Fertility, sub-fertility + infertility in the cow

Question 1

changes in cow fertility

Answer 1

increased milk yields have decreased fertility

calving rates are also decreasing with time

Question 2

sub-fertility - causes

Answer 2

structural, functional, management causes

infectious agents

Question 3

sub-fertility - signs

Answer 3

no observed oestrus
regular or irregular returns to oestrus after natural service or AI
presence of abnormal vulval discharge
abortion + stillbirth

Question 4

no observed oestrus

Answer 4

some heifers don’t reach puberty - congenital abnormalities eg. ovarian aplasia + hypoplasia ( freemartinism is most common cause)
acyclical or anoestrus (not enough energy)
ovarian cysts
showing signs but not detected
cycling but no visible signs

Question 5

no observed oestrus in heifers

Answer 5

ovarian aplasia + hypoplasia are v.rare
92% of heifers that are co-twins to bull calves are freemartins (beware single born freemartins)
never cycle, small vestigial tract with no ovaries (freemartin)

Question 6

no observed oestrus in cow

Answer 6

anoestrus or true acyclicity
cystic ovarian disease
persistent CL?
pyometra with a persistent CL
sub-oestrus
failure to detect oestrus

Question 7

anoestrus or true acyclicity - causes

Answer 7

high milk yields
inadequate feeding especially energy
poor body condition
stress - lameness, intercurrent disease

Question 8

anoestrus or true acyclicity - clinical exam

Answer 8

rectal palpation shows involuted tract, ovaries feel small, smooth, flat
ultrasound shows follicles <1.5cm, no CL
milk progesterone at 10 day intervals low

Question 9

low IGF-1 levels due to poor nutrition - affects

Answer 9

hypothalamus - decr GnRH secretion
pituitary - decr LH + FSH secretion, response to GnRH
ovary - decr granulosa proliferation + differentiation, LH/FSH supported steriodogenesis, aromatase activity, luteal activity + steriodogenesis
embryo - decr growth, IFN tau production

Question 10

anoestrus or true acyclicity - treatment

Answer 10

wait until milk yields fall, or cow returns to +ve energy balance, incr energy intake if possible
hormones - GnRH or analogue, PRID, CIDR either alone or with GnRH or eCG (equine chorionic gonadotrophin)
better response to hormones with concurrent nutrition improvement

Question 11

follicular + inactive cysts

Answer 11

abnormal
soft, thin walled, fluid filled
single or multiple, one or both ovaries from  anovulatory mature follicle
low P4, same as acyclic cow
persistent

Question 12

luteal cysts

Answer 12

abnormal
thick-walled, fluid filled
usually single from anovulatory mature follicle
high P4, cows are anoestrus
persistent

Question 13

what are ovarian cysts?

Answer 13

fluid filled structures on the ovaries
larger than mature follicle
persist for longer than 10 days
results in aberrant reproductive function
develop from anovulatory graafian follicles in which the granulosa cell layer degenerates with cessation of normal cyclical activity - cow becomes acyclical or nymphomaniacal

Question 14

3 types of cysts

Answer 14

thin walled, oestradiol secreting follicular cyst - true follicular cyst
thick walled, progesterone secreting luteal cyst - luteal cyst
thin walled, inactive cyst - inactive cyst

Question 15

classification of ovarian cysts

Answer 15

thin walled follicular cysts result in acyclicity or nymphomania
lutal cysts result in acyclicity due to -ve feedback of P4 on anterior pituitary
cystic ovarian disease common with up to 20% cows affected in some herds
not to be confused with vaculolated CL

Question 16

why do cysts occur - hypothalamic/pituitary causes

Answer 16

normally LH surge absent or attenuated after calving

cysts occur because of failure of pre-ovulatory LH surge after end of recovery period

Question 17

failure of LH surge

Answer 17

post calving - progressive restoration of ability of hypothalamus to respond to oestradiol to produce LH surge, due to lack of sensitivity of hypothalamic LH surge centre to oestradiol or failure of GnRH release
failure of oestradiol to elicit normal +ve feedback stimulation of LH surge

Question 18

why do cysts occur - ovarian causes

Answer 18

reduced numbers of LH receptors in granulosa cell of cysts vs normal follicles
low insulin + IGF-1 + -ve energy balance causes > NEFAs impair follicular cell proliferation + function

Question 19

ovarian cysts - treatment

Answer 19

cows often develop cysts in post partum that regress on their own
don’t rupture by squeezing rectally
luteal cysts - PGF2a
follicular cyst - GnRH or hCG to cause luteinisation followed by PGF2a, or intra-vaginal CIDR or PRID for 10-12 days
good recovery rates

Question 20

persistent CL

Answer 20

occurence associated with pyometra where pathological changes to uterus interferes with luteolysin production + CL persists which self perpetuates the disease

Question 21

persistent CL - treatment

Answer 21

PGF2a

Question 22

sub-oestrus + failure to detect oestrus

Answer 22

reduced oestrus expression
good environment needed for cows to express oestrus
in high yield cows duration of oestrus is less than traditional 15h

Question 23

signs of oestrus in cow

Answer 23

restless, not eating + decr milk yield
search for other cows in oestrus for mounting
grouping of sexually active cows
bellowing if seperated
clear vulval elastic mucus discharge
stand to be mounted

Question 24

why is oestrus not detected

Answer 24

short oestrus + signs covert
usually poor facilities + observational regimen
cows should be checked 20-30mins 3x a day
use detection aids or synch oestrus with fixed-time AI

Question 25

oestrus detection aids

Answer 25

heat mount detectors/tail paint pedometers changes in vaginal impedence sequential milk progesterone assays

Question 26

reasons for cow not calving after service

Answer 26

10-15% oocytes not fertilised 15-20% embryos die <13 days 10% embryos die 13-42 days 5% foetal death after 42 days

Question 27

regular return to oestrus

Answer 27

where interval between service + return to oestrus is 18-24 days due to fertilisation or early embryonic death

Question 28

irregular returns

Answer 28

intervals either >24 days where cause is late embryonic or early foetal death mistimed AI due to incorrect identification of oestrus

Question 29

causes of fertilisation failure - non bull related

Answer 29

``` anovulation delayed ovulation incorrect timing of AI serving too early postpartum hormonal deficiences + imbalance structural defects of tubular genital tract preventing sperm + oocyte meeting infection of genital tract + endometritis nutritional deficiencies + imbalances stress ```

Question 30

early + late embryonic death - causes

Answer 30

luteal deficiency + hormone imbalance uterine infection with specific embryopathic microrganisms infection with opportunist pathogens + endometritis nutritional deficiencies + excesses heat + other stressors

Question 31

early + late embryonic death - diagnosis

Answer 31

luteal deficiency + hormone imbalance - difficult to diagnose, some success with P4 supplementation using PRID or CIDRs opportunist pathogens + endometritis - unlikely in abscence of clinical signs, treat as for endometritis, cost effective?

Question 32

specific embryopathic micro-organisms

Answer 32

``` campylobacter fetus tritrichomonas fetus mycoplasma, ureaplasma + acholeplasa bovine viral diarrhoea virus (BVDV) infectious bovine rhinotracheitis (IBR) blue tongue virus chlamydophilia psittaci ```

Question 33

treating repeat breeder cow

Answer 33

``` change sire if used repeatedly, natural service if possible use semen from bull with good fertility inseminate at normal time + 24h after hCG or GnRH at time of first AI 11-12 days after AI, GnRH analogue 11-12 days consider use of PRID or CIDR ```

Question 34

effects of infectious agents on fertility of heifers + cows

Answer 34

prevent fertilisation - return to oestrus at normal interval causes early embryonic death - eturn to oestrus at normal interval causes late embryonic death - eturn to oestrus at extended interval causes abortion - still birth, weakly calves

Question 35

endometritis - predisposing factors

Answer 35

``` longer/shorter gestation length retained foetal membranes parity milk yield dystocia + trauma hygiene season of year intercurrent disease nutrition early or delayed return to oestrus ```

Question 36

endometritis - diagnosis

Answer 36

vaginal exam essential - character, volume, smell scoring for severity bacteriology v.difficult

Question 37

endometritis - common bacterial agents

Answer 37

``` trueperella (arcanobacterium) pyogenes prevotella species escherichia coli fusobacterium necrophorum fusobacterium nucleatum ```

Question 38

endometritis - treatment

Answer 38

CL present - PGF no CL - metricure, intrauterine cephalosporin chronic lesions, fail to respond to treatment

Question 39

abortion - define

Answer 39

expulsion of one or more calves 271 days after service either dead or alive for <24h

Question 40

stillbirth - death

Answer 40

birth of dead calf at full term

Question 41

non-infectious causes of abortion/stillbirth

Answer 41

genetic factors - chromosomal/developmental abnormalities endocrine deficiencies + excesses toxic substances heat stress misuse of therapeutic substances such as corticosteriods and PGs dystocia (stillbirth)

Question 42

specific, non-venereal infectious causes of abortion

Answer 42

``` brucella abortus - 6-9 months leptospira spp - 6-9 months listeria monocytogenes - 6-9 months salmonella.spp - variable time trueperella (arcanobacterium) pyogenes mycobacterium tuberculosis - any stage fungi - aspergillus, absidia, mortiella bacillus licheniformis - late abortions neospora caninum - late abortions ```

Question 43

specific, venereal infectious causes of abortion

Answer 43

campylobacter fetus - 5-7 months tritrichomonas fetus - 5 months IBR-IPV virus - 4-7 months BVDV - any stage

Question 44

luteinised follicles

Answer 44

abnormal <2,5cm, no sign of ovulation, larger cavity than vacuolated CL usually single from anovulatory mature follicle occur early postpartum