A study of wool production parameters of genetically different Merino wethers run together

In 1984 a Merino wether trial at Matakanui station, Omakau, Central Otago, was set up to demonstrate the production possible from well-bred Merino wethers. Thirty teams of ten sheep from a variety of environmental and genetic backgrounds took part in the trial. Prizes were awarded for the highest returns per head, highest average clean fleece weight and highest liveweight off shears. Data from 1984, 1985 and 1986 which included fibre diameter, clean fleece weight, greasy fleece weight, clean scoured yield, liveweight and staple length were analysed in relation to within and between group phenotypic variation, repeatabilities and phenotypic correlations. The efficiency of wool growth was also calculated. The design of the trial was critically reviewed. Highly significant (p<0.005) differences existed between some groups for fibre diameter, clean fleece weight, clean scoured yield and staple length in all years. Variation within groups for these characteristic was also present reflecting the selection method used by the competitors and/or the proportion of sheep in a team with penalties upon wool growth due to temporary and/or permanent environmental effects. Between the yearling stage and three years of age, the average fibre diameter increased by 3.1 microns and the average clean fleece weight increased by 1.73kg. The increment of increase in fibre diameter was 37% higher between two and three years of age than between one and two years of age. The opposite occurred with clean fleece weight, whereby the increase between two and three years of age was only 51% of that which occurred between one and two years of age. In the first year the average staple length increased by 15.5mm, yet in the second year a decrease of 1.1mm occurred. On a group basis, clean scoured yield in the first year responded in both a negative and a positive manner. This was a likely effect of genotype environment interaction. In the second year all group yields increased by an average of 2.2% to 72.7% clean scoured yield. Repeatabilities between the yearling stage and three years of age for greasy fleece weight, clean fleece weight, fibre diameter and staple length were high; all being greater than 0.6. During the second and third years of age, fibre diameter and staple length increased, on average, by 1.6 microns and 9.03 mm with every 1 kg increase in clean fleece weight. Correlations showed fibre diameter and staple length to increase, on average, by 1.6 microns and 9.03mm respectively with every 1kg increase in clean fleece weight during the second and third years of age. Clean fleece weight was weakly correlated with liveweight (+0.24 in 1985 and +0.15 in 1986). Greasy fleece weight was a good indicator of clean fleece weight, with a correlation of +0.90 in both 1985 and 1986. No relationship existed between clean scoured yield and greasy fleece weight or fibre diameter. Teams both decreased and increased in ranking when ranked on efficiency of wool growth as compared with a simple ranking based on clean fleece weight. Failure to identify and reduce permanent and temporary environmental influences upon the wool production of individuals was the major fault of the trial design.