Main luteolitic failure cause of inefficiency of the prostaglandins in syn-chronized cows under tropical grazing

Abstract

Our objective was to determine the cause of the low response in the exclusive use of prostaglandin in synchronization programs in cows under tropical grazing compared to the use of progesterone (CIDR). Thirty-five cows with the presence of CL were randomly distributed: first group (GPG; n=23), synchronized with two doses of PGF2α (25 mg, Dinoprost®), with an interval of 12 days. The second group (GCIDR; n=12) synchronized with an intravaginal device (1.9 g progesterone), 2 mg estradiol benzoate and 50 mg progesterone), at day 7 a dose of PGF2α (pm) was administered and at day 8 the CIDR (am) was withdrawn. CL regression, luteolitic failure, progesterone concentration and CL size were determined. The data were subjected to normality test, then to Mann-Whitney U test or independent t student test and chi square. Finding that only 82.6% (19/23) of GPG cows at the second dose of prostaglandins have functional CL (<1 ng/ml of progesterone). Obtaining only in 43.5% of the cows a regression of the CL in the GPG, vs. 91.7% in GCIDR (P=0.0001). In addition, GPG cows showed luteolytic failure of 39.1% and asynchrony of 17.4%. It is concluded, a low efficiency of prostaglandins on the synchrony and regression of CL (luteolitic failure) in cows fed under tropical grazing, attributed to the low efficiency in synchronization programs.