Breeding Horses

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EQUINE
REPRODUCTION
TERMINOLOGY

BOOK

BOOKING FEES

STUD FEE
FOAL GUARANTEE
 Live Foal
 Return
 Color
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
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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:
–
–
–
–
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
Cervix Vagina
Left Uterine
Horn
Uterine Body
MARES
TERMS
• Anestrus
• Diestrus
• Estrous
• Estrus
MARE
CLASSIFICATION
•
•
•
•
•
•
Pregnant
Open
Barren
Maiden
Wet
Dry
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
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
•
•
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
•
•
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 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
•
•
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
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
•
•
•
•
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
• 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
•
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
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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
•
•
•
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
140
120
CR in cm
100
80
60
40
20
0
20
60
100
140
190
Gestation age in days
260
340
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
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