| Sable Cluster Analysis |
|
Data was obtained from the ADGA for 8 dairy breeds. All results were limited to those animals reported as Purebred (PB) or American (AM); however, all animals were included in the pedigree analysis to establish ties between animals, including cases where the ancestors are from another breed. Cluster analysis is a procedure that groups related animals based on pedigree relationship. This is a technique used by NAGP to assess where repository animals are grouping with the currently available genetic pool for each breed. It also establishes a practical approach for obtaining animals for the repository in a way that maximizes genetic diversity. Animals that were included in the cluster analysis included sires of PB and AM offspring born 2010 to present that are also PB or AM themselves.
Table 1 shows the summary statistics based on the pedigree and cluster analyses.
*Sable clusters include Saanen sires producing Sables
Pedigree & Inbreeding Analysis
Figure 1 shows the inbreeding trend for Sable goats. Current inbreeding levels are 5.7% (2013), and have been fairly steady for the past 12 years. Because this breed has another breed pool to pull from, inbreeding should be easier to manage than would normally be expected from a small breed.
Figure 1. Sable inbreeding trend by birth year
Sable registrations have generally seen an increase over time with 289 registrations for 2013 born animals (Figure 2).
Figure 2. Sable goats registered by birth year
The percentage of inbred Sable goats is steadily increasing, with 70% of animals born in 2013 having a non-zero inbreeding coefficient.
Figure 3. Percent of Sables with an inbreeding coefficient greater than zero by birth year
As is expected with a 'young' breed, overall inbreeding is relatively low. This is reflected in the current population (animals born 2009 and later) where 82.6% of the goats have an inbreeding coefficient less than 0.10 (Figure 4).
Fifteen clusters were identified as representing the 300 clustered bucks. The clusters included Sable bucks in addition to Saanen bucks that have produced Sable goats.
Figure 5. Tree diagram for Sable cluster analysis of sires of PB and AM offspring born 2010 and later that are PB or AM themselves (gold line depicts cluster level)
The overall relationship between the clustered bucks is 0.047; only cluster 14 is lower than this value. There are no Sable bucks in the NAGP repository.
Table 2. Sable cluster results showing the number, mean, and variance for between and within cluster relationships
The within and between cluster relationship matrix is shown in Figure 6. With few exceptions, the diagonal (within cluster) has higher relationships than the off-diagonal (between clusters), indicating the cluster analysis has properly allocated bucks to clusters.
return to top
