Factors affecting fleece traits of Angora goat in Argentina

Abstract

Information collected over a fifteen-year period on an experimental flock 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 characteristics of the fleece at subsequent shearings. The variables analyzed were greasy fleece weight (GFW), average fiber diameter (AFD), percentage of 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. For AFD and MF, solely the shearing year was significant ( P<0.05). Data collected from the second and following shearings showed differences ( 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 years 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 increase of AFD. On the other hand, MF shows a positive tendency related to age, for the analyzed interval of ages. In general, assuming comparisons are conducted within years of production, the results showed the importance of adjusting for age of dam, sex and type of birth for fleece weight, for traits collected at 12 months of age. For traits recorded at the second and later shearings adjustment for sex and age effects would be necessary for fleece weight, fiber diameter and log-transformed percent medullation. This result indicated, that to improve the estimation of breeding values in a selection scheme, it is necessary to use different models to adjust the data according to the yearly sequence of shearings.