to air/friction of body and shell causes blood to recede from CAM
- Break up: Egg prevents embryo from fully inflating lungs/air sacs → gas exchange eventually becomes inadequate again → pipping resumes to “break up” or enlarge the pip site opening
- Rotation: After brief rest embryo begins counterclockwise “rotation” (from air cell end) making the opening larger → pushes off shell cap than rests again
– Yolk sac is fully internalized behind umbilical seal (obtains Ab at this time point)
– Residual umbilical vessels dry with full exposure to air
– Preferred to let chick separate itself from shell; pulling away risks tearing vessels and increases risk of umbilical infection
Taxa that have variation in normal hatching process
- Columbiforme: offset air cells, some entirely on side of egg instead of blunt end
- Ratite: embryos lack egg tooth, but do assume same position and make internal pip
– Also use strong legs to break the shell
- Megapode: thinner more porous shells as incubated/buried in substrate in wild; facilitates passive transpiration during development thus has atypical pattern of egg weight loss
– Do not have typical air cell; unclear if have normal hatching position
– Lack egg tooth, use leg and necks for pipping/breaking shell, chicks dig their way to the surface
– Significant amount of fluid is expelled from the egg at hatching
Describe assisted hatching techniques.
What is the main goal of these techniques?
What are signs they may be indicated?
How do you help if there is no progress after an internal pip and the chick is in normal position?
How do you help if there is no progress after an external pip?
How do you help if the external pip is away from the air cell?
- Intervention indicated when lack of expected progress at any stage of hatching process
– Emphasis placed on time between external pip → hatching
– Somewhat arbitrary i.e. CA condor average pip-to-hatch time 72 hrs - Intervention often too premature; can have fatal consequences
- Indicators of embryo suffocation = prolonged lethargy/unresponsiveness, labored respiration, abnormal heart rate, frantic/hyperactivity
- All intervention should be done with aseptic technique
– Embryos do not internalize their yolk sac/acquire Ab until after rotation - Goal to provide access to air (making hole through shell/membranes) and/or create more space for movement (making hole in air cell if needed)
1 - If No Progress after Internal Pip (normal position)
- Intervention: drill hole at top of air cell, cut through shell but not shell membrane
– 2-3mm hole, electric rotary tool (round diamond bit) for larger eggs (flamingo, crane)
– 1-2mm hole, hypodermic needle for smaller eggs (parrot, passerine)
2 - If No Progress after External Pip (normal position)
- Often due to dry shell membranes (dry and shrink from exposure to air) → restricting embryo movement
– Occurs with low humidity, air drafts, and/or in species with lengthy pip-to-hatch interval
- Intervention: open pip site 5-10 mm, moisten shell membrane with artificial tears product with light mineral oil base (or ophthalmic ointment)
– DO NOT use sterile water/isotonic fluid → only moistens temporarily → increases shrinkage when drying
– Cover pip site to prevent more drying (Tegaderm, test tube sealant); leave small 1-3 mm opening
3 - If External Pip Away from Air Cell (often due to malposition)
- Intervention: increase space for embryo to move
– Poke small hole in air cell, place egg with hole downward at 45 degree angle for a few hours (maximum) → embryos body weight will gradually push the air out of the air cell and draw air in through the pip site creating space around the embryo
- Often self-hatch after this without further assistance
How do you determine if a chick needs assisstance if there is no progress after drawdown before the internal pip occurs?
What steps should be taken if the embryo is in the correct position but no progress is being made?
How do you help if the embryo is in malposition and there is no external pip?
- When can the embryo be removed from the shell?
- When are prophylactic antibiotics needed?
What causes an edematous chick?
How do you treat an unretracted external yolk sac?
4 - If No Progress After Drawdown/Before Internal Pip
- Radiographs to determine position/malposition
– Tape surgical wire to blunt end (air cell) and sharp end to use as marker
– Four views: ventral-to-dorsal, then rotate 45 degrees counterclockwise (from blunt end) for the next three images
- Dark void in lungs/trachea indicate pulmonary respiration → less urgent
- Malpositioning can cause pushing/flattening of air cell
If Embryo in Normal Position with No Progress
- Provide access to air: manual hole (5-20mm) made in shell where beak is (locate on rads)
- Moisten inner shell/air cell membrane with sterile water/isotonic fluid to visualize CAM vessels
- Open inner shell membrane, CAM, and amnion using blunt dissection to minimize bleeding
– Amnion should still be intact but no longer fluid filled at this stage
- Moisten membranes with artificial tears/ophthalmic ointment
- Seal opening with transparent material and leave opening 1-3mm
- Position in hatcher with opening in shell at 4-5 o’clock position (view from air cell end) to help membrane stay moist
- Check egg frequently to make sure beak and nares remain clear of membranes
If Embryo in Malposition with No External Pip
- Provide access to air: manual hole (5-20mm) made in shell where beak is (locate on rads)
– Similar to one made in air cell but there may be no air space here
– Moisten inner shell membrane, bluntly dissect through membranes and CAM
- Create more space: may need second hole over air cell to gain more space to move
- Monitor for internalization of yolk sac, closure of umbilical seal, complete shutdown of CAM
- Monitor CAM vessel regression with candling (denser shelled eggs may require manual removal of external shell to evaluate CAM)
– Can remove embryo from shell once ALL of these things happen
- Umbilical vessels can be ligated/cauterized if needed; usually residual so may be crushed and severed 1 cm from the seal and treated with antiseptics (chlorhex, iodine)
- Prophylactic abx warranted for protracted hatching periods or if need invasive procedures
- Parenteral before hatching is complete if embryo large enough
– Dripping solution directly onto CAM has unknown efficacy
Edematous embryos/chicks: usually those that have not lost sufficient egg weight during incubation, and are more likely to be malpositioned
- Normal high humidity (>70%) contraindicated; should not exceed 50-60%
- Excess fluid should be gradually released through the lungs
- Tend to have partially opened umbilical seals - friable and difficult to close with sutures; can apply loose bandaging for 24-48 hours to allow site to dry/scab
Unretracted/residual external yolk sacs
- If umbilical seal remains partially open → reduce and suture the seal shut
- If umbilical seal is closed → amputate residual yolk sac
– Usually closed with unretracted yolk sac due to membrane entrapment with umbilical stalk wrapped around the back of the neck or leg
– Technically can surgically open abdomen and insert yolk sac, but due to weakened state most chicks do not survive this procedure
– MUST provide feeding and supplemental fluids immediately if remove yolk sac
– Loop of intestine is normally externalized before yolk sac is retracted so look for intestine and do not ligate or sever it (can look similar to a residual blood vessel)
Describe egg necropsy protocols.
What is the difference between fertility and hatchability?
When does most mortality occur in the development process?
How do you determine if an egg was fertile or not?
What are the three breakout categories based on candling?
- What subcategories fall within each?
Fertility and Hatchability
* Two most important statistics to evaluate avian repro performance are fertility and hatchability of eggs
* Fertility= ratio of fertile eggs to total number of eggs received; ideally 90%+
* Embryonic development is highly conserved across species and has 3 distinct periods
* 1/3 of mortalities occur in first few days of incubation
– due to chromosomal abnormalities, 15% of development
* Remaining 2/3 in last few days of incubation
– Associated with hatching process and malpositions, 30% of development period
* Should be little to no mortality during middle of incubation (55% of development period)
Egg Breakout Procedures
* All unhatched eggs should be broke and examined.
* Candle egg to evaluate shell quality, shape, damage
* Infertility cannot be confirmed by candling alone- need to open the egg to determine whether fertile or failed early on.
– Infertile blastodisc will appear as dense white spot with small vacuoles
– Fertile blastoderm will be donut-shaped with clear center (area pellucida) with white ring around it (area opaca)
Report breakout results as
“Clear” on Candling:
* I: infertile—blastodisc centrally dense small, white mass
* F: fertile, unincubated—blastoderm donut-shaped
* PD: positive development—no discrete embryo but variable amount of white, membranous tissue on the surface of a watery yolk
* FND: fertile, no development—blastoderm donut-shaped; rare; development ceases at lay due to thermostabilized blastoderm or genetic defect (observed in poultry only)
“Blood Ring” on Candling:
- BWE: blastoderm without embryo—membranes and blood only; blood pooled to the terminal sinus of the early yolk sac vasculature
- ED: early dead embryo (see below)
Obvious Dead Embryo on Candling:
- ED: early dead embryo—H&H stage 1 to 19 (≤3 days in chick embryo)
- MD: mid-dead embryo – H&H stage 20 to 39 (3 to 14 days in chick embryo)
- LD: late dead embryo – H&H stage 40 to 45 (≥14 days in chick embryo)
The term “dead in shell,” abbreviated DIS, has been used extensively but with varying or nonspecific definitions and so should be avoided.
