If you could decrease the maintenance energy requirements of the cows in your herd, while maintaining or increasing production, you could go a long ways toward engineering increased efficiency.
That's the premise and promise of the expected progeny difference (EPD) for mature cow maintenance energy (ME) introduced by the Red Angus Association of America (RAAA) in January.
“This allows you to balance revenue and cost traits in different environments,” says Lowell Gould, RAAA genetics and information systems director. He explains developing the EPD for ME continues that breed's ongoing development of genetic evaluation tools that get past indicator traits such as birth weight and aim directly at economically relevant traits such as calving ease.
In the case of ME, it gets at differences in cost required to maintain a cow that is neither gaining nor losing weight.
Specifically, the ME EPD represents a combination of mature weight, adjusted for size or mass, which results in a metabolic weight EPD, combined with milking ability, and adjusted for body condition. The end result is an accurate measure of differences in the energy required — mega calories per month (Mcal/mo.) — to maintain a cow.
As an example, a bull with an ME EPD of 5.0 Mcal/mo. would be expected to sire, on average, daughters that require 15.0 fewer mega calories per month for maintenance than daughters of a bull with an ME EPD of 20.0 Mcal/mo.
The Efficiency Equation
“The mature energy EPD doesn't predict cow efficiency, so it doesn't necessarily predict cow profitability,” cautions Keith Long, seedstock manager of the Bell Ranch in northeastern New Mexico. “It predicts a cost, obviously. The question is whether or not a lower maintenance animal is necessarily more profitable.”
Long is a fan of the new EPD. In fact, the Bell Ranch began working with Cornell University in 2001 to develop a genetic prediction tool for cow efficiency. His point is that selecting for maintenance energy alone — just like selecting solely for any other single trait — is an invitation to disaster.
“This new EPD will help identify those animals that can produce efficient replacement females, but the ME is not an efficiency EPD,” emphasizes Bob Hough, RAAA Executive Secretary. “Efficiency is a ratio of output per unit of input. This EPD describes the input side of that equation.”
Using the bulls cited earlier, if the production of the daughters sired by each was equal, then those that inherited the genes for lower maintenance requirements would be more efficient. The tough sorting comes in situations where genes for higher maintenance also produce more than lower maintenance peers. Figuring how much added maintenance cost the added production is worth varies with each operation.
In other words, the perfect ME in one environment can be the worst in another. Perhaps more than any other current EPDs, the ME demands that it be used in combination with others.
Unlike reproduction traits where there is an assumed value — the goal is a calf each year — choosing a desirable level for a cost trait like ME depends on nutritional resources and production goals.
“With this EPD you can really start putting together the entire economic package and do so more economically,” Gould says. “The main thing to understand in using it is your resources, especially if you're in a situation where resources are limited.”
Energy Goals Vary
For instance, at the Bell Ranch, where the environment demands a low-input philosophy, Long says, “I'm going to use it to moderate body size and mature weight.”
Although the ME doesn't get at lactational energy directly, it does indirectly given the impact of milk on maintenance requirements (higher milking cows require more energy whether lactating or dry). Long believes they will also be able to use the ME EPD to help moderate milk at the same time.
Moreover, Gould explains, “With this EPD we will find higher growth cattle with moderate mature size, and we will find cattle at a given size and milk potential that are able to maintain their body condition. In the end, producers will have the tools to better select animals that fit their unique combination of environment, feed resources, management and market.”
Knowing what ME level fits the bill in an operation may take some time to learn, however.
“Selecting for mature maintenance energy EPD will be different across environments,” Long explains. “I'm not sure it will be clear initially on which direction an operation needs to go with it. But, I suspect there are few instances where you'd want to push it too high or too low.”