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mga, prostaglandin, lh, postpartum, beef cows


A study utilizing 64 Angus and Simmental multiparous beef cows was conducted to evaluate the administration of MGA-PGF on the onset of estrus, conception rate, and to determine blood serum hormone profiles (P, & LH). Cows utilized were at least 30 days postpartum and stratified by age, breed, and days postpartum into two groups: a treatment group (n=32) which received MGA orally for 14 days and a control group (n = 32) which did not receive MGA. Cows in the study were bled weekly for 9 weeks to monitor serum P, levels. Cows with serum P4 ≥ 1 ng/mL were considered to have cyclic activity. Cows in both groups were injected with PGF2a 17 days after the last MGA feeding date and bred Al following observed estrus. The number of days from the start of MGA feeding to first detected estrus was lower for treated compared to control cows (19.50 a 3.70 and 34.31 a 3.28, respectively, P< .01). The average number of julian days to first estrus was lower for treated compared to control cows (143.81 ± 2.46 and 154.34 ± 3.25, respectively, P= .01). Conception date in julian days was also lower for the treated animals compared to control cows (156.46 + 2.98 and 166.55 ± 3.21, respectively, P= .01). Treatment animals had a higher level of progesterone from the start of MGA feeding until the end of the bleeding period compared to the control animals (.41 ± .04 and .19 ± .04, respectively, P< .001). The average progesterone hormone level in treated cows was higher 48 hours before injecting PGF,, compared to the control animals (1.59 ± .12 vs 0.33 ± .12, P< .001). Blood serum analyzed for LH concentration was collected 3 days prior to PGF2a injection (Period 1) and 4 days following the PGF2a injection (Period 2). Mean LH levels between treatment and control groups were not different for the 7 days (1.58 ± .07 ng/mL and 1.70 ± .07 ng/mL, respectively, P= .25). When analyzed by periods, mean LH levels for Period 1 were lower (1.44 ± .08 ng/mL) than mean LH levels for Period 2 (1.84 a .07 ng/mL, P< .01). Results from the present study suggest that MGA decreased days to first detected estrus, resulted in earlier conception, increased conception rate, increased progesterone hormone levels, and increased cyclic activity.

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South Dakota State University


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