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Feed and methane test phase characteristics

 
Methane test phase
Feed and traits Feedlot Chamber
grain
Chamber
roughage
Feed type Grain based Grain based Alfalfa based
Feed offered Ad libitum Restricted1 Restricted2
ME content of feed, MJ/kg DM 12.6 12.6 9.0
Methane measurement equipment3 GEM RC RC
1Restricted to 70% of feedlot DMI.
2Restricted to 1.2 times maintenance energy requirements.
3GEM and RC refer to GreenFeed emission monitors and respiration chambers, respectively.



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Definition of traits

 
Trait name Abbreviation Units Definition
Start weight Start BW kg BW in feedlot at start of RFI test by regression of BW on test day
Test weight Test BW kg Midtest BW for RFI test by regression of BW on test day or BW taken on morning before being put into respiration chamber
Average daily gain ADG kg/d In feedlot by regression of BW on RFI test day
Dry matter intake DMI kg/d DMI during methane test
Feed conversion ratio FCR kg/kg DMI/ADG
Residual feed intake RFI kg DM/d Difference between measured DMI and expected DMI
Methane production rate MPR g/d Methane produced
Methane intensity MI g/kg gain MPR/ADG in the feedlot
Methane yield MY g/kg DM MPR/DMI
Residual methane production, first form RMPJ g/d MPR net of expected MPR from DMI using formula of Johnson et al. (1995)
Residual methane production, second form RMPR g/d MPR was regressed against DMI, with the residuals being RMPR



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Descriptive statistics for animal performance, feed efficiency, and methane emission traits of Angus cattle in the 3 methane test phases

 
Animal and methane test type1 Units Mean SD Minimum Maximum
Animal background information2
    Sire (n = 4) RFI-EBV kg/d 0.11 1.10 −0.97 1.42
    Accuracy of sire RFI-EBV % 68 6 59 71
    Dam RFI-EBV kg/d −0.05 0.69 −1.03 1.25
    Accuracy of dam RFI-EBV % 61 6 53 74
    Midparent RFI-EBV kg/d 0.03 0.83 −1.00 1.12
    Start BW kg 410 36 342 499
Feedlot test3
    Start of test age d 579 16 537 606
    Test BW kg 454 38 383 548
    ADG kg/d 1.40 0.20 0.97 1.95
    DMI kg/d 12.2 1.1 9.9 14.8
    FCR kg/kg 8.9 1.4 5.8 12.0
    RFI kg/d 0.0 0.8 −1.8 1.9
    MPR g/d 144 16 118 190
    MI g/kg 103 14 72 124
    MY g/kg 11.7 1.5 9.5 15.9
    RMPJ g/d 20 17 −7 66
    RMPR g/d −2 16 −21 44
Chamber grain test4
    Start of test age d 687 15 648 711
    Test BW kg 519 49 413 646
    DMI kg/d 7.2 1.5 3.6 11.6
    MPR g/d 106 23 66 177
    MY g/kg 15.0 3.1 10.4 23.3
    RMPJ g/d 34 20 2 101
    RMPR g/d 0 19 −32 68
Chamber roughage test5
    Start of test age d 722 18 684 759
    Test BW kg 544 43 460 640
    DMI kg/d 7.6 0.7 5.4 8.7
    MPR g/d 144 18 99 195
    MY g/kg 19.0 1.9 15.7 25.6
    RMPJ g/d −8 15 −35 38
    RMPR g/d 0 14 −26 44
1Test BW = test period BW; FCR = feed conversion ratio; RFI = residual feed intake; MPR = methane production rate; MI = methane intensity; MY = methane yield; RMPJ and RMPR = residual methane production with expected MPR calculated using Johnson et al. (1995) and regression of MPR on DMI, respectively.
2RFI-EBV denotes EBV for residual feed intake.
3n = 41, comprising 22 steers and 19 heifers.
4n = 59, comprising 29 steers and 30 heifers.
5n = 57, comprising 28 steers and 29 heifers.



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Phenotypic correlation coefficients among methane traits within each of the 3 methane test phases1

 
Methane test and traits2 MY MI RMPJ RMPR
Feedlot test3
    MPR 0.71 0.57 0.78 0.95
    MY 0.33 0.99 0.89
    MI 0.38 0.51
    RMPJ 0.94
Chamber grain test4
    MPR 0.42 0.76 0.82
    MY 0.89 0.85
    RMPJ 0.99
Chamber roughage test5
    MPR 0.69 0.68 0.79
    MY 1.00 0.99
    RMPJ 0.99
1All the correlation coefficients are significantly (P < 0.05) different from zero.
2MPR = methane production rate; MI = methane intensity; MY = methane yield; RMPJ and RMPR = residual methane production with expected MPR calculated using Johnson et al. (1995) and regression of MPR on DMI, respectively.
3n = 41 animals.
4n = 59 animals.
5n = 57 animals.



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Phenotypic correlation coefficients for methane traits across the 3 methane test phases

 
Chamber grain test
Chamber roughage test
Trait1 MPR MY RMPJ RMPR MPR MY RMPJ RMPR
Feedlot test
    MPR 0.27a,2 0.46b,3
    MY 0.40b 0.54b
    RMPJ 0.43b 0.58b
    RMPR 0.43b 0.58b
Chamber grain test
    MPR 0.47b,4
    MY 0.36b
    RMPJ 0.38b
    RMPR 0.41b
aCorrelation coefficients are significantly different from zero at P < 0.10.
bCorrelation coefficients are significantly different from zero at P < 0.05.
1MPR = methane production rate; MY = methane yield; RMPJ and RMPR = residual methane production with expected MPR calculated using Johnson et al. (1995) and regression of MPR on DMI, respectively.
2n = 41 animals.
3n = 40 animals.
4n = 57 animals.



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Phenotypic correlation coefficients between animal performance and feed efficiency traits in the feedlot test

 
Trait1 Test BW DMI RFI FCR RFI-EBVmp2
ADG 0.41b 0.17 0.00 −0.83b −0.37b
Test BW 0.67b 0.00 −0.03 −0.30b
DMI 0.73b 0.39b 0.24a
RFI 0.41b 0.56b
FCR 0.49b
aCorrelation coefficient is significantly different from zero at P < 0.10. n = 59 animals.
bCorrelation coefficient is significantly different from zero at P < 0.05. n = 59 animals.
1Test BW = test period BW; RFI = residual feed intake; FCR = feed conversion ratio.
2Denotes midparent EBV for residual feed intake.



View Full Table | Close Full ViewTable 7.

Phenotypic correlation coefficients between methane traits and animal performance and feed efficiency traits

 
Methane test and traits1 MPR MI MY RMPJ RMPR
Feedlot test2
    ADG 0.19 −0.69b 0.24 0.23 0.22
    Test BW 0.47b −0.08 −0.05 0.05 0.28a
    DMI 0.28a 0.26 −0.48b −0.39b −0.04
    FCR −0.01 0.68b −0.47b −0.42b −0.22
    RFI −0.05 0.16 −0.54b −0.52b −0.29a
    Midparent RFI-EBV3 −0.09 0.21 −0.22 −0.25 −0.18
    Midparent RFI-EBV4 0.08 0.30a −0.27a −0.27a −0.09
Chamber grain test5
    DMI 0.55b −0.50b −0.13 −0.02
    Feedlot FCR −0.20 −0.12 −0.21 −021
    Feedlot RFI −0.05 −0.19 −0.23 −0.21
    Midparent RFI-EBV3 −0.04 −0.10 −0.13 −0.12
    Midparent RFI-EBV4 0.01 −0.10 −0.11 −0.01
Chamber roughage test6
    DMI 0.61b −0.14 −0.17 0.00
    Feedlot FCR −0.31b −0.29b −0.27b −0.30b
    Feedlot RFI −0.37b −0.48b −0.49b −0.49b
    Midparent RFI-EBV3 −0.35b −0.39b −0.39b −0.40b
    Midparent RFI-EBV4 −0.15 −0.35b −0.36b −0.33b
aCorrelation coefficient is significantly different from zero at P < 0.10.
bCorrelation coefficient is significantly different from zero at P < 0.05.
1Test BW = test period BW; FCR = feed conversion ratio; RFI = residual feed intake; MPR = methane production rate; MI = methane intensity; MY = methane yield; RMPJ and RMPR = residual methane production with expected MPR calculated using Johnson et al. (1995) and regression of MPR on DMI, respectively.
2n = 41 animals.
3Denotes midparent EBV for residual feed intake.
4Coefficents recalculated after first fitting Test BW in the linear models; see Materials and Methods for further explanation.
5n = 59 animals.
6n = 57 animals.