Sheep Performance, Behavior, and Thermal Status in Silvopasture Systems.

Silvopasture systems integrate trees for timber or fodder with forages for grazing ruminants. Reports of forage and animal productivity from these systems have been variable. In some cases, animal gains are similar or better despite lower forage yield. We explored the relationship between grazing system, body temperature, grazing behavior, and animal performance in this study. Black walnut and honeylocust-based silvopasture systems were compared with open pastures in a randomized complete block design (r=3). Pastures were rotationally stocked with six or seven lambs depending on forage availability. All sheep were weighed and fecal samples from a subset of the lambs were taken every four weeks. Body temperatures and grazing behavior measures were recorded within a replicate within a week, and these measures were taken sequentially within each of three experimental periods. Ewe lambs (n=3) within each experimental unit were equipped with a vaginal temperature sensor (3 days) and a wideband audio recording device (1 day). Weather stations within each experimental unit were used to calculate environmental Wet Bulb Globe Temperature (WBGT) index and time lapse cameras documented sheep behavior every 60 seconds. Prehension events were detected using software that analyzed the acoustic signals from the recordings. Forage availability measurements taken with a rising plate meter indicated no difference between the honeylocust silvopasture (4888±103 kg/ha) and the open pasture (4870±103 kg/ha; P=0.9916), though forage availability in the black walnut silvopastures (3507±103 kg/ha) was lower than that within the other treatments (P<0.0001). Lamb average daily gains (ADG) did not differ (P=0.2002) among systems (0.060 kg/day), although parasites appear to have kept ADG low in all systems. Total gain in walnut silvopastures was lower than in the open pastures and honeylocust silvopastures due to the lower stocking rate over the season. Preliminary observations indicate that the sheep in silvopasture systems had longer foraging periods.