Bovine repro Flashcards
Where are GnRH, FSH, LH, oestrogen and progesterone produced from? What do they act on?
GnRH: hypothalamus, acts on pituitary to produce FSH and LH
FSH and LH: anterior pituitary, FSH acts on follicles, LH acts on egg
Oestrogen: follicle
Progesterone: corpus luteum
Stages of follicle growth? What does growth of follicles depend on?
Initiation of follicle growth -> recruitment -> selection and dominance -> ovulation
Primoridal follicles -> primary follicles -> secondary follicles (antrum formation)
Atresia of follicles along the way
Preantral follicle growth for 3 months - GF dependent, gonadotropin influenced
Antral follicle growth for 2 oestrus cycles - gonadotropin dependent, GF influenced
Stages of the bovine oestrus cycle?
Day 0: ovulation - follicle releases oocyte for fertilisation, collapsed follicle develops into CL
Day 6: CL is mature, secretes progesterone
Day 16: luteolysis
Oestrus -> metoestrus -> dioestrus -> protestrus
Follicles continue developing in waves through dioestrusbut hormones prevent ovulation
How big is a dominant follicle?
> 9mm
Hormone levels after calving? When does the first follicle wave emerge postpartum for dairy and beef cows? Does the first dominant follicle ovulate/what does it depend on? How long until first oestrus? Nature of first ovulation?
Low progesterone and oestrogen
Resumption of FSH surges increases within 3-5d, at 7-10d intervals
Emergence of first follicle wave: 5-10d post partum
First post partum follicle wave -> first dominant follicle
Ovulates if sufficient E2 from DF for LH/FSH surge
Capacity for E2 secretion depends on DF size, LH pulse frequency (nutrition, health), IGF-I bioavailability (nutrition)
First oestrus: 2-3 weeks in dairy unless ill/NEB, 3w-3m in beef as increased inhibition
Nature of 1st ovulation: silent
What regulates the LH pulse frequency post partum?
Declining NEB BCS at calving DMI Disease state Suckling and calf presence (beef)
What does success of AI depend on?
Use of proven/fertile sires
Reliable oestrus detection
Best time to inseminate cows?
In oestrus not dioestrus!
12h before ovulation?
Duration of cow signs of heat?
Coming into oestrus: 6-24h (mucus discharge, swelling of vulva, holding milk, bawling, restless, mounts other cows)
Standing oestrus: 6-18h (all above plus stands to be mounted)
Going out of oestrus: 12-24h (same as coming into)
Signs of a cow in oestrus?
Sniffing vulva Chin resting Licking Bunting Mounting head to head Standing to be mounted (only 50% of cows will do)
Methods of oestrus detection of cows?
Visual observation
Paint/chalk/kamar - not all animals show standing heat
Record keeping - start looking 18d after last oestrus
Teaser bull
Chin balls
Milk progesterone
Activity meters - pedometers
What must be done to increase pregnancy rates with AI routine?
Tweezers not fingers Thaw at 37 degrees for 40 seconds Keep warm Chilling once thawed is bad Dry thoroughly
Early embryonic development stages?
Fertilisation -> zygote -> 2-cell -> 4-cell -> 8-cell -> morula -> blastocyst
Which hormone is crucial for embryo growth?
Progesterone
What controls calving?
ACTH from calf pituitary -> cortisol from calf adrenal gland -> increased prostaglandin and reduced progesterone from placentomes
Infusion causes premature labour
Ablation causes prolonged pregnancy
How is submission rate calculated?
No. animals served/No. eligible/3 week cycle
First service submission rate: eligible = all animals after earliest service date who have not yet been served
All services submission rate = all animals after earliest service date who are not yet pregnant
What is ‘pregnancy rate’? What is ‘preg rate’?
Pregnancy rate: % pregnant of those served
Preg rate: number pregnant/number eligible to be served/3 weeks
When does ovulation occur in cows?
24h after heat
Timeline of physiological events to calf between ovulation and calving? When can embryo transfer be done? When does failure of inseminsation occur cumulatively?
24h after heat, day 0: ovulation (2% failure)
Day 2: fertilisation (15% failure)
Day 4: entry into uterus (16-32 cells)
Day 6-7: ET can be carried out
Day 8-13: maternal recognition of pregnancy (45% failure)
Day 21-23: interdigitation and expansion
Day 23: heart begins beating
Day 28: amnion remains spherical
Weeks 5-6: distension of uterus (50% failure)
Weeks 6-7: Sexual differentiation of foetus
Weeks 8-9: genital tubercle migration
Length of normal bovine oestrus cycle? Type of breeder? Type of ovulation? Which ovary ovulates?
18-24 days
Non seasonal
Spontaneous ovulation
Right ovary has 60% of ovulations
What happens during regeneration of the endometrium post-calving?
Septal mass = early evidence of necrosis of septum
Sloughing of necrotic septal mass 5d post partum, fully sloughed by 10-15 days, leaves vascular stubs
Smooth surface of stratum compact by 19d post partum
Normal by 25d+
Why are retained foetal membranes a problem?
Delays involution of uterus
Reduces milk yield
Problems with uterine infections?
Damages the uterus
Suppresses hypothalamic GnRH and pituitary LH secretion
Localised effects on ovarian function
Main uterine infection pathogens?
E.coli Trueperella pyogenes Dichelobacter nodosus Fusobacterium necrophorum (BoHV4)
Risk factors for uterine bacterial infection?
Dystocia
Abortion
Twins
RFM
Reduced DMI in dry period NEB after calving Milk fever/vitamin D Vit E/selenium Vitamin A Iodine
Definition and grades of metritis?
= Inflammation of the uterus caused by bacterial infection, with a reddish-brown (purulent), soul smelling uterine exudate detectable in the vagina, within 21d after parturition
Grade 1: enlarged uterus and purulent uterine discharge but no pyrexia/illness
Grade 2: ‘puerperal metritis’ - overt systemic illness (decreased milk yield, fever >39.5C, reduced appetite)
Grade 3: ‘toxaemic metritis’ - signs of toxaemia (cold extremities, dullness)
Definition, diagnosis and treatment of pyometra in cows? Cause?
= Intrauterine accumulation of pus in the presence of a CL and a closed cervix
Mixed bacterial infection, similar to endometritis
Diagnosis: no signs of heat, enlarged uterus, CL, US for pus
Treatment: PGF
Definition of clinical endometritis?
= Inflammation of the endometrium, with a purulent uterine discharge detectable in vagina 21 days or more post partum (usually caused by bacterial infection)
Uterine discharge scoring?
0 = clear or translucent 1 = flecks of white or off-white pus 2 = <50ml exudate containing <50% white or off-white material 3 = >50ml exudate containing purulent material, usually white or yellow but occasionally bloody
Average calving-conception?
80 days
What factors increase the calving-conception time in order from worst first?
Drop in social status Caesarean Bad calving Lameness Endometritis RFM Dystocia Mastitis Milk fever Low BCS
Sub clinical endometritis? What is it? % affected? Risks?
Inflammation of the endometrium, usually caused by bacterial infection Increased PMN in cytology Not necessarily any bacteria cultured 5-50% of cows in herd affected Risks: NEG/ketosis, metritis
Cystic ovarian disease: Clinical signs? What do follicular cysts look like and do? What do luteal cysts look like? When most common?
Anoestrus -> nymphomania Follicular cysts: - fluid filled - internal diameter >25mm - thin wall <3mm, - ovulates within 10 days - secrete oestradiol for first half of cyst lifespan - other follicles cannot develop during oestrogen phase - prolonged oestradiol inhibits LH surge - turnover of persistent follicles does occur but rarely do they luteinise - repeated waves of anovulatory follicles Luteal cysts: - luteinised follicular cyst - >25mm external diameter - thick wall >3mm (indicates progesterone production) - fluid filled lacuna - duration 10 days Most common <60 DIM
Factors associated with cystic ovarian disease?
High milk production NEB and ketosis - raised NEFAs Twinning and periparturient problems Genetic predisposition Higher parity Excess BCS at drying off
Diagnosis of cystic ovarian disease?
Palpation/ultrasound - degree of uncertainty
Milk progesterone
First stage labour in cows - what is it? how long can it takes? signs?
= dilation of cervix
May take 3-6h
Separates herself
Appetite decreases
May frequently alternate between lying and standing
Thick string of mucus often seen hanging from vulva
Towards end, bouts of abdominal straining occur more frequently, usually every 2-3 mins - pushed uterine contents against cervix, giving more stimulation to dilate
Second stage of labour in cows - What is it? What happens?
= delivery of calf
Begins with appearance of membranes (water bag) at vulva
May last several hours
Water bag ruptures with sudden rush of fluid
Cervix dilates with further pressure from calf
Powerful reflex and voluntary contractions of abdominal muscles and diaphragm (straining) expels the calf
Third stage of labour - What is it? How quick should happen?
Expulsion of placenta
Usually happens within few hours
RFM if not expelled within 12 hours after delivery of calf?
What are ideal calving facilities?
Individual pen 12 x 12ft+ - like to calve alone Easy to clean out between calvings Gate +/- quick release headlock -to easily catch cow for examination/assistance ofcavling Milking facility Well bedded and dry Good access to food and water Good lighting Well ventilated Quiet
When to intervene with a calving? Problem if intervene too early?
If intervene too early when cow in first stage labour, can prevent full dilatation of cervix
Only intervene if:
- no progress after 1h of water bag showing
- showed signs of first stage labour but has not progressed to second stage after 6h (possible twisted uterus)
- appears in extreme discomfort
- significant bleeding from vulva
Most common causes of dystocia?
Malpresentation
Foeto-maternal oversize - large calf, fat dam, young/poorly grown dam, dead emphysematous calf
Congenital abnormality - Schistoma reflexus, spina bifida, hydrocephalus
Hydrops allantois
Schmallenberg virus
Primary inertia - hypocalcaemia
Diagnosis of dystocia?
History - age, parity, breed, previous problems, how long straining, attempts by farmer, water bag broken?
Cow attitude, BCS, behaviour
General examination e.g. if recumbent and not bright/bloated
Obstetrical examination - vulva slackened, vaginal exam, rectal exam
What to pay attention to during vaginal examination for dystocia?
Lesions (tears) or haemorrhage Position of uterus and calf Relaxation and dilatation of vulva, vagina, cervix Signs of life from calf Possibility of extraction Position of umbilical cord
What to do if dystocia confirmed?
Restrain Clean Lubricate Identify 3 Rs: reposition, repulsion, rotation Extract!
Aids to help delivering calf with dystocia?
Position cow downhill or uphill
Best lube = J-lube
Pump warm water and lube into uterus - fill her up, makes space
Sink plunger for repulsion
Epidural anaesthesia
Clenbuterol - relaxes uterus but she won’t help in delivery, increases uterine blood perfusion
Phone colleague if no progress in 20 mins or need help e.g. lots of bleeding, twisted uterus, breech, needs caesarean
Ropes/chains - above fetlock has higher risk of leg fracture, below fetlock has higher risk of slipping off, double loop has minimal chance of leg fracture or slipping off
How to decide if calf in anterior presentation can be delivered per vaginum?
Head should be easily lifted into pelvis and remain there without flopping back into uterus - C section if not
Forelimbs crossing over = insufficient room for calving per vaginum as cow’s pelvis is putting pressure on humeri and width of shoulders is too large
Should be able to easily bring calf up so fetlocks are a hands breadth out of vulva - means shoulder is within pelvic canal, failure to achieve means too big for extraction per vaginum
Should be able to easily slide hand between foetal cranium and maternal sacrum - c section if not
How to decide if calf in posterior presentation can be delivered per vaginum? What to check?
Assess space by sliding hand over tail head
2 people should be able to exteriorise limbs to point where hocks are past vulva - failure = rules out per vaginum
Check position of umbilical cord - if round hock will break cord as pull calf and may die/drown before out - advise farm of risk, can do c section or calve and take risk
When is an episiotomy done? What must be done prior? How done?
Uncommonly used in cattle - almost totally reserved for heifers
In HF heifers, 5-10% may need
Narrow vestibule and vulva - vulva not fully slackened and dilated but cervix dilated and calf entering pelvic canal
Try manually stretching vulval lips with arms for 20mins before resorting to episiotomy
Perineum area contamination risk high - requires antibiotics
Caudal epidural anaesthesia
Cut at 10-11 O’clock or 1-2 O’clock position
Controlled cut, rather than tear vulva during traction
Make incision when calf’s head passing through vulva
Sutures - interrupted deep dissolvable, interrupted or continuous skin sutures
Complications of episiotomy?
Wound infection and breakdown
Distorted vulva conformation - pneumo-vaginum, uro-vaginum (poor conception rates)
Weak point to muscles which may affect ability to calve naturally in future
If cut at 12 O’clock - rectovaginal fistula
Embryotomy of calf? Drugs needed? When are full and partial embryotomies done?
Must have sufficient space
Caudal epidural anaesthesia
Clenbuterol
Sufficient lubrication
Full embryotomy:
- large dead calf
- abnormal calf (foetal monster)
Partial embryotomy:
- hip locked (euthanasia if still alive, cut off trunk as close to vulva as poss, pass wire to split pelvis, reps one hindquarter and remove other)
- head back, unable to correct and dead calf (remove head using passing method)
- leg back, unable to correct and calf dead (remove leg with passing method, must ensure elbow shoulder and scapula removed or no narrowing will be achieved)
Passing method of placing wire for embryotomy?
Pass wire by hand around area of calf needing removal
Where appropriate attach curved snare director or another form of weight
Thread wire through each side of embryotome, tighten, check wire in correct place by palpation before sawing
Cleat method of placing wire for embryotomy?
Place obstetric chain on limb
Thread wire through embryotome
Place the loop of wire in between the cleats on the leg
Advance embryotome laterally up limb to just past top of scapula/anterior aspect of greater trochanter
Unhook wire from between cleats, pass obstetric chain through loop, to allow wire to be tightened up the medial aspect of the limb to lie in axilla or between hindlimbs
Check position of wire before sawing
How to remove head and trunk for embryotomy?
For head:
- cut as far caudal along neck as poss
- embryotome placed lateral or ventral
- avoid cutting cervix or vaginal wall
For thorax/trunk
- using obstetric hook advance the trunk
- remove as much of trunk as possible by using passing method of wire placement
- pull/cut out any parts of GIT interfering with ability to feel remnants of foetus
- remove rest of trunk if necessary or leave hind quarters
- split pelvis using passing method
- extract one hindlimb at a time
Check for twin
Check for damage to uterus, cervix, vagina
Remove foetal membranes if possible
Anti-inflammatories and antibiotics advised
Complications of embryotomy/foetotomy?
Uterine/cervical/vaginal tears - from sharp bone edges or incorrect rough handling of embryotome
RFM
Metritis
Adhesions
When do most uterine torsions occur? Risk factors? Which way do most twist?
Most occur at onset of parturition Risk factors: - poor rumen fill - space in abdomen - hilly land - process of standing up/laying down Majority are anti-clockwise (when stood behind cow) 90->360 degrees
Signs of uterine torsions at calving? Examination findings?
Appear to start calving but don’t progress
No straining as Ferguson’s reflex not stimulated
May just see slightly raised tail
Dry cow off colour/down/toxic
Vaginal exam - arm ‘corkscrews’, may just feel ‘lip’ in front of cervix, may not be able to feel cervix or calf
Rectal exam - palpation of torsion
Correction methods for uterine torsion?
‘Swing’ calf with coordinated allotment of abdomen to flip calf and uterine horn back into correct position - must be able to reach and firmly grasp calf by hand/rope
Twist legs of calf and uterus may twist too
Roll cow - majority of cows require cow to be rolled from left lateral onto back and into right lateral, if calf can be reached grasp leg firmly or place calving rope and hold firmly while cow rolled, if calf can’t be reached can place plank across abdomen and weighed down to apply pressure to abdomen while rolled
C section - if unable to untwist uterus
Complications of uterine torsions?
If high degree of torsion -> blood supply occluded -> friable tissue -> dead emphysematous calf and toxic cow if not noticed early
Indications for C section?
Foetal oversize/foeto-maternal disproportion
Irreducible uterine torsion
Insufficient cervical dilatation
Foetal malpresentation if unable to reposition
Abnormal calf where embryotomy not feasible
Dead/emphysematous calf where embryotomy not feasible
Constricted vagina and vestibule where massage has not relieved constriction
Elective: double muscled breeds, embryo transfer calves (wait for 1st stage labour)
C section of cow - Anaesthesia? Sedation? Pre-op meds? Position?
Anaesthesia - caudal epidural (block Ferguson’s reflex), paravertebral nerve block
Sedation - avoid unless unsafe without, xylazine will cross placenta and decrease viability, clenbuterol must be used as uterine tone increased but exterioristation of uterus may still be difficult
Pre-op meds:
- Tocolytic (clenbuterol)
- NSAID
- antibiotic
- calcium if appropriate
Position - standing or right lateral (either way, must stay that way)
C section of cow - method?
Left flank approach
Clip and sterile prep flank
Incise from 1 hands breadth below transverse processes, approx length from tip of finger to point of elbow - angled or vertical
Locate uterine horn containing calf and exteriorise
Incise uterus
- normal presentation: incise greater curvature from point of hock to tip of toe
- breech: incise greater curvature from carpus to tip of toe
- avoid cutting placentomes - ligate any bleeding caruncles
Remove calf
- locate umbilical cord and ensure not torsed, prevent early rupture and rupture too close to body wall on extraction
- extend incision if needed carefully
Check for twins
Remove foetal membranes
Suture uterus - 2 layers, inverted, absorbable, round bodied needle, monofilament
Clean off contamination from uterus, rumen and remove blood clots from abdomen
Close muscle and peritoneum in 2 layers, and skin
Apply antibiotics to muscle layers - shown to reduce risk of wound infection
Post op meds - oxytocin, calcium if needed
How to alter C section method if emphysematous calf?
Paramedian incision
Very low flank incision
Sedation/drop - large epidural, xylazine, xylazine and ketamine
C section complications? Signs? Treatment?
Haemorrage: post op check may show cow off colour, tachycardia/murmur, pallor - re-open, locate site of bleeding and ligate
Peritonitis: off colour, pyrexia - re-open, identify any site of leakage, flush abdomen with sterile fluid, if palpable on rectal exam 7d post-op then poor prognosis
Localised adhesions
RFM
Metritis
Wound infections/seroma/breakdown/emphysema
Poor fertility due to: delayed uterine involution, RFM, endometritis, salpingitis, adhesions, abortion
Factor affecting uterine prolapse in cows post partum? Survival? Effect on production?
Hypocalcaemia
2 week survival 80% (better if live calf)
50 day increase in calving-conception
Replacement technique for uterine prolapse of cow?
Standing or sternal with hindlimb extended out behind her
Caudal epidural +/- clenbuterol
Protective cover under uterus
Removed foetal membranes and clean off contamination
Apply lube and gradually feed back in - avoid using finger tips as may rupture uterus, feed in sections starting close to vulva or every from horn yips
Once replaced, ensure horn tips fully everted by using a bottle to extend the reach of your arm, or fill uterus with water
Give oxytocin, NSAIDs, antibiotics, calcium
Buhner’s suture?
What are the main factors affecting cyclicality of cows?
Lameness
Low BCS
High yield
Risk factors for milk fever?
Difficult calving
RFM
Endometritis
Subclinical low Ca
Effect of post partum mastitis, BCS loss and lameness on oestrus and luteal activity etc?
Mastitis:
- first CL and first oestrus are later
- smaller follicles
- reduced fertility
- take longer to ovulate if synchronised
Increased BCS loss:
- increased days to first ovulation after calving
- lower first service pregnancy rate
Lameness:
- first CL and first oestrus are later
- lower intensity of oestrus
- reduced oestrus behaviours
- don’t respond as well to a progesterone synchronisation regime
Effect of milk yield on oestrus signs?
Shorter duration of being mounted (e.g. 6h)
Lower incidence of standing oestrus
Shorter duration of standing
More silent heats
What does oestradiol production by first dominant follicle depend on 1-21d after calving?
IGF-1
Define abortion in cows?
Calving that occurs before 270d gestation
Must be reported (due to Brucella risk)
Measures to monitor for Brucellosis in cows?
All abortions to be reported
Monthly routine bulk milk sampling
APHA decides if individual case to be testing
Stat testing = dam’s blood + vaginal swab + milk
Which infectious agents causing bovine abortion have vaccines?
Lepto
BHV1
BVDv
Brucella
How much does a replacement animal cost following a culled cow?
£1500-2000
Definition of primary abortive agents?
Destroys integrity of foeti-maternal unit
E.g. placentitis due to hypoxia
Allows opportunistic pathogens to invade placenta and foetus
Alters microbiological profile within pregnant uterus
What primary infectious abortive agents are there in cows?
Brucella abortus BVDv Leptospirosis borgpetersensii (commensal in repro tract) Neospora BHV1 Parainfluenza 3 Bacillus licheniformis Fungi
Define secondary (opportunistic) abortive agents of cows?
Usually associated with chorionitis/amnionitis
Placental steroidogenesis abolished (progesterone)
Associated inflammatory cascade and prostaglandins causes:
- luteolysis
- relaxation of cervix
- foetus expelled
What secondary abortive agents of cows are there?
Gram +ve: - T pyogenes - Listeria monocytogenes - Staph aureus - B-haemolytic Strep Gram -ve: - E.coli - Fusobacterium necrophorum - Histophilus somnis - Leptospirosis borgpetersensii - Pseudomona aeruginosa - Salmonella dublin/typhimurium Others: - Mycoplasma bovigenitalium - Yersinia pseudotuberculosis - Ureaplasma divers
What are the 3 possible routes of infection of bovine abortive agents?
Resident flora of reproduction tract during pregnancy - at time of service in cattle e.g. Ureaplasma diversum
Transplacental (contaminate amnion) - Bacillus licheniformis in cattle, Chlamydophila abortus in ewes
Haematogenous - viruses e.g. BVDv, BHV-1
What foetal lesions are associated with transpacental infection of abortive agents in cows?
Ureaplasma diversum -> conjunctivitis, bronchopneumonia, peri-bronchiolar cuffing
T progenies -> bronchopneumonia
What foetal lesions are associated with haematogenous infection of BHV-1 in cows?
Peri-bronchiolar mononuclear inflammatory cell infiltration and vasculitis
Centrolobular necrosis of liver
Foetal lesions associated with iodine deficiency?
Thyroid hyperplasia (foetal weight in kg/2to3 = expected weight of thyroid in g)
Foetal lesions associated with selenium/vitamin E deficiency?
Cell membrane protein associated with removal of oxidation products
Myocardial degeneration
Mixed inflammatory cell infiltration with some mineralisation - chorionitis
What foetal lesions are associated with haematogenous infection of BVDv in cows?
Pale liver without autolysis
Fatal focal myocarditis with mononuclear inflammatory cell infiltration
Radio-opaque lines
Cerebellar hypoplasia
Formula to relate foetal tibial length to gestational age?
If tibial length <58mm, days = 68 + (1.7xL)
If tibial length 58-163mm, days = 114 + (0.91xL)
If tibial length >160mm, days = 105 + L
Approximate timing of bovine abortions?
BVD, Salmonella, T progenies, M tuberculosis - any time
Trichomonas - 2-4 months
Neospora - 4-6 months
Campylobacter - 4-8 months
Mycotic, lepto, listeria, IBR, IPV - 4-9 months
Bacillus/Chlamydia - 5-9 months
Brucella - 6-8 months
Foetal immunity - when does T cell recognition of self occur? When are antibodies produced?
T cell recognition of self: 90-120 days The more complex the antigenic stimulus, the later in gestation Abs are produced - BDVv after day 140 - Salmonella dublin after day 165 - Fungi after day 200
IBR - Agent? Signs? Diagnosis? Prevention?
BHV-1 Unusual to have resp and retro symptoms Latent carriers - trigeminal ganglion Recrudescence - stress Serology - ELISA Swabs - IF Vaccines - protection in face of outbreak (into-nasal, marker vaccine)
Neospora caninum - What is it? Phylum? Definitive host? When does it cause abortion? Transmission? Outcome?
Intracellular parasite
Definitive host - canidae
Phylum = Apicomplexa
Dogs: bradyzoite ingestion -> oocysts in faeces, transplacental transmission -> puppies may have disease (neonatal paresis), Ab response
Most commonly diagnosed cause of abortion
Usually 4-6 month gestation
May cause early embryonic death - manifests clinically as infertility (rare)
Congenitally infected heifers most at risk of abortion in first gestation
Cows infected by oocysts ingestion (exogenous) -> abortion or PI calf born
Recrudesence of infection in cow -> transplacental (endogenous) -> abortion of PI calf born
10%: Abortion
80%: Birth of clinically normal PI calf
10%: Birth of clinically normal uninfected calf but may be weak
95% of calves born to infected dams are themselves infected
Endemic abortion pattern:
- annual abortion rate >3%
- endogenous transpacental transmission
- very efficient, common route
Epidemic abortion pattern:
- abortion storm >10% of at risk cows abort over a 12 week period
- associated with exogenous transplacental transmission
Diagnosis of Neospora in cows?
Maternal serology (ELISA) fluctuates though reproductive cycle
- nothing at 12-18mo (little use screening young stock)
- use increasing levels as evidence of recrudescence
- test in second half of pregnancy
- eliminate other causes
Test calf at birth - indicates dam infected if calf +ve
PM of dead foetus - brain histopath, non suppurative encaphalitis
Control of Neospora?
Keep dogs away from cattle feed and water and don’t allow to eat placentas
Identify positive cows - serology of whole herd
Cull seropositive animals and offspring - often not practical as high prevalence so expensive
Breed to beef and do not keep or sell as replacement heifers
Use sexed semen to get more heifers from uninfected animals
Embryo transfer to negative recipients
PI cows are immune to further challenge but may recrudesce
Causes 35% of abortions in UK
BVD - Type of virus? Incubation period? When are Abs present? Genotypes? Biotypes? What happens if infection during pregnancy?
Pestivirus
Incubation period 5-7d
Abs present 14-21d after initial infection
Genotype I - mildly/moderately pathogenic, most common type in N Europe
Genotype II - virulent type, problem in N America, severe diarrhoea and moderately mortality rates (30%)
2 biotypes within each genotype:
- non cytopathic: rarely causes clinical disease (unless genotype II) but crosses foeti-maternal barrier
- cytopathic: associated with mucosal disease in PI animals
Infection during pregnancy of non cytopathic:
- First trimester (0-95d): foetal resorption or abortion
- 95-120d: immunotolerance (PI)
- 120-285d: seropositive foetus +/- congenital lesions, abortion may occur due to placentitis
Consequences of BVD?
Lowered pregnancy rates - reproduction tract epithelia and follicles affected
Abortion - compromised foeti-maternal barrier allows secondary bacterial infection (placentitis and foetal pathology)
PI calves
Congenital abnormalities - cerebellar hypoplasia, microphthalmia, cataracts
Mucosal disease - PI animals then infected with cytopathic biotype
Problems with BVD PI calves?
Don’t recognise virus as foreign as infection occurs before immune system development
Ab negative, Ag positive (serum for Ab, heparin for Ag)
Susceptible to MD if encounter secondary infection with cytopathic virus (don’t mount an immune response) - usually via mutation of resident strain
Often poor-doers as BVD is immunosuppressive - but can make to adulthood and produce PI calves
Clinical signs of BVD mucosal disease?
Ulceration of mucosal (particularly tongue, soft palate, gingiva and oesophagus)
Ill thrift
Diarrhoea
+/- Concurrent respiratory disease (immune suppression)
Diagnosis of BVD?
Seroconvert over 3 weeks
Bulk milk Abs (quarterly) - vaccination will render useless
Detect PI in blood from 1mo (<30do MDA interferes)
Ear notch tissue test when tagged
Check test (5 bloods per group_
Bulk tank PCR detection limit one in 300
Probably 50% dairy herds are but tank BVD Ab+ve (70% in UK cattle)
Leptospirosis - Main 2 types in UK cattle? Where do the bacteria go? Transmission?
L interrogans serovar Hardjo (type hard-prajitno)
L borgpetersensii serovar Hardjo (type hardjo-bovis)
Bacteria can reside in kidneys
Excreted for months-years via urine
Survive long periods in water
Spread by contact with skin, mucous membranes or orally
75% of adult UK cattle have been exposed to L hardjo
Clinical signs of Leptospirosis in cattle?
Often unapparent and cow in latent state
Persistent infection of reproduction tract - infertility, shedding in discharges
Abortions, still births, weak calves in acute infections
RFM
Diagnosis of Leptospirosis in cattle?
Bulk milk Ab testing gauges level of infection in herd
Serology by MAT
Identification of leptospires from aborted tissue, blood or urine by IF or PCR
Treatment, risk factors and control methods for leptospirosis in cattle?
Antibiotics - prolonged course of dihydrostreptomycin or oxytetracycline
Early treatment aids prognosis in preventing latent carrier status
Risk factors/control:
- buying in stock - screen or avoid
- running a bull with cows - use AI
- co-grazing with sheep - don’t
- watercourses - fence off
Vaccinate - all breeding stock and replacement heifers from 4mo, annually
Difficult to eradicate because of latent infection
Salmonella - Most common serovar associated with bovine abortion? Sources? Control?
S.Dublin
Sources: faeces, feed, fomites
Shedding increased by stress e.g. around calving
Can vaccinate 2 months pre-calving plus youngstock
Treat sick
Hygiene!
Trichomonas foetus - Clinical signs? Infection route?
Confined to repro tract of cow and bull Spread by natural service - less common now due to AI Clinical signs: - occasionally abortion - more commonly poor pregnancy rates - pyometra and endometritis
Why has vaccination not eradicated BVD?
<20% of Ab +ve herds have PI milking
Half primary vaccine course given at incorrect time
24% given vaccine at correct time relative to service
20% given wrong dose or route
1/3 doses kept open longer than one month
1/3 farmers never refer to data sheet
Buy trojan horses ie cows with PI on board
PME for abortion cases?
Crown-rump length - gestational age Thyroid gland weight Fractures/haemorrhages Fluid compartment-itis Placentitis Liver rupture meningeal haemorrhage/oedema
What samples to use for abortion case?
Placentome or placenta Spleen -> BVD PCR Liver - IBR and bacteriology Stomach contents - bacteria e.g. Salmonella, Campy Kidney - Lepto Brain - Neoplasia Left ventricle Thyroid Eyelid - Ureaplasma, fungal hyphae in hair follicles Tired dam serology
Formulae for thyroid weight and foetal age using CRL?
Thyroid weight (g) = foetal weight (kg)/2to3
Foetal age 1st trimester (days) = (CRL(mm)+87.8)/2.74
Foetal age 2nd and 3rd trimester (days) = (CRL(mm)+297.1)/4.70
Antibodies in blood or milk for abortion investigation?
Ab following natural infection is long lasting for BVD, BHV1 and L Hardjo
Ab levels following inactivated vaccination can be low and short lived for BVD and BHV1
Single samples - exposure or vaccination?
Use paired sera for current infection
Bulk milk BVD/Lepto/IBR/Neo
BVD Ag PCR on bulk tank if <300 cows
If +ve: do a first lactation (homebred) screen (pooled)
Diagnosis and treatment of Campylobacter foetus? Control?
Preputial washing of bulls and culture
- phosphate buffered saline warmed, prevent faecal contamination
Vaginal mucus collection of cows for culture/ELISA
- select 12 females most recently identified as problem, detects IgA, only 50% of infected will produce positive result, 50% of positives become negative within 6 months, from 7 weeks to 10 months PI
Low Se - 30% in bulls, lower in cows
Treatment: systemic streptomycin, sheath lavage with pen/strep
Control:
- use AI for at least 2 seasons or longer
- separate infected from non infected herds
- autogenous vaccine of unknown efficacy
- cull older bulls
- treat younger bulls
Equation for the genetic variation in a population?
Vp = Vg + Ve
What is the heritability for: body conformation, udder conformation, milk fat/protein %, growth rate, milk yield, BCS, BHBA, reproduction traits?
Body conformation, udder conformation, milk fat/protein %: 0.6 Growth rate, milk yield: 0.35 BCS: 0.3 BHBA: 0.08-0.4 Reproduction traits: <0.1
What does pleiotropy mean?
Genes affecting more than one trait
What positive and negative genetic correlations are there in relation to dairy cows?
Negative: - milk/fat% - milk/protein% - milk/fertility - milk/BCS - BHBA/reproduction traits Positive: - milk/fat yield - milk/protein yield - milk/mastitis - SCC/mastitis - BCS/repro - lameness/milk yield
