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Post by strojanherefords on Oct 22, 2013 17:08:15 GMT -6
Given that EPDs are gospel to many in the beef business, I find it bothersome that information on the mechanics of EPD's is not readily available. Personally, I believe that EPD's are gamed by those who know the secret sauce. It would be great, someone could post an explanation of the formulas used in calculating EPDs so we can have a discussion about there advantages and disadvantages.
After all the Gipper said to the evil empire "doveryai no proveryai"
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Post by George on Oct 22, 2013 20:09:06 GMT -6
Given that EPDs are gospel to many in the beef business, I find it bothersome that information on the mechanics of EPD's is not readily available. Personally, I believe that EPD's are gamed by those who know the secret sauce. It would be great, someone could post an explanation of the formulas used in calculating EPDs so we can have a discussion about there advantages and disadvantages. After all the Gipper said to the evil empire "doveryai no proveryai" EPDs are a huge matrix solved by a super computer. They can definitely be "gamed". That was proven with P606 among others. Always look at the accuracy number. Anything less than .6 in accuracy and those numbers should be looked at with skepticism. .6 to .8 accuracy begin to have some reliability and EPDs with .8 accuracy and higher are some that you can have some faith in
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talin
Yearling
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Post by talin on Oct 23, 2013 9:04:03 GMT -6
I tried to dig into this also but have decided that with the GE EPD's that it may not be that useful to try to reverse engineer the equations.
The gaming I see a lot of is the selective use of GE EPD's even in the last 6 months patterns are emerging 4R are improved with GE EPD's and 20X influenced not so much.
I am looking forward to going to KC and see what I can gleam always what is not said is probably more enlightening.
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Post by rockmillsherefords on Oct 23, 2013 17:58:28 GMT -6
Actually its just a couple Aussie’s hanging out in some guy’s basement. AHA mails the them data as they get it, they add or subtract for age of dam, add the the numbers together, divide by number of animals to get the average and boom! their done. That’s why they can only do updates twice a year, that stuff takes time.
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Post by strojanherefords on Oct 23, 2013 18:42:55 GMT -6
So 200 plus views, three replies and nobody knows where to find an explanation of the Australian's methodology. I would like to understand the program better before expressing my issues. But seeing that no explanation is readily forthcoming, I think it is time. My biggest issue with epds is that they are used to compare calves born to bulls that are not used in multiple sire groupings.
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Post by rockmillsherefords on Oct 23, 2013 19:10:02 GMT -6
George is right, it’s a pretty complicated formula these days, sometime around the mid to late eighties they published at least part of the formula they used in a Hereford World or whatever it was called then, I don’t keep copies so I can’t look it up. A few years ago they upgraded the program to include such things as “age slicing” along with some other (at that time ) high tech improvements that were supposed to make the calculations more reliable. They also posted an article on this in the hereford world, don’t remember when that was though, maybe around 2002/3.
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Post by Deleted on Oct 23, 2013 19:39:12 GMT -6
I agree with George, its a complicated formula. It includes adjustments for many factors. I really think the only way epds can be gamed is if the producer sends in false data. And no formula will prevent that.
One thing that seems different now than years ago, is it seems like the animals own performance data is more heavily weighted than when epds first came out. Although it could have something to do with how they are updated as soon as the performance data is sent in instead of only every 6 months. With todays method, if you send in performance on a calf that has a over 100 ratio birth weight, it will immediately increase its weaning and yearling weight epds above its parent's average. A lot of the trait leaders, that didn't come from high epd parents, have high individual rotios.
As for GE-EPDs, they have become not much more than a function of the similarity of the subject animal's genes as compared to the proven bulls for each individual trait. Just a reinforcement of the trait leaders' genes.
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Post by bookcliff on Oct 23, 2013 20:03:21 GMT -6
I tried to dig into this also but have decided that with the GE EPD's that it may not be that useful to try to reverse engineer the equations. The gaming I see a lot of is the selective use of GE EPD's even in the last 6 months patterns are emerging 4R are improved with GE EPD's and 20X influenced not so much. I am looking forward to going to KC and see what I can gleam always what is not said is probably more enlightening.
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Post by shumakerherefords on Oct 23, 2013 20:03:30 GMT -6
I have held off hoping someone could offer a better answer. But here are my speculations and observations. A calf will have EPD as soon as he is registered. Those EPDs are an average of the sire and dam EPDs. When weaning data is submitted those EPDs change based of the calf's ranking within his contemporary group. Say a calf has a weaning weight of 450 lbs. If his contemporary group averaged 400 lbs then his ratio would be 113 and his WW EPD should increase (but just how much is something of a mystery hidden within the statistical analysis).
Now if that same 450 lb. calf was included in a contemporary group that averaged 500lb. then his ratio would be 90 and his WW EPD should go down.
There is a very strong correlation between birth, weaning and yearling EPDs built into the software and very often you will see the BW EPD increase for a calf with a high weaning ratio and vice versa.
So you can see how a breeder could 'game the system' by selecting contemporary groups to make an individual look better or a sire group look worse. That is one reason I look for animals with large contemporary groups (and hopefully multiple sires).
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Post by guffeygal on Oct 23, 2013 20:09:20 GMT -6
"Actually its just a couple Aussie’s hanging out in some guy’s basement. AHA mails the them data as they get it, they add or subtract for age of dam, add the the numbers together, divide by number of animals to get the average and boom! their done. That’s why they can only do updates twice a year, that stuff takes time."
:-) Good one!!!!
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Post by bookcliff on Oct 23, 2013 20:23:14 GMT -6
So 200 plus views, three replies and nobody knows where to find an explanation of the Australian's methodology. I would like to understand the program better before expressing my issues. But seeing that no explanation is readily forthcoming, I think it is time. My biggest issue with epds is that they are used to compare calves born to bulls that are not used in multiple sire groupings. After being reared on em then embracing em then moving to making matings on em, I have come to light at the end of the tunnel, they are a bastardized system of numbers easily manipulated by those whom use creative contemporary groups, those who don't know how to submit data properly and those who flat out lie. go back and read the mature cow wt epd thread her on Hereford Talk as an prime example of this. futhermore under AHA's own admission at last years annual meeting they figure that there are just about as many unreported, fabricated or improperly collected BW's as those that were properly taken and reported. at first (and those who have been in this business that are pushing 50 on can tell you) they were supposed to be so we could compare cattle from different management and enviroments. now when you push the powers to be, they say the are only supposed to compare cattle within herd not across herds. futhermore they have no validity whatsoever in a linebreeding program because they are designed such that they need a wide range of ratio to function properly if there is or was ever such a thing. additionally if you bring in data on phenotypic traits that is totally subjective like udder scores you will have even more trouble in my mind. finally, the computer system has had occasional issue with losing the ratioes on cattle and consequently those cattle and their progeny revert back to a pedigree estimate (I have had this personally happen). couple that with the age regression that occurs that we have all seen but the powers to be say doesn't occur and it really turns surreal. Consequently, I have come to a place where I no longer have any faith or belief in them unless you can show me reams of data backing up what they say and then why do I need them in the first place. don't even get me started on index EPD's
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Post by bookcliff on Oct 23, 2013 20:29:54 GMT -6
Actually its just a couple Aussie’s hanging out in some guy’s basement. AHA mails the them data as they get it, they add or subtract for age of dam, add the the numbers together, divide by number of animals to get the average and boom! their done. That’s why they can only do updates twice a year, that stuff takes time.
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Deleted
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Post by Deleted on Oct 23, 2013 20:50:28 GMT -6
The epd formula will use the calves ratios to weight the epds based on the epds of all of the contemporaries in the group. Idk if that is done when the performance data is sent in or just every six months when the analysis is done.
A high ratio doesn't necessarily mean the calf will have a high epd, unless it's contemporaries have high epds.
With any given ratio, If the calf's contemporaries have low epds, then the calf's epds won't be as high as they would be if the calf's contemporaries had high epds.
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Post by mrvictordomino on Oct 23, 2013 20:57:37 GMT -6
I have held off hoping someone could offer a better answer. But here are my speculations and observations. A calf will have EPD as soon as he is registered. Those EPDs are an average of the sire and dam EPDs. When weaning data is submitted those EPDs change based of the calf's ranking within his contemporary group. Say a calf has a weaning weight of 450 lbs. If his contemporary group averaged 400 lbs then his ratio would be 113 and his WW EPD should increase (but just how much is something of a mystery hidden within the statistical analysis). Now if that same 450 lb. calf was included in a contemporary group that averaged 500lb. then his ratio would be 90 and his WW EPD should go down. There is a very strong correlation between birth, weaning and yearling EPDs built into the software and very often you will see the BW EPD increase for a calf with a high weaning ratio and vice versa. So you can see how a breeder could 'game the system' by selecting contemporary groups to make an individual look better or a sire group look worse. That is one reason I look for animals with large contemporary groups (and hopefully multiple sires).
Personally, I want all my calves to be measured against each other and sires compared also. My data is important to me as I am my first customer. Multiple contemporary groups wouldn't tell me much in ratio comparisons. I know you could influence EPD's though. Now true differences in management or any other reason might be OK to have different codes, but in my opinion there is no reason to spit your cattle up into groups when all conditions are equal if you want the data to be meaningful. Just my opinion.
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Post by dougthorson on Oct 24, 2013 6:58:32 GMT -6
I was just waiting for Bookcliff to say his part so I could say I agree. EPD's are nothing more than a tool to look at after you make your pick to make sure there isn't something way out of wack and might help you from making a huge mistake. The key to using them properly is to make your selection before you look at them.
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Post by Deleted on Oct 24, 2013 7:54:19 GMT -6
i kinda like to go by PFG's rather than EPD's.
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Post by Deleted on Oct 24, 2013 12:32:25 GMT -6
So you can see how a breeder could 'game the system' by selecting contemporary groups to make an individual look better or a sire group look worse. That is one reason I look for animals with large contemporary groups (and hopefully multiple sires).
Personally, I want all my calves to be measured against each other and sires compared also. My data is important to me as I am my first customer. Multiple contemporary groups wouldn't tell me much in ratio comparisons. I know you could influence EPD's though. Now true differences in management or any other reason might be OK to have different codes, but in my opinion there is no reason to spit your cattle up into groups when all conditions are equal if you want the data to be meaningful. Just my opinion. Bingo. That is why we want to see everything. We want to se the ratios, actual and adj.. bw, ww and yw, not just the EPD's. If you deal with reputable breeders, they will give you everything bit of data they have, and you can trust the numbers. They aren't playing the contemp. group game like some do. There should be a big difference in environment or management for someone to have multiple contemporary groups.
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Post by Deleted on Oct 24, 2013 14:22:58 GMT -6
Any differences in management or environment ought to be in separate contemporary groups. If your ratios aren't accurate, then the epds that result from those ratios won't be accurate either. The size of the contemporary groups only tells you how many comparisons are being made. The more comparisons that are made, then the higher the accuracy number that will be given to the epd by the computer. You could have huge contemporary groups, but if the data isn't accurate, then the epds won't be either and if the contemporary groups aren't split when they need to be then the data and ratios sent in won't be accurate. The number of herds the data comes from and the integrity of the people collecting it ought to be about as meaningfull as any information you can get about the data. Epds are way over-emphasized in the market. All this gets sorted out over the long haul and the guys who are fudging the data are gonna do themselves in. One thing that is overlooked by the epd formulas is the inbreeding coefficients. If you have been raising cattle of a certain bloodline for many years and you go out and buy a bull that has birth data suggesting he's a low birthweight bull, but that bull is a major outcross to your cows, then you will run the risk of getting higher birthweights when you mate him to your cows. IE: If you have a herd of polled cattle, bred that way for many generations, and you go out and buy a Line 1 bull up at Miles City, then your probably gonna get birthweights that are higher than what the simple average of the parents birthweight epds would suggest. And the opposite could very well be true also, if you have a herd of several generations of horned Herefords and go out and buy a polled bull of totally different bloodlines, then you could very easily get higher birthweights than what the average of the bw epds would suggest.
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Post by shumakerherefords on Oct 25, 2013 11:27:27 GMT -6
One of the great mysteries, for me at least, is how they determine how much of the weaning weight is attributed to the genetic growth potential of the calf and how much is attributed to the mother's milk production.
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Post by kph on Oct 25, 2013 13:34:51 GMT -6
The thing that's so frustrating to me, and we all have them, is for example a cow with a 105 wn. ratio on 8 calves and a wn. EPD of 37. Almost 10 lbs below avg. and my herd average is above breed avg.. What more do they want from her? Dont get me wrong, I believe in EPDs and follow them, but they have to be taken with some common sense.
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Post by dougthorson on Oct 26, 2013 9:01:43 GMT -6
Just the fact that this conversation is still going and after 20 replies there is no real answer should be answer enough. Nobody knows how they are figured but some belive(rightly so IMHO) they can be manipulated and yet a lot of commercial producers take them for gospel because the "science" sold them. Add the fact that a lot of seedstock producers make a lot of the mating decisions based on them. Seems like a hell of a way to run an industry.
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Post by Carlos (frmaiz) on Oct 26, 2013 9:58:24 GMT -6
Looks like lots of people, around here at least, are breeding "numbers" instead of breeding sound cattle. Today numbers sell but it may not be so in the future. But who knows.
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Post by strojanherefords on Oct 26, 2013 17:29:56 GMT -6
I think that the idea behind EPD's is a good one, however since we are on a breed wide program we are ultimately dependent on each other to properly administer TPR. To illustrate the complexity administering the record keeping consider this not so abstract thought experiment... My ideal weight for a mature cow is 1300-1400 pounds and I plan on accomplishing that goal by sorting the cows by weight into three groups: cows under 1300 pounds, cows 1300-1400 pounds and cows over 1400 pounds; and breeding those cows to two bulls. I will breed the cows under 1300 pounds to bull A to increase frame size, and I will breed the cows over 1400 pounds to bull B to decrease frame size. The rest of the cows, I do not care what bull they are breed to so I will flip a coin to pick the bull to use. These cows will be managed identically from breeding to weaning. So the question is how many comparison groups are there?
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Post by Deleted on Oct 26, 2013 18:57:13 GMT -6
I think that the idea behind EPD's is a good one, however since we are on a breed wide program we are ultimately dependent on each other to properly administer TPR. To illustrate the complexity administering the record keeping consider this not so abstract thought experiment... My ideal weight for a mature cow is 1300-1400 pounds and I plan on accomplishing that goal by sorting the cows by weight into three groups: cows under 1300 pounds, cows 1300-1400 pounds and cows over 1400 pounds; and breeding those cows to two bulls. I will breed the cows under 1300 pounds to bull A to increase frame size, and I will breed the cows over 1400 pounds to bull B to decrease frame size. The rest of the cows, I do not care what bull they are breed to so I will flip a coin to pick the bull to use. These cows will be managed identically from breeding to weaning. So the question is how many comparison groups are there? 2, heifer calves and bull calves. If you castrate some of the bull calves prior to weaning, then those calves should be reported as steers and split from the bulls into a 3rd contemporary group.
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Post by bookcliff on Oct 26, 2013 19:12:04 GMT -6
One of the great mysteries, for me at least, is how they determine how much of the weaning weight is attributed to the genetic growth potential of the calf and how much is attributed to the mother's milk production. Alan, back in teh mid 80's there was some research done on this for AHA. as to what extent I can't tell you, but I do know that Twig Marston milkded out some of K-States regiesterd cows as part of his Master thesis and the data wqas collected by AHA. at the time the talk was that other land grants were diong it too for the same purpose but as to haow many cows and which universitities I don't know. I can tell you that while I didn't have to help Twig with this personally when i was on the cowboy crew at the time at KSU (Buck Roote got shafted into helping him put the milking machines on--kinda wish now I'd helped if for no other ereason is it would have been a good story to tell if a person was in on itfirst hand) there was more than one cow that got milked only a time or two and got throw out of the study becuse she was less than cooperative. Also as Jay Middlesworth about this. his dad made him milk a bunch of thier registered cows one calving season for this thing.
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