EPD's with reciept cows

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Mar 4, 2007
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I know I'm not the only one that notices a low birthweight EPD on a bull with an actual birthweight of 90lbs and wondered what the heck was going on. Is this because of the reciept cow? How much does the recipient cow contribute to the actual birthweight of a bull calf? Is it 100%? 50%? 0%. Now with the WW I understand that the reciepient will contribute considerably to the WW of the calf. It still makes me wonder though when a bull has a high WW score yet weaned under average. I'm real curious on ya'lls thoughts on this.

Actual birthweight can vary anywhere between 55 lbs and 140 lbs depending on the genetics, the nutrition, the length of the pregnancy, and the volume of the cow; but the EPD only varies from -.9 to 8.3 between the best 1% and the worst 1% of the breed (I am using Hereford as the example). That is only a 9.2 lb spread in the EPDs and the real world spread in a calf crop CAN be 50-70 lbs. The EPD is just an average. ANY bull probably has some 75 lb calves and some 90 lb calves out there. All the EPD is telling you is that a -.9 EPD bull is going to have more light ones than heavy ones and that at +8.3 EPD bull is going to have more heavy calves than light ones. A big long wide sprung deep ribbed mature cow is going to throw heavier calves than small frame heifers will. IF I had to guess I would guess that the cow (fetal environment) probably is responsible 80% of the birth weight expression and the genetics of the calf are only about 20%.
The receipt cow may affect BW somewhat, but I wouldn't give it as much credit as Brandonm2. Genetics and breed type will play their part as much as the environmental conditions. The thing to remember is that EPD does not reflect the “actual” BW you will see, instead like Brandonm2 indicated, it is based on the data received in the generations behind the animal, and the type of management and contemporary groupings those animals were reported under.

An EPD which is 2.0 lower then another animal’s only suggest that that animal should sire/bear calves with an average 2 lbs lower then the other animal…which is also still dependent on the amount of data, and the accuracy of that data, which has been submitted to create the EPD. If all the calves in a contemporary group weigh an average of 92 lbs actual, and the animals who gave the ET calf it’s EPD’s average was only 90 lbs in that group (even if they only sired/bore one calf in a group of 30), then their EPD’s will adjust to show their tendency to throw a lighter calf compared to the others, and subsequently it will reflect in theirs and their offspring’s EPD’s. Some of the previous generations EPD’s (and their accuracies), will tone the sharp changes in EPD’s down a little, but the actual BWs of the offspring and the contemporary groups being reported on year after year will eventually reflect the actual animals potential.

Some programs genetically calve out larger calves, like Canadian breeding. You may find a Canadian sire that has a -1.0 for BW EPD, but in actuality he could still be averaging 90 lb actual weight in his calves, it’s just that his 90lb calves are much smaller then the contemporary group average season after season. If you use these genetics on a cow herd that is bred for, and consistently bears small calves, and put him in a contemporary group with your bulls (who are bred with similar genetics as the cows), it may still mean a larger actual BW (maybe 85 lbs) for the Canadian bulls calves despite him being a -1.0 and your bulls being a 4.0 in your program (4.0 in your program may mean an average of 80 lbs calves).

In a bull that has been used in herds all over the country, his low BW EPD’s along with a high accuracy “may” just mean exactly that…. ..in any program he may have the higher potential to sire lower BW calves then the average, but not always. Cow herd genetic base, environment, nutrition, and management all play their part in the end, so knowing actual BW’s of animals and their offspring plus the type of contemporary groups they were reported in will make a difference.

EPD’s are really just indications of potential based on data received. They are made more reliable by the amount of data submitted, which in turn increases the accuracy of the potential.

Hope I really confused you here!.......

To quote brandonm2 (adding my bold words)

“All the EPD is telling you is that potentially a -.9 EPD bull is going to have more light ones than heavy ones and that potentially an +8.3 EPD bull is going to have more heavy calves than light ones.”…..Remember, these are based on the comparisons of the groups that the animal, it's line and it's offspring were reported in......and the amount of data submitted.

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