Uterine contraction patterns and fertility in early postpartum ewes

Three experiments were conducted to determine: (1) the direction of uterine contractions in Days 32 and 52 postpartum ewes (Experiment 1); (2) the eff ect of PGF(2 alpha) on direction of uterine contractions (Experiment 2); an d (3) the effect of PGF(2 alpha) on fertility rates in Day 32 postpartum ew es (Experiment 3). In Experiment 1, non-lambing (>90 days postpartum) and l ambing ewes (day of lambing=Day 0) received medroxyprogesterone acetate (MA P) vaginal sponges for 8 days and 500 IU of eCG at sponge withdrawal (Days 30 or 50 postpartum). At the time of eCG injection, ewes were divided into the following groups: (1) non-lambing (control; n=29); (2) Day 32 postpartu m dry (n=15) and lactating (n=16); and (3) Day 52 postpartum dry (n=14) and lactating (n=16). At estrus or 60 h post-eCG, the uterus was exteriorized through a mid-ventral incision, and the origin and direction of uterine con tractions were recorded for 10 min. In Experiment 2, ewes received MAP spon ges on Day 16 postpartum followed by 500 IU of eCG on day of sponge removal (Day 30). At estrus, the ewes were divided into the following treatments: (1) two injections of saline 4 h apart (n=10) and (2) 12.5 mg of PGF(2 alph a) followed by another 12.5 mg 4 h later (n=7). After the second injection, ewes were laparotomized and uterine contractions were counted. In Experime nt 3, estrus was induced in postpartum ewes, and ewes were mated to two ram s, then received the same two treatments as described in Experiment 2 (ramsaline; n=32 and ram+PGF(2 alpha); n=28). Two days following mating, ewes w ere laparotomized and the oviducts flushed for recovery of ova. In Experime nt 1, lactational status had no effect, therefore, the data were pooled. Co ntrol ewes had a greater percentage (p<0.05) of uterine contractions (69%) moving towards the oviducts than did Day 32 (8%) or Day 52 (43%) awes. In E xperiment 2, PGF(2 alpha) treatment increased the proportion of contraction s (p<0.05) moving toward the oviducts (controls 16%, PGF(2 alpha) 42%). Num ber of PGF(2 alpha)-treated ewes (Experiment 3) with fertilized ova were no t significantly different from the control ewes (5/32 versus 2/28; respecti vely). In conclusion, it can be said that the direction of uterine contract ions moving toward the oviducts increased as the postpartum interval progre ssed or if they received PGF(2 alpha) injection. PGF(2 alpha) treatment did not improve fertility rates in Day 32 postpartum ewes. (C) 2000 Elsevier S cience B.V. All rights reserved.