Estimation of human-edible protein conversion efficiency, net protein contribution, and enteric methane production from beef production in the United States

Abstract

A model was developed to estimate beef’s contribution toward meeting human protein requirements using a summative model of net protein contribution (NPC) and methane production. NPC was calculated by multiplying the ratio of human-edible protein (HeP) in beef to the HeP in feedstuffs by the protein quality ratio (PQR). PQR describes the change in biological value of HeP that occurs when plant-derived HeP is converted to beef. An NPC > 1 indicates that the production system is positively contributing to meeting human requirements; systems with NPC < 1 reduce the net protein available to meet human requirements. Scenarios were arranged as a 2 × 2 factorial with two sets of dietary inputs and two sets of production parameters. Dietary inputs represented either inputs used in a previous report estimating HeP (previous diet; PD) or inputs more representative of conventional beef production systems (current diet; CD). Production parameters were either drawn from previous reports (previous parameters; PP) or chosen to characterize current industry standards (current parameters; CP). The HeP conversion efficiency (HePCE) for current industry diets and production parameters (CDCP) (kg HeP yield/kg HeP input) was greatest in the cow–calf sector (2,640.83) compared with stocker (5.22) and feedlot (0.34), and other scenarios followed a similar trend. In addition, the entire production system had an HePCE of 0.99 for CDCP; the previous model diets and production parameters (PDPP) scenario estimated HePCE to be 0.46, and other scenarios were in between. For the CDCP scenario, 56%, 10%, and 34% of the HeP were produced in the cow–calf, stocker, and feedlot sectors; PDPP was similar (59%, 13%, and 28%, respectively). PQR averaged 3.04, 3.04, and 2.64 for cow–calf, stocker, and feedlot sectors, respectively, indicating each sector enhances the biological value of the HeP fed. The NPC was greatest for the cow–calf sector (8,794), followed by the stocker and feedlot sectors (8.85 and 0.23, respectively). The entire beef value chain had a PQR of 2.68 and NPC ranged from 1.01 to 3.11, which correspond to PDPP and CDCP, respectively. Overall, 3.05 kg of CH4 were produced per kilogram HeP for CDCP and 2.58 for PDPP, with the cow–calf sector being greater than the feedlot sector (4.53 vs. 0.94 kg CH4/kg HeP, CDCP). Our results suggest that each individual beef sector and the entire value chain produce more high-quality HeP than is consumed in production. Accordingly, beef is a net contributor to meeting human protein requirements.

Feeding Dairy Cows With “Leftovers” and the Variation in Recovery of Human-Edible Nutrients in Milk

“…These are not trivial components of the overall dairy system; Thoma et al (2013) attributed 13% of dairy farm greenhouse gas emissions to beef production, and Tichenor (2015) suggested that this may be an underestimate. Nevertheless, dietary strategies similar to those evaluated herein can also contribute to net HE protein production in beef systems (Baber et al, 2018), and it is likely that our comparisons would hold for net beef + milk production, assuming ECO diets were employed across a farm. Future studies employing a lifecycle assessment using our approach would provide a more comprehensive estimation of net production of HE nutrients by the dairy industry.…”

Sobre algunos mitos y realidades de la ganadería bovina

“…En contraste con las cifras, comúnmente se arma que 1 kg de carne requiere 2,8 kg de alimento comestible para los rumiantes y 3,2 kg para monogástricos. Sin embargo, el valor proteico de los productos derivados del ganado es 19 % superior a la calidad del producto ingerido para producir esa proteína (Baber et al, 2018;Flachowsky et al, 2017). La producción de proteína de origen bovino es altamente eciente y se puede considerar como una fuente de alimento de alto valor biológico para los humanos.…”

“…Los alimentos de origen animal tienen mayor contenido de proteína verdadera que los alimentos de origen vegetal y el valor biológico de la proteína animal es aproximadamente 1,4 veces mayor que el de la proteína vegetal (Baber et al, 2018;Flachowsky et al, 2017). Además, se cree que la cantidad y la calidad de la proteína ayudan a regular la ingesta de alimentos en humanos (y otros animales) y reducir o controlar la obesidad (Simpson & Raubenheimer, 2005).…”

Recent advances to improve nitrogen efficiency of grain-finishing cattle in North American and Australian feedlots

“…For example, Groenestein et al (2016) estimated that the quantity of feed N required to produce meat is greatest for beef (~5 kg N/kg meat) and least for broiler chickens (~2 kg N/kg meat). However, in contrast to non-ruminants, because most of the protein in the diets of the cow herd, grazing stocker cattle and finishing cattle is from human-non-edible protein sources, cattle production actually increases the value of low-quality grass, grain and by-product proteins to highquality human-edible protein sources (Baber et al 2018). Approximately 40-60% of the N consumed daily by feedlot cattle is excreted in urine with 20-30% of N consumed being excreted in faeces .…”