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

This study evaluated the relationship between rectal temperature (T _REC , °C) and vaginal temperature (T _VAG , °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 T _VAG 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 T _REC and T _VAG was small, in which T _VAG was on average 0.22 ± 0.01 °C lower than T _REC . Individual twenty second T _REC and T _VAG data were used to determine the pooled mean T _REC and T _VAG and then to highlight the within measure variation over time. The coefficient of variation was, on average, lower ( p < 0.001) for T _VAG (0.38%) than T _REC (0.44%), indicating that T _VAG exhibited less variation. Overall, the results from the current study suggest that a strong relationship exists between T _REC and T _VAG, and that T _VAG may be a more reliable estimate of core body temperature than T _REC in grazing Bos taurus heifers.