Selecting for improved Feed Efficiency

Oct 7, 2008 12:02 PM

By Jason K. Ahola, University of Idaho

By the spring of 2009, it will be pretty clear to cow/calf producers that feed cost is the largest variable cost on their operations.  In response, producers need to realize that in the “profitability equation” (where profit = revenue – expenses) feed cost is the largest variable over which they have control. And, in the face of rising feed costs, we’re way behind in the genetic selection for improved feed efficiency.

The ability to reduce feed intake (and therefore feed cost) without negatively affecting reproduction, growth, carcass performance, or meat quality is becoming a priority in beef cattle selection programs.  Until recently, the seedstock industry focused primarily on developing genetic predictions only for growth and carcass traits, primarily since they were easy and inexpensive to measure.

Selection for growth and carcass performance has resulted in substantial genetic improvement. Unfortunately, these traits only focus on the ‘revenue’ side of the profitability equation.  Further, most producers have inadvertently focused on maximizing production of these traits in an attempt to maximize revenue, with limited consideration for cost.  In contrast, efforts to develop expected progeny differences (or EPDs) for key ‘cost’ traits, such as feed efficiency, are not yet widespread.

Measuring Feed Efficiency is Hard
Unfortunately, there are two major challenges associated with genetically predicting feed efficiency:  1) historical methods used to calculate and select for feed efficiency are generally lacking, flawed, and/or unproven, and 2) collecting daily feed intake on individual cattle is very expensive.

Calculation Challenges.  Historically, feed efficiency has been primarily measured and reported as a ratio – the Feed Conversion Ratio or FCR.  It is calculated by dividing the amount of feed consumed by the number of pounds gained.  So, for an animal that consumes 21 lbs of feed (on a dry matter basis) and gains 3 lbs, its FCR would be 7 (21 lbs ÷ 3 lbs = 7).

The challenge with using the simple FCR calculation is that it ignores an animal’s body weight, rate of gain, and composition (i.e. amount of fat stores).  As a result, selection based on FCR unintentionally leads to animals that are faster gaining but also have a greater mature size.  In some cases, this can lead to deleterious effects on reproduction and profitability.

High Cost of Data Collection.  Collecting individual daily feed intake on seedstock cattle is very expensive.  Unless animals are fed alone in individual pens, the only methods to collect individual intake data for cattle in group pens require the use of costly technologies.

Calan gates have been around for decades, and have been used extensively by most land-grant universities.  However, labor is needed to operate and manage them.  GrowSafe, a recently-developed alternative from Canada, allows large pens of animals to be evaluated for individual feed intake with limited labor required.

Beyond collecting daily feed intake data on individual animals, cattle weight gain must also be measured regularly (typically every 2 weeks during a 70-day test) in order to effectively characterize feed efficiency.  The high frequency of weighing is due to the significant variation that occurs with body weight due to weather, water intake, health, etc.

A final challenge in determining feed efficiency during a test relates to variation among test locations.  To generate valuable data, uniformity in rations, rates of gain, and test length is needed.

We’re Playing Catch-up
The U.S. beef industry is in dire need of two things:  1) agreement on how best to measure and genetically-predict feed efficiency, and 2) an elaborate infrastructure to evaluate cattle individually for feed intake during a uniform test period (such as the tests that occurred during the heyday of central bull test stations).

In addition to generating a large amount of feed efficiency data, accurate methods to predict feed efficiency are needed.  This might include the analysis of tissue samples (for blood hormone concentrations), low-cost genetic markers, or correlated traits that can be measured easily.

oday, there are really no widespread genetic predictions for feed efficiency in beef cattle.  However, a few years ago some breed associations began offering a genetic prediction for differences in the amount of dietary energy required by daughters of a bull.  These new EPDs include the Maintenance Energy (ME) EPD from the Red Angus Association of America, and the Cow Energy Value ($EN) EPD from the American Angus Association.

Unfortunately, the units associated with these two EPDs are not consistent.  The Maintenance Energy (ME) EPD is reported on a megacalorie (Mcal) per month basis, while the Cow Energy Value ($EN) EPD is expressed in dollars saved per cow per year.  Therefore, a negative ME EPD is considered favorable while a negative $EN is unfavorable (Table 1).

The ME EPD assumes that the energy content of average quality range forage is 0.86 Mcal/lb (on a dry matter basis).  Therefore, the offspring of a sire with an ME EPD of +6 will require approximately 7 lbs (6 ÷ 0.86 = 7) more feed each month (on a dry matter basis) compared to offspring of a sire with an ME EPD of 0.

Data used for the creation of these EPDs does not include any actual feed intake data collected during a specified test.  Instead, previously-available data that correlate to cow energy requirements were used:  mature cow body weight at weaning (adjusted for body condition score) and Milk EPD.  This is based on the fact that a sire producing daughters with greater milk production (i.e. higher Milk EPDs) and more growth (as seen by larger mature sizes) will require more dietary energy to maintain her body weight.

Australian seedstock producers have taken a different approach to predicting feed efficiency.  The Angus Society of Australia publishes an expected breeding value or EBV (generally equivalent to an EPD) for a trait referred to as Net Feed Intake.  This trait, also referred to more commonly in the U.S. as Residual Feed Intake (RFI), is an estimate of the genetic difference in feed intake after growth rate and body weight have been accounted for.  It is an alternative method of characterizing feed efficiency in beef cattle, and is based on actual feed intake data.

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