111 Development and Comparison of Methodology for Estimating Beef Cattle Contribution to Human Food Supply 1. Human Edible Protein Conversion and Methane Production. (1st March 2018)

• Record Type: Journal Article
• Authors: Baber, J R; Sawyer, J E; Wickersham, T A
• Is Part Of: Journal of animal science. Volume 96(2018)Supplement 1
• Page Start: 59
• Page End: 60
• Publication Date: 2018-03-01
• Subjects: human edible protein -- beef cattle -- methane; Livestock -- Periodicals; Livestock; Electronic journals; Periodicals; 636.005
• DOI: 10.1093/jas/sky027.111
• Languages: English
• ISSNs: 0021-8812

Abstract

Abstract: Cattle contribute to the food supply by converting human-inedible biomass into high-value beef products. Feeding human-edible feedstuffs and producing enteric methane are costs associated with beef production, and these systems have been implicated as inefficient, food competitive, or environmentally deleterious. Assertions are often made based on inputs that may not represent current production systems. A summative, deterministic model was developed to estimate human-edible protein (HeP) yield and methane production (per unit HeP) in beef systems, and to compare these metrics across each sector (cow-calf, growing, and feedlot) and the entire beef value chain. Feedstuffs used in cattle diets were categorized as human edible, inedible, or partially edible. Production of HeP in cattle at various stages of production were calculated using published relationships between EBW and protein, adjusted for inedible carcass products. Human-edible protein conversion efficiency (HePCE) was calculated as the ratio of HeP produced as beef to HeP consumed in each production stage. Methane production was calculated utilizing standard equations based on proportion of forage in diet within each production stage, and total methane production was expressed per unit HeP. Scenarios were arranged as a 2 × 2 factorial with 2 sets of dietary inputs and 2 sets of production parameters. Diets reflected those used in previous modeling reports (PD) or industry-current diets (CD) incorporating more coproducts. Production parameters were from previous modeling reports (PP) or characterized current industry (CP), yielding PDPP, CDPP, PDCP, and CDCP scenarios. The HePCE for CDCP (kg yield/kg input) was greatest in the cow-calf sector (8, 055.3) compared to stocker (17.04) and feedlot (0.68), and other scenarios followed a similar trend. The CDCP scenario had estimated lower HePCE (8, 055.3) than other scenarios (mean=9, 184.0). Total production system HePCE was 1.85 for CDCP; and 0.63 for the PDPP scenario. Others were intermediate. For the CDCP scenario, 54, 10, and 36% of total HeP was produced in the cow-calf, stocker and feedlot sectors; PDPP was similar (57, 13, and 30%, respectively). Overall, 2.53 kg of methane were produced per kg HeP for CDCP, and 2.29 for PDPP; in all scenarios methane yield was greater in the cow-calf sector than the feedlot sector (3.89 vs 0.76). Scenarios reflecting current industry practice suggest that more HeP is produced than consumed by cattle; such models provide useful estimates of the beef system's contributions to human nutrient supplies and methane yield relative to protein contribution.