Marker-assisted selection in sheep and goats

Sheep and goats are often kept in low input production systems, often at subsistence levels. In such systems, the uptake of effective commercial breeding programmes is limited, let alone the uptake of more advanced technologies such as those needed for marker-assisted selection (MAS). However, effective breeding programmes exist in a number of countries, the largest ones in Australia and New Zealand aiming for genetic improvement of meat and wool characteristics as well as disease resistance and fecundity. Advances have been made in sheep gene mapping with the marker map consisting of more than 1 200 microsatellites, and a virtual genome sequence together with a very dense single nucleotide polymorphism (SNP) map are expected within a year. Significant research efforts into quantitative trait loci (QTL) are under way and a number of commercial sheep gene tests have already become available, mainly for single gene effects but some for muscularity and disease resistance. Gene mapping in goats is much less advanced with mainly some activity in dairy goats. Integration of genotypic information into commercial genetic evaluation and optimal selection strategies is a challenge that deserves more development.