Relative economic value of wool processing parameters for New Zealand strong wool between 2003 and 2007
Price trends for a total of 147,416 lots of wool in the strong wool segment of the New Zealand clip sold at auction between 1 July 2003 and 30 June 2007 were analysed by multiple regression analysis to determine the effect on price of five key characteristics known to affect wool processing performance. Changes in exchange rate were allowed for by covariance against the exchange rate of the US dollar on the day of the auction. The residual standard deviation within the data set was 20.4 c/kg clean. Mean values of the slope of the regression, or relative economic value, were 0.4 ± 0.2 c/ kg clean/mm change in barbe length, -1.9 ± 0.9 c/kg clean/μm change in mean fibre diameter, 2.5 ± 0.5 c/kg clean/CIE Y value change in brightness, -5.0 ± 0.6 c/kg clean/CIE Y-Z value change in intensity of yellowness and -16.8 ± 3.0 c/kg clean/% change in vegetable matter contamination. These estimated values align closely with values estimated in 1991 for the New Zealand clip as a whole confirming that despite the significant changes that have occurred within the wool processing industry the economic significance of individual wool characteristics to wool processors have not changed.
Wool staple tenacity in New Zealand Romney sheep: heritability estimates, correlated traits, and direct response to selection
A flock of New Zealand Romney sheep was established and selected as yearlings on the basis of fleece staple tenacity. The foundation flock was screened from contributing source flocks, with outliers of high or low staple tenacity as yearlings relative to the source flock mean contributing to a ‘high’ line and a ‘low’ line, respectively. A randomly selected control line was established because staple tenacity was known to be affected by yearly changes in feed supply. Staple tenacity of yearling fleeces was found to be heritable (0.41 ± 0.03). After 10 years of within-line selection, the line selected for increased staple tenacity had staples 53% stronger (33.9 N/mm2) than the control (22.1 N/mm2), while staples were 38% weaker in the line selected for decreased staple tenacity (13.8 N/mm2). Staple tenacity was genetically (0.67 ± 0.04) and phenotypically (0.44 ± 0.02) correlated with fibre diameter, and also with staple length (0.38 ± 0.07 and 0.32 ± 0.02, respectively). Longer, thicker fibres likely contributed to positive genetic (0.31 ± 0.07) and phenotypic (0.29 ± 0.02) correlations between staple tenacity and clean fleece weight. The indirect aim of selection was to improve fibre length after carding. Pooled wool samples were prepared from selection line groups of yearlings within sex each year, and a relationship between fibre length after carding measured on these samples and mean staple tenacity of the groups was observed (R2 = 0.514, P < 0.001). Within the tenth (last) year of selection, the high staple tenacity line produced the longest carded fibres (Hauteur: 103 mm) and the decreased staple tenacity line produced the shortest (87 mm), with the control line intermediate (96 mm).
Pasteurella haemolytica serotype 1 colonization of the nasal passages of virus-infected calves.
Nasal passages of calves with a virus-induced respiratory tract disease became colonized by Pasteurella haemolytica serotype 1 after they were inoculated intranasally with P haemolytica. Inoculation with infectious bovine rhinotracheitis virus caused a more severe clinical illness and resulted in a greater degree of colonization with P haemolytica than developed after inoculation with parainfluenza-3 virus. Nasal passages of parainfluenza-3 virus-inoculated calves were colonized to a greater degree with P haemolytica than were those of healthy, nonstressed calves. Calves were susceptible to P haemolytica colonization during or shortly after virus-induced illness, even though they had been previously exposed to P haemolytica and had serum antibody and nasal secretion antibody to P haemolytica.