Lower-performing animals can have a significant impact on indices such as BW and PW. Understanding the impact these animals have on your herd can help when making culling and breeding decisions, especially when reviewing which portion of your herd you’re keeping replacement calves from.
This article shows you how to use MINDA to estimate the impact keeping or removing these animals may have on your future herd.
How the concept works
The concept itself is simple. By removing animals with the lowest X, the average X of the herd increases, allowing you to estimate the potential improvement in your herd index before making any decisions.
Using PW as an example and focusing on the bottom 5%, we can work through the calculation below.
Work out the PW points gain from removing the bottom 5%
(Current Herd PW – bottom 5% average PW) x 5%
Work out the new herd PW Index
Current Herd PW + PW points gain
How do I work this out for my herd?
Step 1: Check your current herd PW
From the Dashboard select Reporting then select Custom Report. In report details report you'll find your herds PW (275).
Note: You don’t need to select a Group of animals to generate the report, you just need to see the current herd PW which can be viewed in report details.
Step 2. Use the Culling Guide to find the bottom 5% animals
From the Dashboard select Reporting then select Culling Guide from the reports available under End of Season. The Group will default to Numbered Animals.
Select the target percentage of animals you want to look at removing (i.e. 5%).
The criteria you add will be the index you want to focus on (i.e. PW).
Note: You can skip setting a PW Criteria, but make sure to set the priority as High.
Once you've added the Criteria, scroll to the bottom of the report to see the average PW of the bottom 5% group (-83). Alternatively, you can also click Print to PDF, and see the average in the downloaded PDF report.
Step 3. Work out the potential herd index increase
Now you can estimate how much your herd PW would increase if those animals were removed.
Let’s put it into the formula:
Work out the PW points gain from removing the bottom 5%
(275 – (-83)) x 5%
= 358 PW difference x 0.05 = 18 PW points gain
Work out the new herd PW Index
275 + 18 = 293 PW
So, if the bottom 5% PW animals were removed, the current Herd PW would increase from 275 to 293 PW.
Helpful Tip
If you add Calf Birth ID and Calf Fate as attributes in the Culling Guide or in a Custom Report, you can see whether any of the lower-performing animals have produced replacement calves.
Alternative option: Custom Report
If you prefer, you can also use a Custom Report instead of the Culling Guide. A Custom report displays both the current herd PW and the bottom percentage group average on the same screen, but you will need to manually calculate the number of animals in your bottom percentage group.
Total animals x percentage required
i.e. herd size is 240 and you want your bottom 5% PW
240 x 0.05 = 12 animals.
Next select the Group to generate the report (usually Numbered Animals), add attribute (i.e. PW), sort PW by lowest to highest, and select the first 12 animals.
Scroll to the bottom of the report (or print to PDF) to view the average PW, then proceed to calculate as described in Step 3.