*disclaimer, I am not a geneticist, we are breaking down these EPDs to our understanding.
I hear about this one at a lot of bull sales and I find MILK is a fascinating EPD since it’s not necessarily measuring what the name would lead you to believe. So, in true Data Genie fashion, let’s dive into it.
MILK doesn’t measure the milk in the bucket (maybe it does in dairy but not in beef 
). It’s expressed through pounds on the calf. More specifically, it is predicting the maternal contribution to pre-weaning growth.
ASA defines it as “the difference in maternal pounds of weaning weight from an individual’s daughters due to milk.”
Angus defines it as “a predictor of a sire’s genetic merit for milk and mothering ability as expressed in his daughters compared to daughters of other sires. In other words, it is that part of a calf’s weaning weight attributed to milk and mothering ability.”
So…how does this impact us?
On the seedstock side, think about the phenotype that we’re actually collecting and submitting here that contributes to the EPD. We aren’t putting these beef cows in a milk parlor and measuring pounds of milk or trying to milk them out in an open field. We’re weighing the calves they raise and using those records, contemporary groups and relationships within the genetic evaluation to help separate the calf’s direct genetic potential for growth from the maternal contribution of the dam.
This makes it imperative for seedstock breeders to submit complete and accurate weaning weights on calves in properly defined contemporary groups and maintain accurate dam/progeny records. Remember our contemporary group saying, “when in doubt, split it out” since contemporary groups are what help the evaluation account for environmental and management differences. At it’s most basic definition, animals that have an equal opportunity to perform.
On the commercial side, what does MILK mean to a producer buying bulls to keep replacement heifers out of?!
The goal isn’t maximum MILK. It’s selecting for an appropriate level of maternal production for your resources. Finding the percentile range that aligns best with your environment, input/forage resources and management is where you’ll find your optimum. Sometimes we’re outkicking our coverage by continually selecting for more production than our environment can economically support.
Milk requires nutrients. Mature size requires nutrients. Growth requires nutrients.
If our inputs can’t support the production we’ve selected for, maintaining females in the condition needed for reproductive performance becomes increasingly challenging and can be an uphill battle.
Penny for your thoughts…how much maternal production can your environment economically support? As you look at those MILK EPDs, take a look at Mature Weight (MW) and Cow Energy Requirement (CER) in ASA or Cow Energy Value ($EN) in Angus. Think about the ideal female you’re trying to build to best fit your environment and then use the EPD and genomic tools available to assist you with hitting that target more consistently on average.
datageniellc.com 