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Modeling ruminant methane emissions from the U.S. beef cattle industry
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Computer models were constructed to estimate methane emissions from cow/calf, replacement heifers, burs, stockers and feedlot sectors of the U.S. beef cattle industry. Methane (CH4) yields were calculated based on net energy values and forage/grain levels. Criteria in the models included: percent grain in diet, average daily gain, body condition score, frame score and the types of technologies used, (ionophore, growth regulating implant, adequate protein/energy and mineral supplementation), cows stage of production and peak milk production (kg/d), age of dam, sex, and in feedlots, percentage of grain in starter, intermediate and finishing rations. Methane production for a cow on a 365 d breeding cycle ranged from a high of 87.7 kg CH4/yr when consuming low quality coastal forage without an ionophore, to a low of 44.0 kg CH4/yr when consuming a balanced corn silage diet and utilizing ionophore technology. Calves grown to weaning at 205 d of age, consuming milk and a low quality coastal diet with no technology produced 12.5 kg of CH4, which decreased to 8.7 kg when all technologies were applied. Calves on milk and corn silage diet with no technology produced 7.5 kg of CH4, which decreased to 5.2 kg when all technologies were applied. Stocker calves with a common weight end point of 318 kg and consuming- low quality coastal with no technology produced 13.4 kg of CH4, which decreased to 12.0 kg with an ionophore and 10.4 kg when all available technologies were applied. Stockers on a high quality coastal diet with no technology produced 7.5 kg of CH4, which decreased to 5.8 kg when all when all technologies were applied. Methane production in feedlot cattle on grain diets was reduced from 4.7 kg to 4.2 kg by an ionophore as opposed to 5.9 kg vs. 5.3 kg when finished on corn silage rations. In feedlots, cattle finished on a high concentrate diet without technologies produced 4.7 kg of methane, which decreased to 3.7 kg when all technologies were applied. Feedlot calves entering this sector directly after weaning and utilizing grain-based diets currently produce. 13 kg of methane vs. .26 kg if same calves enter feedlot after a 180 d stocker phase and utilize forage based diets. Considerable opportunities exist, especially in the cow/calf sectors, for technologies which will enhance energy recovery, and further reduce methane emissions by the U.S. beef cattle industry.
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Turk, Danny Carroll (1993). Modeling ruminant methane emissions from the U.S. beef cattle industry. Master's thesis, Texas A&M University. Available electronically from
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