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Title: Using carbon emissions, oxygen consumption, and energy retention estimates to calculate dietary energy partitioning and estimate ME intake by beef steers

Author
item Gunter, Stacey
item BURRUS, COLLEEN - Southern Arkansas University
item Moffet, Corey
item GREGORINI, PABLO - Lincoln University - New Zealand

Submitted to: Proceedings of International Symposium on the Nutrition of Herbivores
Publication Type: Abstract Only
Publication Acceptance Date: 5/2/2018
Publication Date: 9/28/2018
Citation: Gunter, S.A., Burrus, C., Moffet, C., Gregorini, P. 2018. Using carbon emissions, oxygen consumption, and energy retention estimates to calculate dietary energy partitioning and estimate ME intake by beef steers. Conference Proceedings of International Symposium on the Nutrition of Herbivores. 9:405.

Interpretive Summary:

Technical Abstract: Take home Message: Estimating ME intake by grazing cattle seems possible using respiration gas exchange estimates. Introduction: We hypothesized that carbon dioxide, methane, and oxigen exchange estimates in breath clouds could be used as biomarkers to ultimately estimate dry matter intake in grazing beef cattle when integrated into backward dietary energy partitioning calculations. Here, we aimed to estimate heat production through spot short-term measurements of gas consumption and emissions and the Brouwer (1965) equation, estimate energy retention via average daily gain, and estimate metabolizable energy intake (NASEM, 2016). Material and methods: Our experiment used 8 cross-breed beef steers (initial BW = 241 ± 4.1 kg) for a 77-d feeding period (June through August) to determine performance, respiration gas exchanges, energy retention, and heat production. Steers were housed in a pen equipped with individual feed bunks and access controlled by Calan gates. Steers were randomly assigned to 1 of 3 treatments as a multiple of ME intake (MEx) at maintenance (7.43 Megacalories of Metabolizable energy/day): 1.1 (1.1M, n = 3, dry matter intake = 4.10 kilograms), 1.4 (1.4M, n = 2, dry matter intake = 5.44 kilograms), and 1.8 (1.8M, n = 3, dry matter intake = 7.41 kilograms). Diets fed were long-stemmed wheat hay (Triticum aestivum L.; 15% crude protein, 64% total digestible nutrients) plus a daily supplement with 1.03 kilograms of alfalfa (Medicago sativa L.)/wheat middling pellets (15% crude protein) delivered via an automated head-chamber system (GreenFeed, C-Lock, Inc., Rapid City, SD USA) which measured carbon dioxide and methane emission, and oxygen consumption. On day 1, 14, 35, 56, and 77 of the experiment, body weight was recorded after a 17-hour fast to adjust for gastrointestinal fill. Heat production (Megacalories/day) was calculated from gas emissions and consumption [heat production = (3.866 × carbon dioxide (liters/day) + 1.200 × oxygen (liters/day) – 1.431 × nitrogen (grams/day)) × 1,000; Brouwer, 1965] and urinary nitrogen output [grams/day; 2.39 × 0.55 nitrogen intake (grams/day) – 3.61 × dry matter intake (kilograms/day); Dong et al., 2014]. Intake of metabolizable energy was calculated by adding heat production and to the energy retention estimates (NASEM, 2016). Dependent variables were analyzed with the MIXED procedure (SAS Institute, Inc.; Cary, NC USA) and LSMEANS separated with linear (L) and quadratic (Q) for unequally-spaced treatments. Results & Discussion: Average daily gain and ending BW increased linearly (Probability < 0.01) with increasing MEx. Likewise, carbon dioxide emissions and oxygen consumption increased linearly (Probability = 0.01) with MEx, but methane did not. The urinary nitrogen excretion increased linearly (Probability < 0.01) from 1.1M to 1.8M (32, 40, and 52 grams/day, standard error = 0.6, respectively). Energy retention and heat production increased linearly (Probability < 0.01) with increasing MEx. Hence, the predicted metabolizable energy intake increased linearly (Probability < 0.01) from 1.1M to 1.8M (11.74, 12.62, and 15.30 megacalories/day, standard error = 0.425, respectively). Performance, gas exchange, energy retention, and heat production by steer fed at three multiples of maintenance Treatments Contrast Item 1.1M 1.4M 1.8M SE L Q Average daily gain, kilograms 0.12 0.29 0.65 0.078 < 0.01 0.55 Ending body weight, kilograms 251 263 291 6.0 < 0.01 0.55 Gas exchanges, liters/day Carbon dioxide emission 1,957 2,090 2,274 65.7 0.01 0.97 Methane emission 227 237 237 11.1 0.41 0.69 Oxygen consumption 2,384 2,460 2,775 99.2 0.01 0.49 Energy retention, megacalories/day 0.34 0.77 2.03 0.221 < 0.01 0.33 Heat production, megacalories/day 11.40 11.84 13.26 0.425 < 0.01 0.53 Conclusion: These results indicate that exchange estimates of carbon dioxide, methane, and oxy