02904naa a2200253 a 450000100080000000500110000800800410001902400250006010000150008524501310010026000090023150001410024052020480038165300180242965300150244765300290246265300080249165300190249965300240251870000180254270000180256070000190257877300530259710539862019-10-11       2016    bl uuuu     u00u1 u    #d7 a10.1071/AN154772DOI1 aHERD, R.M.  aProxies to adjust methane production rate of beef cattle when the quantity of feed consumed is unknown.h[electronic resource]  c2016  aArticle history: Received 24 August 2015, accepted 11 November 2015, published online 9 February 2016. http://dx.doi.org/10.1071/AN15477  aAbstract: The aim of this experiment was to evaluate the utility of CO2 production rate (CPR; g CO2/d) and animal weight (WT) data as proxies for feed-intake to adjust methane production rate (MPR; g CH4/d) in situations where dry-matter intake (DMI) is not known. This experiment measured individual-animal DMI, MPR and CPR in the feedlot, and then again on restricted quantities of grain and roughage diets in open-circuit respiration chambers. Of the 59 cattle tested in the feedlot, 41 had MPR and CPR recorded, and 59 and 57 had test results on the restricted grain and roughage rations. Methane production relative to DMI by individual animals was calculated as methane yield (MY; MPR/ DMI) and as residual methane production (RMPDMI; calculated as MPR less predicted MPR based on DMI). A second form of residual methane production: RMPCO2, was calculated by regressing MPR against CPR to determine whether animals were producing more or less CH4 than predicted for their CPR. Carbon-dioxide production rate was positively associated with DMI in all 3 test phases (R2=0.25, 0.45 and 0.47; all P<0.001). The associations for MY with MPR:CPR were moderate and positive: R2=0.49 in the feedlot test; R2=0.37 in the restricted grain test; and R2=0.59 in the restricted roughage test, and with RMPCO2 R-square were 0.57, 0.34 and 0.59 in the 3 test phases (all P<0.001). The R-square for RMPDMI with MPR:CPR in all 3 tests were 0.50, 0.79 and 0.69, and with RMPCO2 R-square were 0.68, 0.79 and 0.68 (all P<0.001). The high R-square for MY with MPR:CPR and RMPCO2 and even higher R-square for RMPDMI with MPR:CPR and RMPCO2 in all 3 test phases showed that CPR can be used to adjust MPR data for DMI when DMI is not recorded. In the feedlot test, where animal WT data was recorded over 70 days, MPR adjusted for WT and WT gain had R-square with MY and RMPDMI of 0.60 and 0.83 respectively (P<0.001) offering the possibility that animal WT data determined over an extended time period could also be used as a proxy for DMI in adjustment of MPR.  aGANADO VACUNO  aGAS METANO  aGASES EFECTO INVERNADERO  aGEM  aGREENHOUSE GAS  aRESPIRATION CHAMBER1 aVELAZCO, J.I.1 aARTHUR, P. F.1 aHEGARTY, R. S.  tAnimal Production Science, 2016, 56, p. 231-237.