Audio and Time-Lapse Imagery Analysis of Lamb Grazing Behavior in Silvopasture Systems

Silvopastures – systems where trees are intentionally managed in conjunction with forages – provide distributed shade for grazing livestock. The objective of this study was to determine the grazing behavior and productivity of lambs in silvopasture systems. The growth of lambs in black walnut (Juglans nigra) silvopastures and lambs in honeylocust (Gleditsia triacanthos) silvopastures was compared to the growth of lambs in open pastures during three summers. Intravaginal temperature sensors were constructed from blank controlled internal drug release (CIDR) devices and small temperature loggers. Body temperatures of ewe lambs (n = 9) were recorded every 10 minutes for three days within a replicate within a week. For one day of each week in the second and third summers, a wideband audio recording device was also secured on the ewes to detect prehension events. Time-lapse cameras documented sheep behavior every 60 seconds. In the silvopastures, the lambs spent over 90% of daylight hours within shade boundaries. During the hottest part of the day (1300 – 1700 h), ewes in the open pasture had 0.4 °C hotter vaginal temperatures than ewes in the black walnut silvopastures (P ≤ 0.0202). Ewes in the open pasture experienced more fluctuation in day to nighttime core temperature change (P < 0.0001). Lambs in silvopastures spent more time lying down than animals in the open pastures (P ≤ 0.01), while lambs in the open pastures spent more than two hours longer each day standing (P < 0.0001). Lambs in the black walnut silvopastures spent more time grazing (488 ± 14 minutes · day^-1) than lambs in the honeylocust silvopastures (438 ± 14 minutes · day^-1; P = 0.0493) and lambs in the open pastures (417 ± 14 minutes · day^-1; P = 0.0026). There was no difference in grazing time for lambs in the latter two systems (P = 0.5597). Spectral analysis revealed that the lambs in the black walnut silvopastures grazed more frequently than the lambs in the other systems. The acoustic analysis, though limited by recorder durability to 47 complete recordings, revealed no difference in total bites taken per day (P ≥ 0.7222) or in the morning (P ≥ 0.2069), afternoon (P ≥ 0.5816), and evening periods (P ≥ 0.9337).