Mare Reproductive Physiology Colin Mitchell BVM&S CertEP MRCVS Hexham

Content Anatomy ( structure ) Physiology (function ) When to breed Expectations Pregnancy diagnosis Twins

Puberty Onset of reproductive activity Occurs at 12 – 24 months of age Well –fed spring born fillies reach puberty in their second spring Variable factors

Mare Anatomy 2 ovaries Y – shaped uterus / womb Cervix Vulva Breeding Soundness Examination

Physiology Ovaries Oestrogens Progesterone Influence behaviour and reproductive tract

Physiology Follicles grow on the ovaries and release oestrogen Once follicles mature – ovulation Release of ovum (egg)

Physiology Structure remaining is the corpus luteum (CL) Progesterone produced from CL

Physiology Winter Anoestrous Transitional Period Oestrus Dioestrous Winter Spring Summer

Transitional Period After winter anoestrous Before seasonal polyoestrous ( breeding season ) Long, irregular oestrous cycles Low levels of oestrogens, no ovulation Numerous follicles present on ovaries

Oestrous Oestrous cycle usually 21 / 22 days Period of sexual receptivity – 5 /6 days Affected by daylight ( April – Oct ) Behaviour due to absence of progesterone Ovulation takes place between 24 – 48 hours before end of oestrous Follicles usually 35 – 50 mm at ovulation

Oestrous Signs Stands to be mounted Raises the tail Leans towards stallion / does not kick Everts the clitoris ( winking ) Squats and urinates

Dioestrous Lasts 15 days Presence of CL Production of progesterone Actively rejects stallion

When to breed Natural breeding within a cycle Early breeding season Foal heat

Breeding methods 1.Pasture breeding 2.Hand breeding 3.Artificial Insemination

Hand Breeding Lower risk of injury Time consuming “Teasing” every other day Mated when in season – usually from day 3

Summary 5 day oestrus 16 day dioestrus ovulation oestrogenprogesterone

Summary 5 day oestrus 16 day dioestrus ovulation Teased * * * * * * * oestrogenprogesterone

Summary 5 day oestrus 16 day dioestrus ovulation Teased * * * * * * * Mated * * oestrogenprogesterone

Early Breeding Man imposed breeding season Under lights Hormonal manipulation

Under Lights 8 – 10 weeks to be effective 7am – 11pm – add light at end of day 4m x 4m box – 150W clear bulb Newspaper test Good bodily condition, housed and well fed Healthy, good de-worming, regular dental checks

Foal Heat 330 day pregnancy To foal yearly, needs to be back in foal by 25 days post foaling Mare unique – return to fertile oestrous & ovulate within two weeks Use this “foal heat” ??

Foal Heat Most mares return to heat 5 – 8 days after foaling Significant reduction in diameter of uterus occurs very rapidly – involution Delayed involution – difficult birth, abortion or retained placenta Foaling events VERY important Assess involution

Foal Heat Accurate foaling history Post foaling examination 5 – 8 days Institute early therapy Complications :- 1.Lower pregnancy rate ( & subsequently) 2.Lower foaling rate

Foal Heat Breeding Do we or don’t we……………? Factors to consider: 1.Will foal race? 2.Will foal be sold young at Sales?

Expectations TB mares – pregnancy rate 73% TB mares – foaling rate 67% Ponies have slightly better rates

Expectations Mares average conception rates per cycle : 1.Natural service: 65 % 2. Fresh / chilled AI: 55 % 3. Frozen AI: 45 %

Pregnancy Rate 1.Fertility of stallion 2.Fertility of mare 3.Management of the mare at mating

Mare fertility Age Health Condition Reproductive conformation Previous breeding history Breeding Soundness Examination

BSE Categorises mare in attempt to determine likely breeding potential : 1.Satisfactory breeding potential 2.Questionable breeding potential 3.Unsatisfactory as a potential brood mare

BSE History General physical External genitalia Swabs – CEM Speculum Internal exam (manual) Internal exam (ultrasound) ******************** Further tests 1.Cervical / endometrial swabs 2.Endo biopsy 3.Endoscopy

Vulval Conformation Full firm vulval lips Vertically orientated Meet evenly in midline 80%+ below pelvic brim Anus “above” lips

Vulval Conformation Anus drawn forward “shelfing” of vulval lips Above pelvic brim

Caslicks Occasionally necessary Prevents air / infection being “sucked” into vagina MUST be removed prior to foaling

Reproductive Expectations Conc. Rate Foaling Rate AGE 13 65% YEARS

Pregnancy Diagnosis Advantages : 1.Management of the mare 2.Re-breed 3.Sales / insurance 4.Stud fees ( NFNF / NFFR ) 5.Twin management

Pregnancy Diagnosis 1.Ultrasound / manual palpation 2.Blood test later in gestation 3.Others available – less reliable

Ultrasound 2 scans 1 st scan 15 days In foal / twins

Ultrasound 2 nd scan 25 / 26 days Heartbeat / twins

Ultrasound No risk to mare / foal The procedure / examination is potentially dangerous to mare & vet

Manual Palpation Need adequate restraint 42 days upwards ( problem if twins ) Usually done October to confirm pregnancy

Blood Tests Small mare / fractious mare Inadequate facilities Problem if twins 1.eCG – from 45 days – false positives 2.Oestrone sulphate – from 100 days

Twins Double ovulation Undesirable – uterus cannot easily sustain Abortion; birth of two weak foals; birth of 1 live, 1 dead; birth of 2 dead foals at term Single pregnancy / monitor and return to oestrus if not naturally reduced

Twins Identify with early scans Manual reduction – before 16 days Takes time / patience and experience

Twins If mare aborts / re-absorbs after day 45, unlikely to breed that season – production of eCG. Monitor and react by day 32

Ultrasound Scanning Invaluable in breeding plan Not infallible

Any Questions……..?