Effects of hay maturity on the enteric methane emission, intake, and energy metabolism by beef heifers

Authors: Friend, Emalee; Gunter, Stacey; Moffet, Corey; BECK, PAUL - Oklahoma State University

Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 10/27/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Twelve heifers (initial BW=296 ± 30 kg) were used to determine the effect of wheat (Triticum aestinum L.) hay maturity (HM) on energetics and gas emissions when harvested at 3 maturities and fed for three 7-d periods. Heifers were randomly assigned to 1 of 3 maturities including immature hay cut at stem elongation [Zadok score (Tottman, 1987) = 3.1, 37% NDF], intermediate maturity hay cut at boot stage (Zadok = 3.9-4.1, 55% NDF), and mature hay cut at milk stage (Zadok = 7.9, 63% NDF). Hay was fed for ad libitum intake plus a daily supplement of 0.90 kg of pellets (12% CP) were offered via an automated head-chamber system that measured heifer CO2, CH4, and O2 fluxes. The experiment was designed as a split-plot with HM as the main plot, period the subplot, and beginning body weight (BW) as a covariate; main effects were compared using linear and quadratic contrasts. Dry matter intake (DMI) had a negative linear response with HM (P = 0.05), but DMI did not differ (P = 0.13) among periods. Neither HM nor period had an effect (P = 0.16) on total enteric CH4 emissions. However, CO2 emission and O2 consumption had a positive quadratic response to both HM (P = 0.02) and period (P = 0.03). Heat production (HP) had a positive linear effect (P < 0.01) to HM and negative quadratic response to period (P < 0.01). Hay maturity and period had a significant negative linear effect (HM, P < 0.01) and quadratic (period, P < 0.01) effect on metabolizable energy (ME) intake (ME = HP + retained energy). These results indicate that as HM decreased it has a negative effect on DMI, CO2 emissions, O2 consumption, HP, and MEI, but did not have an effect (P = 0.16) on total enteric CH4 emission.

Technical Abstract: Twelve heifers (initial BW=296 ± 30 kg) were used to determine the effect of wheat (Triticum aestinum L.) hay maturity (HM) on energetics and gas emissions when harvested at 3 maturities and fed for three 7-d periods. Heifers were randomly assigned to 1 of 3 maturities including immature hay cut at stem elongation [Zadok score (Tottman, 1987) = 3.1, 37% NDF], intermediate maturity hay cut at boot stage (Zadok = 3.9-4.1, 55% NDF), and mature hay cut at milk stage (Zadok = 7.9, 63% NDF). Hay was fed for ad libitum intake plus a daily supplement of 0.90 kg of pellets (12% CP) were offered via an automated head-chamber system that measured heifer CO2, CH4, and O2 fluxes. The experiment was designed as a split-plot with HM as the main plot, period the subplot, and beginning body weight (BW) as a covariate; main effects were compared using linear and quadratic contrasts. Dry matter intake (DMI) had a negative linear response with HM (P = 0.05), but DMI did not differ (P = 0.13) among periods. Neither HM nor period had an effect (P = 0.16) on total enteric CH4 emissions. However, CO2 emission and O2 consumption had a positive quadratic response to both HM (P = 0.02) and period (P = 0.03). Heat production (HP) had a positive linear effect (P < 0.01) to HM and negative quadratic response to period (P < 0.01). Hay maturity and period had a significant negative linear effect (HM, P < 0.01) and quadratic (period, P < 0.01) effect on metabolizable energy (ME) intake (ME = HP + retained energy). These results indicate that as HM decreased it has a negative effect on DMI, CO2 emissions, O2 consumption, HP, and MEI, but did not have an effect (P = 0.16) on total enteric CH4 emission.