Claires Lectures

17 day cycle, oestrus lasts 24-42 hours,6-8% of ewes in oestrus each day of the breeding season ........would take 17 days to inseminate/mate flock that are naturally cycling 

Oestrus synchronisation: the use of synthetic hormones to synchronise oestrus in a flock

Advantages of synchronisation:

• plan serving days, well-established method 
• change breeding season to when wanted
• plan lambing period (block), higher twinning rates possible
• feeding and vaccination more accurate
• similar lamb weights
• no teaser male needed to detect oestrus

Disadvantages- labour intensive, extra ££, reduced fertility, more natural with rams

Ewes lamb in unison thereby facilitating management during pregnancy and parturition

Increased fertility means more ewes pregnant. Increased fecundity means more offspring per female

Stimulation of oestrus and ovulation may also be effective outside the normal breeding season (oct-feb) permitting out-of-season breeding

Progestogen method

• progesterone sponge or pregnant mare serum gonadotrophin
• sponge at luteal phase (0-12 days) PMSG at 12-13 days between luteal and oestrus

Advantages: relatively cheap £4-5/ewe, quickest days to ovulation and most reliable to synchronise

Disadvantages: environmental contamination: residual progesterone and antibiotics (accumulate in tissues), not 'clean, green and ethical'. pregnancy rates lower than untreated

Prostaglandin method

start at day 5 for 3 days (luteal stage) then 12 days later at day 17 again for 3 days (end of the luteal stage also). or day 1 (follicular) for 3 days and 13 for 3 days. 

Advantages: PG rapidly metabolised in lungs so no accumulation, clean green and ethical, easy application. Disadvantages: pregnancy rates lower than progesterone method/untreated, £> sponges, cant synchronise when not in breeding season

Advantages:

• synchronised breeding
• use of incapacitated males
• prevention and control of disease
• lower ram maintenance
• out of season breeding -use in season semen
• stored semen, > genetic gain rate 50/year vs 1000/2-3 weeks 
  
• ease of transport
• higher breeding efficiency, remove sub-fertile rams. inseminate all females 

Disadvantages:

• inbreeding (management issue)- more prevalent in small flock/herd, ensure selection intensity isn't too high, can have opposite effect with more sires available >genetic pool
• Reduced fertility- pregnancy rates can be less than with natural mating, can be caused by semen factors or unsuccessful oestrous synchronisation
• Cost- technician, drugs, hormones, semen- cost per insemination relatively low

Laparoscopic AI- 20m sperm, 70% fertility with FT sperm, in the uterine horn

Cervical AI- up to 180m sperm, 70% fertility with fresh, <20% with frozen, in the cervix

Vaginal AI- 300m fresh sperm, 70% fertility, FT not effective, in the vagina

The timing of AI dependent on deposition site

Cervical- 55h after sponge removal

Intra-uterine: 60-66hrs after sponge removal

Should AI prior and close to ovulation= fresh sperm viable for 3-5 d in repro tract, cryo sperm have reduced fertility (max 12 hrs), oocyte viable for 24 hours post ovulation

Limitations of laparoscopic AI: Costly (£20/ewe), time-consuming, requires technical ability, not considered welfare friendly, can only be used in recognised sheep breeding schemes and performed by vet/vet tech

Limitations of cervical AI: Fresh semen: fertility rates above average(70%) but fresh semen is only viable for 24 hours 

Cryo semen: fertility rates approx 20%, lambing rate ranges from 6.7-57%(not commercially viable)

FT sperm are unable to transverse the cervix

Transcervical AI

intrauterine- 73% lambing rate

Deep cervical- 2.5-4cm 61% lambing rate

Mid cervical- 1.5-2.5 cm deep 47% lambing

Superficial cervial- 0.5-1.5cm deep 39% lambing rate 

Cervical os- 19% lambing rate

Limitations to TCAI

• cervical trauma

Cervical anatomy- 2-7 cervical rings that interlock and are misaligned

lumen narrow- 2-3mm at rings 2-3

Research

modify inseminating pipette- flexible pipettes but inconsistent effects on lambing and fertility

relax the cervix prior to insemination

can we mitigate the alterations that occur on the sperm membrane during storage

look at sperm transit in the repro tract 

Sperm transit in ewe reproductive tract

stored sperm have difficulty passing through the cervix. Fluorescent fresh and liquid stored sperm deposited in cervix and uterine horn base. Number of sperm determined post insemination 4h, number of sperm reaching uterus (cervical AI) and UTJ(Uterine AI) significantly reduced for stored sperm

Effect of Cervical Mucus

40-70% fertility with FT semen and cervical AI

reduced visco-elastic properties of cervical mucus

increased hyaluronan conc. in cervical mucus

more sperm can penetrate

(Richardson et al, 2011) 

Epididymal sperm incubated with seminal plasma can transverse the cervix 

When EP sperm used for lap AI, no reduced preg rates

No difference in sperm motility between samples

Exposure to seminal plasma increases ability to transverse the cervix 

Semen collection- teaser female, artificial vagina(AV), ram(trained to mount female)

Electroejaculation 

Main disadvantages of using electroejaculation are urine contamination, lower sperm concentration and motility. In addition, most EJ performed under sedation

Disadvantages of using AV – ram requires training 

Collection of semen- sex sorting, store genetics (freeze), incapacitated rams, faster genetic gain, utilise whole ejaculate(more doses per ejaculate) , test fertility, control disease spread 

Semen analysis- motility, concentration, morphology, CASA, acrosome integrity, isperm.....Ram semen typically  contains 2 – 6 x 109 (2-6 billion) sperm/ml.......Each ejaculate should measure 1-2ml in volume...>15% abnormal sperm should not be used for semen freezing or AI

at least 70% motile needed. Viability assessment, morphology assessment 

Want creamy, wave scored 4-5

Semen collection- teaser female, artificial vagina(AV), ram(trained to mount female)

Electroejaculation 

Main disadvantages of using electroejaculation are urine contamination, lower sperm concentration and motility. In addition, most EJ performed under sedation

Disadvantages of using AV – ram requires training 

Collection of semen- sex sorting, store genetics (freeze), incapacitated rams, faster genetic gain, utilise whole ejaculate(more doses per ejaculate) , test fertility, control disease spread 

Semen analysis- motility, concentration, morphology, CASA, acrosome integrity, isperm.....Ram semen typically  contains 2 – 6 x 109 (2-6 billion) sperm/ml.......Each ejaculate should measure 1-2ml in volume...>15% abnormal sperm should not be used for semen freezing or AI

at least 70% motile needed. Viability assessment, morphology assessment 

Want creamy, wave scored 4-5

Prostoglandin: CL only sensitive to PG on days 5 – 14 of cycle (mid-late luteal phase). Early CL unresponsive to PGf2a. Need 2 injections to catch any that were not caught in first wave of PG.

Synthetic PGs used e.g. cloprostenol (110 x more effective than PG).

Reduced pregnancy thought to be associated with reduced ability fro sperm to transverse reproductive tract.

Progestogen: Exogenous P4 does not affect the CL, therefore treatment must be as long as life of CL (12-14 days). Some research has attempted to use sponges fro 7 days only, and has even washed them then reinserted them into sheep. The re-used sponges had lower levels of P4, and a 7 days tmt reduced fertility (no. sheep pregnant after service).