What type of breeder is the mare?
When is the thoroughbred breeding season?
March through to July
When is a mare in cyclic oestrus in the northern hemisphere?
April to mid-August
What is the main thing that causes the change in seasonal cyclic activity?
Increasing daylight length
What are the three main things that control seasonal cyclic activity?
Reduced melatonin secretion by pineal gland
Reduced GnRH inhibition from hypothalamus
FSH and LH secreted by anterior pituitary gland
Describe how the pineal gland can affect seasonal cyclic activity in the mare
Gland interprets daylight length and regulates melatonin secretion
Melatonin nocturnally produced by pituitary gland
Inhibits Hypothalamic-Pituitary-Ovarian axis
Daylight increases then melatonin level decreases and inhibition of HPO axis downregulated
Leads to GnRH production by hypothalamus
What are some other factors in the mare that can play a role in the transition from anoestrus to normal cycling?
What is needed for a mare to be able to return to cyclicity?
Large enough quantities of GnRH
Stimulate FSH and LH production by pituitary
What are the three functional seals between the uterus and exterior?
Vulva, cervix and vestibule
What happens to the perineal conformation with age and multiparity?
Anus displaces cranially
Upper commissure of vulva dragged cranially - sloping vulva
What are older, multiparous mares more predisposed to due to their altered perineal conformation?
Describe control of cyclic activity from FSH stimulation to luteinisation
FSH stimulates ovarian follicles
Follicles secrete oestrogen - behaviour change, tract changes, LH stimulation
Follicles secrete inhibin - inhibit FSH secretion
LH stimulates ovulation and luteinisation
Follicle collapses and luteinises - oestrogens and inhibin cease
Describe control of cyclic activity from corpus luteum formation to PGF2alpha secretion
Corpus luteum secretes progesterone - tract changes, behaviour changes
If conception maternal recognition occurs at 14 days post ovulation
Recognition causes blastocyst capsule oestrogens to be produced - prevent endometrial gland secretion of PGF2alpha
No recognition causes endometrial gland secretion of PGF2alpha
Describe control of cyclic activity from PGF2alpha secretion to FSH stimulation
PGF2alpha causes luteolysis of CL
CL stops progesterone secretion
Inhibition of: sexual behaviour, tract changes, LH secretion
FSH secretion stimulates ovarian follicles
Describe a mares behaviour in oestrus
Submissive Ears forward Legs straddled Tail held high Urinating Everting clitoris
Describe a mare in dioestrus
Tail clamped down
Describe the change in each of the 5 hormone levels over one cycle in a mare
Oestrogen - starts to increase day 17, peaks day 3-5, decreases from day 5 until day 10
Progesterone - Increases rapidly from day 5, peaks at day 8 until day 14, drops until day 20
LH - maintains a low base level, increases from day 1, peaks at day 7, rapidly decreases from day 7 until day 12
FSH - maintains low base level, increases from day 3, peak at day 6, drop between days 6 and 8, increases to a higher peak on day 10, decreases on day 10 back to base level on day 14
PGF - maintains a low base level, increases from day 13, peaks at day 15, decreases from day 15 back to base level on day 17
What day of the cycle does ovulation occur?
How long is oestrus in the mare?
Describe hormonal changes during equine pregnancy
Blastocyst capsule secretes oestrogens from day 14
2nd wave of ovarian follicles ovulate and produce progesterone
Chorionic girdle forms endometrial cups which secrete eCG from day 35-100
Foetal gonads secrete oestrone sulphate from day 100-term
What are the four layers of the scrotum?
Skin - sweat glands
Tunica dartos - smooth muscle raises and lowers the testes
Fascia - allows mobility for vertical and lateral movement
Vaginal tunic - abdominal cavity through inguinal canal to bottom of scrotum, watery fluid facilitating movement
What varies in the male horse from month to month?
What is the size of mature horse testicles?
When does the pre-pubertal stage in the male horse begin?
Around 6 months of age
What age do most colts actually become able to sexually reproduce?
14 months of age - first age they produce sufficient sperm
What are the 6 stages of spermatogenesis in the horse? How long does it take?
Spermatagonia Preimary spermatocytes Secondary spermatocytes Spherical spermatids Elongated spermatids Spermatazoa
Takes 57 days
Describe the movement of sperm from the seminiferous tubule to ejaculationt
SPerm freed from tubule
Pas into straight tubule and rete testis
Moved through efferent ducts to proximal epididymis
Fluid resorbed in caput epididymis
Sperm matured in corpus epididymis
Sperm stored in cauda epididymis and ampullae
Seminal plasma added by seminal vesicles and prostate
Gel added by seminal vesicles
Ready for ejaculation
What could traumatic injury in the testes result in?
Antisperm autoantibody production
What protects the sperm from the stallion’s immune system?
Sertoli cells - coordinate germ cell differentiation, form blood-testis barrier isolating them from immune system
Describe the spermatic cord in the stallion
Extends from abdominal inguinal ring to testicular attachment
Suspends tests in scrotum
Passage for - ductus deferens, nerves, blood vessels, external cremaster muscle
What produces testosterone in the testis?
What does the adenohypophysis produce in stallions?
How does the hypothalamus regulate sexual behaviour in the stallion?
Gonadotrophic releasing hormones
Secreted in short pulsatile bursts in response to neural stimulation
What releases oxytocin and what does it do?
Facilitates rhythmic contraction of seminiferous tubules
Help evacuate sperm
What do Sertoli cells produce in the stallion? What do they do?
Inhibin and activin
What controls testosterone production in stallions?
How does erection occur?
Penis stiffens and lengthens
Corpus cavernosum engorged first then corpus spongiosum
Initiated by cerebral responses to sexual stimulation
Penile arterioles dilated by parasympathetic over-ride of normal sympathetic control
Blood shunted to fill and disten corpus cavernosum and spongiosum
Describe emission in the stallion
Movement and deposition of sperm and fluid
Goes from ductus deferens and cauda epididymis with fluids from accessory glands in the pelvic urethra
Sympathetic impulses control
Describe ejaculation in the stallion
Expulsion of semen through the uretha
Series of strong pulsatile contractions - urethralis, bulbospongiosus
5-7 jets of semen
What four things do we need to prepare for in the mare breeding season?
Health - vaccinations, worming, venereal disease screening
Cycling mares - barren mares, maiden mares, rested mares, recently foaled mares
What does the HBLB codes of practice cover?
Bacterial infections - Taylorella equigenitalis (CEMO), Klebsiella pneumoniae (capsule types 1,2 and 5), Pseudomonas aeruginosa
Viral infections - Equine viral arteritis, equine herpesvirus 1, equine infectious anaemia, equine coital exanthema
Strangles - streptococcus equi
When should pre-season screening be done?
After 1st January and before 15th February
Describe how to swab for bacterial infections in stallions
Tease stallion to penile erection
Stand by stallion’s left shoulder
Penis held with gloved hand
Pre-moistened and pre-labelled normal-tipped swabs passed in order
Where should swabs for bacterial infections be taken? How many times?
Urethral, urethral fossa, prepucial smegma, pre-ejaculatory fluid swabs
2 times seven days apart
What screening is done for viral infections in stallions?
1 serum sample for EVA titre
1 serum sample for EIA test
Vaccinated stallions will be positive
Why are stallions vaccinated against EVA?
Can become carriers
Semen becomes contaminated and mare becomes useless
Freezing and storing does not kill virus in sperm
What swabs are done in mares for pre-season screening?
Late foaling mares swabbed one month before due date
Additional clitoral swabs for dystocia/treated mares - Klebsiella, Pseudomonas
What swabs are taken for bacterial infections in the mare?
1 set clitoral sinus and fossa swabs
What samples are taken for viral infections in the mare?
1 serum sample for EVA titre
1 serum sample for EIA test
What two cultures need to be ruled out in mares with dystocia?
What additional swabs need to be done in mares with dystocia?
Smear when in oestrus more than 7 days post antibiotic treatment
What should swabs be immersed in and how quickly should they be sent to designated laboratories?
Immersed in Amies charcoal transport medium
Sent no more than 48 hours after collection
What are the clinical signs for bacterial venereal disease?
Vaginal discharge 2 days after mating/AI
No clinical signs
Early return to oestrus - less than 15 days
What should be done if bacterial venereal disease is suspected?
Swab uterus, clitoral fossa and sinuses
Stop mating and AI
What should be done with bacterial venereal disease?
Improve management of teasing and stud hygiene - prevent stallion sniffing vulva of more than one horse, change gloves between teasing mare, don’t tease genitalia, use disposable equipment
Trace contacts and notify authorities
Treat uterus with appropriate antibiotics
Clitorectomy to remove carrier status
Re-swab 3 times 7 days after treatment
Only mate when negative swab results are confirmed and with agreement of all concerned
What can Equine Viral Arteritis cause?
Brick-red conjunctivitis Fever Depression Filled legs Skin rash Abortion Early pregnancy failure
What should be done if EVA is suspected?
Notifiable disease in UK
Blood samples for antibodies
Nasopharyngeal swabs and tissues for PCR and culture
Why should we be careful with importing stallions from abroad?
COuld contain endemic diseases from Europe that are not present in the UK
Quarantine and run tests again
DOn’t rely on foreign government tests
What should be done with horses with EVA?
Trace contacts and notify authorities
Follow-up blood samples after 1 month - static titres from same laboratory
Semen cultures - 1/3rd may become permanent shedders, notify DEFRA, castration/euthanasia if positive
Pre-vaccination seronegative test result in passport
6-monthly vaccination of stallions and teasers
No carrier status in mares - safe if static or falling titre
What does equine herpesvirus cause?
Respiratory infection Nasal discharge Abortion risk Ataxia Paralysis Incontinence
Which horses are most at risk of EHV-1?
Horses out of training
What should be done with horses with EHV-1?
Segregate from breeding stock and pregnant mares
What is the vaccination used for equid herpesvirus?
Equip EHV 1,4 licensed for use against abortion
January and July for all non-pregnant horses
January and July plus 5th, 7th and 9th months of gestation for pregnant mares
What is essential for controlling equid herpesvirus on stud farms?
Managing horse cohorting
What is equine coital exanthema?
Equivalent to genital herpes
Pox-like lesions appear on penile, puputial, vulval skin 5-9 days
How long is the recovery for equine coital exanthema?
What should be done with equine coital exanthema?
Allow recovery time