FACTORS AFFECTING FLEECE TRAITS OF ANGORA-GOAT IN ARGENTINA

Information collected over a fifteen-year period on an experimental fl ock were analyzed to evaluate the effect of year, age of dam, sex, and type of birth on the characteristics of the fleece at first shearing and the effects of year, age at shearing, and sex on the characteristi cs of the fleece at subsequent shearings. The variables analyzed were greasy fleece weight (GFW), average fiber diameter (AFD), percentage o f medullated fibers (MF) and corrected greasy fleece weight (CGFW). At first shearing significant statistical differences were detected (P < 0.05) for year, dam's age, sex, and type of birth for GFW and CGFW. F or AFD and MF, solely the shearing year was significant (P < 0.05). Da ta collected from the second and following shearings showed difference s (P < 0.05) due to year of production, age at shearing time, and sex for the four variables analyzed. GFW increases to a maximum at 3-4 yea rs of age, while CGFW is practically constant between 2 to 4 years of age, thus suggesting that the increase in fleece weight is due to an i ncrease of AFD. On the other hand, MF shows a positive tendency relate d to age, for the analyzed interval of ages. In general, assuming comp arisons are conducted within years of production, the results showed t he importance of adjusting for age of dam, sex and type of birth for f leece weight, for traits collected at 12 months of age. For traits rec orded at the second and later shearings adjustment for sex and age eff ects would be necessary for fleece weight, fiber diameter and log-tran sformed percent medullation. This result indicated, that to improve th e estimation of breeding values in a selection scheme, it is necessary to use different models to adjust the data according to the yearly se quence of shearings. (C) 1998 Elsevier Science B.V.