Submitted to: Journal of Dairy Science
Publication Type: Abstract only
Publication Acceptance Date: 11/2/2009
Publication Date: 4/21/2010
Citation: Lopes, F., Combs, D.K., Hoffman, P.C., Esser, N.M., Coblentz, W.K. Grazing Behavior of Heifers Measured by Handheld GPS. Journal of Dairy Science. 93:2300. Interpretive Summary:
Technical Abstract: The objective of this study was to assess how previous grazing experience affects animal movement on pasture. Portable GPS units were used to monitor movements of 32 Holstein (n=21) and Holstein-Jersey (n=11) yearlings. Total distance walked was measured and analyzed as a randomized complete block experimental design. Two heifer groups (n=8 per group) had been exposed to pasture from August through October 2008, while the other two groups had been continuously housed in a bedding pack barn since weaning. All 4 groups were housed in the same bedding pack barn from November 2008 until the start of the experiment. In June 2009, the four groups of heifers were assigned to one of 4 Italian ryegrass pastures, thus, the experimental unit was the pasture. Each pasture was 1.73 ha and was divided into 3 paddocks with cross wires. Each group was allocated 266 ± 67.4 kg of forage DM/head initially. Portable GPS units (Trackstick TM) were attached to neck collars on each heifer at 0600 hr for the first 5 consecutive mornings that the heifers were turned on the pastures. The GPS units recorded the location of each heifer at one minute intervals for the next eight hours. Heifers were then returned to the barn, the GPS units removed and the heifers remained in the barn until the next morning. Movements of heifers that had grazed in 2008 differed from those with no previous grazing experience. The heifers with grazing experience walked further (5.49 vs. 3.56 km, P<0.05) than heifers that had no prior grazing experience during the first two days. By the third day of the experiment, distances traveled were similar for both groups. After the first week of grazing, heifers remained on the pastures continuously and movements were monitored by the GPS units every two weeks through August, 2009 (7 periods, 2 consecutive days per period). In subsequent recording periods the distance traveled per eight hours was less than recorded during the first week (3.57 vs. 2.30 km, P<0.05) and did not differ between groups.