A study done in Saudi Arabia with lactating Holsteins compared responses to superovulation in July (hot season) and December (cool season). Mean ovulation rates were 7.1 and 12.1, fertilization rates were 85% and 96%, and recovered embryos considered transferable was 46% and 74% for hot and cool seasons, respectively. A similar study comparing lactating cows with maiden heifers yielded 31% and 63% transferable embryos, respectively, during the summer, with no differences observed during the winter, illustrating the significant effect of lactation on thermoregulation during the summer.