Demonstrating heritability of footrot resistance at the central progeny test (CPT)

The two key objectives of the FeetFirst project are:

  • To develop a genomic breeding value (gBV) that will reliably predict genetic resistance to footrot in fine wool sheep.
  • To establish the genetic correlations between footrot resistance and other important traits, enabling breeders to incorporate selection for footrot resistance into a balanced breeding objective.

The data being generated by the fine-wool central progeny test (CPT) is crucial to achieving both of these objectives.

We recently collected foot score data for the progeny from the 2014 CPT (following a footrot challenge in the wether progeny).  The sire averages ranged from 2.50 to 3.43 (on a 0 to 4 scale), showing the variation between sires in their genetic resistance.

The 2014 CPT sires included seven of the top-performing rams from the ram footrot challenge trial undertaken in 2013-14.  These seven rams ranked 2nd, 5th, 6th, 11th, 14th, 19th and 22nd for footrot resistance out of the 41 sires in the 2014 CPT, demonstrating the heritability of genetic resistance.

Visit the central progeny test page for further information about the fine-wool CPT managed by NZM.

 

Doing things right at Omarama Station

NZM would like to congratulate Richard and Annabelle Subtil of Omarama Station for their success in the Ballance Farm Environment Awards.  The Subtils and their stock managers, John and Kirsten Mathias, are putting into practice the principles that underpin NZM’s production science programme. They are committed to improving each aspect of their farming operation – from genetics to nutrition, to their on-farm systems.

In this video we speak with Richard and Annabelle about the steps they are taking to lift performance and profitability at Omarama Station - from breeding and feeding, to using new technology to track their progress. Click here for more information.

Combining EBVs with EID

Lewis Frost (genetics consultant to AllFlex) and NZM’s Production Science Manager, Dr Mark Ferguson, were guest speakers at the Omarama Station field day held on 6 November 2015. They spoke about how estimated breeding values (EBVs) can be combined with electronic identification (EID) to build a high performance Merino system.

The focus at Omarama Station is on selecting the right replacements (both rams and ewes), and managing their progeny to help them reach their genetic potential. This means selecting their rams based on both visual appraisal and EBVs for the traits that drive profit, then tracking how those genetics translate into ewe flock performance, using EID. 

Already the Subtils are finding that EID can help them separate the passengers from the performers. For more information, click here

Condition scoring

Monitoring the body condition of your ewe flock at key times throughout the breeding cycle – weaning, mating, scanning, set stocking and tailing – is a quick and effective way to ensure that the right ewes are getting the additional feed that they need. 

In this video, NZM’s Production Science Manager Dr Mark Ferguson shows how condition scoring is done. Click here for more information.

Lamb Survival Study

In collaboration with Murdoch University in Western Australia, NZM is studying how reducing mob size at lambing can lift lamb survival and pay dividends at weaning.

Initial results show that the difference, in twin-bearing ewes, between a mob size of 250 ewes and a mob size of 100 ewes is 16 extra lambs weaned per 100 ewes!  To put this in perspective, the average condition score of the ewes would need to be lifted by about 0.5 of a condition score (e.g. from 2.5 to 3.0) to achieve a similar result. 

We are collecting lambing data from across New Zealand and Australia, as well as undertaking mob size trials on selected properties. Thank you to those who have already contributed their lambing results. If you would like to be part of the study, contact the NZM Production Science Team.

Genetics of footrot and a FeetFirst update

In these two videos, NZM’s Production Science Manger, Dr Mark Ferguson, speaks about the genetics of footrot and why we are developing a new genetic test to build more resistance to the disease in New Zealand's fine wool sheep, as well as giving an update on the FeetFirst project (including the development of a genomic breeding value (gBV) for footrot resistance and the expanded central progeny test).

Genetics of footrot

There are three key things that need to come together in order for a footrot outbreak to occur on a farm – there needs to be a host (and, unfortunately, our fine wool sheep are one of the more susceptible hosts in the sheep world), the bacteria that causes footrot (Dichelobacter nodosus), and the right environmental conditions (sufficient warmth and moisture for the bacteria to multiply).

Both the environment and the presence of the bacteria are very difficult to control.  However, through breeding, we are able to select sheep (the potential host) that are less susceptible to footrot infection.  This is why the aim of the FeetFirst project is to build a new genetic test that will enable us to shift the fine-wool sheep population over time to be more resistant to the disease.

In terms of resistance to footrot, there are many attributes that contribute – from the the sex and age of the animal, to the breed of the sheep and the different genetics within that breed, to the interaction between the sheep’s genes and its environment.

Many genes across the sheep genome are associated with footrot resistance.  Therefore, looking at a single gene marker will only ever give us a limited picture of an animal’s genetic resistance to footrot.  

The new genetic test will be in the form of a genomic based breeding value for footrot resistance.  The test looks at the whole genome and tells us which sets of genes contribute more to resistance (or susceptibility).  

The focus is not on finding an individual animal that is resistant to the disease; it is about moving the whole fine-wool sheep population to a state that is more resistant.

This does not mean every animal within that population will be resistant to footrot – it simply means that, on average, the population will be more resistant than it is currently.


FeetFirst update - July 2015

We would like to acknowledge the great support from the industry for the FeetFirst project – our growers who contributed through DNA sampling of their sheep, all the vets who assisted with sampling, and our co-funders Merino Inc. and the Ministry for Primary Industries (through the New Zealand Sheep Industry Transformation (NZSTX) project).

We have collected DNA samples from several thousand sheep on commercial farms – both sheep that did and did not get footrot under a challenge – and analysed the DNA to get a genotype from each animal.

This first dataset allowed us to make an initial prediction of the heritability of footrot resistance in fine-wool sheep of between 20 and 30 percent.  That is, approximately 20 to 30 percent of the variation between individuals is explained by genes.  This represents an opportunity for New Zealand’s fine-wool sheep industry to make some significant gains.

A second dataset, which consisted of sire genotypes only – it was unknown whether the sires were resistant to footrot or not – was compared to the first dataset and we were able to predict the likelihood of those sires (and their progeny) getting footrot (see graph below).

The third dataset we have is the central progeny test data.  A large number of progeny have been bred from a range of industry sires nominated by the stud sector.  We have challenged the male progeny with footrot and scored each of the individual feet.  That information has been utilised to validate the initial dataset and again we found that the predicted heritability of genetic resistance to footrot is between 20 to 30 percent in fine-wool sheep.

The results show a big variation in the genetics out there for resistance to footrot.  Our aim is to help the industry identify the animals that are more resistant to the disease.  This will provide ram buyers with greater access to rams that are more resistant and, over time, make their own flocks more resistant to footrot.