Core body temperature monitoring with passive transponder boluses in beef heifers

摘要

Experiments were conducted over 82 d (Nov. 04 to Jan. 24, 49 degrees N, mean ambient temperature - 3.6 to -12.6 +/- 1.6 degrees C) to determine the effects of fever, photoperiod and pen setup on the rate (MR) and frequency (MF) with which heifers were monitored and the body (rumen) temperatures (BTr) obtained with a cattle temperature monitoring system (MaGiiX). Magnetic, inductively Coupled full duplex radio-frequency identification (RFID) transponder boluses containing thermistors were administered per os to 72 heifers (7.9 +/- 0.5 mo of age and 283 +/- 23 kg body weight) housed in one of four pens, in outdoor shed-lot facilities, each with a panel reader co-located with the water bowl. A mixed ration (59% dry matter) was provided at 1500 daily. Fencing was arranged within pens for water motivated (WM) acquisitions during exps. 1 (Initial), 2 (Fever) and 3 (Photoperiod), or for either WM or activity motivated (AM) acquisitions during exp. 4 (Pen Setup). Overall, most heifers were monitored daily (Mode MR 100%), several times per day (MF 7.8 +/- 0.5), mostly during the afternoon and evening rather than night and morning 6-h periods, and BTr (37.8 +/- 0.2 degrees C, range 22 to 42 degrees C) were usually lower (P < 0.05) for the arternoon than night. A 2 degrees C increase in mean BTr caused by fever was detected (P < 0.05) when monitoring was scheduled rather than unscheduled. Extended (16 h) in contrast to natural (8 h) photoperiod increased (P < 0.05) evening MR (96.8 vs. 83.5 +/- 1.9%) and MF (3.8 vs. 2.5 +/- 0.2), and morning-BTr (38.0 vs.37.4 +/- 0.11 degrees C). Pen setup for AM in contrast to WM acquisitions increased (P < 0.05) MR and MF and BTr (by 1 degrees C) in all periods of the day. The technology has excellent potential for non-invasive monitoring of BTr in heifers.