Genomic Testing & Selection Resources for Sheep

Fact Sheets

Brief guides for collecting tissue, hair, and blood samples for genetic testing, and a brief guide for interpreting genomic tests in sheep.

Sample Collection Guide

Methods for Sample Collection

Note: collection methods may differ based on which genomic test is used. Always check with the company to determine which sample type is best for submission.

Tissue Sampling Units (TSUs), Ear Notches, & Tails

Tissue sampling units, or TSUs, punch a small tissue sample from the ear into a tube with preservation solution. This sampling procedure can be combined with tagging, when the sample is taken at the same time as the tag is inserted into the ear. TSUs can be stored at room temperature in a cool, dry place before shipping at room temperature.

Ear notches and tails can also be taken when tagging and/or docking, and placed into a container such as a plastic bag or tube before storing in the freezer until shipping. Notches and tails should be frozen and shipped on ice packs or dry ice to preserve DNA.

Whole Blood and Blood Cards

Blood can be collected from a tail or jugular draw into a purple top tube (containing EDTA to prevent clotting). Whole blood should be stored in the fridge and shipped within a few days on ice packs.

Blood can also be spotted onto a FTA blood card covering the entire circle or square on the card, and be sure to let the card dry before storing in a cool, dry place.

Blood cards can be shipped at room temperature.

Semen

Semen straws should be properly labeled with unique IDs for each animal, and packaged protectively in a cane or hollow pen (without ink) to prevent breakage during shipping.

Semen samples should be shipped on ice packs or dry nice to preserve DNA.

Sampling Tips

Keep detailed and clear records during sampling to prevent duplicated or skipped animals.

Make sure samples are not contaminated with manure, dirt, and debris.

Clean sampling tools between animals to prevent cross-contamination of DNA.

Store samples out of sunlight and heat, and ship accordingly to prevent DNA degradation.

Genomic Testing in Sheep

Parentage

Samples from multiple rams and/or ewes can be submitted and offspring are matched to the correct parent using genetic information. An output example is given in the table below:

Single-Gene Tests

Single-gene or single-SNP tests are reported as a genotype in letters or numbers, or affected/carrier/clear depending on the test.

Examples of single-gene tests include ovine progressive pneumonia (OPP) resistance, Callipyge, fecundity, and scrapie (RR = greater resistance, QR = intermediate resistance, QQ = less resistance), as shown below:

Estimated Breeding Values (EBVs)

Estimated breeding values (EBVs) incorporate information from the animal’s performance, pedigree, and progeny. Genomic EBVs (GEBVs) include genetics which increases accuracy. Values are often reported as an animal’s deviation (+/-) from the breed mean, which is not always 0. EBVs are calculated through the National Sheep Improvement Program (NSIP), and an example output is given below:

Selection Indices

Selection indices incorporate several traits at specific statistical weights into a single value for selection. Selection indices are generally reported often as a dollar ($) value compared to breed average. An example is given below:

EBV and GEBV Terminology Key

A large collection (may not be entirely complete) of EBVs/GEBVs are defined in the tables below: