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The present study aimed to determinate the effect of external progesterone (P4) supplementation on luteolysis in cows under heat stress. Forty-eight (n=48) dairy cows in the period from July–September 2018 were part of and at day 35±3 postpartum scored for BSC, synchronized using PG-3-G + Ovsynch protocol and randomly allocated into two treatments: PRID group (n=27) treated with external P4 device between G1 and PGF and CON group (n=21) left without treatment. Collection of blood samples to assess P4 concentrations was done at Pre-PG, at G1, at PGF, at 72 h after PGF (at timed artificial insemination TAI) and at d 21 after TAI. The pregnancy diagnosis was done at d 21 and d 30 after TAI by ultrasound. The average temperature-humidity index (THI) was 79.5±0.6. At G1, the P4 was significantly lower in the PRID group (1.84±0.99 ng/mL) in comparison to the CON group (2.97±1.82 ng/mL). In contrast, at PGF, there was a tendency (p=0.09) of increased P4 concentration in PRID group compared with the CON group (4.26±1.68 and 3.74±2.39 ng/mL), respectively. At TAI, more PRID cows (p=0.0001) had a lower P4 (0.06±0.03 ng/mL), in comparison to CON (1.28±2.41 ng/mL). At d 21 and d 30 after TAI, more PRID cows were predicted and diagnosed pregnant (16/27 or 59.25% and 13/27 or 48.14%) compared with the CON group (11/21 or 52.38% and 8/21 or 38.08%) respectively, but without any significant differences. Supplementation of the P4 during the Ovsynch protocol increases the P4 before TAI and reduces the incomplete luteolysis in heat stressed dairy cows.

eISSN:
1857-7415
Language:
English
Publication timeframe:
2 times per year
Journal Subjects:
Life Sciences, other, Medicine, Basic Medical Science, Veterinary Medicine