Last update: November 22, 2010 02:21:33 PM E-mail Print

 

GENETICS OF FIBRE PRODUCTION IN GOATS

 

M. A. Snyman

 

Grootfontein Agricultural Development Institute, Private Bag X529, Middelburg (EC), 5900, South Africa

 email:  Gretha Snyman

 


The two major fibre producing goat types in the world are the Angora goat, which produces mohair, and the cashmere breeds, which produces cashmere. Fleece traits which contribute to the economic value of mohair are fleece weight, fibre diameter, staple length, style and character and evenness of fleece. Economically important cashmere traits are down weight, down fibre length, down fibre diameter, down yield percentage and colour of down fibres. Breeding plans for Angora and cashmere goats in various countries are aimed at improving these traits. All of these economically important fibre traits mentioned show continuous variation in their phenotypic expression. Various tools are available as selection aids for the improvement of such traits, ranging from phenotypic selection (hand-and-eye), performance testing (objective measurement of traits and use of selection indices) and estimated breeding values to QTLs and marker assisted selection.

 

Relatively high heritability estimates were published for the various cashmere traits, ranging from 0.30±0.05 to 0.62±0.15 for down weight, from 0.23 to 0.70±0.19 for down fibre length and from 0.39±0.16 to 0.79±0.23 for down fibre diameter. Corresponding values for mohair traits were somewhat lower, ranging from 0.30 to 0.45 for the various traits. These heritabilities indicate that selection based on quantitative genetic principles should be effective. Progress made in the fine hair Angora goat flock at the Jansenville Experimental Station in South Africa, where selection was based on BLUP of breeding values, bears testimony to this.

 

The development of molecular biology during the past three decades has opened up exciting new means for studying livestock genetics and animal breeding. In contrast with cattle, pigs and chickens, genomic research in sheep and goats are still in its infancy, even more so in the case of goats. According to the INRA goatmap database, there are currently 263 genes and 621 loci assigned to the different chromosomes. Furthermore, 1170 PCR markers and 323 micro-satellites have been identified. Some research projects in goats involving genome scanning for disease and milk production related traits are currently underway. The only documented work regarding genome screening for QTLs for fibre traits in Angora goats, is that being carried out in Argentina.

 

It is obvious that goat breeding practices around the world are still based on quantitative genetic principles, with which satisfactory results are obtained. In future, however, selection based on genotype could become important, especially in traits with lower heritabilities and which are difficult to measure objectively, such as lustre in mohair.