HDI: Our Very Own Index

While at World Dairy Expo, a person working a booth for a genetics company asked David which bulls we were currently using (while I was filling out their survey to win a gift certificate).  He paused for a moment and then responded “I can’t remember, she’s my genetics person.” and then asked me which bulls we were using.  It actually resulted in a pretty good conversation about our herd goals and how we were using breeding and genetics to try to achieve them.

Background Info

I’m responsible for the majority of our sire selection (picking semen to buy) and mating (picking semen to use). Together David and I have developed goals for our herd. The short version is that we want pretty, moderate-framed cows that are above average producers, calve and breed back easily and live forever. No, I really don’t think it’s too much to ask. Except maybe the live forever part.  Anyway, we try to select bulls based on these goals and then mate each cow using a bull whose traits compliment her own.

We started out buying genetics exclusively from ABS. Our rep is a friend/family/neighbor. We buy all of our breeding supplies from him, and he takes care of filling our tank with liquid nitrogen. Each AI company puts out a book with lots of pictures and data about each of their bulls. They also have websites.  Here’s ABS list today. If you didn’t click the link, or can’t count that high, that’s 70 bulls. And that’s just their “proven” list.  It contains bulls with numbers based on data collected from their daughters. They also sell 46 genomic bulls. Genomics is a technology that analyzes a bull’s DNA to predict traits that he will transmit to his offspring.

As we expanded our AI program, we also started buying semen from Select Sires, Genex, Sierra Desert Breeders, and recently, Dairy Bulls Online. And after picking up their book at World Dairy Expo, we’re seriously considering contacting a rep from Accelerated Genetics. I didn’t count the bulls from these other companies, but the point is that we have well over 500 bulls to choose from when selecting our genetics.  This is amazing in that we have the option to be very picky, and overwhelming because that’s a lot of numbers, even for me.

The Problem with Industry Indices

How do we sort through it all? If you look at a bull’s proof (pick any one at any one of those sites), you’ll see numbers that indicate just about every trait you can imagine a cow to have (and probably a few you can’t imagine). There are multiple indices provided to help you sort through the bulls without looking at every single trait, but these indices don’t necessarily match up with our goals for our herd. They also don’t reflect the reliability numbers within the proof that distinguish proven and genomic bulls.

HDI: Our Personalized Index

Given all of this, and my affinity for numbers, I set out to develop my own index, one that considers the traits that we consider a priority. For obvious reasons, we call it the HDI (Heim Dairy Index).  Keep in mind my short description of our ideal cow above as I attempt to explain. Also, I’ll warn you now this is going to get a little technical. Here’s the overview: We look heavily at production traits (milk, fat, and protein), keep an eye on type traits (don’t want them too low, but don’t require the highest), set thresholds for health traits (SCS and DCE can’t be too high, and DPR can’t be too low), and follow guidelines for stature and strength (we generally want more moderate framed, durable cows).

To start out, I determined goal values for each trait.  Then I developed formulas that produced numbers for each trait depending on how close to the goal value the bull’s number for that trait was.  I used the bulls we have used in our herd (which are already in a spreadsheet) to adjust these formulas so that the values range from approximately -3 to +3, with most of values falling toward the middle, between -2 and 2.

This chart shows the approximate weights of each trait in our index.

I then weighted each value base on a percentage related to its priority in our breeding program.  I added the weighted numbers together and, in order to achieve some relationship with the reliability (genomics vs. proven numbers), I multiplied by the production reliability.  There are different reliability values for different traits, but production is weighted heavily in our index, so I felt that it was reasonably accurate to weight the entire index using that value.  Also, because it seems that lbs of milk drop off as reliability increases, I factored that value before weighting it and adding it in, so it is further reduced by its reliability.

How We Use HDI

We’ve been using the index for quite a while now, and I’m still tweaking it occasionally.  Probably my favorite thing is that as our goals change, or our herd changes, we can adjust the index to suit new conditions.  For example, production is a huge concern for us.  As our overall production increases, and we’ve got more lbs of milk on the maternal side of each mating, we’ll likely reduce the weight of that trait in our index, but right now it’s something we are focusing on improving.

Don’t get me wrong, we’re not blindly following some formula that I made up.  The HDI is simply another tool we can use to weed through the huge number of bulls available.  We still search through company books and websites to find bulls to calculate the index for, and we factor in other traits that aren’t in the index such as conception data.  We also look at the numbers themselves, and try to strike a balance.  Some bulls don’t meet every requirement, but each mating has two sides, and a bull may serve a purpose by excelling at traits our cows lack while having deficiencies that we think can be counteracted by the cow’s own merits. In each mating (and therefore, in sire selection) we also must consider pedigrees (the bulls and cow families the animal descends from). And we still consider price; genetics are important, but so is a budget – this is still a business.

The Results

So what did we decide?  We currently have semen from 25 bulls in our tank, 3 of which are gender selected. I’ll give you some examples.

We’re using some well-known proven bulls:

We’re using some newer proven bulls:

We’re using some genomic bulls:

Final Thoughts

If any of you actually got to this part, you’re probably as nerdy as I am.  Or you’re related to me. Regardless, whether your impressed, ashamed or indifferent, this is what happens when an engineer is your genetics person.

3 thoughts on “HDI: Our Very Own Index

  1. I like it! Three cheers for nerds. I’m in a similar scenario with the sheep EBVs, where the standard indexes are designed around barn lambing, grain systems, and they aren’t ideal for what’s a priority in a grass system.

    In sheep, we don’t have the ability to shop for AI sires, so EBVs are used more for selection of replacement ewes, or picking a sire from a particular farm, or at a sale. I am still hand-sorting through 100-some scores to decide my keeper ewes: I do a “bubble sort” where I compare two, pick the top, then compare her to the next in the list, etc, until I go thru the list.That winner “bubbles up” to the top, and I do it again for the next. I do it in batches. But I’m starting to get too many to be able to do it manually, it takes a long time (and the right frame of mind). (And we don’t have nearly as many metrics as you do!)

    I may try to see if I can create my own index, what a great idea. That would at least help me rank ewes in “chunks” across the bell curve, to more quickly ID the top and bottom ones, which is really want I want to see the most.

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