This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by THWAITES, C. J. Search for Related Content PubMed PubMed Citation Articles by THWAITES, C. J.

EMBRYO MORTALITY IN THE HEAT STRESSED EWE

Summary.: Continuous hot-room exposure during the first 15 days of pregnancy raised the rectal temperatures and respiratory rates of mature Merino ewes to about 104 to 105° F and 170 respirations/min respectively and led to the death of 83% of embryos.

Similar ewes subjected to a diurnally variable heat stress, which raised their rectal temperatures and respiratory rates to about 104 to 105° F and 220 respirations/min during an 8-hr 'day' and allowed them to fall to about 102° F and 140 respirations/min respectively during a subsequent 16-hr 'night', experienced an embryo mortality rate of only 35%.

Control ewes, housed similarly, but at natural temperatures (33 to 65° F), had rectal temperatures and respiratory rates of about 101 to 102° F and 20 respirations/min, respectively, and suffered the loss of 19% of their ova.

The results illustrate the mitigating effects of a daily period of respite from high temperatures and indicate that this, rather than differences in acclimatization to heat and lack of radiant heating in the hot-room, is the major factor to be considered when comparing the effects on embryo mortality of heat stress in the field with those of periods of continuous heat stress in the hot-room.