Supplemental polyethylene glycol influences preferences of goats browsing blackbrush

Supplemental polyethylene glycol (PEG) increases intake of foods high in ta nnins, but it is not known if PEG affects preference when herbivores forage on a variety of foods that differ in concentrations of macronutrients and tannins, We investigated how macronutrients, tannins, and PEG affected pref erences of goats (Caprus hircus) for current season's and older growth twig s from the shrub blackbrush (Coleogyne ramosissima Torr.), In blackbrush, c urrent season's twigs are higher than older twigs in macronutrients, but go ats prefer older twigs because high levels of tannins in current season's t wigs decrease preference. We conducted a pen trial and a paddock trial. Dur ing the 7-day pen trial, goats were offered current season's twigs and olde r twigs throughout the day. Eight goats were supplemented with 20 g PEG mix ed with 100 g ground alfalfa (Medicago sativa L.) pellets, and 8 goats were supplemented with 100 g ground alfalfa pellets. Goats supplemented with PE G ate more current season's twigs than goats that did not receive PEG (P = 0.04). During the 17-day paddock trial, 10 goats were supplemented with 50 g PEG mixed with ground alfalfa/barley (Hordeum vulgare L.), and 10 goats w ere supplemented with ground alfalfa/barley, Goats supplemented with PEG pr eferred current season's to older twigs, whereas PEG-unsupplemented goats p referred older to current season's twigs (P = 0.0001). Goats had equal pref erence for juniper (Juniperus osteosperma Torr.) trees (P = 0.243), Collect ively, our findings show that supplemental PEG can change food preferences.