Wool sheep production systems for the Western Highveld of South Africa

[摘要] English: The aim of this study was to evaluate the biological and economical feasibility of wool sheep farmingin the Western Highveld of South Africa.The performance of young sheep utilizing Digitaria eriantha Steud. (Smuts finger grass) both duringthe winter and summer periods, fertilised at rates of 60 kg N + 10 kg P/ha vs. 120 kg N + 20 kgP/ha, was investigated. Rainfall, both in terms of quantity and distribution, was the most criticalfactor during both the summer and winter seasons. During the winter period, the quantity ratherthan the quality, of the foggage was the limiting factor. The results of this study, with the belownormal rainfall recorded, showed that stocking rates of two, four and six sheep/ha for a six monthperiod are sufficient for the maintenance requirements of wooled sheep. During these dry seasonsa fertilization rate higher than 60 kg N + 10 kg P/ha had no beneficial effect as far as mass gain/hais concerned. The results obtained during the summer period were also very disappointing, mainlydue to a lack of available pasture. Rotational grazing, instead of continuous grazing, shouldprobably rather be applied during the summer period.The biological and economical feasibility of three various wintering strategies (silage, foggage/cropresidues 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 andcrop 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 decidingfactor 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 resultedin 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 recoveryin body mass.Ewes wintered on maize silage as the sole roughage source returned the highest body masses andbody mass gains. However, this advantage was not transferred to the performance of their progenyand the quality and quantity of the wool produced. The conclusion was made that natural proteinsupplementation should be provided additional to the silage, especially for woolled sheep. Cost ofthe silage will also exert a great influence on the financial viability of this enterprise, as this provedto be the highest feed cost.Maize crop residues proved to be an invaluable, high energy feed source that becomes available at acrucial 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 highestclean wool mass (kg). The greater fiber diameter was also not so severe as to cause a reduction inprice.The poor performance of the ewes on winter veld was disappointing. In the long term, this does notappear 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 thatthey 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 theanimals of the silage treatment the lowest gross margin for all the parameters tested (gross marginper small stock unit and per ewe), the only exception being the gross margin/ha, which was higherfor 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 utilisingfoggage/maize crop residues during the winter months.

[发布机构] University of the Free State