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Heifer genomics at a glance - highlights



Ever wondered what heifer genomics is and how you could implement it into your business? A large number of participants logged on last week Tuesday for the first Genomics at a Glance session to find out just that. This hour session unpacked the basics of genomic testing allowing participants to gain a better understanding of the technology, how it works, the most practical and beneficial ways to implement it in your operation, how to get started, and what support is available.

The buzz and curiosity for how genomics works and how it can benefit a dairy farm business was infectious. The night saw a large number of questions flooding in, which included:

Q: Is genomics only for purebred Holstein and Jersey herds?

A: While genomic testing first started in Holstein and Jersey animals and their crosses, it has been extended in 2021 to include red breeds and their crosses. These three breeds cover 95% of the Australian dairy cow population. Purebred or crossbred animals sired by a Holstein, Jersey, Aussie Red, Ayrshire or Illawarra bull can be genomically tested. There isn’t enough domestic data to calculate genomic values for Brown Swiss and Guernsey but you can contact DataGene for information on international platforms that cover these breeds.

Q: I have just bought some heifers and am wondering if I can still genomic test them, even though I know nothing about their pedigree?

A: Yes, you can still genomic test these heifers. The reliability of the Australian Breeding Values (ABVs) generated will be lower than if the pedigree was known. If you have no sire and no dam then the reliability will be about 10% lower but you will still have a greater understanding compared to when you started. If the sire and/or dam have a DNA sample on file then we can 'discover' the sire and/or dam. This also helps to compile the breed.

Q: How do I store samples collected using TSUs and how long do the samples remain stable prior to shipping to the laboratory?

A: A DNA sample stored in a TSU (tissue sampling unit) is quite stable if kept in a cool, dark location. It can be stored for a year, but you will likely want to send it sooner to get your results back and make meaningful decisions based on the data.

Q: What about using international evaluation systems for confinement cows or TMR fed or feedlot cows rather than BPI which seems to be more targeted to pasture based?

A: The Balanced Performance Index is the only selection that has been validated to work in Australia under the five different feeding systems employed by Australian farmers, including partial and total mixed rations (PMR and TMR). Dr John Morton looked at the interaction between feeding systems and in a project called ‘Feeding the Genes’. These interactions were studied using data from 505 commercial Australian dairy herds with a wide range of feeding systems. Data from 240,000 lactations and almost 118,000 cows were used. The results show that in all feeding systems, the daughters of higher BPI sires produce more milk solids than daughters of lower BPI sires. For more information on this work, see the Feeding the Genes factsheet here. Most genomic service providers offer the option to select an Australian or international evaluation system.

Figure 1. Impact of sire BPI on milk solids yield (Feeding the Genes).

Kg milk solids/cow/305d lactation for every 50 unit increase in sire BPI

 

Holstein

Jersey

Mod-high bail

6.1

5.9

PMR

4.8

6.0

Hybrid

8.0

n/a

TMR

11.6

n/a

Q: Do I have to use the BPI? Can I make a custom index?

A: Australia uses Australian Breeding Values (ABVs) to express the genetic merit of dairy cattle for a given trait. ABVs are available for 40 traits including various production, type (conformation), health and management traits. Australia also has two breeding indices, the Balanced Performance Index (BPI) and Health Weighted Index (HWI). Both these indices account for the traits that affect a cow’s lifetime contribution to the dairy business: production, health and fertility, longevity, workability, type and feed efficiency. The difference is in the amount of emphasis given to specific traits. Most dairy farmers want to breed to improve more than one trait at once, so Breeding Indices take the hard work out of breeding for multiple traits by combining them in a single value. They are based on rigorous scientific analysis and industry priorities. However, most genomic testing platforms, including DataVat allow you to place additional emphasis on traits that may be of particular importance to your business (e.g. fertility, heat tolerance).

Beyond the introductory Genomics at a Glance session there are two additional genomics extension offerings, allowing participants to enhance their knowledge and practical skills in using genomics.

Firstly, Genomics in Practice, a half day on-farm workshop designed to unpack the practical implementation and utilisation of genomics in a herd. You will cover sampling using TSUs, assessing and interpreting results and making decisions from the results.

Secondly, Genomics in Action, an online national discussion group is intended for those already testing and wanting to extract more value from their results. There will be the inclusion of both national and international speakers to enable a variety of shared learning experiences.

To find out more about genomics visit dairyaustralia.com.au/genomics. If you are interested in any of the available extension activities, please get in contact with your local RDP or email Kristen Davis on kristen.davis@gippsdairy.com.au


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