Livestock Reproduction

Question 1

Initiation of Puberty: Heifers

Answer 1

4 mo - 2 yrs
Sires with larger scrotal size = earlier
Autumn birth earlier than spring
BW: occurs when heifer reaches 40 - 50% of mature weight

Question 2

Estrus Cycle: Heifers

Answer 2

Non-seasonal breeders
Cycles: 3 weeks duration
Estrus = d0, 12-18h
Metestrus = d1-3, ovulation 24-30h after onset of estrus
Diestrus = d4-18
Proestrus = d19, behavioral estrus begins

Question 3

Characteristics of Proestrus

Answer 3

Period of rapid follicular growth
Progesterone low
Estrogen increasing

Question 4

Characteristics of Estrus

Answer 4

Period of sexual receptivity
Stands to be mounted
Clear vaginal mucus (cattle)
Estrogen high
Spike in LH

Question 5

Characteristics of Metestrus

Answer 5

Short period after estrus
Bloody vaginal mucus (cattle) = too late to breed
Progesterone increasing

Question 6

Characteristics of Diestrus

Answer 6

Luteal phase
Significant concentrations of progesterone
LH pulsatile decreases
Pulses of prostaglandin secreted by uterus cause regression of CL

Question 7

How many ovulations per cycle are associated with cattle?

Answer 7

Typically 1
Less 2
Rare 3+

Question 8

Reproductive Management Goals: Heifers

Answer 8

Heifers should have 1st calf by 2yr of age
Maximize beef heifers to calve early in season

Question 9

Estrus Detection: Heifers

Answer 9

Standing to be mounted
Secondary: attempting to mount others, mucous vulval discharge, vulval swelling/reddening, bellowing, restlessness, trailing other cows, chin resting

Question 10

Synchronization: Heifers

Answer 10

Improves pregnancy rates and reduces days open in lactating dairy cows

Question 11

Initiation of Puberty: Does

Answer 11

6 - 8m
Intro of buck will synchronize group
Breeding should be delayed until 60% adult weight attained

Question 12

Breeding Season: Does

Answer 12

August - March (Esp. Oct - Dec)
Seasonally polyestrus

Question 13

Estrus Cycle: Does

Answer 13

Estrus: 12-24h, restless, bleats, wags tails, slight vaginal discharge
Metestrus: refusal to mate until CL formation, no vulvar hemorrhage
Ovulation: spontaneous (12-36h after onset of heat)
Diestrus: CL function, 18d
Proestrus: 1 day duration, buck closely follows but doe will not stand

Question 14

Estrus Detection: Does

Answer 14

Teaser buck: introduced at beginning of season doe will show heat 5-8d
Buck jar
Side-to-side or up-and-down tail flagging
Speculum exam of cervix (vaginal mucosa reddened at beginning of hear, increases as head progresses, cloudy at end)

Question 15

Synchronization: Does

Answer 15

Extending luteal phase through progesterone products - intravaginal sponges, controlled internal drug release devices, feed supplementation
Shortening of luteal phase through prostaglandin products

Question 16

Initiation of Puberty: Ewes

Answer 16

Dependent on nutrition, growth rate, photoperiod

Question 17

Breeding Season: Ewes

Answer 17

Fall and winter months
Seasonally polyestrus (16-17d estrous cycle)
Photoperiod

Question 18

Estrus Cycle: Ewes

Answer 18

Estrus: 30-36h, shake tail and turn head to look back at lamb, vulvar swelling with copious thin vaginal mucus
Metestrus: refusal to mate until formation of CL
Ovulation: spontaneous
Diestrus: CL function, squat/urinate at rams approach and move away if he is aggressive
Proestrus:

Question 19

Estrus Detection: Ewes

Answer 19

Transition to summer
Novel ram introduction = most powerful stimulus
Not all ewes marked or standing to be mounted are cycling (may already be pregnant)

Question 20

Synchronization: Ewes

Answer 20

Inducing luteolysis with prostaglandins (one for two injections)
Delaying estrus and ovulation (progesterone injections, intravaginal sponges, implants, feed additives)

Question 21

Puberty Initiation: Camelids

Answer 21

After 12m of age
After 65% of adult body weight attained

Question 22

Estrus Cycle: Camelids

Answer 22

Do not have estrus cycles like other species
Sexual receptivity up to 36 days
Receptive females = ventral recumbency after being pursued by male
Ovulation occurs 26h after natural mating
Induced ovulators
CL begins to decline 12d after mating if not pregnant

Question 23

Synchronization/Induction: Camelids

Answer 23

Progesterone supplementation to prolong luteal phase
Ovulation inducing agents (GnRH, LH, hCG)

Question 24

Initiation of Puberty: Gilts

Answer 24

5-8m
Boar exposure

Question 25

Estrus Cycle: Gilts

Answer 25

21d estrus cycle
Estrus: sexual receptivity 1-4d, ovulation occurs 36-44h after onset of estrus
Diestrus: CL function = increased prog evident 2-4d after estrus
Proestrus: peak estradiol

Question 26

Estrus Detection: Gilts

Answer 26

Pen mating
Look for lordosis
Lactational anestrus is present, estrus apparent 3-7d after weaning

Question 27

Synchronization: Gilts

Answer 27

Inducing luteolysis: unlike other large animals, swine are not responsive until late in estrous cycle, so not practical
Prolong life of CL: mating, allytrenbolone administration

Question 28

Mating System: Gilts

Answer 28

Insemination not more than 24h before of 4h after ovulation
Pen mating (1:8 boar:sow ratio)
Hand mating
Artificial insemination