321 Evaluation of Heifer Forage Efficiency Through RFI and Greenhouse gas Emissions. (21st September 2022)

• Record Type: Journal Article
• Authors: Briggs, Emma A; Horton, Kade; Moore, Mikayla F; Lalman, David
• Is Part Of: Journal of animal science. Volume 100(2022)Supplement 3
• Page Start: 153
• Page End: 153
• Publication Date: 2022-09-21
• Subjects: beef cattle -- greenhouse gases -- residual feed intake; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/skac247.284
• Languages: English
• ISSNs: 0021-8812

Abstract

Abstract: The objective of this study was to evaluate the relationship between beef heifer feed efficiency and subsequent greenhouse gas emissions using an unprocessed hay diet. Fifty-four Angus and Angus Herford cross heifers were subject to a 71-day hay intake test using individual intake technology (C-Lock Inc., Rapid City, SD) with a stocking rate of 3.6 heifers per feeder. Heifers were blocked by BW into 2 drylot pens (HEAVY, n=21; LIGHT, n=33) at the Oklahoma State University Range Cow Research Center located near Stillwater, OK. Throughout the study, heifers were fed a long-stem, unprocessed, grass hay diet (10.8% CP, 2.0 Mcal ME, and 56% TDN) with 21-d adaptation. A subset of 39 heifers were used for the collection of gas flux data using an open-circuit, portable, gas-quantification system (GreenFeed, C-Lock Inc., Rapid City, SD) to measure (means±SD) oxygen consumption (3, 118±330.9 g/d), carbon dioxide production (4, 664±467.9 g/d), and methane production (169±23.4 g/d). Phenotypic measures (means±SD) for dry matter intake (DMI), average daily gain (ADG), average body weight (BW), and residual feed intake (RFI) were 6.75±1.12 kg, 0.15±0.2 kg, 312.7±30.5 kg, and 0.08±0.84 kg, respectively. Predicted DMI was calculated using a multiple regression equation (-3.11 + 0.13*BW 0.75 +0.76*ADG; P< 0.05; R2=0.43) in R. To further evaluate forage efficiency, heifers were segregated by 0.5 SD into three RFI categories of efficient (n=13), average (n=31), and inefficient (n=10) resulting in means of 5.8, 6.76, and 7.94 kg DMI and 0.16, 0.16, and 0.15 kg ADG, respectively. There was no significant difference (p< 0.05) between RFI categories for ADG, CO2, CH4, and O2. Phenotypic correlations of DMI with CO2, CH4, and O2 were 0.59, 0.45, and 0.61, respectively. Efficient heifers consumed 21% less forage compared with inefficient heifers, suggesting that improvement in forage utilization can be achieved when efficiency is evaluated using an unprocessed grass hay diet.