Delivering genetic improvement

摘要

Selection on fleece weight with emphasis on reduction of fibre diameter, by way of an index, is the general recommendation of geneticists to advance the cause of the wool-sheep industry. This involves tedious measurement of fleece characteristics, with the incumbent difficulty of data interpretation. The rationale behind these recommendations is that most selection emphasis is on the important genetic production traits. But, is this the case? Neither fleece weight nor fibre diameter are primary genetic characteristics, but represent the sum total of the various genetic traits contributing to this total, plus the non-heritable effects of nutrition, state of health, competition, stress factors and so on. These environmental effects are least when sheep are run in one mob, but, still, some differences exist. For such reasons, progress by measured index-based selection is likely to be slow, and unacceptable to breeders who want rapid progress.