Ewe fertility Issues

Why does ewe fertility matter?

affects productivity on farms, knowledge = power

What type of breeders are sheep?

seasonal

What is important to remember about the breeding cycle of a sheep?

peak fertility late autumn, first estrus or two are silent, 17 day cycle

When does ovulation occur in sheep?

toward end of estrus

What type of breeders are does (goats)?

seasonally polyestrous in temperate regions (decreasing daylength)

tropics breeds nonseasonal

What is important to remember about the breeding cycle of a doe (goat)?

high milk production after parturition can suppress estrus behavior

cycle 21 days, short cycles (5-7 days) in transition period

What does standing estrus look like in does (goat)?

24 hr in doelings

2-3 days in mature does

vaginal discharge - thin, clear, colorless becoming thick and white towards ovulation

How does a doe maintain pregnancy?

depends on the CL

What is the purpose of a sweeper ram?

mark all the ewes he serves which indicates all the ewes still actively cycling and thus not pregnant

When is the best time to scan ewes for pregnancy to detect the number of lambs transabdominally?

after 12 hours of fasting and days 45-90 of gestation

In other places when can transrectal ultrasound be used to determine pregnancy in sheep?

30 days

What is the target for pregnancy for breeding in the first 17 day cycle?

75-92%

What is the target for pregnancy for breeding by the second estrus cycle?

98%

What is the target for pregnancy at the >45 days scan?

less than 2-3% barren

What is the target for pregnancy at lambing?

less than 5-6% empty

What are individual ewe problems with subfertility?

free-martins, hermaphrodites, ovarian cysts, persistent CLs

What can cause low ovulation rates in ewes during breeding?

timing of breeding season, body condition and nutrition, ewe breed, age of ewes, latitude and altitude, PMSG injections, dietary phytoestrogens, prolonged stress

What are questions you should ask about ovulation rates in ewes?

are the ewes cycling? number of ova per cycle, are the ova healthy?

How does the timing of the breeding season affect fertility?

seasonal reproductive cycles

ovulation rates highest in midseason

hill breeds vs lowland breeds

reduced seasonality

What reduced seasonality does dorset horn sheep deal with?

june to february, peak august to december

What european breeds deal with reduced seasonality?

spain, greece, finland

What equatorial sheep deal with reduced seasonality?

non-seasonal, barbados hair sheep

When are most hill breed sheep fertile?

late october to early january

When are most lowland breed sheep fertile?

august/september and some even starting in july

How does breeding out of season affect fertility?

increased barren ewes, reduced number of lambs per ewe, longer lambing period

How can you prevent fertility issues when breeding out of season?

hormonal or light manipulation

How does BCS and nutrition of ewes affect fertility?

highest ovulation rates at optimal BCS 3-3.5 (cheviot >2.5)

avoid condition loss, nematodes, flushing

What BCS does flushing affect the most?

2.5-3

How do you raise a ewes BCS by 0.5?

4 weeks of grazing really good pasture

How does flushing work?

increase the plane of nutrition from 3 weeks before breeding and maintained at a higher rate until 2 weeks after breeding

How does peresence of gastrointestinal nematodes affect ovulation?

associated with reduced ovulation rates but ewes with lower BCS or young ewes are more susceptible so can be difficult to work out primary cause of reduced ovulation

What is the target breeding BCS and target scanning percentage for lowland breeds?

3.0-3.5, 195

What is the target breeding BCS and targe scanning percentage for upland breeds?

3, 175

What is the target breeding BCS and targe scanning percentage for hill breeds?

2.5, 116

How does breed affect fertility?

some breeds are more prolific and expected to have 2+ lambs

How do young ewes have different fertility?

cyclicity starts later and is shorter

less active in seeking the ram

length of estrus behavior (30min-24hr)

higher stress levels

need to be >60% of mature bodyweight

What prolonged stress can affect fertility?

prolonged wet weather, stressful handling, dog worrying, bullying of young ewes by older ewes

How does latitude and altitude affect fertility?

suitable for the breed of sheep and variation of onset of estrus

lowground flocks further south = earlier

hill flocks further north = later

How does dietary phytoestrogens affect fertility?

interfere with reproductive hormone cycle

What common phytoestrogens can affect fertility?

red clover, lucerne, mycotoxins (not often in UK, estrogenic effects or liver damage)

What is embryonic death and how does it affect fertility?

failure of implantation (day 19) → delayed return of estrus

embryo death post implantation → barren ewes if breeding period is limited

resorption, early fetal death, detected at scanning

How does higher ovulation rates affect embryonic loss rates?

increases

What kinds of embryonic death can there be?

whole or partial loss (reduced placent per embryo)

How does partial embryonic loss affect the lambs still growing?

remaining fetuses have smaller placenta with smaller number of placentomes compared to a normal pregnancy with equivalent final number of fetuses

What are some common causes of embryo death?

prolonged stress, inflammatory/protein losing disease, nutrition, selenium deficiency, iodine deficiency, toxoplasma gondii infection, border disease virus infection, drugs

When is prolonged stress the most impactful?

around implantation (day 19)

especially in the first 42 days

What stressors can cause fertility issues?

stressful handling, gathering, driving, transport, persistent rain, dipping

What inflammatory/protein losing disease can cause fertility issues?

subacute liver fluke, sheep scab, severe haemonchosis

How does subacute liver fluke cause inflammatory/protein losing disease?

Both blood sucking adult fluke are present in the bile ducts and gallbladder, while juvenile fluke are migrating through the parenchyma of the liver causing inflammation

The liver damage and reduced circulating protein can cause embryo death in high proportions of pregnant ewes in late autumn or early winter

How does severe sheep scab cause inflammatory/protein losing disease?

significant protein loss through damaged and exudative skin, affected sheep may eat less due to intense pruritus and large areas of skin may be inflamed and release inflammatory factors

if ewes become clinically affected in early pregnancy can result in high barren rates

How does haemonchosis cause inflammatory/protein losing disease?

generally occurs in the summer and early autumn, so for flocks aiming for early lambings and so breeding in the mid to late summer

can cause significant blood loss resulting in anemia and hypoproteinemia

What aspects of nutrition can affect fertility?

severe undernutrition

overfeeding - suppresses progesterone concentrations

prolonged feeding of brassicas

phytoestrogens (red clover)

trace elements

What trace elements deficiencies can you correct to increase litter size?

selenium, iodine, copper, cobalt, manganese, iron

How does selenium deficiency cause fertility issues?

embryo mortality at 3-4 weeks → increased barren rates

How can you test for selenium deficiency?

blood sample → glutathione peroxidase (previous 2-3 months intake) or selenium (recent intake, expensive)

How does iodine deficiency cause fertility issues?

first third of pregnancy → less lambs per ewe

late pregnancy → high perinatal lamb death ± goitres (>0.4g thyroid:1 kg BW)

What can cause iodine deficiencies?

pasture deficiencies and brassica feeding

How can you test for iodine deficiency?

blood sample - inorganic iodine levels - indicate deficiency but difficult to interpret

How does toxoplasma gondii cause issues with fertility?

oocysts from cat feces in feed and on pasture, high barren rates, abortion

How can you test for toxoplasma gondii?

blood sample - seroconversion - test barren and normal ewes minimum of 6 each

How can you prevent toxoplasma gondii?

vaccination

How does border disease virus cause ferility issues?

high barren rates, abortion, congenital deformities, persistently infected lambs (PI), immunosuppression in transient infection

How can you test for border disease virus?

blood sample - antibody = exposure, antigen = transient vs persistent infection

What drugs and toxins can affect fertility?

levamisole, corticosteroids, prostaglandins, etc.

What can doe breeding failure be attributed to?

short cycles, cystic ovaries, hydrometra/cloud burst, nutrition, toxoplasma gondii

How can nutrition affect fertility in does and how?

macro-nutrition (reduced conception and embryo survival)

selenium deficiency (reduced conception), or toxicity (reduced conception and embryo survival)

Iodine deficiency (reduced embryo survival)

Copper deficiency (reduced embryo survival and nymphomania after several years)

What are some history question you should ask when investigating ovine abortion? (13)

previous reproductive rates on farm, sheep breed, timing and length of mating, ewe:ram ratio, age spread of ewes, age spread of rams, type of fields used for breeding, nutrition and supplementations, body condition of ewes and rams, potential stressors during/after mating, records of raddle marks, farm disease history, vaccination status

What on farm investigations should you do for the flock?

observe the group of ewes for lameness, environment, nutrition and BCS (minimum 10%)

What on farm investigations should you do for the individual?

clinical examination, BCS, a selection of representative barren ewes (6-10), all rams

What diagnostic tests can help with fertility issues?

fecal sample, abortion samples, skin scrapes, serology, blood samples, metabolic prolifes

What can fecal samples help with diagnostically for fertility issues?

liver fluke, nematodes

What abortion samples help with diagnostically for fertility issues?

fetus and placenta

What blood samples help with diagnostically for fertility issues?

trace elements - selenium, iodine, cobalt, copper (minimum 6 but 10 for cobalt)

serology - toxoplasma and border disease (6 barren and 6 pregnant)

metabolic - recent energy intake, recent and longer term protein status

What can affect your investigation of fertility issues?

timing can affect diagnostic rate

delay some investigates - ram pre breeding soundness investigation, data analysis, trace element blood samples, trace element supplementation trial and nutrition assessment