A Discussion About EPDs

[Herefords.US]

That's an easy one, neither! If basing it strictly on EPDs and the difference #1 is too big and #2 is too small

dun

:lol: I always hate it when someone gives an answer totally different from the choices available! :roll:

OK! My answer, given that information, is that I would choose Cow #2 because I would "bet" that the 10% positive difference in weaning weight(over 3 calves) indicates a cow that ACTUALLY produces a heavier calf at weaning. This difference eventually would be reflected in the Milk and Growth EPDs, although probably never fully realized.

But I'm still not fully inebriated by the EPD kool-aid, like some are!

I e-mailed Dr. Dan Moser and posed this same question to him. I received a very nice reply, as well as the predicted answer from someone who is "sold" on EPDs.

But I found his reasoning sound and it gives a different perspective of one who is convinced that EPDs are the best measure of a cow's potential.

Here is his reply:

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George:

Thanks for your message. You've posed an interesting question. Here's your question again and my response:

GW> Given: two 5 year old females in the same 100 cow herd that are essentially equal in phenotype and size:

Cow #1 EPDs WW +50 YW +90

Cow #2 EPDs WW +25 YW +50

All other EPD data is essentially the same and they were bred to the same bull each year (three different bulls). However Cow #1 has weaned 3 calves at 95% avg. WW ratio (all below avg) and Cow #2 has weaned 3 calves at 105% avg. WW ratio (all above average).

Their calves have been similar phenotypically as well. Which cow would you choose to purchase for your herd and why?



DM> I would purchase Cow #1, assuming they were priced the same, and also assuming my goal is to increase growth in future generations of my herd. I also assume that the calves' weaning weights have been submitted to AHA for use in calculating the cows' current EPDs. However, I wouldn't pay a lot more for Cow #1 than I would for Cow #2.

Despite Cow #2 outperforming Cow #1 on their first three calves, Cow #1 is still the better bet to wean the heavier calf next time (assuming milk is the same). The ratios (as well as the pedigrees of the cows) were used in calculating the current EPDs, and the EPD is the best estimate at the
current time of each cow's growth genetics. Producers often assume that since Cow #2 has been the most productive so far, that will always be the case, but that's not necessarily true. With only three calves, she's far from proven, and she'll never have enough calves to really prove herself the
way a bull can. The randomness of genetics allows that Cow #2 might have passed on a better than average sample of her genes just by chance, and that Cow #1 may have passed on a poorer than average sample, but that should correct itself over time, luck tends to average out. I would expect Cow #1
not only to out perform Cow #2 on the next calf, but by large enough of a margin after three more calves such that Cow #1 would have a higher ratio on six calves, assuming the cows are mated to the same bull each year. I expect her to more than make up the difference, but if the differences we see right now continue, Cow #2 will ultimately have higher EPDs, if both
have enough calves.

If the cows had been mated to different bulls, then the ratios are even less useful, because they don't account for selective mating the way EPDs do.

My point is, that while the EPDs aren't a perfectly accurate estimate of acow's genetic potential, they're better than anything else we can use in selection. As I wrote to Tom, there's no good way to predict a cow's genetic merit to a high degree of accuracy, but EPDs are always better than
ratios or actual weights, because the EPDs use the weights plus the pedigree, with an optimal weighting of that information.

Even though Hereford is primarily a maternal breed, by far the most genetic improvement is made through sire selection, not heifer selection, cow culling, or even buying cows from other operations. Rather than buy cows, the best investment would be to keep the cows you have, and buy semen on proven bulls with the absolute best balanced EPDs or favorable index values,
unless you can buy cows with EPDs far superior to what you have, at a reasonable price. In just one or two generations, you'll make more progress than you ever could selecting females.

<remainder = unrelated information = deleted>

Best regards,

Dan

Dan W. Moser
Dept. of Animal Sciences and Industry
Kansas State University
785.532.2459 [email protected]

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I also sent him a link to this thread and invited him to join in, if he chose(dared?) to!

George

 

[KNERSIE]

George,

I am like dun on this one, I would choose neither of the two, but my reasoning is somewhat different.

I prefer a WW of around breed average or slightly above as I don't want to be left behind when it comes to growth up to weaning age. When it comes to the YW I prefer slightly below breed average, but definately don't want any animal with a YW EPD significantly higher than the breed average. My reasoning behind this lunacy is that I want to breed early maturing animals that grow quickly without increasing frame size or rather without the risk of frame creep.

With the EBVs we use we also have a 540 day weight, I take the spread in the growth into account more than the actual numbers, I don't want the jump from ww-yw-540day weight to be too drastic as this is often an indication of later maturity.

In an ideal world my EBV spread for growth would be something like this.

average BW, slightly above average WW, average YW, below average 540d weight.

But after all this is said and done, EBVs play second fiddle to my eye and the phenotype I desire for my conditions. I have seen too often that less ideal animals with very good EBVs perform poorer than more ideal types with very ordinary EBVs.

 

[ollie?]

I'd buy the one with the most volume, best feet, soundest udder, and the easiest on the eye. Save all that paper to start fires in the winter.

 

[DOC HARRIS]

Well, I must say - this has been a fascinating thread! It covers EPD's and, incidentally, a fact that I have hammered on for months now - - that is - - that EPD selectivity and PHENOTYPE observation MUST BE CONSIDERED in the same breath and at the same time! To NOT do so would be as absurd as attempting to empty a bathtub with an eyedropper. . .or directing your breeding program using only cows - or only bulls! It takes two to tango, and Genotype and Phenotype go together. We can quarrel about EPD's until the cows refuse to come home, but the evidence refutes the validity of putting all your eggs in the EPD basket to the EXclusion of using your TRAINED (I said TRAINED) observation skills of understanding Phenotype. And the converse is true using Phenotype only and ignoring the selective use of EPD's!

Dan Moser's reply to George covered the spectrum of more than just EPD's. It took into consideration different breeds, different types of beef cattle (Maternal and Terminal), and, perhaps the most significant factor of this senseless arguement - the randomness of genetic inheritance factors, which can never be predicted with any degree of accuracy.

The best that can be expected in animal breeding technics is to be able to endeavor to BALANCE the use of EPD's and Phenotype, and verify the results with DNA technology. It might discourage imprudent and shortsighted breeding practices.

Beef Cattle breeding encompasses careful balancing between several protocols - and a lot of good management technics .

DOC HARRIS