A COMPARISON OF THE DIETS SELECTED BY MERINO AND DORPER SHEEP ON THREE RANGE TYPES OF THE KAROO, SOUTH AFRICA UNA COMPARACIÓN DE LA DIETA SELECCIONADA POR OVEJAS MERINO Y DORPER SOBRE TRES TIPOS DE PASTOS DEL KAROO, SOUTH AFRICA Du Toit, P.C.V. Northern Cape Department of Agriculture. Nature Conservation and Redevelopment. Grootfontein Agricultural Development Institute. Private Bag X529. Middelburg 5900. Eastern Cape Province. Republic of South Africa. ADDITIONAL KEYWORDS PALABRAS CLAVE ADICIONALES Selective grazing. Late developmental stage grass Pastoreo selectivo. Estados de desarrollo de la species. Mid-developmental stage grass species. hierba. Early developmental stage grass species. SUMMARY The diet selected by Merino and Dorper sheep in the diet selected by the Merino and Dorper was studied in the Arid Karoo, in the False Upper sheep breeds lie between 2 and 3 percent during Karoo and in the Noorsveld. The relative the growing season. This difference was not differences in their food preferences and their large, however, it is clear that different grazing adaptability to the different compositions of niches exist and that the animals selectively herbage on offer in the different range types was graze different parts and proportions of the studied. It was found that Merino sheep selected herbage on offer. more grass while Dorper sheep selected more karoo bushes and the woody component in the Noorsveld. In the Arid Karoo there was a 6 to 8 RESUMEN percent difference in the diet selected. Most of the differences were noted during the plant reser- Se estudió la dieta seleccionada por ovejas ve storage and dormant seasons. It was found Merino y Dorper en el Arid Karoo, el False Upper that these two breeds select very similar diets Karoo y en el Noorsveld. Se estudiaron las dife- during the growing season. In the Eastern Mixed rencias relativas en sus preferencias alimenti- Karoo there was an 11 to 25 percent difference in cias y su adaptabilidad a las distintas composi- the diet selected by the Merino and Dorper sheep ciones de la hierba presente en los distintos tipos breeds during the growing season. This range de pastos. Se encontró que los Merinos seleccio- offers different niches to the grazing animals and nan más gramíneas y los Dorper más arbustos they selectively graze different proportions of the del Karoo y el componente leñoso en el Noorsveld. vegetation on offer. In the Noorsveld the difference En el Arid Karoo hubo un 6-8 p.100 de diferencia Arch. Zootec. 47: 21-32. 1998. DU TOIT en la dieta seleccionada. La mayoría de las the sheep are suitable to that area. diferencias fueron observadas durante el alma- Recommendations regarding the cenamiento de reservas por la planta y los perio- raising of the stocking rates have been dos de letargo. Se observó que las dos razas published elsewhere (Botha et al., 1983 seleccionan dietas muy similares durante la es- and Du Toit et al., 1995a and 1995b). tación de crecimiento. En el Eastern Mixed Karoo The purpose of this paper is to study hubo un 11-25 p.100 de diferencia en la dieta the ability of these two breeds of sheep seleccionada por las ovejas Merino y Dorper to adapt to the herbage on offer in durante la estación de crecimiento. Este pasto three widely differing arid range types, ofrece diferentes nichos a los animales en pasto- with the main aim to assess the reo y ellos pastorearon selectivamente diferen- suitability of running these breeds in tes proporciones de la vegetación presente. En el these range types. Noorsveld la diferencia en la dieta seleccionada por ambas razas se sitúa entre el 2 y 3 p.100 durante la estación de crecimiento. Esta diferen- EXPERIMENTAL AREA cia no fue grande pero sin embargo está clara en los distintos nichos de pastoreo y que los anima- les pastorean selectivamente diferentes partes y The studies were conducted on three proporciones de la vegetación presente. research farms at Carnarvon, Groot- fontein and at Jansenville. Carnarvon Experimental Station is INTRODUCTION situated in the Arid Karoo (Veld Type 29, Acocks 1988), while the research The diets that different breeds of site is situated at 30°57’S and 21°59’E, animals select may be used to study at an altitude of between 1000 and their adaptability to the different 1300 m. The mean annual rainfall is compositions and types of herbage 203.5 mm with 14 percent falling in offered for grazing in three different spring, 34 percent in summer, 41 range types. With this in mind, it was percent in autumn and 11 percent in decided to study the diets selected by winter. The mean minimum (July) two sheep breeds, the Merino sheep, temperature is 8.1°C and the mean being a very selective grazer and maximum (January) temperature is Dorper sheep, being a fairly non- 23.5°C. A frost free period of 240 days selective grazer (previous obser- occurs from mid-September to mid- vations, confirmed during this trial), May. in the Arid Karoo, in the Eastern Mixed The vegetation at Carnarvon is low Karoo and in the Noorsveld. Various growing and sparse and consists mainly proposals have been made as to the of karoo bushes, with Eriocephalus suitability of combining these sheep ericoides, E. spinescens, Pentzia breeds with other small stock breeds spinescens, Pteronia glomerata, P. and species in order to make better use adenocarpa, Rosenia humilis and R. of the vegetation. However, before glandulosa dominant, while Felicia recommendations regarding the raising muricata, Monechma incanum, Plin- of the stocking rates can be made, it thus karooicus and Salsola tuberculata should be clearly established whether are fairly common. The grasses, mainly Archivos de zootecnia vol. 47, núm. 177, p. 22. DORPER AND MERINO DIET SELECTION short grass species, of the mid- to late in different stages of degraded developmental stages are characteristic grassland. Mixed with the mid- and of the soils on which they occur, with early developmental stage grasses are Eragrostis lehmanniana, Stipagrostis the karoo bushes Eriocephalus ericoi- ciliata and S. obtusa occurring on the des, E. spinescens, Felicia muricata, red kalahari sands, Aristida diffusa F. filifolia, Pentzia incana, Plinthus and Heteropogon contortus on doleri- karooicus, Pteronia glauca, P. trice- tic soils, while Fingerhuthia africana, phala, Rosenia humilis and Sutera Eragrostis nindensis and Stipagrostis pinnatifida. obtusa are found on the shale derived Jansenville Experimental Station is soils. Stipagrostis namaquensis situated in the Noorsveld (Veld Type frequently occurs along the dry water 24, Acocks 1988), while the research courses. site is situated at 32°58’S and 24°41’E, Grootfontein Agricultural Develop- at an altitude of between 300 and 700 ment Institute is located in the False m. Mean annual rainfall is 264 mm, Upper Karoo (Veld Type 36, Acocks although in rain shadows it is as low as 1988) it is locally referred to as the 170 mm. Twenty five percent of the Eastern Mixed Karoo, owing to the rain falls in spring, 33 percent in almost equal contribution of grass summer, 32 percent in autumn and 10 species and karoo bush species to the percent in winter. The mean minimum species composition. The research site (July) temperature is 11.5°C and the occurs at 31°28’S and 25°02’E, at an mean maximum (January) temperature altitude of between 1000 and 1500 m. is 26.5°C. The mean annual rainfall is 359 mm The area around Jansenville is with 15 percent falling in spring, 30 largely frost free and as a result many percent in summer, 50 percent in trees and shrubs are found in the autumn and 5 percent in winter. The Noorsveld; with Euphorbia coerules- mean minimum (July) temperature is cens and Portulacaria afra the 7.9°C and the mean maximum (Janua- dominating shrubby species, with trees ry) temperature is 20.9°C. A frost free such as Acacia karroo, Boscia albi- period of 180 days occurs from mid- trunca, Grewia flava, G. occidentalis, October to mid-April. Pappea capensis and Schotia afra. The stable vegetation at Groot- Tall, late developmental stage grasses fontein consists mainly of dense stands include Cenchrus ciliaris, Cymbopo- of the late developmental stage, tall gon plurinodis, Digitaria eriantha, grass species, Cymbopogon plurinodis, Panicum deustum, P. maximum and Digitaria eriantha, Hyparrhenia hirta, Themeda triandra while the following Sporobolus fimbriatus and Themeda karoo bushes are found, Felicia triandra. The mid-developmental stage muricata, F. filifolia, Monechma grasses Eragrostis lehmanniana and spartioides, Pentzia incana and Aristida diffusa and the early develop- Rosenia humilis. Typical Noorsveld is mental stage grasses A. congesta and a rather monotonous vegetation type Cynodon dactylon become dominant with a sparse covering of the karoo Archivos de zootecnia vol. 47, núm. 177, p. 23. DU TOIT bushes and grasses occurring in al., 1959). The weighed particles, amongst the Euphorbia coerulescens, summed per species, were expressed where the range becomes degraded as a percentage of the weight of all the very easily, leaving large bare patches. points identified. This indicated the percentage of the selected diet actually consisting of a particular plant species. MATERIALS AND METHODS The plant species were grouped into five functional groups on the basis of Ten dry ewes and 10 castrated their growth form, i.e. karoo bushes, males of the Merino and Dorper breeds grasses, annual plants, trees & shrubs were fistulated at the oesophagus and noors. Because of the special (Bredon et al., 1967). These animals interest in the karoo bushes, grass and were allowed to graze normally until annual (ephemeral or opslag) species the fistula extrusa samples were groups, these were treated separately. required. They would then have However, no recourse was taken to become accustomed to the range plant further subdivide the karoo bushes into species and would therefore graze palatable, less palatable and unpala- normally during sampling.