Livestock Reproduction Flashcards
1
Q
what does theriogenology mean
A
therio = beast/animal
gen = creation/generation
ology = study of
2
Q
when are heifers initiated into puberty?
A
- yearling heifers
- may range from 4mo-2 years
3
Q
genotype of heifers initiated into puberty
A
- bos taurus breeds earlier than bos indicus
- sires with larger scrotal sizes have heifers reaching puberty earlier than small scrotal size
4
Q
what season do heifers go into puberty?
A
autumn birth go thru puberty earlier than ones born in spring
5
Q
body weight of heifers in puberty
A
major factor; if an animal cannot maintain homeostasis with nutrition, reproduction goes onto the backburner
occurs when heifer reaches 40-50% mature weight
6
Q
are cows seasonal or non seasonal
A
non seasonal
7
Q
how long are cow estrus cycles
A
3 weeks (17-25 days)
8
Q
cycle of a cow
A
- proestrus: day 19 after ovulation (CL has regressed): behavior estrus begins
- estrus: day 0: day of ovulation: averages 12-18 hours, demonstrating standing heat behavior, sexual receptivity of female
- metestrus: day 1-3: final follicular maturation, ovulation: 24-30 hours after onset of estrus. formation of early CL: preogesteone levels rising as luteal cells forming
- diestrus: day 4-18 (longest in all species): luteal phase with signficant concentrations of progesterone (P4) peripherally
9
Q
is estrogen low or high during diestrus
A
low! progesterone high
10
Q
what is proestrus?
A
- period of rapid follicular growth
- progesterone low
- estrogen increasing becuase follicles are going up in size
11
Q
what is estrus
A
- period of sexual receptivity
- stands to be mounted
- clear vaginal mucus** important clinical sign
- estrogen high
- spike in LH
- 12-18 hours duration: short!
12
Q
what is metestrus?
A
- short period after estrus
- bloody vaginal mucus: clinical significance is that it’s too late to breed- capillaries following rapid decrease in estrogen after ovulation
- progesterone increasing
- 2 days in duration
13
Q
you see a heifer that has bloody mucus discharge. the producer asks if it is an okay time to breed. what do you say
A
no because you have missed estrus window: when mucus goes from clear to hemorrhagic this indicates that the cow is now in metestrus and not estrus
14
Q
what is diestrus?
A
- luteal phase: super high P4 levels
- day 4/5 of cycle
- LH pulsatile decreases
- producers try to synchronize for timed AI
- pulses of PGF2a secreted by uterus cause regression of the CL: local utero-ovarian control, transferred via venous effluent into artery via counter current exchange!!
15
Q
follicular dynamics in bovine species
A
- initiated by increase in FSH
- have anywhere from 2-4 waves of follicular growth in a given cycle: different from other species! 2 waves most common
- see cohort of follicles go up and down
- 1 follicle maintains dominance and will be the one to go onto ovulate
- largest continues to grow: growth phase, stasis, regression (if not dominant)
16
Q
how many ovulations are in cows
A
usually 1, but can have many
17
Q
postpartum period in cattle
A
- anestrus period variable after calving: have variable length of lactational anestrus where they won’t cycle
- affected by season, nutrition, nursing
- most dairy cows take 24 days to next ovulation
- most beef cows take 60 days to ovulation
18
Q
what are the repro goals in cattle?
A
- heifers should have 1st calf by 2 years of age
- maximize beef heifers to calve early in season: heavier calf weaning weights, timely rebreeding, increases herd longevity
- dairy heifers should have 1st calf by 2 years of age: maximize lifetime milk production, recoup rearing costs
19
Q
when should heifers have their first calves?
A
by 2 years of age
beef: earlier in season to maximize weight
dairy by 2 years to maximize lifetime milk production
20
Q
estrus detection in cows
A
- standing to be mounted: definitive sign!
- mounted by other cows
- onset of standing heat closely related to ovulation
- oocyte available for fertilization after 8-10 hours after ovulation
21
Q
what are secondary signs of estrus in cows?
A
- attempting to mount other cows (usually the one standing is the one in heavy estrus)
- mucus
- swelling/reddening of vulva
- bellowing, restlessness
- chin resting
- lip curling
22
Q
estrus detection aids in cows
A
- pressure-sensitive mount detectors and trailhead markings: applied with adhesive to topline over rump, marking tail head with livestock chalk, pain or crayon and observe rubbing off
- estrus detector animals: vasectomized or surgically altered bulls or hormonally treated animals (freemartin heifers)
- electrical resistance of repro tissue fluids (rare)
- pedometer (common)- device or chip implant to track movement of animals
23
Q
synchronization strategies in dairy cattle
A
- sync many animals to come in at same time to maximize repro efforts
- OV synchronization improves pregnancy rates and reduces days open in lactating cows (lysing an animals CL all at the same time and get on progesterone supplement)
24
Q
initiation of puberty in does
A
- well fed european breeds show signs early (6-8 mo)
- intro of buck will sync group of doelings
- breeding should be delayed until 60% of adult weight! nutrition super important
- higher conception rates and safer births
25
breeding season of does
august-march: esp oct-dec
short day breeders
seasonally polyestrous (20-21 day estrous cycle)
photoperiod: driver of cyclicity: secretion of melatonin from pineal gland during darkness: happens when melatonin increases
26
cycle lengths of does
1. proestrus: 1 day duration, buck closely follows
2. estrus: 12-24 hours, estradiol, restless, wagging tails, slight vaginal discharge (easily missed)
3. metestrus: refusal to mate,** until formation of CL, no vulvar hemorrhage
4. ovulation: spontaneous: 12-36 hours after onset of heat
5. diestrus: CL function, 18 days, high levels progesterone
27
estrus detection in does
- teaser or breeding buck: shows heat 5-8 days
- buck jar: rag rubbed on buck's scent galnds caudomedial to horns and store in jar, opened and presented warm to doe
- side to side or up and down tail flagging
- speculum examination of cervix: mucus reddened, mucus production increases as heat progresses and turns cloudy at end of estrus
28
synchronization protocols of does
- extending luteal phase thru progesterone products: gives flexibility to manipulate cycle: use a CIRD-G (similar to cattle) or intravaginal sponges soaked in progesterone, feed supplementation (MGA)
- shortening luteal phase: shorten through administering prostaglandin products: lutalyse, estrumate
29
initiation of puberty in ewes
- dependent on nutrition, adequate rate of growth and photoperiod
- must experience long days and then decreasing daylength
- suffolk and white faced ewe lambs show pubertal estrust at 30 weeks
- silent ovulation or short luteal phase may be seen (not great, can be tricky to see receptivity in 1st phase)
30
breeding strategy effects in ewes
- light control programs
- temperature
- age/breed
- nutrition
- stress
- season
- ram introduction
31
breeding season of ewes
fall and winter
32
cycle lengths of repro in ewes
1. proestrus
2. estrus: 30-36 hours, shake tail and turn to look at ram, vulvar swelling and small amounts of mucus
3. metestrus: refusal to mate until formation of CLs
4. ovulation: spontaneous (>5mm diameter)
5. diestrus: CL function, squat/urination at ram's approach and move away if he is aggressive
33
estrus detection in ewes
- transition: summer: novel ram introduction is the most powerful stimulus! teaser rams can be used to hasten breeding season
- ram exposure = LH increase and ovulation without estrus
- once cycling, fertile rams should be used for as many mating opportunities as possible
- teaser rams introduced for one cycle length
- not all ewes marked or standing to be mounted are cycling, may already be pregnant
34
synchronization protocols for ewes
- inducing luteolysis: PGF2a: single injection or 2 (9-11 days apart for timed AI)
- delaying estrus and ovulation: daily or bid injections of progesterone, intravaginal sponges, implants, feed addititves
35
puberty initiation in llamas and alpacas
- puberty: females should be bred after 12 mo fo age and not before they attain 65% of their projected mature adult weight
- non seasonal in north america but seasonal in natural habitats
36
repro management of llamas and alpacas
- do not have estrous cycles like other species
- sexual receptivity up to 36 days
- receptive female assumes ventral recumbency after being purseued by male
- coitus prolonged compared to other species: 10-50 min
- ovulation occurs 26 hrs after natural mating
- ovulation-inducing factor (OIF) present in seminal plasma of camelids = induces ovulation (nerve growth factor beta)
37
what species do not have estrous cycles like others?
llamas and alpacas
38
how is repro management of llamas and alpacas different
- dominant follicle anovulatory unless coitus happens
- copulation necessary prelude to ovulation
- CL begins to decline 12 days after mating if not preggo
- unreceptive females may run away from or spit at males
39
how can you synch ovulation of llamas and alpacas?
- progesterone supplementation to prolong luteal phase: devices, implants, prog inj
- ovulation inducing agents: GnRH or analogue, LH, breeding with vasectomized male
40
initiation of puberty in gilts
- 5-8 months (most commonly 165 days)
- dependent on genetics and environment
- season: wild pigs seasonal, domestics managed year round
- social environment: gilts in small groups or large exhibit delayed puberty
- pens of 6-12 ideal
- nutrition: feed finishing diet ad libitum
- boar contact: minimum of 10 min daily, primer effect from pheromones, signaler effect elicits lordosis = standing heat
41
cycle lengths of sows
- breeding season: 21 day estrous cycle
- proestrus: estradiol concentrations peak between 18-20 days
- estrus: ovulation: sexual reception 1-4 days, ovulation occurs 36-44 hours after onset of estrus, follicles destined to ovulate reach 5-12 mm
- diestrus: luteal phase: CL function: increasing progesterone evident 2-4 days after estrus
- ovulation rate: # of ova released at estrus affected by age, breed, nutrition
42
how do you detect estrus in sows
- boar used in pen mating systems
- observation of lordosis
- swelling/reddening of vulva, vocalization, ear popping, boar seeking behavior
- lordosis posture cannot be maintained due to muscle exhaustion: house boar away from females
- lactational anestrus present: estrus apparent 3-7 days after weaning
43
how can you sync sows cycles
- inducing luteolysis: PGF2a: UNLIKE LA: swine not responsive until late in estrous cycle (days 12-14, impractical!)
- prolong life of the CL: mating --> treat with PGF2a --> abortion and return to estrus
43
mating systems of sows
- insemination not more than 24 hours before or 4 hours after ovulation
- pen mating
- hand mating
- AI: used to mate majority of sows in US
