All the Data, All the Time... Part II – Cow size is more than just weight. At Mushrush Red Angus, we weigh every cow when we wean her calf, and we collect a Body Condition Score (BCS) at the same time. We gather this data at weaning so every cow will be in the same phase of her annual Production when data is captured. By collecting this data within the appropriate contemporary group, we can better define an equal opportunity to compare weights. Comparing across contemporary groups can be misleading and inaccurate. For example, comparing the mature weight of fall cows against spring cows is not always giving the best comparison of the cows. This is also why cow weights and BCS from one ranch shouldn’t be compared to that of another ranch. Environmental differences, supplemental nutrition, rainfall, stocking rate, and a host of other factors may differ between contemporary groups. We encourage our customers not to compare weights of our fall-calving cows and calves to our spring-calving cows and calves due to very different environments even though genetics are nearly identical. Lactating cows in production through the winter, can have very different actual weights then our spring calving herd, who benefit from Flint Hills forage during its peak. This can reflect in the calves actual performance, too. In our 2nd Quarter newsletter, we discussed how mature cow size effects ranch profitability through its impact on cow herd maintenance requirements, reproductive rate, stocking rate, and cull cow value. The traits of Mature weight (MW) and mature height (MH) are moderate to highly heritable (».45 and ».62 respectively) and are highly correlated (».80), so a change in one trait is very likely to result in a similar change in the other. Given the reasons above, it’s easy to understand the significant role mature size plays in cowherd profitability; what is surprising is that relatively few phenotypic observations are actually collected. Most seedstock providers don’t collect cow weights, and even when they do, weights alone don’t tell the whole story. Age is another factor that impacts cow size. We have been selecting for cattle with rapid early growth and minimal mature size. In other words, steers that grow rapidly to harvest weight and heifers that reach puberty early, develop structural dimension to calve unassisted then “shut down” their growth phase to focus on reproduction and raising calves. Even with these selection goals, cows typically gain weight as they mature to 4-6 years of age. Somewhere around age 10, it is typical for their weight to begin to decline as minor issues, such as worn teeth wear or arthritic joints, make cattle less aggressive foragers. Red Angus calculates genetic predictions for Mature weight which are used in the published Maintenance Energy (ME) EPD. The EPD for mature weight utilizes Age, along with weights and BCS, taken within meaningful contemporary groups. The weights are adjusted to a common age of 5 years and a common BCS of 5. 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 this data within our Fall born bulls or amongst our Spring born bulls. However, we realize that trying to compare a 2-yr-old that weighed 990 lbs. at a BCS of 3 and an 8-yr-old that weighed 1225 at a BCS of 7 is a daunting task at the speed of an auction. Thus, our 2017 bull sale catalog will incorporate a simplified more user-friendly presentation of this data. It will be a single number expression of cow weight, already adjusted for differences in age and BCS.
Stay tuned…
Our winter newsletter will dig deeper into the subject of mature cow size and actually demonstrate the presentation of mature cow weight data, to aid customers’ preparation for Spring bull sale season.