EQUINE REPRODUCTION

TERMINOLOGY

BOOK BOOKING FEES STUD FEE FOAL GUARANTEE

Live FoalReturnColor

WET/DRY CARE BREEDER

Thoroughbred Other breeds

DEATH & SALES CLAUSE

CHUTE FEE

Stallion Physiology

Onset of sexual maturity 10-24 mo

Life span of sperm in female tract

2-4 days

Survival time with fertilizing capacity

1-2 days

Sperm output

Semen volume/ejaculate 20-100 ml

Sperm concentration X 106 30-800 ml

# sperm/ejaculate X 109 6

Sperm Production

• Sperm Output and Production is influenced by:– Season– Testicular size– Age– Frequency of

ejaculation– Behavior

Number of Sperm Depends On:

• Seasonal Influences (Photoperiod)– Effected Areas

• Ejaculate volume• Sperm numbers• Total sperm/ejaculate• Sperm motility• Willingness to breed• Mounts before breeding• Scrotal size• Testosterone production

Mare Anatomy

• Vulva• Vagina• Cervix• Uterus• Oviducts• Ovaries

Left Ovary

Oviduct

Left UterineHorn

Uterine Body

Cervix Vagina

TERMS• Anestrus • Diestrus • Estrous • Estrus

MARE CLASSIFICATION

• Pregnant• Open• Barren• Maiden• Wet• Dry

MARES

The Open Mare

• Evaluate reproductive history• Establish the time of year to breed • Mare Plan:

– Diagnose possible problems– Implement problem management– Establish estrus calendar

Mares Cycle

0

20

40

60

80

100

120

J F M A M J J A S O N D

% Mares ovulating % Mares in estrus

Perc

ent

Photoperiod Effect

• Reproductive activity in spring is stimulated by an increasing photoperiod

• Mechanism – Alteration of hormone

secretion by the pineal gland and hypothalamus

Receptors in eye

Pineal gland

Hypothalamus

Anterior pituitary

Ovaries

Increasing day length Decreasing day length

Neuropathway Neuropathway

Decreasing melatonin Increasing melatonin

Increasing GnRH Decreasing GnRH

Increasing gonadotropins

Decreasing gonadotropins

J F M A M J J A S O N D

Transition Period

• Increased photoperiod stimulates the hypothalamus and pituitary

• Pituitary hormones (especially FSH) induce follicular development

Transition

• 1-3 waves of follicles develop & regress

• Estrogens produced by developing follicles

• Irregular/prolonged estrus exhibited

• 1 follicle eventually ovulates

• Thereafter, mares ovulate at ~21-day intervals

•21-day estrous cycle

•Estrus 5-7 d

•Diestrus 14-16 d

Estrous CycleSun Mon Tue Wed Thu Fri Sat

1

2 3 4 5 6 7 8

9 10 11 12 13 14 15

16 17 18 19 20 21 22

23 24 25 26 27 28 29

30 31

Estrus Follicular Development &

Ovulation • Anterior Pituitary –

FSH - follicular growth• Pituitary – LH –

maturation of follicle & ovulation

• Follicles reach 20-25 mm in diameter, secrete estrogen.

Prediction of Ovulation

• Number of days in heat• Growth rate of largest

follicle– Average 3-5 mm/day

• Size of largest follicle • Softness of preovulatory

follicle• Ultrasound image

DiestrusCorpus Luteum Formation• Corpus luteum -

secretion of progesterone.

• Progesterone - responsible for keeping the mare out of heat and for maintaining pregnancy.

Prostaglandin Release• Prostaglandin (PGF) -

released from the uterus of a non-pregnant mare 14-16 days after ovulation

Postpartum Estrus

• Foal Heat• Fertile as compared to other species.• Breeding may be necessary to

maintain the 12 mo. Foaling interval.• May be necessary to back up foaling.

Signs of Estrus

• Most consistent– Elevated tail raise– Winking

• Other supporting signs– Leaning– Squatting– Standing still– Urinating

Manipulation Methods

Artificial lighting Shortening Late Transition Inducing Ovulation Estrus synchronization Estrus Synchronization & Ovulation

Induction

Light Stimulus

• 16 hrs daylight per day

• 30-60 days

Progesterone or related compounds Regumate – most

common Normalization of estrus Regulation of estrus Estrus synchronization Long-term suppression of

estrus Delay foal heat Pregnancy maintenance

PGF2

Lutalayse or Estrumate

Shorten the interval between estrous periods

Treatment of a maintained corpus luteum

After foal heat Estrous synchronization

with prostaglandins

Breeding Methods

• Pasture Breeding• Hand Breeding• Artificial

Insemination– Fresh semen– Cooled, shipped

semen– Frozen semen

Cooled Shipped Semen

ADVANTAGES• Cost• Genetics• DiseaseDISADVANTAGES• Cost• Technology/

management• Stallion

variability

Common Problems• Inability to obtain

semen• Poor quality semen• Reordering semen• Failure to predict

ovulation

Frozen Semen

• Success of Frozen Semen – Fertility of stallion’s semen– Fertility of the mare– Skill of the veterinarian/technician

• Maximum Success– Client communication– Choose ideal candidate– History of stallion

Embryo Transfer

• Synchronization of donor and recipient mare

• Embryo flushing• Embryo transfer

procedure

TEN FACTORS INFLUENCING PREGNANCY & PREGNANCY LOSS PER CYCLE

MARE AGE BARREN REPRODUCTIVE

STATUS EARLY BREEDING DATE LATE BREEDING DATE BREEDING FREQUENCY PROSTAGLANDIN FACTOR UTERINE CULTURE &

CYTOLOGY EFFECT OF SEMEN

EXTENDER POST-BREEDING

ANTIBIOTIC INFUSIONS TWINS

Pregnancy Evaluation

• Ultrasound, 14-18 days– ID twins– ID placental

development• Re-evaluate, 40 days• Monitor Placental

function & fetal growth

Gestation Length

• Normal: 335-342 days

GROWTH CURVE

0

20

40

60

80

100

120

140

20 60 100 140 190 260 340

Gestation age in days

CR

in c

m

Late Pregnancy• Abdomen greatly enlarged• Ventral edema• Mammary gland enlargement

– 2-4 wk • Gluteal muscles relax – 7-10

d• Teats fill with milk – 4-7 d • Waxing of teat ends – 1-4 d• Vulva soft & relaxed – 1-2 d

Stages of Parturition

• Stage 1– Onset: initial uterine

contractions– End: rupture of

chorioallantois (water bag)

• Stage 2– Onset: rupture of

chorioallantois– End: delivery of

fetus

Stages of Parturition

• Stage 3 (< 3 hrs)– Onset: delivery of

fetus– End: passage of the

fetal membranes

Foals and Immunity

• Colostrum (first milk) - antibodies

• 1-2 pts of high quality colostrum

• If adequate passive transfer occurs there will be over 400-800 mg/dl IgG in foal’s blood

• Takes ~ 12 hours for all antibodies ingested in colostrum to show up in the blood

Key points• First two weeks- lay the groundwork

by ensuring adequate colostrum• Preventative health program in place• Appropriate nutrition• Problems must be addressed rapidly

when they arise. No time for a “wait and see” attitude