The Effects of Post-insemination Progesterone Supplementation on Pregnancy Rates and Serum Progesterone in Dairy Cows Exposed to Mild Heat Stress
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Date
2006-05-08
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Abstract
Two trials were conducted to determine the effects of progesterone administered by controlled intravaginal drug release devices (CIDRs) on pregnancy rates and serum progesterone concentrations in heat stressed dairy cows. Trial 1 utilized a CIDR from days 5 through 12 after breeding, and trial 2 utilized a CIDR from days 5 through 19 after breeding. Rectal temperatures and blood samples were obtained from cows every other day throughout the trial. Serum progesterone concentrations were measured with radioimmunoassay (RIA). Pregnancy status was determined on approximately day 30 via transrectal ultrasonography. Mean temperature-humidity index (THI) values were 73.5 for trial 1 and 75.1 for trial 2. These THI values indicated that cows in both trials were subjected to mild heat stress conditions. No significant differences were found between CIDR treated and control cows in serum progesterone concentrations. In trial 1, pregnancy rates were 31.8% vs. 33.3% for control and CIDR treated cows, respectively (p = 0.25). In trial 2 pregnancy rates were 33.3% vs. 26.7% for control and CIDR treated cows, respectively (p = 0.29). In conclusion, supplemental progesterone administered to heat stressed dairy cows after breeding did not improve pregnancy rates or increase serum progesterone concentrations.
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heat stress, progesterone, CIDR, dairy cattle
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Degree
MS
Discipline
Animal Science
