What question did this study set out to answer?

This research aims to assess the relationship between forage intake, feed efficiency, and greenhouse gas emissions during lactation and gestation in beef cows.

May 31, 2026Open Access

The relationship of forage intake, residual feed intake, and greenhouse gas emissions between lactation and gestation in beef cows

Key Points

This research aims to assess the relationship between forage intake, feed efficiency, and greenhouse gas emissions during lactation and gestation in beef cows.
Conducted over two years with 67 mature Angus and Angus-cross cows.
Cows were monitored for dry matter intake and emissions during 85-day lactation and gestation trials.
Used K-means clustering to categorize cows by feed efficiency based on residual feed intake.
Efficient cows consumed 18.8% less hay during lactation and 27.8% less during gestation compared to inefficient cows (P < 0.001).
Strong correlations were found between dry matter intake and residual feed intake across lactation and gestation (r = 0.82 and r = 0.68, respectively).
No significant differences in productivity metrics like body weight, gain, or milk yield were observed between feed efficiency classifications (P ≥ 0.52).

Abstract

Abstract The objective of this research was to evaluate dry matter intake (DMI), residual feed intake (RFI), and greenhouse gas emissions between lactation and gestation in mature beef cows fed an unprocessed grass hay diet. A two-year experiment was conducted using 67 mature Angus and Angus-cross cows (n = 41, Year 1; n = 26, Year 2) which included a minimum 85-d early-mid lactation trial (LACT) followed by a minimum 85-d early-mid gestation trial (GEST) in both years. Cows were housed in drylot pens at the Oklahoma State University Range Cow Research Center. Each pen was equipped with an individual intake monitoring system (SmartFeed, C-Lock Inc., Rapid City, SD) with a stocking density of 2.7 cows per feeder in Year 1, and 2.9 cows per feeder in Year 2. Cows were offered ad libitum access to long-stem, unprocessed bermudagrass hay (≥12.6% CP and ≥ 57% TDN, LACT; ≥12.4% CP and ≥ 54% TDN, GEST) and a mineral supplement. An open-circuit, portable gas quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) was placed in pens to measure carbon dioxide (CO2), methane (CH4), and oxygen (O2) flux. Cows were classified by K-means clustering into three categories of feed efficiency based on RFI of efficient (n = 23, LACT; n = 23, GEST), moderate (n = 27, LACT; n = 25, GEST), and inefficient (n = 17, LACT; n = 16, GEST) classifications. Efficient, moderate, and inefficient LACT DMI means were 13.9, 15.1, and 16.8 kg/d, and GEST DMI means for the 3 groups were 11.5, 12.6, and 15.2 kg/d respectively (P 0.001). Efficient classified cows consumed 18.8% (LACT) and 27.8% (GEST) less hay than inefficient classified cows (P 0.001). There were no differences for body weight (BW), average daily gain (ADG), milk yield, body condition score (BCS), or calf weaning weight (WW) between classification groups in either physiological stage (P ≥ 0.52). There were strong (P 0.001) positive phenotypic correlations for DMI (r = 0.82) and RFI (r = 0.68) between LACT and GEST. There were positive phenotypic correlations (P 0.001) between DMI and CO2, CH4, or heat production (HP) during LACT (r = 0.70 CO2; r = 0.61 CH4; r = 0.65 HP) and GEST (r = 0.58 CO2; r = 0.52 CH4; r = 0.58 HP). The results from this study suggest that identifying feed efficient mature cows based on RFI results in lower DMI with no difference in output metrics, and that RFI remains constant across physiological stages.

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