Underfeeding and overfeeding heifers can result in poor or over-conditioned animals. With the heifer inventory currently being very limited, doing what we can to produce good quality heifers will go a long way. Mature body weight (MBW) is the weight that an animal reaches once it has stopped growing. Farmers use this as a tool to balance rations specifically tailored to their herd. “As a result, rations need to be balanced on the correct MBW, or else this can result in over-conditioned heifers,” said Gail Carpenter, an extension dairy specialist, in an Iowa State University Dairy News and Views article. However, body composition can change as cows get older. Just like humans, once cows reach maturity, it is metabolically easier to put on fat rather than muscle.

Because the herd has different requirements for growth, collecting MBW data on third- and fourth-lactation cows is crucial to diet formulation. However, collecting this data can be difficult. The best practice for measuring MBW is collecting weight data from a scale. If a scale is unavailable, bodyweight tapes can be another viable option. It is important to note that body weight tapes do not have the same accuracy as a scale and should be balanced out.

Carpenter advises to not use cull cow weights to estimate mature body weights, as cull cows are usually over- or under-conditioned compared to the rest of a herd. Determining MBW is no easy task, but it can provide beneficial insight about your herd.