Animal Age

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Animal age can also profoundly affect diet selection and tolerance to secondary compounds. Metabolic requirements change with age, so older animals need less food and spend less time foraging. Compared with adults, young, growing animals need diets higher in crude protein and energy and lower in fiber. Their search for a more nutritious diet takes more energy. This, combined with limited foraging knowledge, may lead younger animals to try novel foods and retry foods that once made them sick.

For example, younger animals appear more willing than older animals to consume less desirable forages like juniper. Animals just weaned are expanding their diet choices, so they are also more willing to try novel foods.

As herbivores age, their incisor teeth wear, so they are less able to graze and achieve maintenance requirements, particularly on short forage. Incisor wear also influences forage selection. Goats with worn teeth tend to avoid grasses and choose a higher proportion of tender- leaved shrubs than goats with unworn incisors.

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