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We can't put a bull into our calf crop - only his genes. EPD's are a powerful and convenient way to tell us about those genes - the Expected Progeny Difference.
EPD's are measured in the same units for which a producer gets paid - namely pounds. They represent the best guess at the exact increase or decrease in pay weights a producer can expect by using one bull instead of another. If I've been selling my year-old steers to slaughter at 1250 pounds while using a set of Red Angus bulls with yearling EPD's of +45 pounds, and I switch to bulls with EPD's of +25 pounds, my pay weights will only go down to 1230 pounds, the same 20 pounds I've changed the EPD's. The cowherd may change a little to vary this result just a bit.
Just as important, all Red Angus EPD's are directly comparable from one herd to another. I can look at +45 bulls from a herd in Utah and +25 bulls from one in Illinois, and know that the net result in my herd will still be only 20 pounds difference. It makes no difference if one set of bulls weighs 1100 pounds and the other 1300 pounds. The only thing my calves get from the bulls is some genes.
Because EPD's are averages or estimates, they have certain statistical properties. The actual results in my herd will always differ somewhat from any estimate. There are practices the breeder of the bulls can follow to cut down on the unpredictability. He can sell me a proven bull with a high "accuracy" figure (70 or 80 percent is good) - some breeders don't even show accuracy figures for their proven bulls. He can use high-accuracy bulls in his own program (females have too few progeny to ever get high accuracy). Or at the very least, he can practice consistent selection over a long period of time. Programs which move with the shifting winds give more variable results, as do ones which selectively mate animals with low accuracies (a speculative form of "stacking EPD's").
EPD differences between bulls translate directly into pay weight differences in the calf crop because the cowherd doesn't change much in a year. Thinking a little about that cowherd is a good starting point for deciding how best to get the kind of calves we want. The cowherd has been built from the genes of the bulls we've used previously - a ten to twelve year period would catch most of them.
When we introduce a pound of change by using a bull, that pound goes into the daughters we keep as well as the steers we sell (pay weight). And if we breed that daughter to another bull just like the last one - a bull who brings one pound into the herd - then in this next calf crop we'll actually get some extra, something from the daughter as well as the pound from the bull. In the case of birth weight, the female has twice the effect of the sire, so the extra that comes in from the cowherd is very considerable indeed. (A technical note here: current calculation methods do not reflect these maternal impacts so one has to be very cautious about the conclusions one draws from the birth EPD alone - once animals have progeny, the EPD's start to fall into line.)
We can use the EPD's available in individual bulls to draw up a sort of blueprint for the changes we want to bring to our herd. It is prudent to remember that it may be more efficient to make changes in management rather than genetics. To increase my slaughter weights by 20 pounds, I might consider feeding my steers an extra seven days as an alternative to paying for +45 yearling EPD's instead of +25. The extra yearling EPD carries with it the penalty of an increase in the size of my females, with an extra cost for feeding those cows all year.
Maybe we can change everything by management? More nutrition, to cow or calf or both, increases any weight; less nutrition lowers them. (Neither one changes EPD's which are information about genes.) With weaning weight, it is a viable alternative. Groups of genetically identical calves can easily differ by l50 pounds under different practices. Likewise milk production and yearling weight can be made to vary enormously. For certain goals, changing nutrition or other management may be the answer.
Birth weight stands alone. We can change the actual weight with nutrition, just like any other weight. But interest in birth weight is not directed at the weight itself - it is obviously not a pay weight. It is, however, closely correlated to two other traits - calving ease and herd efficiency (through mature weight). Neither of those characteristics is easy to modify by management alone.
Everyone connects birth weight with calving ease. But what about Birth EPD's? And is calving ease a trait for genetic or management control? A change to better nutrition increases both sides of the calving ease equation (cow size and calf size); it does the same with the herd efficiency equation (inputs and outputs).
Some research observations:
- Birth weight alone influences calving ease by 65 percent.
- Only one-third of the influence on the birth weight of a calf comes from its sire, whereas twice that amount, roughly two-thirds, comes from the dam.
- The shape of the calf influences calving ease.
- Pelvic size and its angle influence calving ease, as does size and maturity of the heifer.
- Gestation length greatly affects birth weight; weather and temperature over the last 30 days can affect gestation length.
We would add the following observations: Birth weight or EPD data are not easy to translate into terms of calving difficulty because we all speak different languages. Our cowherds are different. We manage heifers differently. Our expectations and tolerances for calving assistance differ. And in Red Angus, most of us never assist anything but an occasional first-calf two-year old.
Some years ago, we did a study covering many years of our data. We found that a one pound change in our herd average birth weight corresponded to a 7 to 10 percent change in the calving assistance rate in our first-calf heifers. We defined calving assistance as any type of human participation whatever in a birthing (a much broader definition than that used by researchers at, for example, Clay Center). The data indicated minimum feasible level at about 10 percent and another threshold at about 25-30 percent, which we called a "worry level". Below the worry level, we would almost never have to use a puller or give a Caesarean section. Above the worry level, hard pulls might be frequent.
Today, we can translate these results into Birth EPD's. We would have guessed that a one pound change in the Birth EPD's of the bulls used would translate into a 7-10 percent change in calving assistance. However, because a bull only has half the influence on birth weight of the dam, it appears that a two pound change in Birth EPD is generally needed to get an immediate 10 percent change in calving assistance. Then the problem: when the daughters are themselves calved, mated to similar bulls, they will contribute the effect of their own genetic two pounds plus the two pounds from the bulls. At that point, calving difficulty can quickly go way over the worry level. It does take a number of years for this maternal effect to gradually work its way into a herd.
Whether one chooses to use Birth EPD's or not, it helps to understand this delayed reaction and what it means for a herd in the future. Replacements are usually picked from the entire herd. As a result, most are often taken from older dams - they weigh more and look better. If one uses high birth weight bulls on one's cows, those birth weights will be bred into most of the replacements. One's level of calving assistance can actually continue to increase despite the use of moderate bulls on the heifers. The female contributes twice as much as the bull to the birth weight of the progeny. So if one is continually injecting higher birth weights through the female side, it won't do much good to try to control it by just the bulls used on the heifers. It is like climbing up stairs by going down three after each two you go up. If reducing calving assistance is a goal, then the truth is that it is even more important to use moderate birth weight bulls on one's cows than on one's heifers!!! The idea promoted by some that there are bulls which one should only "use on cows" is fine only if one sells all those calves.
Most of our observations over the years are between birth weight and mature size. Research has continually reaffirmed the close correlation. On a mature basis, we have found that a cow will weigh very close to 15 times her bull calfs birth weight. Stated another way, a calf will normally weigh a little under 7 percent of its dam. That can vary up to 8 percent without her requiring any assistance, but when she has a calf over the 7 percent area, that calf usually matures out at a much heavier weight than she did. We want high yearling and slaughter weights, not high mature weights - the former are pay weights, the latter a cost weight. The females which give us the most beef per acre per year fall in a middle ground. The largest cows decrease our herd efficiency. Our main measure of efficiency is the ratio of the normal weight of steers slaughtered at 13-16 months to the mature weight (5-10 yrs old) of their dams, taken at weaning. Currently, that ratio is around 106 percent. Based on a Pill Thesis study of our herd by David Schafer at Colorado State University in 1991, that ratio is about 5 percent higher than it would have been had we not maintained moderate mature size while selecting for growth.
The best method of selecting against large cows (in the absence of mature size EPD's) is to select for moderate birth EPD's. The birth weight of bulls born to our mature cows is about 78 pounds. This translates into mature weights in the 1150 pound range (slaughter weights of 1200 to 1300 pounds - frame sizes in the 4« to 5« range - carcass weights in the 800-850 pound range). We avoid 90 plus birth weight animals (+ 2-4 Birth EPD's in our herd) not because of calving assistance implications, but rather because of the 1400 pound cows those birth weights lead to. Those females haven't been able to produce even their own weight in beef for us in the same 13-16 months, (not to mention the 106 percent attained by our herd as a whole). Even if they could produce that much, 1400 pound yearling steers are outside the range desired by packers.
There is another cost. Increasing numbers of producers have found they must grow their young heifers in a feedlot to get them to the weights and sizes necessary to have high birth weight calves unassisted. To "routinely have an 85 pound calf without assistance", a heifer needs to be over 1050 pounds, and she needs to get there before early gestation or extra weight will go into the calf. In our area, it takes a lot of feed to run heifers at those weights.
To summarize our experience with multiple trait selection, we have found that the usual differences in Yearling EPD (20 or 30 pounds) often turn out not to be very significant at all in determining actual slaughter and pay weights - the price of corn is usually more important. On the other hand, very small differences in Birth EPD (as little as two or three pounds) have a surprisingly large impact on both calving assistance and herd efficiency, and ultimately decide how much beef we can produce per acre.
In order to maintain adequate growth in one's herd while selecting for more moderately sized females, the 1 to 15 ratio between birth weights and mature cow weights is not a bad guideline. It gives an idea of the mature weights one can expect from a given birth weight. And it gives a quick-and-dirty method for evaluating a Yearling EPD in the context of the Birth EPD that accompanies it.
EPD's help us to move our programs in directions that we desire. We can use the information they provide, but the better we understand all that information, the less likely we are to get carried to expensive extremes. Even as we make changes to benefit next year's calf crop, additional changes will be creeping into our cowherd. EPD's let us see both.
There are several links to articles explaining EPD's and how to use them on our links page.
The new Red Angus Association and indices are now given for each sale animal, in the box just above the EPDs in the catalog (or just above the video display box on our Sales page). The index number is followed by the 'Percentile' showing how that animal ranks compared to all other Red Angus bulls or heifers. A higher index number results in a lower 'Percentile' number, which means a higher ranking within the breed, and is therefore better. The development of these indices by the RAAA is described in an article written by Larry Keenan and reprinted on page 6 in the our current catalog or somewhat more briefly here or here.
The familiar Birth Weight or Yearling Weight EPDs, for example, are measured in pounds of increase in weight, whereas these indices are measured in ‘dollars of increase in profitability’ - the expected increase in profit that each animal is expected to generate per mating of that animal. A bull with a HerdBuilder Index of 160, compared to a second bull with an index of 110, should produce 160 - 110 = 50 dollars of expected increased profit for each cow to which he is mated, compared to the second bull (note that this is ‘per mating’, not ‘per calf produced’). The index considers and weights all economic factors – fertility, calving ease, maintenance costs, growth rate, stayability, carcass quality, etc. - according to best available science.
You will find Beckton bulls individually and as a group ranking in the top of the breed for profitability, as measured by these new indices.
Beckton's Reference Sire A-2, Beckton Accent W180 C2 (data from 2017 catalog)
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