Sunday, 26 June 2011

Numbers Galore

A few days ago I did a blog on ultrasounding carcass traits in animals and had mentioned EPD's, today I will go into a little more depth on EPD's.

EPD stands for expected progeny differences. Here is an example of EPD's for an animal. To some of you this may look like just a bunch of numbers, I will do my very best to explain what the numbers are and mean.

  • Calving Ease - is an EPD that has a multitude of factors that impact calving ease from gestation period, feed, climate, cow size to breed. Calving ease is how well a cow will calf, we want calving ease to be higher so that most of them will be unassisted.
  • Birth Weight is the EPD that gets calculated using the birth weights of the bulls and cows progeny as well as the calves birth weight. The lower the number the better. This bull for example has a birth weight EPD of +3.6 and he is used on cows. Our one heifer bull has a birth weight EPD of -1.1 which is low and part of the reason he is used on heifers because you want heifer's calves to have low birthweights so that they can easily calf and don't need assistance.
  • Weaning weight is based on the weight of the calf's and its parents weight at weaning (when we take the calves away from the moms). In this case it is the higher the number the better. For example if another bull at an EPD of 0.0 this bull with the weaning weight of +55.8 will sire offspring with an average of 55.8 pounds heavier at weaning then the bull with an EPD of 0.0.
  • Yearling weight is the same as weaning only it applies to when the animal is a year old.
  • Milk  is another one of those EPD's that you want higher numbers. You can't have a cow that doesn't produce any milk so you want high EPD's, it is a measure of the amount of pre-weaning performance gained by calves which can be attributed to the milking ability of a bull's/cow's daughters. The EPD is expressed in pounds of calf.
  • Total Maternal is half the weaning weight plus the milk of the mother.
  • Maternal Calving Ease is the calving ease of the mother.
  • Scrotal Circumference is determined and adjusted from the yearling scrotal circumference of a bull's or cow's progeny, in centimeters and again the higher the EPD the bigger the better.
  • Cow Weight is the EPD of the cow weight.
  • Stayability is the probability that a bulls daughters will stay in the herd for so many years.
  • MPI is maternal productivity index.
  • FMI is feedlot merit index
  • Fat is determined from the ultrasound measurements and the lower the number the less fat the animal has and the better.
  • REA is the rib eye area EPD also from ultrasound, higher numbers mean larger rib eyes.
  • MARB is the marbling of the animal also determined from the ultrasound with higher EPD numbers also meaning more marbling.
The middle row is the accuracy of the EPD's and is very important when looking at the EPD's. For example the calving ease EPD is seven percent accurate.
The row at the bottom is the average EPD's of all the calves born in 2009 of the Hereford breed. An average is made every year of the calves and is used as a guideline to compare an animal to the average. EPD's of different breeds cannot be compared because each breed has their own methods of calculating EPD's and they are simply not comparable.

EPD's showed graphically in percentiles.
EPD's are a lot of numbers but are very useful in choosing herd sires to breed cows to. Through EPD's breeders can also increase the productivity and characteristics of their herd. They are also used to decide which cows to put with which bulls, for example if one cow has a low milking EPD, then we would stick her with a bull that has an above average, high milking EPD and the calf should average out and increase in milking EPD. EPD's are useful in herd management and are starting to be used more by breeders in their herd and in selecting bulls. Please comment and let me know if you have any questions!


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