Relationship between Rectal Temperature and Vaginal Temperature in Grazing Bos taurus Heifers.

This study evaluated the relationship between rectal temperature (TREC, °C) and vaginal temperature (TVAG, °C) in grazing Bos taurus heifers, to develop an understanding of the reliability of these measures as estimates of core body temperature. Nineteen Angus heifers (BW = 232.2 ± 6.91 kg) were implanted with intra-rectal and intra-vaginal data loggers. Rectal temperature and TVAG were simultaneously recorded at 20 s intervals over 18.5 h. Heifers were housed as a singular cohort on grazing pastures for the duration of the study. A strong linear relationship (R² = 0.72, p < 0.0001) between the measurement sites was identified. The mean difference between TREC and TVAG was small, in which TVAG was on average 0.22 ± 0.01 °C lower than TREC. Individual twenty second TREC and TVAG data were used to determine the pooled mean TREC and TVAG and then to highlight the within measure variation over time. The coefficient of variation was, on average, lower (p < 0.001) for TVAG (0.38%) than TREC (0.44%), indicating that TVAG exhibited less variation. Overall, the results from the current study suggest that a strong relationship exists between TREC and TVAG, and that TVAG may be a more reliable estimate of core body temperature than TREC in grazing Bos taurus heifers.