93 Predicting Metabolizable Energy from Digestible Energy for Growing and Finishing Beef Cattle and Relationships to Prediction of Methane

Abstract

Abstract Reliable predictions of metabolizable energy (ME) from digestible energy (DE) are necessary to prescribe nutrient requirements of beef cattle accurately. Our objectives were to add new data to a previously published database and re-evaluate the relationship between DE and ME and to describe and evaluate new methane prediction equations derived from the DE:ME relationship. The previous database, which included 87 treatment means from 23 respiration calorimetry studies was updated to evaluate the efficiency of converting DE to ME by adding 47 treatment means from 11 additional studies. Diets were fed to growing-finishing cattle under individual feeding conditions. A citation-adjusted linear regression equation was developed where dietary ME concentration (Mcal/kg of dry matter [DM]) was the dependent variable and dietary DE concentration (Mcal/kg) was the independent variable: ME = 1.0001 × DE – 0.3926. The slope did not differ from unity; therefore, the intercept defines the value of ME predicted from DE. For practical use, we recommend ME = DE - 0.39. Based on the relationship between DE and ME, the citation-adjusted loss of methane was calculated and yielded a citation-adjusted value of 0.2433 Mcal/kg of DMI. Recognizing that methane production decreases per unit of intake energy as DMI increases above maintenance, we also examined the relationship between multiples of maintenance intake and daily energy lost as methane. This citation-adjusted relationship was: CH4, Mcal/kg = 0.3344 – 0.05639 × multiple of maintenance. Both the 0.2433 value and the result of the intake-adjusted equation can be multiplied by DMI to yield an estimate of methane production. Further research is needed to determine whether coefficients to predict methane from DMI could be developed for specific diet types, levels of DMI relative to body weight, or other variables that affect the emission of methane.