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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
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