Effect of recombinant alpha interferons on fertility and interestrous interval in sheep

Abstract

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.