Questions and answers for the Agri-Tech Catalyst Texel Society-SRUC project: Using genomic technologies to reduce mastitis in meat sheep.
– Using Genomic Technology to Reduce Mastitis in Meat Sheep
Genomics is the study of genes. In sheep breeding, we use genomics to understand which genes are influencing certain traits. We do this by using SNPs to detect tiny variations in DNA sequences. It is these tiny variations that might explain which particular sequence of DNA is responsible for a trait of interest.
Genomics is an incredible tool that has the potential to change the nature of sheep breeding. Genomic breeding values are a much more informed way of predicting the genetic merit of individual sheep as you are directly analysing whether that animal carries a known gene or set of genes which have been found to influence a particular trait. The areas where genomics will be of most use will be in the traits which are hardest to measure, such as disease resistance, meat quality or traits which are sex linked such as milk yield. We must, however, continue to take measurements of the existing traits as well as start measuring new traits, especially those involving disease.
This project will undertake a genome-wide association to identify significant SNPs for resistance to mastitis in pure and crossbred Texel sheep using recently-available high density (700,000) and low density (1000) Single Nucleotide Polymorphism (‘SNP’) beadchips. These are like using a gene road map to help researchers compare an individual DNA to the parts of the genome mapped on the beadchip.
Mastitis is a hugely costly disease within the sheep industry. It is estimated that 5% of all ewes in the UK suffer from acute mastitis, and a further 20-30% suffer from sub-acute mastitis. It is understood that sheep have a genetic ability to resist the disease, and importantly this genetic ability is moderately heritable which makes breeding for mastitis resistance more than achievable. This project is a major step towards offering breeders a tool that can assist them when making breeding decisions for improved mastitis resistance. A simple DNA test will reveal which animals are more susceptible and which ones are more resistant.
The British Texel Sheep Society is the first sheep breed society to begin developing genomic breeding tools. This requires a large effort to establish accurate genomic EBVs (GEBVs) within a breed. However, the BTSS prides itself on being an innovative and progressive organisation. Furthermore, we are in a very fortunate position to have a relatively large well recorded population and the additional resources at hand to carry out such research and produce useful GEBVs.
27% of all rams used in the UK are Texels and 12% of all breeding ewes in the UK have been sired by a Texel ram. This shows that the Texel breed is very much ingrained into our sheep industry, and although it is classed as a terminal breed, it is also a common crossing breed to produce breeding females. Therefore, the potential influence this research could have on the whole industry is vast.
The project involves recruiting 25 large performance recorded Texel flocks. These flocks need to be as large as possible, as well as having a significant impact on the Texel breed in terms of producing breeding stock. This means that the genetics in that flock will be relevant to the rest of the breed.
Each flock will then be visited on a minimum of two occasions; once at four weeks post lambing, and once at weaning time. All the ewes will then have milk samples taken, have their udders scored for confirmation and teat placement and have nasal swabs taken (for DNA analysis). In addition we plan to take foot scores from all ewes, as this is a valuable opportunity to gain an understanding behind the resistance of footrot, and hopefully it will help us to develop genomic breeding values for footrot alongside the mastitis breeding values.
The largest part of what we need from you is your cooperation. This is a large project that hinges on the collection of reliable and accurate data. The technical manager of the project will come out to your farm on a suitable date (for both you and us) and will carry out all of the measurements. Carrying out the measurements may take some time and could possibly take all day. You will neither have to pay for anything or supply any equipment apart from ensuring the sheep are in a handling area for us to be able to catch, handle and carry out the measurements on each sheep. Ideally if you have labour available on the day to assist that would be of benefit.
There will be an element of organisation to ensure that you are prepared before we come out. Then we will come to your farm on two occasions which could take up to all day to complete the testing on both occasions. But the exact time will obviously depend on your flock size. This would happen over two visits per season and over two lambing seasons in 2015 and 2016.
All the data we collect will be treated with confidentiality. We will not share any individual farm data with anyone apart from SRUC (who are carrying out the academic research) who will also treat your data with complete confidentiality. Any published findings will not reveal data from individual or named farms.
At the end of the project, we aim to give you GEBVs for resistance to mastitis. You will be the first farms to have access this tool. Potentially, you will be able to DNA test rams for resistance to mastitis. This will then give you confidence in using rams that will produce ewes that are less susceptible to mastitis.
In addition, we will be able to give you benchmarking data for the level of mastitis and foot problems you get on your farm in comparison to the other test farms on the program. This is a useful tool for you to use at your disposal. Again, we will not share with you the levels of mastitis and foot problems from named farms, just as we will not name your flock when sharing your data with other farms.
If you continue to use the GEBVs, and select highly resistant animals then over time you will be able to reduce instances of mastitis in your ewes. This should be a massive selling point for your flock, especially when selling rams for breeding female replacements.
We believe that our breed must be continuously evolving in order to beat the challenges in today’s sheep industry. It is identified that mastitis is a problem within the industry, and this project is the BTTS’ response to combatting the disease using the latest technology available. Having GEBVs for mastitis and other traits (especially health traits) will add significant value to the Texel breed and, with your valuable contribution to the project, it will ensure that Texels remain the most popular sire used in the UK.
Because of genetic variation, only pure Texels and sheep with high proportions of Texel in them will be able to use the GEBV for mastitis. In order to safe guard the Society and its members, the Society will hold the key to the GEBVs and only Society members will be able to exclusively use the new GEBV for mastitis having tested specific animals.
We understand that there is an element of risk of disease spread by coming onto your farm, especially in the first visit which is so soon after lambing. When we come to your farm we will bring clean, disinfected clothing and equipment. When handling udders and feet, we shall wear latex gloves. When we leave we will then clean and disinfect clothing and equipment again.