Sheep - Reproduction Flashcards
(44 cards)
stages of parturition
preparation - cervix dilation, restlessness -3-6 hours but quicker after more pregnancies
active labour - contractions -30-60 mins - lamb delivered
afterbirth - 2-3 hours. if multiple lambs then individual placentas for each one.
castration
benefits -
easier to manage - can have the male lambs in a group with ewes without fighting or unwanted pregnancy
reduces ram taint in meat
usually easier to slaughter and skin
methods -
rubber band - before 7 days
burdizzo (emasculator) - before 3 months
surgical - any time after 3 months, done by vet - needs pain relief
not before 24 hours
lamb rejection
causes -
inexperience - first pregnancy
difficult or long labour
mismothering - another ewe licking lamb first
just not having strong maternal instinct - can be genetic
environmental stressors
too many lambs
sick or disfigured lamb
weird smells on lamb
intervention -
confining lamb and ewe in a small space together - ewe might work it out, but risk of lamb injury
bottle feed lamb (+ colostrum)
graft lamb onto another ewe - usually one with a dead lamb
keep lamb warm
cycle manipulation
teaser ram
melatonin implant - bring season forwards
gonadotropin injections - LH and FSH - bring season forward and increase conception rates, best after progesterone treatment
photoperiod manipulation - if indoor system, artificial light
progesterone -
intra-vaginal sponges or CIDRs - synchronise cycles
breeding - october/november
lambing - february-april
disbudding
in first few weeks once buds are there but not yet fused with skull
methods -
hot iron
caustic paste
pain management - NSAID
infection - antiseptic spray
benefits -
less injury risk to other lambs and handler
easier to manage in small spaces if no horns
aesthetics - eg show sheep
risks -
infection
pain
incomplete removal - can growth partial horns from remnants
bleeding
flystrike if done in summer
length of gestation
152 days (around 5 months)
indications for c section
large lamb
malpresentation that can’t be corrected
uterine torsion or rupture
incomplete dilation
vaginal prolapse
straining for more than an hour without progress
water bags ruptured but no visible lamb after an hour
stopped pushing
ram mot
toes - lameness, feet
testes - shape, firmness, lumps, sperm analysis
teeth - gaps, jaw, able to eat well
tone - BCS 3.5-4 at start of breeding
treat - vax, worming, shearing, correct any lameness
pregnancy vaccinations
clostridial diseases - heptavac
enzootic abortion - chlamydia
4-6 weeks before lambing - 2 doses
lamb vaccines
protected by maternally derived antibodies to 8 weeks
usually just clostridial disease - 8 weeks and again 2 weeks later
BCS targets
ewes -
3 - 3.5 at breeding
2.5 - 3 at lambing
maybe a bit lower for hill sheep
common parturition complications
dystocia
uterine prolapse
vaginal prolapse
pregnancy toxemia (twin lamb)
milk fever
retained membranes
grass staggers
common lamb conditions
joint ill
navel ill
hypothermia
watery mouth - e coli
meningitis
septic peritonitis - often a progression of navel ill
coccidiosis
msk injuries from birth - fractures, nerve damage, internal bleeding
hypocalcemia signs
stiff gait
ataxia
uncoordination
tremors
salivation
depression
tachycardia
can be fatal if untreated
usually before lambing - from 4 weeks before to up to 6 weeks after
hypocalcemia causes
insufficient dietary calcium
impaired calcium absorption - plants with oxolates bind calcium so can’t be absorbed
increased calcium demand from pregnancy - esp if twins or triplets
pregnancy hormones can sometimes inhibit bone calcium mobilisation
more common in older ewes and when there are stressors in late pregnancy
hypocalcemia diagnosis
signs and rapid response to calcium treatment - differentiates from conditions with similar signs (mastitis, twin lamb, grass staggers)
hypocalcemia prevention
keep bcs at appropriate level - not too high
calcium supplementation in feed - clover, limestone - to make sure enough esp during late pregnancy and lactation
salt in food to help magnesium absorption
make sure getting enough sunshine or supplement vitamin D
hypocalcemia treatment
IV calcium
sometimes also with glucose and magnesium
if doesn’t respond may have ketosis present - give IV dextrose or propylene glycol
heat detection
signs -
reddened vulva, discharge
restlessness, increased movement
increased vocalisation
behaviour -
seeks out ram
mounting
standing to be mounted
rubbing head or neck against ram
teaser rams - can observe ewe behaviour
chin ball markers on rams to mark ewes when the ram mounts
heat detection patches - on ewes back, changes colour when ewe mounted
electronic heat patches - can detect more subtle estrus signs
pedometer - but expensive, sheep farming isn’t that lucrative
AI
benefits -
gene selection
lower disease risk
can synchronise to improve efficiency
don’t have to deal with a ram
Methods -
cervical insemination
laprascopic
more involved than in cows, not so common as just chucking some rams in the field
parasite considerations
more affected when just born - small, no immunity, often kept inside
cocci - builds up quickly in pens
nematodirus - can kill quickly before even showing in fec
often increase in ewe parasites late pregnancy - immune challlenge
twins and triplets more susceptible to cocci - less milk, often kept in same size space together so builds up quickly
management -
treat ewes
clean pens
colostrum
ewe nutrition
lamb nutrition - malnourishment increases risk of cocci esp
minimise stress
treat navels - immune challenges increase risk
monitor - fec
keep low stocking densitys
scanning
80 days post ram
identify barren ewes
group by number of lambs - get nutrition right
signs of pregnancy/pd
no return to heat
vulva enlargement - 6 weeks
weight gain and rounder abdomen - noticeable at about 12 weeks
udder development - gradual then big increase in 24 hours before lambing
primary causes of abortion or stillbirth
infectious -
chlamydia - enzootic abortion
campylobacter
toxoplasma gondii
listeria
salmonella
border disease - like sheep bvd
non-infectious -
nutrition - insufficient vitamins or minerals, or energy
metabolic - twin lamb, milk fever
trauma
stress
toxins
genetic defects
NB - abortion causes often also cause weak lambs if the lambs survive them
