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In response to a recent question from a producer, the topic this week addresses the difference between a couple of growth performance measures commonly used in beef production. It also includes some anecdotal evidence observed on a handful of Angus calves being fed at the Oklahoma State University (OSU) Purebred Beef Cattle Center.
The Beef Improvement Federation defines weight per day of age (WDA) and average daily gain (ADG) as follows:
• WDA: Weight of an individual divided by its age in days.
• ADG: Measurement of the average daily body weight change over a specified period of time of an animal on a feed test.
Both are measures of growth that are easy to calculate but are distinctly different. For example, if a calf was born weighing 80 pounds and later weaned at 200 days of age weighing 500 lbs., the WDA (500 divided by 200) is 2.5 lbs./day. The ADG of the same calf from birth to weaning would be 2.1 lbs./day (500 minus 80, divided by 200).
The measure of WDA is useful to evaluate on young growing cattle from approximately weaning to yearling time. The measure of ADG has been used in performance testing for decades and is commonly used to measure the growth performance of pens of finishing cattle. Both these measures would be based on the genetic potential of calves to grow as well as the environmental effects of factors like weather and the plane of nutrition. ADG could also be heavily influenced by plane of nutrition prior to the testing period which could impact the amount of compensatory gain during the test period.
The OSU Purebred Beef Center is currently developing a group of four Angus heifers and a group of four Angus bulls to potentially exhibit in Angus Pen of Three Show at the Cattlemen’s Congress Show in Oklahoma City, OK, in January.
The calves were born from Jan. 17 to Feb. 25. The calves were on a 14% crude protein creep ration, fed ad-lib, for several months prior to weaning in mid-August. Six of the eight calves have Weaning and Yearling EPDs in the best 5% of non-parent Angus cattle. The other two rank in the best 20% of the breed for Weaning and Yearling Weight EPDs.
Based on weights taken at the beginning of October when the calves were 219-258 days of age, the range of actual weights, ADGs and WDAs of the calves are summarized as follows.
• Bulls — Weight range: 970-1,110 lbs. ADG range: 3.83-4.1 lbs. WDA range: 4.14-4.41 lbs.
• Heifers — Weight range: 780-815 lbs. ADG range: 2.9-3.2 lbs. WDA range: 3.2-3.55 lbs. — Mark Z. Johnson, OSU Extension beef cattle breeding specialist
