The rate of consumption of bush and grass by goats in a representative acacia karroo savanna community in the Eastern Cape

Abstract

Consumption of browse and grass in a representative Acacia karroo savanna community was measured. Acacia karroo was preferred to grass. It was selected almost exclusively when available at high leaf densities. Grass was consumed in significant amounts only when approximately 50 % of the available A. karroo leaf had been consumed. Maximum daily intake was 78 g.W^−0,75 _kg.day⁻¹ and decreased with decreasing amount of browse on offer. When approximately 90 % of the available A. karroo leaf had been removed, the goats had consumed only 30 % of the available grass. Total intake of browse plus grass was lower during the period when the goats changed from consuming mostly A. karroo to consuming mostly grass. Goats did not appear to select a diet according to their nutritional needs, as judged by feeding tables, when this was possible. This may be due to protein indigestibility caused by tannin complexing by A. karroo, luxury consumption of A. karroo as a favoured food, an adaptation by goats to use browse more efficiently than grass, or differences in palatability between A. karroo and grass.

Uittreksel

Ondersoek is ingestel om die inname van struike en gras in ‘n verteenwoordigen.de Acacia karroo savanne gemeenskap te bepaal. Acacia karroo is bo gras verkies. Dit is uitsluitlik benut toe dit beskikbaar was teen hoë blaardigthede. Gras is slegs in betekenisvolle hoeveelhede benut nadat ongeveer 50 % van die beskikbare A. karroo blare reeds benut was. Die maksimum daaglikse inname was 78 g. W^−0,75 _kg.dag⁻¹, en het verminder met ‘n afname in die beskikbare hoeveelheid struike. Na benutting van ongeveer 90 % van die beskikbare A. karroo blare, het die bokke slegs 30 % van die beskikbare gras benut. Die totale inname van struike en gras was laer gedurende dieperiode toe die bokke hoofsaaklike van ‘n A. karroo‐inname na ‘n hoofsaaklik gras‐inname verander het. Dit wil voorkom asof bokke nie hulle dieet, soos in voedingstabelle aangedui word, volgens hulle voedingsbenodigdhede selekteer nie. Dit mag moontlik toegeskryf word aan ‘n prote'ien‐onverteerbaarheid deur tannien‐komplekse in A. karroo, oordadige inname van A. karroo as ‘n gunsteling voer, ‘n aanpassing van bokke om struike meer doeltreffend as gras te benut, of verskille in smaaklikheid tussen A. karroo en gras.

Additional index words:

• Browse
• goats
• dietary switching
• rate of consumption
• foraging ecology