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An AHA response.
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<blockquote data-quote="bigag03" data-source="post: 623927" data-attributes="member: 9247"><p>Ok, I'm going to get on my soapbox now. I have watched this board for a long time and finally felt the need to comment a couple of weeks ago. I tend to sit by and watch, but this topic and topics of the like have been very common lately and I feel I have some knowledge to offer, so here I go.</p><p></p><p>Those of you that think that we will have a universal set of EPDs or that the across-breed EPD chart are the savior of all breeding problems clearly don't understand EPD's, what they represent or how they are calculated.</p><p></p><p>1) Heterosis is real, more variable than most would like to admit, and very hard to predict. This is the main reason that we will never have a uniform set of EPD's. Example: You have an Angus bull and a Hereford bull and use them on your Angus cows. You will see a major difference in sire group comparisons for all traits than your neighbor that uses the same two bulls on his Hereford cows. This is because on your place heterosis has an affect on the Hereford sired calves and on your neighbors place, heterosis has an affect on the Angus sired calves.</p><p></p><p>2) Under the same rationale as reason #1, across-breed EPD's only work when comparing bulls used on a third breed or with equal representation in the breed of cow. Example: Across-breed EPD's cannot be used in the example from #1; however if you were comparing the same Angus bull and Hereford bull for use on Charolais cows (or even F1 Black Baldies) then across-breed EPD's can be used because the level of heterosis is the same for calves by both bulls.</p><p></p><p>3) EPD's are a fancy term for statistical analysis without terms like mean and standard error. Instead we have an EPD for a given trait and an accuracy. The accuracy of an EPD is influenced like all statistal analysis...more numbers=higher accuracy. The number of repetitions (calves) are much more influential than the accuracy of cow's EPD (or even lack thereof). The use of non-registered cows in research studies can be used in the calculation of EPDs provided you are creating a fair comparison. Example: I want to compare the carcass characteristics of calves sired by 4 Hereford sires. The cows for my study are 400 F1 black baldies. I gate cut the cows into 4 - 100hd groups (random selection of groups) and AI each of the groups to different bulls. Grow the calves out measuring whatever data you feel like collecting all the way through the rail. During the entire study, cows are managed the same, calves are managed the same...try to control as many environmental influences as possible. The resulting data is extremely valuable in the comparison of those sires and there is no reason not to include it in the EPD calculation.</p><p></p><p>4) The AHA database is miles behind the accuracy of the AAA database and George hit the nail on the head. It is because the Hereford breed does not utilize AI enough to compare these bulls accross enough different environments to better remove environmental affects from the calculation.</p><p></p><p>5) I don't believe that any of the major breed associations would ever merge their database with another one. That would be like GM turning over their financials to Ford and asking them to be fair in the way they use that data. NOT GOING TO HAPPEN! The breed associations are a business.</p><p></p><p>OK, I think I just fell of my soapbox. I look forward to input from the CT board.</p></blockquote><p></p>
[QUOTE="bigag03, post: 623927, member: 9247"] Ok, I'm going to get on my soapbox now. I have watched this board for a long time and finally felt the need to comment a couple of weeks ago. I tend to sit by and watch, but this topic and topics of the like have been very common lately and I feel I have some knowledge to offer, so here I go. Those of you that think that we will have a universal set of EPDs or that the across-breed EPD chart are the savior of all breeding problems clearly don't understand EPD's, what they represent or how they are calculated. 1) Heterosis is real, more variable than most would like to admit, and very hard to predict. This is the main reason that we will never have a uniform set of EPD's. Example: You have an Angus bull and a Hereford bull and use them on your Angus cows. You will see a major difference in sire group comparisons for all traits than your neighbor that uses the same two bulls on his Hereford cows. This is because on your place heterosis has an affect on the Hereford sired calves and on your neighbors place, heterosis has an affect on the Angus sired calves. 2) Under the same rationale as reason #1, across-breed EPD's only work when comparing bulls used on a third breed or with equal representation in the breed of cow. Example: Across-breed EPD's cannot be used in the example from #1; however if you were comparing the same Angus bull and Hereford bull for use on Charolais cows (or even F1 Black Baldies) then across-breed EPD's can be used because the level of heterosis is the same for calves by both bulls. 3) EPD's are a fancy term for statistical analysis without terms like mean and standard error. Instead we have an EPD for a given trait and an accuracy. The accuracy of an EPD is influenced like all statistal analysis...more numbers=higher accuracy. The number of repetitions (calves) are much more influential than the accuracy of cow's EPD (or even lack thereof). The use of non-registered cows in research studies can be used in the calculation of EPDs provided you are creating a fair comparison. Example: I want to compare the carcass characteristics of calves sired by 4 Hereford sires. The cows for my study are 400 F1 black baldies. I gate cut the cows into 4 - 100hd groups (random selection of groups) and AI each of the groups to different bulls. Grow the calves out measuring whatever data you feel like collecting all the way through the rail. During the entire study, cows are managed the same, calves are managed the same...try to control as many environmental influences as possible. The resulting data is extremely valuable in the comparison of those sires and there is no reason not to include it in the EPD calculation. 4) The AHA database is miles behind the accuracy of the AAA database and George hit the nail on the head. It is because the Hereford breed does not utilize AI enough to compare these bulls accross enough different environments to better remove environmental affects from the calculation. 5) I don't believe that any of the major breed associations would ever merge their database with another one. That would be like GM turning over their financials to Ford and asking them to be fair in the way they use that data. NOT GOING TO HAPPEN! The breed associations are a business. OK, I think I just fell of my soapbox. I look forward to input from the CT board. [/QUOTE]
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