The importance of environmental modification to enhance fertility in heat stressed cows was readily recognized. Widespread use of sprinklers, fans and shade in warm regions of the world is due in large part to cooperative studies done with colleagues in ISRAEL via BARD funding (D. Wolfenson, M. Berman, C.R. Staples and W.W. Thatcher). Subsequent research examined effects of heat stress on embryonic survival in order to develop methods to reduce these negative effects. As mentioned above embryo transfer and/or timed embryo transfer can be used to increase pregnancy rates during the summer. Furthermore, the Ovsynch program has also increased either pregnancy rate to the timed insemination or accumulated pregnancy rates following timed insemination during the summer heat stressed period