Laburn, Helen

The chapter, "The thermal physiology of the ruminant fetus" was written by the listed authors including Alida Faurie (Douglas College Faculty). This volume contains 26 chapters in sections on regulation of feed intake, rumen microbiology and fermentation, nutrient absorption and splanchnic metabolism, tissue maintenance and utilization of endogenous body reserves, tissue growth, reproduction, pregnancy and lactation, ruminant physiology and genetics, and host resistance to parasites and pathogens. The chapters are the plenary papers presented at the IX International Symposium on Ruminant Physiology in Pretoria, South Africa during October 1999. This chapter discusses the fetal body temperature homeostasis, feto-maternal thermal relationship, birth-related changes in body temperatures, and preterm labour and abortion in ewes.

Maternal and fetal body temperatures were measured in five Boer goats, of mean mass 64 +/- 8 kg, using temperature-sensitive radiotelemeters implanted intra-abdominally. Body temperatures were recorded every 5 min. Throughout the last month of gestation, fetal temperature was approximately 0.6 (o)C higher than that of the mother, in normal laboratory conditions (ambient air temperature: 21-24 (o)C). This feto-maternal temperature difference between the goat fetus and its mother is similar to that found in other mammals, including sheep. When the pregnant goats were subjected to short-term heating and cooling, the difference between maternal and fetal body temperatures changed. Thus the mean difference between fetal and maternal body temperatures decreased from 0.4 to 0.2 (o)C during 2 h of heating, while it widened from 0.3 to 0.7 (o)C during 6 h of cooling. These data support the idea that the fetus is thermally protected from excursions of body temperature during changes in the mother's thermal environment. Reports of goat stock losses and abortions during cold spells in their natural habitats may be the result of more severe and/or prolonged cold exposures that not only adversely affect fetal or maternal body temperature, but also influence other aspects of metabolism.