Ovine Observer

New breeding values to target more live lambs

Emma McCrabb, Clara Bradford and Peta Bradley
Meat and Livestock Australia
Author Correspondence:


Number of Lambs Born (NLB) and Number of Lambs Weaned (NLW) have been the primary Australian Sheep Breeding Values (ASBVs) used to improve reproduction. While NLB and NLW have been useful selection traits to improve reproduction, they can mask the true extent of lamb losses. As NLW targets net reproduction, breeders are not able to target the specific stage of the reproductive cycle they wish to improve. The Animal Genetics and Breeding Unit based at the University of New England and Sheep Genetics have developed new reproduction research breeding values (RBVs) that allow producers to target different stages within the reproduction cycle. The new RBVs were released for LAMBPLAN (maternal breeds) in 2019 and for MERINOSELECT in 2020.

How was the data collected?

Data is required to estimate the heritability and correlations for new traits. As such, to enable genomic prediction for traits, a reference population where animals are genotyped and phenotyped (measured) for the trait of interest needs to be established. The MLA Resource Flock captures phenotypes and genotypes for a range of traits including the difficult to measure carcase and eating quality information. However, the daughters from the industry sires used in the Resource Flock are not retained and recorded for reproduction. To capture records and develop a reference population for the new reproduction component traits, breeders were engaged as satellite flocks to the MLA Resource Flock. Key steps in this process included:

  • Short-listing Merino and maternal flocks that had a minimum of three years of historical reproduction records for the current Number of Lambs (NLW) analysis
  • Contacting breeders to be involved as a satellite flock
  • As part of the satellite flock breeders were required to:
    • genotype all their maiden ewes
    • record these ewes for all on-farm reproduction traits
    • retain all ewes for two joinings, including dry ewes and ewes that lambed and lost

There were four drops of ewes from maternal flocks included as part of this project. Breeds sampled included Border Leicesters, Coopworths, Maternal Composites and Corriedale, with more than 28 breeders engaged across five states as part of the research dataset. Once the maternal RBVs had been established, the process was repeated for Merino breeders, engaging 16 flocks from four states.

Since the release of the Maternal RBVs in 2019 there has been an increase in the number of records for all traits across industry flocks, partially as a result of the release of the RBVs. The increase in reproduction data has already allowed the re-estimation of genetic parameters in 2020 for the Maternal RBVs. 

What are the new reproduction RBVs?

Table 1 summarises the traits reported as part of the new reproduction RBV analyses including the unit in which the breeding values are reported and the trait description.

New reproduction RBV traits
Table 1 A summary of the new reproduction RBV traits

These traits are reported as an adult and/or yearling traits.

YERA is not currently available for the MERINOSELECT analysis as there were not enough records in Merinos to accurately estimate the genetic parameters.

How do you use the new RBVs?

These RBVs are reported alongside ASBV traits on the Sheep Genetics website. They are highlighted in purple to distinguish them from routine ASBVs and to define them as being in their research phase. As more data is recorded, it is intended that these RBVs will be transitioned to ASBVs within three years.

Percentile band tables are available on the website to give producers an idea of industry benchmarks for these RBVs. These aim to provide context around the values to make them more meaningful to producers. This allows breeders to include RBV traits in their SMART breeding objective.

These RBVs can be included in a breeding objective by:

  1. Using the percentile band tables to identify where the flock currently sits
  2. Using this table to determine a direction of gain and target value to be included in your breeding objective

Where can I find more information?

The Research Breeding values (RBVs) are delivered by Sheep Genetics, a business unit of MLA. Sheep Genetics have support staff that are able to assist in any enquiries related to the new breeding values or genetic evaluations in general. Alternatively, there are also fact sheets explaining these on the Sheep Genetics website.

Sheep genetics contact:
P: 02 8055 1818

Supplementary to Sheep Genetics, MLA has also developed a genetics hub.  An online website that has a range of tools and resources for commercial producers. On the hub cattle and sheep producers can find:

  • ‘Pick the performer’ graphics demonstrating the value of investing in quality breeding values
  • Videos of commercial producers demonstrating how breeding values have helped increase profits in their herds and flocks
  • How-to animated tutorials outlining the basics of breeding values, setting a breeding objective, indexes and picking a high-performing sire
  • Videos explaining the different traits available for cattle and sheep
  • Contacts and other resources for further support.<--pagebreak-->