A note on divergent selection for total fleece weight in adult Angora rabbits: direct response to selection on total fleece weight at first and second harvest.

Abstract

In order to explore the genetic variability of wool production and other quantitative traits, an 8-cohort divergent selection experiment for total fl eece weight (TFW) was carried out in French Angora rabbits. Studies were made on the wool production of a total of 669 female rabbits born between 1994 and 2001 and having produced wool from fi rst to 12 th harvests. The aim of the selection experiment was to obtain two divergent lines (low and high) on TFW. From preliminary analysis, the dataset was separated into three subsets according to the harvest number: one for each of the fi rst two harvests and one for the third to the 12 th harvests. In this paper, wool production data of the fi rst and second harvests was analysed separately. Response to selection for total fl eece weight at 3-12 harvest (TFW3-12) on this trait at fi rst and second harvest was the aim of this paper. The second objective was to study the possibility of utilising values of the fi rst or second harvest to estimate breeding values and as selection criteria for total fl eece weight in the French Angora rabbit. Preliminary analysis of the data for non-genetic factors was done by the GLM procedure of SAS. Genetic parameters and breeding value estimates were carried out using a BLUP animal model using ASReml. A linear mixed model for a bivariate analysis of total fl eece weight at fi rst or second harvest and TFW3-12 was used. Heritability estimates of total fl eece weight at fi rst and second harvests were 0.36 and 0.38, respectively, and were similar to that observed at later harvests (0.35). The genetic correlation between TFW3-12 and fl eece weight at fi rst harvest was close to zero indicating that wool production at fi rst harvest is a different trait from that of subsequent harvests. Genetic correlation estimates observed at second harvest were high (0.76) and response to selection at second harvest was similar to that observed for TFW3-12. These observations confi rm that total fl eece weight at fi rst harvest is a different trait from TFW3-12. In French Angora rabbits, the high genetic correlation between TFW3-12 and total fl eece weight at second harvest suggests the possibility of selection at this time for TFW3-12.

Estimation of Genetic Parameters for Wool Traits in Angora Rabbit

“…The direct heritability (h 2 ) estimates from all the models ranged from 0.18 to 0.41 for clip I and II and 0.17 to 0.35 for clip III; respectively. From the most appropriate model 4, however, moderate estimates of heritability for clip I (0.22±0.04), II (0.20±0.06) and III (0.21±0.06) were found and were in agreement to moderate estimates derived from REML (Allain et al, 1999) and ASREML (Rafat et al, 2009) animal models in French Angora. Consistency in h 2 indicates about the maintenance of the genetic variability in latter clips, also.…”

“…While, the genetic correlation between clip I and III of German Angora was negative and the phenotypic correlation was positive and low (0.20). Similarly, a very low (close to zero) genetic correlation between clip I and clip III and others had been estimated in French Angora (Rafat et al, 2009). This possibly indicates that genetic factors determining clip I are different to those which determine clip III.…”

“…Further, wool traits could be improved by direct and indirect selection methods in Angora rabbits (Allain et al, 2004;Rafat et al, 2007Rafat et al, , 2008. Initial wool clips were found important in early selection, due to their high genetic correlation with latter clips (Rafat et al, 2009) and significant genetic correlation exists between wool yield and corresponding body weight in Angora rabbits (Jelinek et al, 1980;Garcia and Magofke, 1982;Singh et al, 2006). Likewise, correlated responses for body weight after selection for fleece yield in Angora rabbits have been observed experimentally (Qinyu, 1992;Rafat et al, 2008).…”

“…Animal models using Derivative Free Restricted Maximum Likelihood (DFREML) procedure are widely used to estimate the genetic parameters for different economic traits in livestock. However, there is limited information available on applicability of such an animal model procedure for wool traits (Rafat et al, 2009) and growth traits (Niranjan et al, 2010) in Angora rabbit. The objective of this study was, therefore, to estimate genetic components for wool traits using DFREML procedure with various combinations of direct and maternal effects in German Angora rabbit reared under sub-temperate Himalayan conditions.…”

Optimum wool harvest interval of angora rabbits under organised farm conditions in East China

“…Angora wool production varies during the lifespan of the animal. Factors that affect wool yield include the interval between wool harvests length, harvesting methods (shearing vs. plucking), harvest number, animal sex, live weight and seasons, among others (Rochambeau and Thebault 1990). In China, the common traditional wool harvest intervals are 60, 73 and 91 d. However, the fibre length varies by harvest interval.…”