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This work explored whether a well-characterized recombinant human interleukin-6 (hIL6) protein will influence in vitro produced (IVP) bovine embryo development and survival after cryopreservation. Cumulus oocyte complexes were collected from abattoir derived ovaries, matured for 24 h, and fertilized using pooled semen from Holstein bulls. Zygotes were treated with 0, 25, 50, or 100 ng/mL hIL6 on day 5 post-fertilization. Only the 25 ng/mL treatment increased the percentage of blastocysts that formed, but an increase in ICM cell numbers was observed in each hIL6 treatment, with the lowest hIL6 treatment having the same magnitude of response as the middle and highest hIL6 concentration. No effects on TE cell numbers were observed. The second study involved cryopreserving (via slow freezing) hIL6-treated blastocysts, then examining post-thaw blastocyst survival by incubating for 24 h in the absence of hIL6 treatments. None of the hIL6 concentrations affected blastocyst re-expansion and hatching rates. An increase in ICM cell numbers was evident in embryos supplemented with 100 ng/mL hIL6 but not lower concentrations. No differences were detected in TE cell numbers after thawing; however, an increase in the difference of TE cell number from before to after freezing/thawing was detected in blastocysts treated with 100 ng/mL hIL6. Moreover, a reduction in the percentage of TUNEL-positive TE cells was observed after thawing in blastocysts exposed to 25, 50 and 100 ng/mL hIL6 before cryopreservation. No changes in pre-freezing versus post-thawing ICM cell numbers and percentage of TUNEL-positive ICM cells were observed. In …