New CT EBVs

Results:

Genetic parameters were produced for individual breeds and in a combined approach.

Most traits showed a medium-high heritability, indicating real potential to change these traits through genetic selection. The outputs from this project are now being used to change the genetic evaluations produced by Signet.

The Problem:

The CT scanner has been used to measure a number of novel new measurements in terminal sire sheep breeds. However, these need to be converted into estimated breeding values (EBVs) to enable producers to use them in ram selection.

Aims and Objectives:

This project aims to use the archives of existing CT images to:

(i) produce new, previously unexploited, phenotypes (CT-predicted IMF; vertebrae number and spine lengths; eye muscle area, CT-measured eye muscle depth);

(ii) estimate genetic parameters of these traits across different breeds;

(iii) investigate the potential impact of including these traits alongside current breeding goals.

Approach:

The objectives of the proposed work will be to:

1. measure vertebrae number and spine length in the thoracic and lumbar regions of previously-scanned rams and upload to BASCO

2. calculate CT-predicted IMF for each of these rams, using previously-derived prediction equations, and upload to BASCO

3. collate data sets for each breed with >200 ram lambs scanned, incorporating new CT traits (eye muscle area, CT muscle depth, CT-IMF, vertebrae numbers, spine lengths), pedigree information, existing production and CT data from BASCO

4. estimate genetic variation and heritabilities for each new CT trait, in each breed with sufficient CT data

5. estimate genetic and phenotypic correlations amongst new CT traits and existing traits in the breeding programme

6. perform an across-breed genetic analysis for new and existing carcass traits

7. provide a report of the results, including recommendations for the incorporation of new CT traits into breeding programmes