Many of the studies on food aversion have used concentrates or food flavors. A few have used shrubs. I’ve often been asked if animals would generalize an aversion to all grasses if they were averted to one grass. My answer has always been: “No not all grasses.” Generalizing the aversion to other grass species would depend on how similar the flavors are between grasses and the strength of the aversion.
A study by Ginane and Dumont answer the question at least between perennial ryegrass and tall fescue. Researchers used a fairly low dose of LiCl (70 mg/kg body weight) to condition an aversion with sheep to ryegrass that was tall in stature. They also looked if animals would avoid a plant based on height. After conditioning, sheep avoided short ryegrass, but readily ate tall fescue that was tall in stature. Sheep did not avoid grass based on height.
Researchers also conditioned sheep to avoid timothy hay but sheep continued to eat red fescue hay after conditioning.
Sheep may use physical characteristics to search out certain foods. But when it comes to eating a food, it’s flavor that matters, not height, not color, or other physical characteristics of the food.
Reference: Ginane, C., and B. Dumont. 2006. Generalization of conditioned food aversions in grazing sheep and its implications for food categorization. Behavioural Processes 73:178–186. doi:10.1016/j.beproc.2006.05.006