Low-dose natural prostaglandin F2α (dinoprost) at timed insemination improves conception rate in dairy cattle

The primary objective was to determine if low doses of PGF2 alpha (dinoprost) given intramuscularly (im) concurrent with timed artificial insemination (TAI) would improve conception rates in dairy cattle. A secondary objective was to determine if body condition score (BCS) and parity would influence conception rates, either independently or in interaction with PGF2 alpha treatment. In experiment I, 307 lactating Holstein cows were randomly assigned to receive either 5-mg PGF2 alpha im (PGF2 alpha treated, n = 154) or 0-mg PGF2 alpha (control, n = 153) at TAI (Day 0). Blood samples were obtained on Days 10, 3, 0, and 7 to determine plasma progesterone (P4) concentrations. Pregnancy was confirmed 30 to 32 days after insemination by transrectal ultrasonography. In experiment II, 451 cows were randomly assigned to receive either 10-mg PGF2 alpha im (PGF2 alpha treated, n = 226) or 0-mg PGF2 alpha (control, n = 225) at TAI, and pregnancy was confirmed 45 to 50 days after TAI by palpation per rectum. Pregnancy data were analyzed by CATMOD (SAS). In experiment I, PGF2 alpha treatment, BCS, and parity did not affect conception rate (35.7% vs. 37.0% for PGF2 alpha treated vs. control; P > 0.05). However, in experiment II, conception rates were higher in cows given 10-mg PGF2 alpha than those in control cows (45.8% vs. 36.0%; P < 0.05), in cows with high BCS than in cows with low BCS (52.1% vs. 30.4%; P < 0.01), and in primiparous than in multiparous cows (47.6% vs. 34.4%; P < 0.01), but their interaction with PGF2 alpha treatment did not affect conception rates. In summary, 5 mg of PGF2 alpha given im concurrent with TAI failed to enhance conception rate in lactating dairy cows, whereas 10 mg of PGF2 alpha significantly increased conception rate. (C) 2015 Elsevier Inc. All rights reserved.