Production of interferon by red deer (Cervus elaphus) conceptuses and the effects of roIFN-tau on the timing of luteolysis and the success of asynchronous embryo transfer

The role of interferon in early pregnancy in red deer was investigated by ( a) measuring production of interferon by the conceptus, (b) testing the ant i-luteolytic effect of recombinant interferon-tau in non-pregnant hinds, an d (c) treatment of hinds with interferon after asynchronous embryo transfer . Blastocysts were collected from 34 hinds by uterine flushing 14 (n = 2), 16 (n = 2), 18 (n = 8), 20 (n = 13) or 22 (n = 9) days after synchronizatio n of oestrus with progesterone withdrawal. Interferon anti-viral activity w as detectable in uterine flushings from day 16 to day 22, and increased wit h duration of gestation (P < 0.01) and developmental stage (P < 0.01). When interferon-tau was administered daily between day 14 and day 20 to non-pre gnant hinds to mimic natural blastocyst production, luteolysis was delayed by a dose of 0.2 mg day(-1) (27.3 +/- 1.3 days after synchronization, n = 4 versus 21 +/- 0 days in control hinds, n = 3; P < 0.05). Interferon-tau wa s administered to hinds after asynchronous embryo transfer to determine whe ther it protects the conceptus against early pregnancy loss. Embryos (n = 2 4) collected on day 6 from naturally mated, superovulated donors (n = 15) w ere transferred into synchronized recipients on day 10 or day 11. Interfero n-tau treatment (0.2 mg daily from day 14 to 20) increased calving rate fro m 0 to 64% in all recipients (0/11 versus 7/11, P < 0.005), and from 0 to 6 7% in day 10 recipients (0/8 versus 6/9, P < 0.01). The increased success r ate of asynchronous embryo transfer after interferon-tau treatment in cervi ds may be of benefit where mismatched embryo-maternal signalling leads to f ailure in the establishment of pregnancy.