Amount of experience and age affect the development of foraging skills of goats browsing blackbrush ( Coleogyne ramosissima)

Abstract

We studied how age and amount of experience browsing blackbrush ( Coleogyne ramosissima) affected the development of foraging skills in goats of different breeds (Alpine, Toggenburg, La Mancha, Spanish and Nubian). Six-month-old goats in 1990 and 18-month-old goats in 1991 were allowed to forage (either 0, 10, 20 or 30 days of experience) on a blackbrush pasture for 4 h day −1. Age affected the development of foraging skills. Young goats consistently maintained a higher number of bites and bite rates than did adult goats. Bite rates increased with more experience browsing on pasture. However, increments were higher in young than in adult goats. Bite rates increased only slightly after 20 days of browsing experience in adult goats, while they were still increasing after 30 days in young goats. Following the acquisition of browsing experience by young and adult goats on pasture, each goat was offered several branches of blackbrush, held erect in a wooden frame, for 5 min day −1 on 2 consecutive days. Performance of goats during these tests resembled that observed on pasture. In general, total number of bites, bite rates and intake of blackbrush during testing were higher for experienced than for inexperienced goats. However, the larger mouth size of adult goats allowed them to take bigger bites and, as a consequence, they had higher intakes than young goats. They also broke twigs of greater diameters. Within ages, goats selected twigs of similar size, but young inexperienced goats selected larger twigs (>1.4 mm) more frequently than did goats with 30 days of experience. Experience also affected prehension mode, i.e. chewing versus breaking twigs. Experienced goats, of either age, relied more heavily than inexperienced goats on breaking rather than chewing. They were also more successful than inexperienced goats at breaking twigs. We conclude that both age and the amount of experience affected the acquisition of foraging skills in goats and that goats forage more efficiently as a result of experience.