Supplemental Polyethylene Glycol Influences Preferences of Goats Browsing Blackbrush.

Supplemental polyethylene glycol (PEG) increases intake of foods high in tannins, 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 preferences of goats (Caprus hircus) for current season\u27s and older growth twigs from the shrub blackbrush (Coleogyne ramosissima Torr.). In blackbrush, current season\u27s twigs are higher than older twigs in macronutrients, but goats prefer older twigs because high levels of tannins in current season\u27s twigs decrease preference. We conducted a pen trial and a paddock trial. During the 7-day pen trial, goats were offered current season\u27s twigs and older twigs throughout the day. Eight goats were supplemented with 20 g PEG mixed with 100 g ground alfalfa (Medicago sativa L.) pellets, and 8 goats were supplemented with 100 g ground alfalfa pellets. Goats supplemented with PEG ate more current season\u27s 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 were supplemented with ground alfalfa/barley. Goats supplemented with PEG preferred current season\u27s to older twigs, whereas PEG-unsupplemented goats preferred older to current season\u27s twigs (P = 0.0001). Goats had equal preference for juniper (Juniperus osteosperma Torr.) trees (P = 0.243). Collectively, our findings show that supplemental PEG can change food preferences