Infertility in sheep and goats Flashcards
Define infertility
sub-optimal reproductive performance (sheep enterprise profitability depends on this)
How can you measure reproductive performance? 3
FERTILITY
FECUNDITY
SURVIVAL RATE
What is the lambing percentage?
Number of lambs reared/weaned/sold per 100 ewes put to the ram
What are the 4 major reasons for poor lambing percentage?
Poor ovulation rate –> increases single lambs
Poor conception rate –> increases barren ewes
High embryonic/foetal loss –> increases barren ewes
High abortion/stillbirth/death –> decreases ewes rearing a lambs
What 4 factors can affect ovulation rate?
BCS - most influential
Season
Age
Genotype/breed
What is the effect of (low or high) BCS on lambing %?
decreased ovulation rate decreased conception rate increased embryonic loss decreased birth weight decreased colostrum production
Why might ovulation rate need to be manipulated?
Season
Breed
BCS
Flushing
How does a rising group of nutrition 2-3 weeks prior to breeding affect ovulation rate?
Increased nutrition –> increased circulation in hepatic portal system –> clears oestrogen out of system faster –> decreased oestrogen –> decreased negative feedback on LH concentration –> increased LH concentration –> increased ovulation
What can cause a poor conception rate? 6
Season Repro tract abnormalities Fertilisation failure Phyto-oestrogens Stress Male infertility
How can season affect conception rate?
Difference in length of breeding season between breeds
all animal may not be cyclic
possibility of short cycles
irregularity in cycling
When will you get an intersex goat (i.e. after what mating?)
polled doe x polled buck
What sheep ovarian problems can you get?
ovarian hypoplasia
ovarian cysts
Are tract abnormalities more likely to affect nulliparous or parous?
parous sheep
Are ovarian cysts more common in nulliparous or parous sheep?
nulliparous
What are causes of fertilisation failure?
Chromosomal abnormalities Age High environmental temperature Nutritional: clover-rich (Isoflavone) pastures Infertility in male
Outline the effect of phyto-oestrogens on conception rate
POOR EFFECT
Isoflavones (oestrogen-like compounds) produced by lucerne, red clover
Decreased conception due to changes in cervical mucous and sperm transport
What can stress affect?
oestrous and ovulation
What can cause male infertility?
Reproductive soundness - genital/physical abnormalities
Age
Ram:ewe
Social hierachy - presence of a dominant but infertile ram
What are doe goats prone to?
Pseudopregnancy/hydrometra/cloudburst = accumulation of aseptic fluid in the uterus in the presence of a persistent CL.
REASONS: lack of conception, early embryonic death, genetics, artificially bred
TREATMENT: PGF2a and oxytocin
What are the main causes of early embryonic death?
Asynchrony Dietary intake Age Mineral deficiencies (especially Se, I) Infections - toxoplasma, border disease virus
What are the main causes of late foetal death?
overfeeding in early pregnancy (placental insufficiency)
Underfeeding in late pregnancy + poor BCS
What are the most common causes of late foetal death in ovines and caprines?
Chlamydophila abortus
Toxoplasmosis
Campylobacter - sheep only
Range of other causes: Brucellosis, leptospirosis, salmonellosis, listeriosis, Border disease, Q-fever
Which 2 infectious diseases may result in the birth of a weak lamb?
Toxoplasmosis
Chlamydophila
How is learned olfactory memory mediated?
Cervical and vaginal stimulation –> NEP release –> glutamate released from olfactory bulb –> stimulates NOS action –> NO produced –> NO potentiates glutamate release (i.e. positive feedback).
Nitric oxide thought to have a role in olfactory memory (sheep between 2 hours before birth and 4 hours post-partum are particularly attracted to amniotic fluid - at other times they are repulsed by this smell)
Practical applications of NOS inhibitors (L-nitroarginine) for fostering of lambs (not currently used in UK)
What might be things to consider for mating the next year if you have a poor pregnancy scanning rate one year?
Pre-mating exam: evaluate male fertility, ewe BCS and general health. Consider mating harness Flushing Pregnancy scanning Submission of aborted foestuses
