EFFECT OF UTERINE MANIPULATION ON POSTPARTUM FERTILITY AND PLASMA 13,14-DIHYDRO-15-KETO-PROSTAGLANDIN F2-ALPHA IN BRAHMAN COWS AND 1ST-CALF HEIFERS

In Trial I, Brahman cows (n = 132) and first-calf heifers (n = 63) were randomly allotted to one of the following groups: controls (n = 65); to receive 2 minutes of gentle uterine manipulation per rectum one time between 29 and 35 days after calving (n = 67); or to receive uterine manipulation at weekly intervals from 9 through 51 days after calving (n = 63). In Trial II, eight mature cows out of each treatment were bled at 30 minute intervals from -60 to 180 minutes relative to the time of uterine manipulation. Uterine manipulation was performed after Time 0. Treatment did not affect (P > 0.1) pregnancy rate in first-calf heifers. However, treatment did affect pregnancy rate in mature cows (P < 0.01) with weekly uterine manipulation being lower (60.5%) than that of the control (83.7%) and the one uterine manipulation groups (89.1%). Conception rate at first estrus after calving was also affected by treatment (P < 0.01) in mature cows, with the weekly uterine manipulation group being lower (3.3%) than the control (30.3%) and the one uterine manipulation groups (36.4%). The proportion of cows conceiving early (by 85 days after calving) was higher (P < 0.01) in the one uterine manipulation group (87.8%) than the control (58.3) or the weekly uterine manipulation groups (57.7%). Mean plasma PGFM (pg/ml) was higher (P < 0.01) on Day 9 (450.5 +/- 15.8) than on Day 16 (244 +/- 15.8), Day 23 (185.1 +/- 15.8), Day 30 (203.1 +/- 15.8), Day 37 (198.7 +/- 17.3), Day 44 (191.6 +/- 18.9) and Day 51 (132.4 +/- 24). Mean plasma PGFM (pg/ml) was lower (P < 0.09) in the weekly uterine manipulation group (103.3 +/- 29.2) than the one uterine manipulation (216 +/- 29.2) and control groups (276.6 +/- 31.6). Proportions of the prepalpation PGFM mean were not affected by treatment on Day 9, 16, 37, 44 or 52 but were higher (P < 0.06) for the weekly uterine manipulation (Day 23) and one uterine manipulation group (Day 30) groups when compared with the control group. One uterine manipulation was effective in increasing fertility in mature cows. Uterine manipulation at weekly intervals decreased fertility in mature cows. One uterine manipulation increased the proportion of mature cows with a 365 day calving interval by 29.5% over the controls. Per rectum palpation of the postpartum cow can cause release of PGF2-alpha.