Food for thought on MILK....
Got Milk? Not the White Stuff… November 2009
It’s a point of confusion for many breeders across the country, yet an important aspect of raising Shorthorns: Milk Expected Progeny Difference (EPD). Listening to young people give oral reasons in judging contests certainly proves the point. One hears more ‘half-truths’ about the meaning of Milk EPD than any other column on the paper. In the simplest of definitions, Milk EPD is really nothing more than the genetically unexplainable portion of weaning weight. After all, the trait is measured in pounds of live calf ‘due to milk.’ A portion of the weaning weight is attributed to the bull’s performance, and a portion to the cow’s performance. What’s left over is lumped into Milk EPD, giving the cow credit, or blame, for raising her calf. For this reason alone, embryo transfer progeny cannot have Weaning Weight or Milk EPDs calculated since the recipient cow did all the work.
There are a number of things that influence Milk EPD, some more obvious than others. It sounds absurd, but Milk EPD really has very little to do with the white stuff that comes out of the udder. We simply do not measure milk the way dairy farmers do. Along these lines, the size of a cow’s udder is a common misconception of Milk EPD. Numerous breeders have shown me Shorthorn cows with large udders, but low Milk EPDs. We can blame this on our first trip down the dairy aisle at the county fair. We logically think, big udder, big milk. Research tells us that the nutritional value of the milk is just as important as the amount consumed. In cowboy logic, you may be looking at a big udder full of “skim” milk. In other cases, the large udder may have a mammary system that’s partially inactive due to a number of environmental factors.
One environmental factor that can cause havoc on Milk EPD is creep feed. It’s not that creep feed is bad or good, but rather hard to figure into the complex math problem that generates Milk EPD. We all know that some calves don’t really like creep feed right away, yet others seem to “camp out” at the feeder until weaning day. When those two calf types are in the same contemporary group, it gets extremely hard to separate genetics from environment. Creep feed can have some biological impact on heifers that may be detrimental to their value as a mature cow. If creep feed is introduced early to heifers, research suggests that fat cells may form in the mammary system, essentially blocking the ability for milk production.
Before you yank the creep feeder or cull the big bag cow, the true value of Milk EPD needs attention. In general terms, cows that put more grow in their calves due to milk need more feed per pound of bodyweight to do it every year. Where feed resources are scarce, breeders prefer moderate milk to ensure cows rebreed on time. Put that same cow in the Corn Belt, and you may have a disappointed breeder come weaning time. We’ve all seen the two-year-old that milks her heart out, but comes up open in the fall. Likewise, we may remember the cow that stayed fat all summer, yet her calf looked like walking death. These are the genetic “pictures” of high and low Milk EPD, respectively. Reproductive organs will not function properly if a cow is in poor body condition, hence the open three-year-old. Management can mask the genetic story of both cows, and the Milk EPD calculation can struggle telling the difference. Patience, proper contemporary grouping, and Whole Herd Reporting (WHR) are the best methods to assess whether you’ve ‘Got Milk.’
Patrick Wall