The fall in rectal temperature seen before parturition in sheep.

Abstract

Several of the domesticated animals show a slight rise in body temperature in late pregnancy and a temperature decline in the period just before parturition (Weisz, 1943). In cattle (Ewbank, 1963), this drop measures some 0-6° C and commences, on average, 54 hr before calving : the large variation in readings about this average, however, makes it impossible to use the temperature drop for a reliable prediction of the possible time of parturition. It has been shown (Ewbank, 1963) that the healthy cow, even when exhibiting external signs of imminent parturition, such as mammary distension, relaxation of the sacrosciatic ligaments and vulval enlargement, is unlikely to calve within the succeeding 12 hr if its rectal temperature is above 38-8° C, the normal tempera¬ ture being 38-5° C. While a similar technique has less application in sheep than in cattle husbandry, any reliable method of indicating the imminence or otherwise of parturition would have value in appropriate research programmes. Few investigators have studied the temperature of the ewe around the time of parturition although McKenzie & Bogart (1934) give the average body temperature of ewes for the 2 days before and the 7 days after lambing as 39-4° C; Hafez, Badreldin & Sharafeldin (1956) found that pregnancy has no effect upon the body temperatures of Egyptian fat-tailed sheep ; and Roberts (1964) briefly reported (without quoting results obtained) that the deep vaginal temperature has little practical value in predicting the time of onset of parturition. One factor affecting body temperature is rate of heat loss and it is of interest that Brockway, McDonald & Pullar (1963) reported an increase in heat loss to the environment for sheep during the last 24 hr of pregnancy. In the present investigation, twelve Clun Forest ewes due to lamb in early March were trained to stand quietly in yolk type head holders and to allow the insertion of a clinical thermometer (N.P.L. certified, ^-min reading) 8 cm into the rectum for approximately 1 min. Temperature readings could be taken to an accuracy of +0-05° C. The animals were allowed outside during the day and kept overnight under an open-sided barn. Temperatures were recorded from