Selection must be based on wool measurements

Press, 20 December 1985, Page 21

Selection must be based on wool measurements

Merino sheep breeders can make faster progress in breeding genetically superior wool producers if they select their ram hoggets on measured clean wool weight and fineness. Dr Barry Wilkinson, head of Lincoln College’s wool science department and wool measurement service, said this at a superfine Merino wool seminar, run by the Wool Board at Black Forest Station in the Mackenzie Country. “Genetic progress, which depends very heavily on the breeder’s ability to select the better animals, is markedly improved if superiority is measured rather than assessed by eye or hand,” Dr Wilkinson said. In the case of fleece weight, for example, numerous comparisons had shown

that eye appraisal was only 30 per cent as efficient as fleece weighing. Similarly, comparisons had clearly demonstrated that large errors were possible if the average fibre diameter (fineness) of an animal’s fleece was assessed by eye and hand rather than measured.

“Clearly, if an animal is mistakenly rated as a high producer, it will not live up to expectations for the remainder of its life, nor will it pass on any superiority to offspring.” Measurement increased the accuracy of selection and helped the breeder avoid continuing to work with animals which only wasted time, effort and resources.

From a Merino breeder’s viewpoint, clean fleece weight and fineness should be the two most important characteristics for measurement and selection, Dr Wilkinson said. These two characteristics had the most influence on wool returns from Merino sheep. Both traits persisted throughout the animal’s lifetime and were highly heritable, so that genetic progress was assured, if good selection procedures were practised. The number of characteristics for which the breeder selects should be kept to a minimum, or no progress would be made at all.

“With very few exceptions,” Dr Wilkinson said, “selection for clean weight

and fineness will largely take care of other important characteristics, either in a positive sense, or in a neutral sense in that they won’t necessarily be affected one way or the other.”

Characteristics improved by selection for clean weight and fineness included length and soundness. Traits not necessarily affected included style, character and evenness, which according to Dr Wilkinson, were not important anyway. With conformational faults and extreme wool types already culled as lambs, clean fleece weight and fineness should dominate the breeder’s selection decisions at ram hogget shearing. Measurement of clean weight identified high yielding, heavy fleeces, measurement of fibre diameter identified the exceptions to the general rule that heavy fleeces were coarser.

The animals could then be ranked on an index, derived from the clean weight multiplied by a relative value based on historical price/ fineness relationships. The ranking could be redefined by including a prediction of susceptibility to fleece discolouration.

“Then and only then should visual appeal provide a final ranking,” he said. “Selecting a few sheep on visual appeal as the first' step and then having them measured is a huge waste of selection potential.” Gains should outweigh the costs, but extension of measurement beyond fleece weighing was fully justified for potential sires.

Rams were responsible for about 80 per cent of genetic progress, compared with about 15 per cent from ewe hoggets and 5 per cent from ewe culling. Testing of stock, other than potential sires, required very careful analysis of the objectives and cost benefits.

Wool testing for production purposes was available from the Wool Testing Authority and Lincoln College’s wool measurement service. No other services had the specialised facilities and quality control procedures to ensure accurate measurements.

The wool testing authority provided production testing in association with its wider role of pre-sale core testing for valuation purposes. Large numbers of samples could be measured for yield and fineness at a unit cost of $2.50. Results were returned two to four weeks after the samples had been received.

The Lincoln College service was a testing and advisory unit, mainly serving ram breeders. Samples were sorted, fully appraised ’and sub-samples withdrawn for reference.

Samples were measured for yield and fineness at a unit cost of $4.75, plus $2 for the predictive test for susceptibility to fleece discolouration.

Sheep were ranked on clean weight and fleece index values, and the data, together with a report, returned two to six weeks after the samples had been receive!