Comparison of restricted selection strategies: an application to selectionof cashmere goats

The problem of restricted selection was investigated. The objective was to compare several strategies to change one trait whilst attempting to restric t changes in a correlated trait. To do so, seven selection strategies to im pose a restriction on fibre quality while maximising fibre quantity were st udied. A closed nucleus scheme for Cashmere goats was generated using stoch astic computer simulation. The nucleus consisted of 200 breeding females. N umber of males (ten) and mating ratio were constant except for those strate gies in which linear programming and mate selection were applied. Unrestric ted or restricted best lineal unbiased prediction (BLUP) were used for eval uation purposes. Selection was carried out during seven years. Comparisons were made in terms of achieved genetic response, variances of response and cumulative level of inbreeding. Most strategies successfully restricted fib re diameter; however, the achieved responses for quantity of fibre and vari ance of responses associated with restricted trait varied greatly among str ategies. Restricted BLUP in two steps resulted in a similar response for fi bre quantity and a better tool to restrict fibre diameter than regular Rest ricted BLUR The use of Linear programming techniques for male selection and Restricted BLUP for females selection appeared to be the most appealing st rategy. This strategy was a good compromise between maintenance of the rest riction and achieved genetic response for fibre quantity. Resulting cumulat ive level of inbreeding varied from 0.045 to 0.101 among strategies. There was no clear pattern of the relationship between level of inbreeding and va riance of response. (C) 1999 Elsevier Science BN. All rights reserved.