Evaluating rumen temperature as an estimate of core body temperature in Angus feedlot cattle during summer

摘要

This study was conducted to determine the relationship between rectal temperature (T-REC) and rumen temperature (T-RUM) and to assess if T-RUM could be used as a proxy measure of core body temperature (T-CORE) in feedlot cattle. Eighty Angus steers (388.8 +/- 2.1kg) were orally administered with rumen temperature boluses. Rumen temperatures were recorded at 10-min intervals over 128days from all 80 steers. To define the suitability of T-RUM as an estimation of T-CORE, T-REC were obtained from all steers at 7-day intervals (n=16). Eight feedlot pens were used where there were 10 steers per pen (162m(2)). Shade was available in each pen (1.8m(2)/animal; 90% solar block). Climatic data were recorded at 30-min intervals, including ambient temperature (T-A; degrees C); relative humidity (RH; %); wind speed (WS; m/s) and direction; solar radiation (SR; W/m(2)); and black globe temperature (BGT; degrees C). Rainfall (mm) was recorded daily at 0900h. From these data, temperature humidity index (THI), heat load index (HLI) and accumulated heat load (AHL) were calculated. Individual 10-min T-RUM data were converted to an individual hourly average. Pooled mean hourly T-RUM data from the 128-day data were used to establish the diurnal rhythm of T-RUM where the mean minimum (39.19 +/- 0.01 degrees C) and mean maximum (40.04 +/- 0.01 degrees C) were observed at 0800h and 2000h respectively. A partial correlation coefficient indicated that there were moderate to strong relationships between T-RUM and T-REC using both real-time (r=0.55; P0.001) and hourly mean (r=0.51; P0.001) T-RUM data. The mean difference between T-REC and T-RUM was small using both real-time (0.16 +/- 0.02 degrees C) and hourly mean T-RUM (0.13 +/- 0.02 degrees C) data. Data from this study supports the hypothesis that T-RUM can be used as an estimate of T-CORE, suggesting that T-RUM can be used to measure and quantify heat load in feedlot cattle.