As a consultant, I've had a recent rash of clients asking me to build geneflow models. These simulate genetic improvement in a population - whether that's a big population (an entire national herd, for example) or a smaller population (an individual farmer's own herd). The main purpose of this is to help someone understand: what is the financial benefit of implementing this technology?
A few technologies have been strange and new, like procedures pioneered for human fertility being considered for dairy cattle reproduction. Others have been focused on management changes; things like implementing genomic testing for heifers or combining sexed semen and dairy beef. Farmers are often good at forecasting costs - but how do you build in the cumulative benefits of genetic gain?
This article is going to be solidly nerdy, so I'd like to apologise to my more socially well-adjusted readers. If the words 'simulation' and 'parameter' bore the heck out of you, then I'd stop reading and go and get some healthy sunlight. If you're interested in building models to make management decisions, however, then hopefully this article can give you a few ideas.
Firstly, we'll assume that you're using Excel - nothing too fancy. In the first tab, let's start with building out the model parameters - the numbers that you'll use for your calculations. At a minimum, you're going to want reproductive parameters like the average number of inseminations per cow, your three-week submission rate, conception rate, the expected heifer calf ratio (if you're thinking about sexed semen) and replacement rate. A good place to find these numbers would be your Fertility Focus Report (especially if you have access to Data Vat) or your herd recording software.
You'll also need herd and genetic parameters, like herd size, the average Balanced Performance Index (BPI) of your cows, the average BPI of sires you're selecting and calf mortality rates. These parameters are best informed using actual farm data but sometimes you might have to substitute industry averages or sensible 'guesstimates' where possible.
Finally, you'll need some economic parameters, like the cost of artificial insemination (or whatever technology you're using) and/or any modifiers to your conception rate. Consider things like the cost of the technician and consumables, as well as your time - something which often gets undervalued. Finally, if you're considering things like sexed or beef semen, it might be helpful to include the cost of a male versus female calf or a beef calf versus a heifer replacement.
To put all these parameters together, let's simulate what one year of genetic gain might look like. In a new tab, set a column of the spreadsheet as 'Year 1', which contains your starting herd size. We'll use this to calculate the average BPI of the heifers entering next year's herd, which is made up of half of your average sire BPI plus half of your average herd BPI.
In 'Year 2', you include this cohort of first-calving heifers and their increased genetic merit contributes to the herd average. You could also consider industry-level genetic gain by including the annual change in your sire team BPI, which will be contributing half of the genetics which make up your replacement heifer average. This rolling genetic gain continues up until the final year of your forecast.
Build in economic parameters
To build in your economic parameters, you'd calculate the number of straws purchased (based on your herd size, conception rate, and number of rounds of AI) and use this to figure out your costs. It's rough, but this first model should represent the 'base' or status quo that you're comparing.
It's important to get this reasonably correct - do the numbers match your actual AI costs? Having a good understanding of your business should help you tweak the base model to be a better reflection of reality.
Once you're happy with the base model, you can then copy and paste it into a new tab and start building in the components that match the new scenario you're considering. This might include increasing the average BPI of incoming heifers if you're using genomic selection or tweaking the heifer calf ratio for sexed semen. It's generally a good idea to consider a risk premium as well - how much more profit would you need to balance out the risk of failure? How high do you think that risk is? And how much more profit is needed, considering the challenges of adopting a new management practice?
If you've come this far and are thinking, 'this sounds like a lot of work' or 'I want something like this for a different management area', there are heaps of different calculators already available on the Dairy Australia website.
Tools like this help you explore the financial consequences of management decisions - although of course, they don't incorporate other important factors, like how excited you might be about the technology and how much they'll take up of your time.
*Ee Cheng Ooi is a cattle veterinarian and livestock systems consultant at AbacusBio. All comments and information in this article are intended to be of general nature only. Please consult the farm's vet for advice, protocols and/or treatments that are tailored to the herd's particular needs. Comments and feedback are welcome at ecooi.vet@gmail.com.
