Diet selection and preference of small ruminants during drought conditions in a dryland pastoral system in South Africa

Abstract

Semi-arid to arid areas are prone to droughts which are frequent occurrences in South Africa’s rangelands. Drought can trigger plant species compositional changes in rangelands thus influencing the availability and quality of forage for livestock. The availability and quality of forage drives livestock production, especially among pastoralists who mainly rely on the natural rangeland to sustain their livestock and livelihoods. The aim of this study was to determine the forage selection of cross-bred sheep, Swakara sheep (Ovis aries) and Boer goats (Capra hircus), during the wet season in the summer rainfall Nama Karoo and winter rainfall Succulent Karoo biomes in Namaqualand, South Africa. Since this dryland pastoral system was experiencing drought conditions during the study period of 2016 & 2017, the focus of the study was placed within this context to determine, (1) the availability of forage for small ruminants, (2) the nature of diet selection of different small ruminant groups and how it vary between the two biomes, and (3) the role livestock species, breeds and season play in forage preferences. We established diet selection, preference and dietary overlap by using direct observation of livestock grazing in the veld. Results indicate that availability of forage influence diet selection and preferences of all small ruminant groups. There was a high dietary overlap between mixed bred and Swakara sheep irrespective of the biomes. During 2016 annual herbs made up a large proportion of the sheep’s diets indicating an overdependence to this forage resource when it became available in the rangeland. However, due to the drought spell extending into 2017, annual herbs became less available and therefore altered the forage choices of both sheep groups. Goats were primarily browsers in the Succulent Karoo biome where shrubs dominate, but were considered grazers in the Nama Karoo biome where grasses were dominant. Moreover, all small ruminant groups in this study showed non-selective grazing tendencies which is an important grazing management tool to ensure that rangeland resources are not over exploited. We conclude by arguing that the mixture of different livestock species by pastoralists is an effective diversification strategy for better use of rangelands with herbaceous and woody plants during drought periods.