Rumen temperature of Brahman, Angus and Charolais steers with and without access to shade

Abstract Text:

Continuous measurement of body temperature (BT) is often difficult and data collection is often restricted to short intervals. Remote assessment of BT through rumen boluses is a method of obtaining consistent BT over long periods of time without compromising animal comfort and potentially degrading carcass value. In this study rumen temperature (T_RUM) of 3 cattle breeds, with and without access to shade, were assessed. Thirty-six steers (12 Angus, Charolais and Brahman) with an initial BW of 318.5 ± 6.7 kg were used in a 180 d feedlot study with 2 treatments: un-shaded and shaded (3 m²/animal; 90% solar block shade cloth). There were 6 steers (2/breed) per pen (162 m²) and 3 pens/treatment. Ten min T_RUM data were obtained over 130 d using rumen boluses. Individual T_RUM data were firstly converted to an hourly average and then mean hourly T_RUM within breed x treatment were calculated. Rumen temperature was analysed using a repeated measures model (PROC MIXED; SAS Inst. Inc. Cary, NC). The model analysed the effect of breed (P < 0.0001), hour (h; P < 0.0001), breed x h (P < 0.0001), treatment x h (P < 0.0001) and breed x treatment x h (P = 0.0036). On average T_RUM of un-shaded Angus were greater (P < 0.05) than shaded and un-shaded Brahman’s by 0.65 ± 0.05 °C and 0.64 ± 0.05 °C respectively. Rumen temperature of shaded Angus were on average 0.46 ± 0.03 °C (P < 0.05) lower than un-shaded Angus between 1200 and 1600 h. Differences were observed between shaded and un-shaded Charolais between 1000 and 1700 h, with the shaded treatment on average 0.48 ± 0.02 °C lower than unshaded. No h or treatment differences were detected between un-shaded and shaded Brahman’s, with a daily mean of 39.08 ± 0.08 °C and 39.07 ± 0.08 °C respectively, indicating that these animals may be utilising breed specific behavioural and physiological mechanisms to regulate BT. These data suggest that providing feedlot cattle with shade during summer improves a non-heat tolerant breed’s ability to regulate BT. The relationship between rectal temperatures and T_RUM were also assessed (r = 0.57) with an average difference of 0.06 ± 0.06 °C indicating that T_RUM  is a robust measure of BT. Therefore the assessment of an animal’s thermal status can be undertaken through the remote assessment T_RUM.

Keywords: Rumen Temperature, Body Temperature, Rectal Temperature