Wool sheep production systems for the Western Highveld of South Africa

English: The aim of this study was to evaluate the biological and economical feasibility of wool sheep farming in the Western Highveld of South Africa. The performance of young sheep utilizing Digitaria eriantha Steud. (Smuts finger grass) both during the winter and summer periods, fertilised at rates of 60 kg N + 10 kg P/ha vs. 120 kg N + 20 kg P/ha, was investigated. Rainfall, both in terms of quantity and distribution, was the most critical factor during both the summer and winter seasons. During the winter period, the quantity rather than the quality, of the foggage was the limiting factor. The results of this study, with the below normal rainfall recorded, showed that stocking rates of two, four and six sheep/ha for a six month period are sufficient for the maintenance requirements of wooled sheep. During these dry seasons a fertilization rate higher than 60 kg N + 10 kg P/ha had no beneficial effect as far as mass gain/ha is concerned. The results obtained during the summer period were also very disappointing, mainly due to a lack of available pasture. Rotational grazing, instead of continuous grazing, should probably rather be applied during the summer period. The biological and economical feasibility of three various wintering strategies (silage, foggage/crop residues and veld) of Merino ewes and their progeny, for both an autumn and a spring lambing season, were also evaluated. This study indicated that the utilisation of Smuts finger grass foggage and crop residues during winter, realised the best results for animals of both lambing seasons. However, the biological and economical availability of the various feed sources would ultimately be the deciding factor on the most appropriate system. Although the animals of the intensive treatment (silage) had the best performance (mainly in terms of body mass and mass gain), the animals of the foggage/ crop residue treatment showed compensatory growth during the summer period. This resulted in little or no differences in the body mass of these two treatments at the end of the summer period. In the case of ewes utilising winter veld, their compensatory growth was insufficient for a total recovery in body mass. Ewes wintered on maize silage as the sole roughage source returned the highest body masses and body mass gains. However, this advantage was not transferred to the performance of their progeny and the quality and quantity of the wool produced. The conclusion was made that natural protein supplementation should be provided additional to the silage, especially for woolled sheep. Cost of the silage will also exert a great influence on the financial viability of this enterprise, as this proved to be the highest feed cost. Maize crop residues proved to be an invaluable, high energy feed source that becomes available at a crucial time in the fodder flow for woolled sheep. This product also has little or no other commercial value. Despite the lower clean wool percentage, animals of this treatment still realised the highest clean wool mass (kg). The greater fiber diameter was also not so severe as to cause a reduction in price. The poor performance of the ewes on winter veld was disappointing. In the long term, this does not appear to be a viable option. Where available, an alternative nutritional strategy should be applied. This extensive treatment can also be seen as a 'Iow cost approach' with reduced inputs and, consequently, a reduced income. Ewes lambing during spring required less supplementation. This was mainly due to the fact that they utilised crop residues during late pregnancy and they raised their lambs during spring. For both the lambing seasons the utilisation of foggage/crop residue realised the highest and the animals of the silage treatment the lowest gross margin for all the parameters tested (gross margin per small stock unit and per ewe), the only exception being the gross margin/ha, which was higher for the intensive treatment than that of the extensive treatment during the spring lambing season. The cost of intensification should, however, be kept in mind. The results of this investigation clearly indicated the biological and economical advantages of utilising foggage/maize crop residues during the winter months.