Climate change is predicted to have a negative effect on the rangelands of sub-Saharan Africa, affecting the distribution, productivity and extent of these rangelands. Similarly, Subtropical Thicket vegetation in the Eastern Cape, South Africa is expected to experience a reduction in plant growth with conditions becoming similar to those experienced under desertification. The transformation of thicket results in a decrease in perennial plant species cover and richness, which is replaced by an ephemeral layer of grasses and forbs. Assessing the responses of herbivores to this transformation thus allows the testing of the hypothesis that climate change and desertification will lead to a broadening of diet and a decline in secondary productivity. In this study, the diet and productivity of Angora goats in intact and transformed thicket in adjacent paddocks was investigated from August 2005 to July 2006. Faecal analysis was used to compare the diets of the Angora goats in the intact and transformed thicket treatments. Goats in the transformed treatment consumed a higher diversity of plant species (94 species) compared to those in the intact thicket (42 species). The higher species richness per faecal sample and the larger seasonal variation in plant species utilized by the goats in the transformed treatment reflected the variability of this treatment in response to rainfall. Dietary shifts to include less palatable species not found in the intact treatment diet were clear, but due to the high rainfall year an abundant ephemeral layer, comprising grasses and forbs, was available in the transformed treatment. The diet quality of the transformed treatment goats was higher, as indexed by faecal lignin, than the intact treatment goats, although there was no statistical difference in the NDF and ash levels between the treatments. There was however, more variation in the nutritional quality of the transformed thicket diet, as indexed by dietary phosphorous, showing that intact thicket retains a more constant nutritional level. There was no difference in the body condition and mohair production of the goats in the two treatments. The hypothesis of broadening of the diet was thus supported, but there was no evidence for the predicted decline in secondary productivity. This study was undertaken during an above average rainfall period and large quantities of nutritious ephemeral grasses were available in the transformed treatment. This resource would not be available in a drought; therefore goats in the intact thicket will likely perform better over longer periods; providing stocking rates are realistic. This is the first study to measure the response of domestic herbivores to transformation either in terms of resource use or production.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nmmu/vital:10720 |
| Date | January 2008 |
| Creators | Milne, Tracey Anne |
| Publisher | Nelson Mandela Metropolitan University, Faculty of Science |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Masters, MSc |
| Format | iii, 59 leaves, pdf |
| Rights | Nelson Mandela Metropolitan University |
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