Different thermotolerances in <i>in vitro</i>‐produced embryos derived from different maternal and paternal genetic backgrounds

<jats:title>Abstract</jats:title><jats:p>The present study evaluated the effects of genetic backgrounds on the developmental competence and thermotolerance of bovine <jats:italic>in vitro</jats:italic>‐produced (<jats:styled-content style="fixed-case">IVP</jats:styled-content>) embryos. First, Holstein (Hol) and Japanese Black (<jats:styled-content style="fixed-case">JB</jats:styled-content>) oocytes were fertilized with sperm from Hol, <jats:styled-content style="fixed-case">JB</jats:styled-content> and a thermotolerant breed (Brahman), and <jats:italic>in vitro</jats:italic> development was evaluated when the embryos were exposed to heat shock on Day 2 (Day 0 = day of fertilization). Sperm genetic backgrounds affected the developmental competence in controls (<jats:italic>P</jats:italic> < 0.05). Second, the effect of sperm pre‐incubation for 4 h on subsequent <jats:italic>in vitro</jats:italic> fertilization was assessed using different sperm genetic backgrounds. The pre‐incubation of sperm did not decrease the embryonic development regardless of the breed of the sperm. A milder heat shock (40.0°C) effect on parthenotes (Hol and <jats:styled-content style="fixed-case">JB</jats:styled-content>) and <jats:styled-content style="fixed-case">IVP</jats:styled-content> embryos were evaluated. <jats:styled-content style="fixed-case">JB</jats:styled-content> parthenotes showed developmental arrest after Day 4, and the rate of development to the blastocyst stage decreased by heat shock, but not in Hol parthenotes. Heat shock decreased developmental competence after cleavage of <jats:styled-content style="fixed-case">IVP</jats:styled-content> embryos regardless of genetic background. The thermotolerance of <jats:styled-content style="fixed-case">IVP</jats:styled-content> embryos would be controlled by both maternal and paternal factors but genetic involvement was still unclear. Further evaluation is needed to reveal the genetic contribution to thermotolerance.</jats:p>