Patterns of selection of Acacia karroo by goats and changes in tannin levels and in vitro digestibility following defoliation.

Abstract

Patterns of browse selection by Boer goats in a representative Acacia karroo community in the eastern Cape were studied. The rate of intake of browse was positively related to the leaf mass per unit length of the shoot. The ease of harvesting leaf material, as determined by the height off the ground, modified the rate of intake. Generally, following browsing, tannin levels increased significantly and in vitro digestibility decreased significantly. These changes in tannin content and digestibility differed in magnitude according to the plant size and age of the shoot and leaf. Generally, the leaf and shoot intake was negatively related to tanning content and positively related to digestibility, thus influencing patterns of selection for different plant parts and size classes of A. karroo. However, some of the results are contradictory.

Keywords: acacia karroo; boer goats; browse; browsing; defoliation; digestibility; eastern cape; goats; harvesting efficiency; in vitro digestibility; intake; leaves; plant parts; south africa