Definition of persistent corpus luteum (CL persistent)
Luteolysis occurs around day 17 of physiological oestrus in the cow. Luteolysis is triggered by the secretion of prostaglandin F2a to ensure initiation of a new oestrus cycle and ovulation. Corpus luteum that persists on the ovary beyond day 20 is considered persistent.
Clinical signs
Cows with persistent corpus luteum are not observed in heat and can be mistakenly considered as pregnant.
The presence of active luteal tissue on the ovary leads to the anovulatory state where growing follicles of consecutive waves proceed to dominance but fail to ovulate. This is due to the negative feedback of progesterone on LH release.
Pathogenesis
The pathogenesis of persistency of luteal tissue in cattle is not yet completely known. The direct underlying cause is undoubtedly inadequate secretion of luteolytic factor – PGF2α.
The following conditions have been associated with prolonged luteal function:
- uterine infections, including pyometra
- high milk production especially in early post partum period
- prolonged treatment with drugs interfering with prostaglandin pathways (NSAIDs, glucocorticoids)
Treatment of persistent CL
Treatment of CL persistent is relatively simple. Luteolytic doses of PGF2α are administered. This can be combined with a dose of GnRh analogue approximately 48-56h later to stimulate ovulation.