2 IDENTIFICATION OF CONTAMINANT SALE LOTS
SUMMARY A trial incorporating the testing of commercial core samples has provided further evidence of wool contamination arising from crossbreeding Merinos with Damara fat tail rams. The trial has also highlighted limitations of the CSIRO Dark Fibre Detector for this purpose in terms of both its subjectivity and the operator time required for a test. Core samples from bales of fleece wool from Merino ewes known to have reared Merino lambs (5 lots), or to have reared Damara crossbred lambs (14 lots), or to have been mated to Damara rams but failed to rear a lamb (6 lots), were tested for pigmented and for medullated fibres by 3 laboratory methods. The tests were performed at AWTA Ltd and SARDI. The wool from the 3 different farm management practices had significantly different (P<0.005) concentrations of pigmented and medullated fibre. The ewes rearing the Merino lambs showed the lowest contamination, those rearing the Damara crossbred lambs showed the greatest contamination, and the remaining 6 lots showed intermediate concentrations of pigmented and medullated fibre. The 2 laboratories were not significantly different (P≥0.05) in their reported concentrations of medullated fibres and of the darkest (CSIRO darkness levels 6 to 8) pigmented fibres. However, for the pale-pigmented fibres (CSIRO darkness levels 4 and 5) and the total pigmented fibre concentration there were differences between the laboratories.
Merino wool contamination from rearing of Damara crossbred lambs
Recent importations and promotion of Damara sheep has raised concerns and debate about potential for Merino wool contamination. This project examined Merino ewe wool contamination arising from the mating of Damara rams and rearing of Damara crossbred lambs. Shirley-blended core samples from 3 commercial greasy wool sale lots known to involve Merino ewes shorn with Damara crossbred lambs at foot (2 lots), or shorn 3 weeks after weaning, were assessed. Contaminant fibres were above commercial expectations for Merino wool and present in every core sample measured. There was no significant difference found between these sale lots. From an experimental flock, composites of fleece samples were carded and the effects of mating or rearing alone assessed. No detectable increase of pigmented or heavily medullated fibres, above very low background levels, were detected among the Merino ewes mated to Damara rams (1 ram per 65 ewes). However, high concentrations of contaminant fibres were found in the Merino ewe wool at weaning of their Damara crossbred lambs and also 3.5 months after weaning; with reduced levels post-weaning. The management strategy of restricting wool exposure to mating effects alone may offer advantage but delaying shearing of ewes after weaning to reduce the contaminant fibre burden was, in this case, not sufficient to overcome potential concerns for wool processing. However, in view of the many potential contributing factors, actual contamination may vary widely between cases and require the advancement of presale measurement to gain buyer confidence and accurate appraisals.
On the fractionation of β-lactoglobulin and α-lactalbumin
Abstract Existing methods for the preparation of α-lactalbumin and β-lactoglobulin are examined critically. It is proposed that the most satisfactory method for the preparation of the whey protein fraction from bovine milk is (NH 4 ) 2 SO 4 fractionation. A number of new gentle procedures for the fractionation of the whey proteins are compared with some existing methods. The distribution of total protein at various stages is determined by total Kjeldahl nitrogen and the kind of protein by starch-gel electrophoresis. The effect of variables, such as pH, salt concentration and temperature on the separation of α-lactalbumin and serum albumin from β-lactoglobulin is studied. Differences in the behavior ( e.g. solubility) of genetic variants of β-lactoglobulin are noted. The solubility of each of the major whey proteins, under similar conditions to those used in the fractionation, is compared with its solubility in the whey protein mixture. The understanding gained of factors important in the fractionation is used in recommending new procedures for α-lactalbumin and β-lactoglobulin isolation.