Infertility in sheep and goats

Question 1

Define infertility

Answer 1

sub-optimal reproductive performance (sheep enterprise profitability depends on this)

Question 2

How can you measure reproductive performance? 3

Answer 2

FERTILITY
FECUNDITY
SURVIVAL RATE

Question 3

What is the lambing percentage?

Answer 3

Number of lambs reared/weaned/sold per 100 ewes put to the ram

Question 4

What are the 4 major reasons for poor lambing percentage?

Answer 4

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

Question 5

What 4 factors can affect ovulation rate?

Answer 5

BCS - most influential
Season
Age
Genotype/breed

Question 6

What is the effect of (low or high) BCS on lambing %?

Answer 6

decreased ovulation rate
decreased conception rate
increased embryonic loss
decreased birth weight
decreased colostrum production

Question 7

Why might ovulation rate need to be manipulated?

Answer 7

Season
Breed
BCS
Flushing

Question 8

How does a rising group of nutrition 2-3 weeks prior to breeding affect ovulation rate?

Answer 8

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

Question 9

What can cause a poor conception rate? 6

Answer 9

Season
Repro tract abnormalities
Fertilisation failure
Phyto-oestrogens
Stress
Male infertility

Question 10

How can season affect conception rate?

Answer 10

Difference in length of breeding season between breeds
all animal may not be cyclic
possibility of short cycles
irregularity in cycling

Question 11

When will you get an intersex goat (i.e. after what mating?)

Answer 11

polled doe x polled buck

Question 12

What sheep ovarian problems can you get?

Answer 12

ovarian hypoplasia

ovarian cysts

Question 13

Are tract abnormalities more likely to affect nulliparous or parous?

Answer 13

parous sheep

Question 14

Are ovarian cysts more common in nulliparous or parous sheep?

Answer 14

nulliparous

Question 15

What are causes of fertilisation failure?

Answer 15

Chromosomal abnormalities
Age
High environmental temperature
Nutritional: clover-rich (Isoflavone) pastures
Infertility in male

Question 16

Outline the effect of phyto-oestrogens on conception rate

Answer 16

POOR EFFECT
Isoflavones (oestrogen-like compounds) produced by lucerne, red clover
Decreased conception due to changes in cervical mucous and sperm transport

Question 17

What can stress affect?

Answer 17

oestrous and ovulation

Question 18

What can cause male infertility?

Answer 18

Reproductive soundness - genital/physical abnormalities
Age
Ram:ewe
Social hierachy - presence of a dominant but infertile ram

Question 19

What are doe goats prone to?

Answer 19

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

Question 20

What are the main causes of early embryonic death?

Answer 20

Asynchrony
Dietary intake
Age
Mineral deficiencies (especially Se, I)
Infections - toxoplasma, border disease virus

Question 21

What are the main causes of late foetal death?

Answer 21

overfeeding in early pregnancy (placental insufficiency)

Underfeeding in late pregnancy + poor BCS

Question 22

What are the most common causes of late foetal death in ovines and caprines?

Answer 22

Chlamydophila abortus
Toxoplasmosis
Campylobacter - sheep only

Range of other causes: Brucellosis, leptospirosis, salmonellosis, listeriosis, Border disease, Q-fever

Question 23

Which 2 infectious diseases may result in the birth of a weak lamb?

Answer 23

Toxoplasmosis

Chlamydophila

Question 24

How is learned olfactory memory mediated?

Answer 24

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)

Question 25

What might be things to consider for mating the next year if you have a poor pregnancy scanning rate one year?

Answer 25

Pre-mating exam: evaluate male fertility, ewe BCS and general health.
Consider mating harness
Flushing
Pregnancy scanning
Submission of aborted foestuses