All the Data, All the Time... Part III – How Age & Body Condition Impact Mature Cow Weight Our last two newsletters illustrate that mature cow size matters. In our Spring newsletter, we discussed how mature cow size effects herd maintenance requirements, reproductive rate, stocking rate, cull cow value, and ultimately becomes a major driver in the profitability of a cow/calf operation. In our Summer Newsletter, we talked about important considerations during the observation of cow size, such as Body Condition Score (BCS), cow age, and appropriate contemporary group management. At Mushrush Red Angus, we’ve been providing our bull customers with the Age, BCS, and weight of each bull’s dam when his weaning weight was taken. With this information, buyers could compare the size of each bull’s dam. However, we realize that trying to compare a 2-year-old that weighed 990 lbs. at a BCS of 3 and an 8-year-old that weighed 1225 at a BCS of 7 is a daunting task at the speed of an auction. Looking ahead to our 2017 sale, we will begin adjusting mature weight to a common age of 5 years and a BCS of 5. Our cowboy logic tells us this is a better way. For example, suppose we have two cows come out of the chute – both weighing 1200 lbs – Exactly the same. However, if Cow A is a BCS of 7 and Cow B is a BCS of 3 – we know these cows are different, but how different are they? • Cow A at BCS 7 is approx. 18% heavier than she would be at BCS 5, she adjusts down to 1017 lbs. • Cow B at BCS 3 is approx. 13% lighter than she would be at BCS 5, she adjusts up to 1356 lbs. Age is another factor that impacts cow size. Our 2-year-olds are generally lighter than our 3-year-olds, who are generally lighter than our 4-year-olds. Cow weights are relatively stable from 5 years of age on. This also fits our cowboy logic; we would expect a 1200 lb. first calf heifer to mature larger than a 1200 lb. 5 year old with the same body condition score. There are similar adjustments in this scenario: • 2-year-olds generally have another 12-15% of additional size before they mature • 3-year-olds generally have another 6-8% • 4-year-olds will typically grow another 2-3% Sometimes those 2-year-olds may look like they’ve got to put on much more than another 13% to reach what we’d expect them to weigh as 5-year-olds, but often part of that difference may be accounted for in our first calf heifers being a lower BCS than our 5-year-old cows. Using our prior examples: if Cow B (BCS 3 at 1200 lbs.) was a 2-year-old, we would expect her weight to increase both as she gains body condition and as she matures. We have already shown that she’d be a 1356 lb cow if we brought her up to a BCS 5. But she’d also gain another 13% in mature growth we’d expect to occur between age 2 and age 5. When we add in that adjustment we see she is headed towards being a really big cow – at least for our herd – adjusting up to approximately 1530 lbs. Now, if Cow A (BCS 7 at 1200 lbs.) is already a 5-year-old, we know she’s done. So the adjusting her weight by BCS is sufficient, and the previously mentioned 1017 lbs. is a more accurate representation of her size. Of course, each year is different, and at Mushrush Red Angus, we have two major contemporary groups between the fall and spring calving herds. That makes comparing actual and adjusted data even more challenging to get good information. When rain is plentiful and feed abundant, our entire herd is heavier than average. Droughts and poor quality or less abundant feed produce the converse result. So even with accounting for differences in age and differences in BCS, we still should not try to compare the weight of an individual cow in our 2017 sale against the weight of some bull’s dam from a previous or subsequent year. The phenotypes of Age, Weight, and BCS are the phenotypes used by Red Angus to calculate a Mature Weight EPD, with age and BCS serving as the adjustment factors for the weight – very similar to the process described above. While Red Angus does not publish the Mature Weight EPD, it is the primary driver of their Maintenance Energy EPD (ME). ME EPD predicts differences in energy required to maintain cow weight/BCS and is expressed in Mcals/ month. The lower the ME, the fewer calories required for that animal to maintain weight and condition. In an effort to provide the most meaningful and user-friendly mature cow data possible, we will begin representing dam's weights readjusted for age and BCS.
This enhanced presentation of Body Condition and Mature Cow weight will be demonstrated in our next newsletter and will help you make better selection decisions at our 2017 March bull sale.