Fertility, sub-fertility + infertility in the cow Flashcards
changes in cow fertility
increased milk yields have decreased fertility
calving rates are also decreasing with time
sub-fertility - causes
structural, functional, management causes
infectious agents
sub-fertility - signs
no observed oestrus
regular or irregular returns to oestrus after natural service or AI
presence of abnormal vulval discharge
abortion + stillbirth
no observed oestrus
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
no observed oestrus in heifers
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)
no observed oestrus in cow
anoestrus or true acyclicity cystic ovarian disease persistent CL? pyometra with a persistent CL sub-oestrus failure to detect oestrus
anoestrus or true acyclicity - causes
high milk yields
inadequate feeding especially energy
poor body condition
stress - lameness, intercurrent disease
anoestrus or true acyclicity - clinical exam
rectal palpation shows involuted tract, ovaries feel small, smooth, flat
ultrasound shows follicles <1.5cm, no CL
milk progesterone at 10 day intervals low
low IGF-1 levels due to poor nutrition - affects
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
anoestrus or true acyclicity - treatment
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
follicular + inactive cysts
abnormal soft, thin walled, fluid filled single or multiple, one or both ovaries from anovulatory mature follicle low P4, same as acyclic cow persistent
luteal cysts
abnormal thick-walled, fluid filled usually single from anovulatory mature follicle high P4, cows are anoestrus persistent
what are ovarian cysts?
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
3 types of cysts
thin walled, oestradiol secreting follicular cyst - true follicular cyst
thick walled, progesterone secreting luteal cyst - luteal cyst
thin walled, inactive cyst - inactive cyst
classification of ovarian cysts
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
why do cysts occur - hypothalamic/pituitary causes
normally LH surge absent or attenuated after calving
cysts occur because of failure of pre-ovulatory LH surge after end of recovery period
failure of LH surge
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
