Genomics is increasingly becoming another decision making tool for cattle producers.
There has been incredible progress and promising adoption rates of genetic evaluation tools, their resulting systems and technologies, over the past decades. Many however, still see the industry in its infancy, as ground-breaking discoveries and advancements unfold in real time.
Regardless of whether you’re an early or recent adopter, or following expert advice, it pays to have a good understanding of their strengths and limitations, and the nuances of heritability, so as to maximise your return on investment and manage expectations.
A quick lesson in heritability and quantitative genetics
The majority of significant livestock traits are not because of a single gene, but are continuous (or quantitative) in nature, determined by numerous genes and the environment in which they are expressed.
Heritability is the extent to which phenotypic (observable/measurable) variance can be explained by the genetic variance whereas broad-sense heritability is the degree to which variation in a trait is genetically determined.
An allele is one of multiple versions of the same gene in an animals DNA. Quantitative traits are continuously variable, arising from a combination of enviromental influence and the positioning of the contributing genes (or alleles) within the DNA. Further adding to the incidence of variation is the phenomenon referred to as epistasis, where the effect of a gene is dependent on the presence of others in their genetic background; the outcome is nonlinear and has profound consequences for the evolvability of phenotypic traits. Phenotypic value (P) is the measurement of an individual animal for a particular trait. It is composed of a genotypic value (C) and a deviation from G due to the enviromental influence (E). This can be summarised as P= G+E.
It is because of this that genetic tools can fluctuate in their predictive power on a case by case basis and are recommended to be used in conjunction with EBVs and visual appraisals.
Why should I use a genomic testing service?
Genomic testing services such as those offered by TEC, allow you to test commercial cattle for their true genetic merit and rank them within your herd. This enables you to keep the genetically superior individuals, refine your selection and maximise genetic gain in the traits that are most important to your herd production goals and breeding objectives.
Measure and manage your herd
Recording and understanding the genetic potential of individual cattle within a commercial herd allows you to rank animals against each other on a range of production traits.
Selecting traits on performance figures has primarily been the main driver of genetic improvement, but we are now able to test their commercial offspring and identify the individuals that will achieve a herd with complete genetic superiority.
One type of genetic testing offered by Igenity provides 16 traits, including calving ease, milk production, growth rate, marbling, fat depth and tenderness.
How many cattle do I need to test and at what age?
While you can test as many animals as you like, a minimum group of 10 is recommended to allow for adequate comparison and selection. The specific requirements and sampling plan for each enterprise will vary, which can be discussed during a consultation where required.
Catlle can be any age, although it’s recommended you test young cattle at marking or weaning to minimise additional handling and allow for exclusion of cattle which are structurally undesirable prior to testing. Testing at an early age also allows selection decisions to be made earlier and management tailored to the replacement individuals if needed.
What type of cattle are eligible to be tested?
Any combination of the following are eligible for testing:
- Red angus
- Maine Anjou.
The benefits of genomic testing cattle
- measure genomic potential of commercial cross bred and pure-bred cattle
- increase the accuracy of replacement heifer selection to match breeding goals and target market
- create custom selection indexes to target specific market end points and herd production goals
- use known genetic merit of your cow herd to assist in bull purchasing
- increase accuracy of commercial in-herd bull selection
- assist with marketing of cattle by providing greater information to buyers.
Article written by Pip Houghton, TEC Livestock Production Consultant.