Breeding Horses

EQUINE
REPRODUCTION
TERMINOLOGY
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BOOK
BOOKING FEES
STUD FEE
FOAL GUARANTEE
 Live Foal
 Return
 Color
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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
Survival time with fertilizing
capacity
Sperm output
Semen volume/ejaculate
Sperm concentration X 106
2-4 days
# sperm/ejaculate X 109
6
1-2 days
20-100 ml
30-800 ml
Sperm Production
•
Sperm Output and
Production is
influenced by:
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Season
Testicular size
Age
Frequency of
ejaculation
– Behavior
Number of Sperm Depends On:
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Seasonal Influences (Photoperiod)
– Effected Areas
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Ejaculate volume
Sperm numbers
Total sperm/ejaculate
Sperm motility
Willingness to breed
Mounts before breeding
Scrotal size
Testosterone production
Mare Anatomy
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Vulva
Vagina
Cervix
Uterus
Oviducts
Ovaries
Left Ovary
Oviduct
Cervix Vagina
Left Uterine
Horn
Uterine Body
MARES
TERMS
• Anestrus
• Diestrus
• Estrous
• Estrus
MARE
CLASSIFICATION
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Pregnant
Open
Barren
Maiden
Wet
Dry
The following is a summary of the major events that occur in the
mare’s oestrous cycle.
Day 0
Day 1
Day 2
Day 5
Day 9
Day 11
Day 13
Day 15
Day 16
Ovulation
LH rising
FSH falling
Oestradiol falling
Oestrus
LH peak
Metaoestrus
Oestrus ends
Dioestrus begins
LH declining
FSH approaching basal levels
Oestradiol approaching basal
levels
Progesterone rising
Progesterone at maximum
FSH rising
FSH peak
FSH at basal levels
PGF2 peak
Progesterone begins to fall
FSH rising
Progesterone falling
Day 18
Day 20
Day 21/0
FSH rising
Progesterone basal
Oestradiol rising
Pro-oestrus
LH rising
Progesterone basal
FSH peak
LH rising
Oestradiol reaching a peak
Oestrus
Ovulation
LH rising
FSH falling
Oestradiol falling
Oestrus
Signs of oestrus
Docility
Urination stance
Lengthening and
eversion of the vulva
Exposure of the clitoris
(winking)
Tail raised
Urine bright yellow
with a characteristic
odour
Acceptance of the
stallion’s advances
Signs of dioestrus
Hostility
Rejection of stallion’s
advances
The Open Mare
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Evaluate reproductive history
Establish the time of year to breed
Mare Plan:
– Diagnose possible problems
– Implement problem management
– Establish estrus calendar
Mares Cycle
120
Percent
100
80
60
40
20
0
J
F
M
A
M
J
% Mares ovulating
J
A
S
O
% Mares in estrus
N
D
Photoperiod Effect
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Reproductive activity in
spring is stimulated by
an increasing
photoperiod
Mechanism
– Alteration of hormone
secretion by the pineal
gland and hypothalamus
J
F
M
A
M
J
J
A
S
O
N
D
Receptors in eye
Neuropathway
Neuropathway
Pineal gland
Decreasing melatonin
Increasing melatonin
Hypothalamus
Increasing GnRH
Decreasing GnRH
Anterior pituitary
Decreasing
gonadotropins
Increasing
gonadotropins
Ovaries
Transition Period
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Increased photoperiod stimulates the
hypothalamus and pituitary
Pituitary hormones (especially FSH)
induce follicular development
Transition
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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 Cycle
Sun
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
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Number of days in heat
Growth rate of largest
follicle
– Average 3-5 mm/day
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Size of largest follicle
Softness of preovulatory
follicle
Ultrasound image
Diestrus
Corpus 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 nonpregnant mare 14-16
days after ovulation
Postpartum Estrus
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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
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Most consistent
– Elevated tail raise
– Winking
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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
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16 hrs daylight per
day
30-60 days
Progesterone or related
compounds
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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
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Pasture Breeding
Hand Breeding
Artificial
Insemination
– Fresh semen
– Cooled, shipped
semen
– Frozen semen
Cooled Shipped Semen
ADVANTAGES
• Cost
• Genetics
• Disease
DISADVANTAGES
• Cost
• Technology/manage
ment
• Stallion variability
Common Problems
• Inability to obtain
semen
• Poor quality semen
• Reordering semen
• Failure to predict
ovulation
Frozen Semen
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Success of Frozen Semen
– Fertility of stallion’s semen
– Fertility of the mare
– Skill of the veterinarian/technician
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Maximum Success
– Client communication
– Choose ideal candidate
– History of stallion
Embryo Transfer
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Synchronization of
donor and recipient
mare
Embryo flushing
Embryo transfer
procedure
TEN FACTORS INFLUENCING PREGNANCY &
PREGNANCY LOSS PER CYCLE
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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
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Ultrasound, 14-18 days
– ID twins
– ID placental
development
Re-evaluate, 40 days
Monitor Placental
function & fetal growth
Gestation Length
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Normal: 335-342
days
GROWTH CURVE
140
120
CR in cm
100
80
60
40
20
0
20
60
100
140
190
Gestation age in days
260
340
Late Pregnancy
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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
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Stage 1
– Onset: initial uterine
contractions
– End: rupture of
chorioallantois
(water bag)
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Stage 2
– Onset: rupture of
chorioallantois
– End: delivery of
fetus
Stages of Parturition
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Stage 3 (< 3 hrs)
– Onset: delivery of
fetus
– End: passage of the
fetal membranes
Foals and Immunity
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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
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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