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MONITORING STRESS BEHAVIOR IN GRAZING BEEF COWS WITH A LONG RANGE PEDOMETRIC SYSTEM
Beef breeding is an extensive operation carried out in vast pastures. Hierarchy within the herd is an important factor which determines priority of access to limited resources and level of feed intake, resulting in stress to the subordinate animals. Hierarchy is mainly passive, thus difficult to detect in conventional breeding systems. Most of the cows that are culled due to low production, are subordinate cows. Identifying subordinate cows may enable the breeder to improve grouping management and thereby minimize stress. This will lead in turn to improved production and lower replacement costs.
Newly developed long range pedometric system, based on RF transmission, providing online activity monitoring, was installed in a cross bred Simmental beef herd of 250 cows, grazing in a 300 ha. pasture in the Upper Galilee, Israel.
Hypothesis was that the average cow will maintain a daily activity routine, while stress will result in deviations of activity expressed in the graph.
30 transmitting tags were mounted on front legs of cows randomly selected.
Analysis of data showed 17 cows with regular activity graphs, i.e lower than average values of activity with lower values of standard deviation (161+105 steps per hour), 13 expressed irregular activity graphs- higher than average values of activity with higher values of standard deviation (209+128 steps per hour).
Observations near the food trough were conducted during feeding time in order to rank cows according to their social status. A cow that reached the trough and wasn’t rejected was ranked “dominant”. Order was established thereafter by number of rejections from the trough each cow received. The lowest ranking cows did not approach the trough during feeding at all.
Comparison between activity graphs and observations showed that dominant cows expressed regular activity graphs, subordinate cows expressed irregular activity graphs.
Cortisol levels in hair samples were taken to validate activity results (0.1975 + 0.039 and 0.2862 + 0.0423 μg/dL for dominant and subordinate respectively, P=0.018). Cortisol level in hair reflects the stress status over a fortnight, thus the effect of sampling-related stress is minimal.
The activity pattern expressed while measuring hourly activity online we believe, reflects the measure of freedom each cow has to choose her ongoing activity within the herd. Assuming that establishing an individual routine is beneficial for cows, detecting those that are unable to do so and grouping them by social order, will minimize stress and improve production.
Keywords: beef breeding, stress