species specific repro

VET30390

Sheep breeding season

September to March (short-day breeder)

Anoestrus period in sheep

April to August

Factors affecting sheep seasonality

Breed, latitude, presence of ram

Ram to ewe ratio

2–3 rams per 100 ewes

Ewe oestrous cycle length

15–17 days

Duration of oestrus in ewe

1–1.5 days

Type of ovulator (ewe)

Spontaneous ovulator

Timing of ovulation (ewe)

End of oestrus

Signs of oestrus (ewe)

Standing to be mounted, tail wagging

Silent ovulation

First ovulation of breeding season without behavioural oestrus

Gestation length (ewe)

144–147 days

Optimal pregnancy scanning time (ewe)

50–100 days

Method of pregnancy diagnosis (ewe)

Ultrasound

Main barrier to AI in sheep

Cervix

Fresh semen AI dose (sheep)

≥250 million sperm

Frozen semen AI dose (sheep)

250–400 million sperm

Laparoscopic AI dose (sheep)

40–50 million sperm

Timing of AI after synchronisation (fresh semen)

~48 hours

Timing of AI after synchronisation (frozen semen)

~56 hours

Fertility (fresh cervical AI sheep)

70–75%

Fertility (frozen cervical AI sheep)

25–50%

Fertility (lap AI sheep)

60–65%

Fertility (natural service sheep)

80–85%

Sheep cycle hormones

Progesterone high in luteal phase, LH surge causes ovulation

Function of PGF2α (sheep)

Luteolysis

Progestagen devices (sheep)

Pessary, CIDR

Time to oestrus after device removal

30–60 hours

eCG function

Synchronisation and increased litter size

Ram effect

Pheromones stimulate LH and induce oestrus

Melatonin function

Advances breeding season

Optimal breeding age (ewe lambs)

7–8 months

Main causes of lamb mortality

Nutrition, weather, dystocia, poor colostrum

Cattle puberty threshold

~50% mature body weight

Age at first breeding (heifer)

13–15 months

Target weight at breeding

~300 kg

Ideal calving interval

365 days

Target conception rate (cattle)

~60%

Target oestrus detection rate

85%

Submission rate

% of eligible cows bred

Conception rate

% of inseminations resulting in pregnancy

Reproductive efficiency

Submission rate × conception rate

Duration of oestrus (cow)

~7–8 hours

Primary sign of oestrus (cow)

Standing to be mounted

Optimal heat detection frequency

~5 times daily

Common issue in cattle reproduction

Missed heats

Postpartum uterine involution

Complete by ~50 days

First ovulation postpartum

Often silent

Negative energy balance effect

Reduces fertility and immune function

Ovsynch protocol

GnRH → PGF2α → GnRH → fixed-time AI

Purpose of Ovsynch

Timed AI without heat detection

Pregnancy rate per Ovsynch cycle

~28–30%

Progesterone devices (cattle)

CIDR/PRID

Optimal duration progesterone treatment

7–9 days

Effect of prolonged progesterone

Persistent follicle, reduced fertility

Treatment of ovarian cysts

GnRH or progesterone device

Treatment of persistent CL

PGF2α

Pig gestation length

114–116 days

Weaning age (piglets)

~28 days

Litters per sow per year

~2.2–2.3

Target pigs per sow per year

28–29

Average litter size (pig)

~14–17 piglets

Puberty in pigs

6–9 months

Recommended breeding time (gilt)

Third oestrus

Pig oestrous cycle length

~21 days

Duration of oestrus (pig)

40–70 hours

Timing of ovulation (pig)

~36 hours after onset of oestrus

Sperm lifespan (pig)

24–72 hours

Ova lifespan (pig)

5–10 hours

Return to oestrus after weaning

4–10 days

Effect of suckling

Suppresses ovarian activity

Embryo mortality (pig)

15–25% (early gestation)

Minimum embryos to maintain pregnancy

≥4

AI dose (pig)

2.5–5 × 10⁹ sperm

Semen storage temperature (pig)

16–18°C

Semen lifespan after collection

Use within 2 days

Factors affecting litter size (pig)

Ovulation rate, fertilisation rate, embryo survival

Mare breeding type

Seasonal breeder

Optimal body condition score (mare)

~3/5

Effect of age on mare fertility

Increased pregnancy loss with age

Pre-breeding exam (mare)

History, physical exam, reproductive exam

Reproductive exam methods (mare)

Palpation, ultrasound, speculum

Ultrasound assessment (mare)

Follicles, CL, uterine oedema

Uterine abnormalities assessed

Fluid, air, cysts

Ideal vulval conformation

Tight seal, slight slope (<10°)

Contagious equine metritis cause

Taylorella equigenitalis

Equine viral arteritis transmission

Venereal and respiratory

EVA risk

Carrier stallions and infected semen

Stages of oestrous cycle (dog)

Prooestrus, oestrus, dioestrus, anoestrus

Gestation length (dog)

64–66 days from LH surge

Implantation timing (dog)

Day 16–18

Pregnancy diagnosis (dog)

Ultrasound, palpation, radiography, relaxin

Ultrasound detection (dog)

Day 15–18 (vesicles), day 21+ heartbeat

Relaxin detection (dog)

25–30 days

Signs of impending parturition (dog)

Temperature drop, nesting, ↓progesterone

Temperature drop significance

Whelping within ~12 hours

Stage 1 labour (dog)

6–12 hours (cervical dilation)

Stage 2 labour (dog)

Foetal delivery (3–12 hours)

Stage 3 labour (dog)

Placenta expulsion

Interval between puppies

5–120 minutes

Pseudopregnancy cause (dog)

Elevated prolactin