Pregnancy diagnosis Flashcards
What is the purpose of pregnancy diagnosis?
Identify fertile animals and thus remove any problem males and females in the herd
Assist with the production system (Rebred / cull or Management change)
When can we assume the aniamal is pregnant?
Assume to be pregnant if no oestrus ~3 weeks after service or insemination (polyoestrus animals)
⇒ The exception is the bitch
What are the problems with just assuming animals are pregnant if they do not return to oestrus?
There might be:
♣ Mis-timing of observations e.g. presence of young suppressing oestrus
♣ Pathological conditions e.g. persistent corpus luteum, Luteal cysts
♣ Short oestrus intervals
What can cause pseudopregnancy?
It can be normal eg the non-pregnant luteal phase in the dog or it can be after pregnancy loss (eg in the mare)
What happens if the pregnancy is lost between day 1-5? Mare.
Embryo lost whilst in the oviduct so there is a normal oestrous cycle
What happens if the pregnancy is lost between day 5-15? Mare.
No maternal recognition of pregnancy so there is a normal oestrous cycle, unless associated with uterine inflammation then you may get a short cycle
What happens if the pregnancy is lost between day 15-36? Mare.
Type I pseudopregnancy
The maternal recognition has occurred so there will be no return to oestrus and the primary CL will persist for its lifespan of around 40 days.
The CL can be lysed by administering prostaglandin
What happens if the pregnancy is lost between day 36 - 40? Mare.
Type II pseudopregnancy
The endometrial cups have formed so there is no return to oestrus and the secondary CL will persist for the normal lifespan (150 days) and the CL cannot be lysed by prostaglandins.
How can we detect pregnancy?
- Protein / endocrinological change associated with pregnancy in urine/blood
No decline in progesterone at a defined time after mating
Species-specific pregnancy specific factors e.g. PAG, hCG, placental oestrogens, relaxin - Fetus or fetal membranes directly or indirectly via Ultrasound examination/ Rectal palpation/ Abdominal palpation/ Radiographic examination
- Physical changes in the dam which are associated with her accommodating a fetus (e.g increased uterine size or uterine artery)
- Maternal changes, secondary to endocrinological changes (e.g. absence of oestrus, change in cervical mucus, vaginal wall thinning)
What is Early conception factor, why don’t we use it as a pregnancy diagnosis?
It is a pregnancy glycoprotein produced within 48h of conception (immunosuppressive?) it comes as a ‘Dipstick’ test for serum / milk for Cattle and horse
However it has unacceptably low accuracy as the conceptus has yet to implant
How can we use progesterone as a pregnancy diagnosis?
Elevated progesterone in blood / milk approx. 22 days from mating
However:
False positives = Progesterone remaining high with no pregnancy e.g. Persistent CL
False negatives = Confusing animals/ Poor sample storage
What hormone can we detect in horses?
eCG from day 36
How can we use oestrogen for pregnancy diagnosis?
The feto-placental unit produces both progesterone and oestrogens
Oestrogen is often found from mid-pregnancy onwards in both plasma and urine
There are higher concentrations of oestrogen in mid-pregnancy than in oestrus so no false positive diagnoses
Pregnancy specific oestrogens (e.g. oestrone sulphate)
What do we use for PD in the bitch?
Relaxin
It is produced by the placenta in the bitch and the horse
What hormone do we normally use in commercial tests?
Placental lactogens eg. PAG
These are luteotrophic and produced by many species.
