|VARNER, M. A.|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/14/1996
Publication Date: N/A
Technical Abstract: Heart-rate elevation is considered to be an indication of stress in cattle. To monitor heart rate, we developed a non-invasive radio-telemetry system. Data were acquired over 72 h from two heifers housed in an experimental animal handling system consisting of a freestall area, a holding area, an automated milking system (AMS), and a second holding area. Automatic grain feeders in holding areas were used to encourage animals to circle through the one-way system. Computer generated histograms show heart rate within a time window from 15 min before to 45 min after selected behavioral events. Average heart rates increased 4.0 +/- 1.4 bpm after cows stood, and decreased 4.8 +/- 1.0 bpm after cows laid. Histograms constructed based on time of peak heart rate within a window +/-3 min of entry of the AMS allowed detection of a response for the animal which was naive to the animal handling system; heart rate increased from 60 to a peak of 86 bpm, and remained elevated for 6.3 min. In contrast, heart rate of the experienced animal remained constant; demonstrating that synchronizing heart-rate peaks does not generate spurious results. Of particular interest are agonistic encounters between animals. The AMS-naive heifer was generally submissive to the AMS-experienced heifer. During one 3 h period where an encounter occurred: the experienced heifer remained in the free stall area, the naive heifer was lying in holding area 1, she stood to circle the system to gain access to forage available only in the free stall area, she began eating, the encounter occurred, she resumed eating, and then left for holding area 1. The naive animal's heart rate jumped 2.6 fold upon rising and remained at this higher level for 80 min. These results clearly show that heart rate can be used to monitor animal anxiety.