In Experiment 1, 12 unmated cyclic ewes received twice-daily intrauterine injections on Days 12 to 14 of one of the following treatments: 1) ovine conceptus secretory proteins (oCSP) containing 25 μg of ovine trophoblast protein-1 (oTP-1) as determined by RIA; 2) 25 or 50 μg recombinant human interferon alpha1 (rhlFN); or 3) 1500 ug of serum proteins (oSP) from a Day-16 pregnant ewe (estrus = Day 0) per uterine horn. Ewes receiving oCSP had longer interestrous intervals (27 ± 2 days; P<0.05) than ewes receiving oSP (17 ± 2 days). Ewes receiving either dose of rhlFN had an interestrous interval of 16 ± 2 days which did not differ (P>0.10) from that of oSP-treated ewes. In Experiment 2, 59 normally cycling ewes, mated on Day 0, received twice-daily intramuscular injections of either 2 mg recombinant bovine interferon alpha1 (rblFN) or placebo on Days 12 to 15 post estrus. On Day 16, pregnancy was confirmed by flushing a morphologically normal conceptus from the uterus. Pregnancy rates for rblFN-treated (80%) and placebo-treated (62%) ewes were not different (P>0.10). Uterine flushings and conceptus-conditioned medium were assayed for oTP-1. Total oTP-1 in conceptus-conditioned culture medium was higher (P<0.02) when conceptuses were from placebo-treated (104 ± 14 μg/conceptus) than from rblFN-treated (56 ± 12 μg/conceptus) ewes; while total oTP-1 in uterine flushings was similar (P>0.10) for placebo-treated (132 ± 15 μg/conceptus) and rblFN-treated (147 ± 17 μg/conceptus) ewes. The interval from mating to subsequent estrus following conceptus removal was 31 ± 1 and 28 ± 1 days for pregnant ewes treated with rblFN and placebo, respectively. Interestrous intervals for nonpregnant ewes were longer (P<0.02) for rblFN-treated (27 ± 3 days) than for placebo-treated (18 ± 2 days) ewes.

This study was conducted to determine whether intrauterine infusion of recombinant bovine interferon-alpha I1 (rboIFN-alpha I1), which has 70% sequence identity to bovine trophoblast protein-1, will prevent regression of corpora lutea anticipated to have a short lifespan. Twenty-six beef cows in good body condition were allotted to four treatment groups at parturition in a 2 x 2 factorial design. Treatments were: group 1, saline; group 2, rboIFN-alpha I1; group 3, norgestomet-saline; and group 4, norgestomet-rboIFN-alpha I1. Norgestomet implants were inserted on days 21-24 postpartum and removed 9 days later (before injection of human chorionic gonadotrophin (hCG)). Ovulation was induced 30 to 33 days postpartum with 5000 or 10,000 iu hCG. Groups 1 (n = 7) and 3 (n = 5) were given intrauterine infusions (rectocervical approach) twice daily with saline on days 1-12 or 13-24 after hCG injection, respectively. Cows allotted to groups 2 (n = 8) and 4 (n = 6) were given intrauterine infusions (rectocervical approach) of 2 mg rboIFN-alpha I1 twice daily on days 1-12 or 13-24 after hCG injection, respectively. Treatment with both norgestomet and rboIFN-alpha I1 delayed (P less than 0.01) luteolysis. Lengths of luteal phases (days; mean +/- SEM) were 8.4 +/- 0.7 (group 1, saline), 14.1 +/- 1.0 (group 2, rboIFN-alpha I1), 18.6 +/- 1.3 (group 3, norgestomet-saline) and 20.8 +/- 1.2 (group 4, norgestomet-rboIFN-alpha I1). Concentration of progesterone in serum was similar among all groups the first 6 days following hCG-induced ovulation, but differed (P less than 0.01) thereafter.(ABSTRACT TRUNCATED AT 250 WORDS)

A study was conducted to determine if charcoal-extracted follicular fluid inhibits FSH-induced follicular development in prepuberal heifers. Thirty-six prepuberal heifers were allotted by breed and weight to a 2 x 2 factorial experiment involving charcoal-extracted follicular fluid and FSH treatments. Heifers were unilaterally ovariectomized and injected (intravenously; 10 ml) every 8 h for 88 h with either charcoal-extracted follicular fluid or saline. Follicle-stimulating hormone (2 mg) or saline was injected (intramuscularly) every 8-h starting 24 h after initiation of charcoal-extracted follicular fluid to 88 h following unilateral ovariectomy. Plasma samples were collected at 8-h intervals from 48 h prior to unilateral ovariectomy to 96 h following unilateral ovariectomy when the remaining ovary was removed. Follicular fluid and total ovarian weight increased following FSH treatment. The increases were not inhibited by charcoal-extracted follicular fluid. Total number of surface follicles was similar among treatments. However, FSH induced a shift in follicular diameter from small (less than or equal to 3 mm) to medium (7 to 9 mm) or large (10 to 13 mm) follicles, which was unaffected by charcoal-extracted follicular fluid. Plasma concentration of FSH, but not LH, declined following charcoal-extracted follicular fluid administration. In summary, charcoal-extracted follicular fluid did not inhibit FSH-induced follicular development in prepuberal heifers when charcoal-extracted follicular fluid was administered at a dosage that reduced circulating concentration of FSH by approximately 40%.

Two experiments were conducted to determine if charcoal-extracted follicular fluid (CFF) from bovine ovaries inhibits FSH-induced follicular development in intact prepuberal heifers. In Exp. 1, thirty prepuberal heifers were assigned to saline, FSH or CFF/FSH treatment groups. In Exp. 2, thirty-two prepuberal heifers were assigned to four treatment groups (Saline, CFF, FSH, CFF/FSH) in a 2×2 factorial arrangement. In both studies, heifers were injected (i.v.) every 8 h for 88 h with CFF (8 ml, Exp. 1; 20 ml, Exp. 2) or saline. Follicle stimulating hormone (3.3 mg with 14% LH, Exp. 1; 3.3 mg with <1% LH, Exp. 2) was injected (i.m.) every 8 h starting 24 h after the initiation of CFF injections and continuing until termination of CFF administration. Plasma samples were collected via jugular venipuncture at 8 h intervals from just prior to (Exp. 1) or 48 h before (Exp. 2) CFF treatment until 96 h after, at which time both ovaries were removed. In both experiments total ovarian and follicular fluid weights increased (P<0.05) following FSH treatment. However, total number of follicles was similar among treatments, FSH induced a shift (P<0.05) from small (≤3 mm) to medium (7 to 9 mm) or large (10 to 13 mm) follicles. None of the above indices of FSH-induced follicular growth were affected (inhibited) by CFF. In summary, CFF did not inhibit FSH-induced follicular development in intact prepuberal heifers.