Comparative Analyses Of Enteric Methane Emissions, Dry Matter Intake, And Milk Somatic Cell Count In Different Residual Feed Intake Categories Of Dairy Cows

This study compared the different residual feed intake (RFI) categories of lactating Holsteins with respect to methane (CH4) emissions, dry matter intake (DMI, kg), milk somatic cell count (SCC, 10(3).mL(-1)), and beta-hydroxybutyrate (BHB, mmol.L-1). The RFI was calculated in 131 lactating Holstein cows that were then categorized into - RFI (RFI < 0) vs. +RFI (RFI > 0) and low- [RFI < - 0.5 standard deviation (SD)] vs. high-RFI (RFI > 0.5 SD) groups. Milk traits were recorded in 131 cows, whereas CH4 and carbon dioxide were measured in 83. Comparisons of -RFI vs. +RFI and low- vs. high-RFI showed 7.9% ( 22.3 +/- 0.40 vs. 24.2 +/- 0.39) and 12.8% (21.1 +/- 0.40 vs. 24.2 +/- 0.45) decrease (P < 0.05) in DMI of - RFI and low-RFI groups, respectively. Similarly, - RFI and low- RFI cows had lower (P < 0.05) CH4 (g.d(- 1)) by 9.7% (343.5 +/- 11.1 vs. 380.4 +/- 10.9) and 15.5% (332.5 +/- 12.9 vs. 393.5 +/- 12.6), respectively. Milk yield was not different (P > 0.05) in-RFI vs. +RFI and low vs. high comparisons. The -RFI and low-RFI cows had lower (P < 0.05) SCC in -RFI vs. +RFI and low-RFI vs. high-RFI comparisons. The BHB was lower (P < 0.05) in low-RFI compared with the high-RFI group. Low-RFI dairy cows consumed less feed, emitted less CH4 (g.d(-1)), and had lower milk SCC and BHB without differing in milk yield.