WHY FEED EFFICIENCY?
The University of Wyoming High Altitude Bull Test strives to provide data that can be utilized to improve multi-trait selection efforts for cow-calf producers across the region. Combining the uniqueness of LREC elevation (7200 ft), as one of the highest Agriculture Experiment Stations in the United States, with the access to individual feed intake monitoring systems we are able to provide a comprehensive set of data that can be used to evaluate bull growth, feed efficiency, risk for pulmonary hypertension (brisket disease), fertility, and carcass traits. As the beef industry continues to face increased feed costs, improvements in feed efficiency while maintaining or improving gain are of the utmost importance. There are various metrics for evaluating feed efficiency and performance, and the benefits of multiple-trait selection apply to these metrics as they do to selection decisions based on EPDs. To bring this data to the 4th Annual High Altitude Bull Test, the final 70 days of the test consisted of a feed efficiency trial where bulls had unlimited access to a grower ration (40% cracked corn, 33% corn silage, 11% dried distillers grain, 13% ground grass hay, complete vitamin and mineral supplement with monensin) were weighed every 2 weeks, and daily individual intake was recorded. These data were used to generate average daily gain (ADG; lb/day), weight per day of age (WPDA; lb/day of age), dry matter intake (DMI; lb/day), feed conversion ratio (FCR; lb DMI/lb gain), and residual feed intake (RFI; lb/day). Below is a description of how each metric was calculated and an explanation of the application of each measurement: • Average daily gain (ADG; lb/day): calculated by regressing individual weight on day; improved accuracy of metric compared to the standard method (final weight-initial weight/days on test); higher ADG indicates greater growth • Weight per day of age (WPDA; lb/day of age): calculated as final body weight divided by age; provides an unbiased metric which evaluates growth performance adjusted for age; higher values indicate greater growth relative to the age of the animal • Dry matter intake (DMI; lb/day): calculated by regression of daily dry matter intake on day; improved accuracy compared to generating average daily intake (sum of all intake/days on test); daily dry matter was evaluated from feed samples and averaged to convert as fed feed intake to dry matter intake; higher values indicate greater feed intake • Feed conversion ratio (FCR; lb DMI/lb gain): calculated as the ratio of DMI to ADG; indicates pounds of feed required to gain 1 pound; lower values indicates more favorable conversion of feed to pounds • Residual feed intake (RFI; lb/day): calculated as the difference in DMI and expected feed intake (EFI); EFI is calculated by regression of DMI on ADG and metabolic mid weight (MMW); EFI represents the expected feed required to meet the growth and metabolic weight of each individual animal; the difference in actual intake (DMI) and EFI indicate the RFI; negative values indicate animals consumed less feed than expected given their growth (ADG) and metabolic weight (MMW)
9 MARCH 28, 2026 IN LARAMIE, WY
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