Effect of Post-Breeding Thermal Stress on Embyronic Mortality in Swine

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Abstract
Three trials were conducted in which pregnant sows were subjected to elevated temperatures early in gestation. Ambient temperature and duration and time of exposure in pregnancy were: (I) 35° C. for 24-hr, on days 1, 5 and 20; (II) 35° C. for 48-hr, on days 1 or 20; (III) 36.7° C. and a relative humidity of 50% for 5 days on days 1 or 20. In all trials, the number of viable embryos per 100 corpora lutea was lower when treatment was begun on day 1 than the control or any other treatments. In trial III, exposure of sows to 36.7° C. on days 1–5 of gestation significantly (P<.05) lowered the number of viable embryos per 100 corpora lutea compared to sows treated on days 20–25. In addition, this treatment caused a significant (P<.05) reduction in the number of viable embryos and viable embryos per 100 corpora lutea compared to the combined results of the control and 20–25 day treated sows. These data indicate that elevated temperature has an adverse effect upon embryonic survival in sows if the thermal stress is applied from days 1–5 of gestation. Exposure of sows from days 20–25 of pregnancy to a thermal stress severe enough to cause the death of four of nine sows so treated had no adverse effects on embryonic mortality in the five survivors. Copyright © 1967. American Society of Animal Science . Copyright 1967 by American Society of Animal Science