Avian Reproduction

Question 1

sexual differentiation (chromosomal) in birds

Answer 1

female: ZW
male: ZZ

Question 2

is sex tissue phenotype genetically or hormonally dictated

Answer 2

gene-based

Question 3

how can sex reversal be induced in chicks

Answer 3

F to M only

OVX or inhibition of estrogen synthesis induces development of testes instead of ovaries

Question 4

parthenogenesis

Answer 4

production of an embryo without fertilization by sperm

possible in some avian species

Question 5

where are male testes located

Answer 5

intra-abdominal

spermatogenesis is NOT affected by heat

Question 6

are birds seasonal or nonseasonal breeders

Answer 6

seasonal long day breeders

Question 7

how does the male reproductive tract change in the breeding season

Answer 7

size of repro tract increases as spermatogenesis resumes (stops in off season) and becomes highly efficient

Question 8

how long can sperm remain viable in the female repro tract

Answer 8

long time (weeks)

Question 9

what ovary is considered the functional ovary in females

Answer 9

left ovary

right is vestigial - will become a testes is L ovary is removed

Question 10

inactive vs active follicle gross appearance

Answer 10

inactive: small, white/yellow
active: large, yolked

Question 11

how does the female reproductive tract change in the breeding season

Answer 11

size of repro tract increases as follicular growth and ovulation resumes

Question 12

steps of egg transit

Answer 12

1. infundibulum
2. magnum
3. isthmus
4. shell gland
5. vagina
6. cloaca

Question 13

magnum

Answer 13

site of albumin deposition

transit time: 3 hours

Question 14

isthmus

Answer 14

site of shell membrane development

transit time: 1.5 hours

Question 15

shell gland

Answer 15

site of calcification of the egg

transit time: 18-22 hours

Question 16

what signals the hypothalamic pituitary gonadal axis in birds

Answer 16

light (long day breeders)

light penetrates through skull –> activates photoreceptors in the brain –> release of GnRH I and II –> stimulates LH/FSH

NOT mediated by light detection through the eyes

Question 17

GnHI

Answer 17

gonadotropin inhibiting hormone

inhibits LH and FSH secretion

Question 18

what produces progesterone in female birds

Answer 18

preovulatory follicle

birds do not get pregnant - do not need a corpus luteum

Question 19

what is the effect of progesterone in female birds

Answer 19

induces LH surge

Question 20

what produces estradiol in female birds

Answer 20

small white follicles

secrete androgens that convert into estrogen in the interstitium of the ovary

Question 21

what metabolic changes are seen during egg laying

Answer 21

• lipid accumulation in liver
• lipid mobilization into blood
• Ca storage in long bones

Question 22

why is Ca stored in long bones

Answer 22

during daylight: Ca for calcifying eggs comes from the diet

during night: no diet = no dietary Ca; Ca for calcifying eggs must come from the long bone stores

Question 23

how are ovulation and egg laying related

Answer 23

1. preovulatory follicle releases progesterone to induce LH surge
2. LH surge induces ovulation
3. ovulation results in PGF2a and PGE2 release
4. prostaglandins stimulate movement from shell gland to vagina
5. triggers vaginal reflex –> stimulates hypothalamus and pituitary –> release of vasotocin
6. vasotocin triggers egg lay

Question 24

clutch

Answer 24

a group of eggs laid by a hen on consecutive days until one day is missed

Question 25

why is there a missed day during egg lay

Answer 25

2nd LH surge will only occur at night, but the interval between 1st and 2nd LH surge is <24 hours, so ovulation and egg lay will become progressively delayed towards dawn

Question 26

moulting

Answer 26

plumage renewal stimulated by an increase in thyroxine; causes feathers to be pushed out birds starve themselves during nesting/brooding --> weight loss --> stops reproductive function --> ovaries/oviduct regress while female incubates clutch