Objective: Study the effect of dexamethasone to inhibit induced corpus. luteal regression with PGF2 treatment.
Design: Clinical trail (Replacement treatment design) Animals: Seventeen Holstein heifers at 15- 17 month of age and 340kg mean body weight.
Treatment: 1-Dexamcthasonc (I 5mg,Im,Colvasone, Nor broke Co. England). 2- PGF2 (25mg ,Im , Lutalyse, Upjohn Co. USA)
Procedure: The numbers, of animals showing lutolysis after the injection of PGF2 . on day 9 of synchronized estrous cycle
(control group) were estimated and then, on the following estrous cycle, the numbers of animals showing lutolysis after the injection of dexamethasone on day 8 and PGF2 on day 9 (test group)
were estimated. Blood samples were collected on day 8 and 13 of
the cycle to assay serum progesterone levels and demonstrate the
activity of CL. Estrous detection and rectal polpation of corpus luteum were established through day 8 to 13 of the cycle Statistical analysis: Fisher exact (two tailed) test.
Results: Corpora lutea of 17 animals of control group (100%) were
regressed after the injection of the PGF2 but CLs of 6 animals of test group (35.3%) were not regressed. The injection of
dexaniethasone , 24h before the induction of luteolysis with PGF2
on day 9 of the estrous cycle significantly inhibited lutelysis
(P >005) CIinia1 Implications: it seems that luteolytic effect of PGF2 which is needed in the case of estrous synchronization and/or uterine infection, may be impaired in treated animal with dexamethasone
as an anti-inflamatory drug. J. Fac. Vet. Med. Univ. Tehran. 58, 2: 111-114, 2003.