THE PREDICTION OF METHANE PRODUCTION OF HOLSTEIN COWS BY SEVERAL EQUATIONS

Ruminants are one of many sources contributing to atmospheric methane. The accuracy of seven published equations for methane prediction was evaluated using a data file consisting of 16 experiments (602 observat ions). Methane energy emissions ranged from .89 to 7.21 Mcal/d for Hol stein cows. The DMI ranged from 9.7 to 28.7 kg/d for lactating cows an d 4.0 to 12.9 kg/d for nonlactating cows. Mean dietary concentrations of ADF, CP, and ether extract were similar for lactating and nonlactat ing cows (20.9, 16.5, and 3.0% for lactating cows versus 21.2, 15.7, a nd 2.9% for nonlactating cows, respectively). Milk production ranged f rom 2.7 to 55.9 kg/d. Prediction equations were ranked by correlation coefficients and error of prediction. Prediction of methane energy los s from lactating and nonlactating Holstein cows with equations based o n the daily total intake or intake of digested cellulose, hemicellulos e, and nonfiber carbohydrates (OM - NDF - CP - ether extract) provided the highest correlation coefficients for reproducibility and the lowe st errors of prediction. Predictions were poor for lactating cows when a quadratic function of DMI was used. In general, equations estimated methane production more accurately and precisely for nonlactating tha n for lactating cows.