Infertility Sheep and Goats Flashcards
Give 4 measures of reproductive performance
- Fertility (% barren, % pregnant)
- Fecundity (no. lambs/kids per pregnancy)
- Survival rate (no lambs/kids that survive to weaning)
- Lambing % (no. lambs reared/sold per 100 ewes put to the ram)
Potential causes of poor lambing %?
- poor ovulation rate - ^ singles
- poor conception and high embreyonic/foetal loss -> ^ barrens
- high abortion/stillbirth rate -> v ewes rearing a lamb
What must be taken into consideration when measuring reproductive performance?
- establishing true output based on breeed, season, environment
- can be compared with previous records or MLC flockplan records for local area or breed
How does BCS affect lambing % in different breeds?
- different optimum BCS for hill and lowland sheep
> excessively ^/v BCS -> - v ovulation, conception rate, lamb birth rate,colostrum
- ^ embreyonic loss
How does flushing work?
- rising plane of nutrition -> oestrogen cleared at a faster rate, -> v negative feedback on FSH
- FSH -> follicle recruitment, selection and dominance
How may time of tupping affect lambing %?
- affects different breeds to different degrees (highland breeds more seasonal than lowland)
- if bred too early or late in the season not all animals may be cycling, cycles may be shorter and irregular
How may the physical repro tract affect conception rates? Is this common?
- abnormalitites eg freemartinism, intersexes
- ovarian hypoplasia or cysts
> uncommon
How may exogenous factors affect fertilisation success?
- high environmental temperature
- clover-rich (isoflavone) pastures
> Bad for fertilisation success
What are isoflavones and how do they affect fertilisation?
- oestrgoen like compounds
- produced by clover, lucerne etc.
- changes in cervical mucus and sperm transport -> v conception
Give egs. of stressors that may affect conception rate
- shearing
- foot trimming
- vax, worming, dipping
When should a reproductive soundness exam be carreid out on a ram?
6-8 weeks pre-tupping (time to rectify problems or buy bew ram)
How may social/herd dynamics affect conception rate?
- depending on season different ram:ewe ratios can be used (summer <40ewes/ram)
- presence of dominant but infertile ram may suppress others
What condition are doe goats prone to? Tx?
> pseudopregnancy (hydrometra, cloudburst)
- presence of persistent CL -> accumulation of aseptic fluid in uterus
- occours due to lack of conception or early embreyonic death (genetic predisposition too)
- Tx: PGF2a and OT (15 IUs)
Why does early embreyonic death occour?
- asynchrony of timing between early embreyonic development and P4 rise
What may cause early embreyonic death?
- diet (overfeeding inversely preoportional to P4 conc)
- age (differences in uterine environment and ovum)
- Se and I deficiencies
- Toxoplasma, border disease virus
