Efficacy of ionophores in cattle diets for mitigation of enteric methane

• Published in: Journal of animal science Vol. 84; no. 7; pp. 1896 - 1906
• Main Authors: Guan, H, Wittenberg, K.M, Ominski, K.H, Krause, D.O
• Format: Journal Article
• Language: English
• Published: Savoy, IL American Society of Animal Science 01.07.2006; Am Soc Animal Sci
• Subjects: acetic acid; air pollution; ammonia; Angus; Animal Feed; Animal Nutritional Physiological Phenomena; Animal productions; Animals; beef cattle; Biological and medical sciences; Cattle - metabolism; cattle feeding; Diet - veterinary; Drug Resistance; duration; Eukaryota - drug effects; feed additives; feed concentrates; Fundamental and applied biological sciences. Psychology; Gastrointestinal Tract - drug effects; Gastrointestinal Tract - metabolism; Gastrointestinal Tract - parasitology; Ionophores - administration & dosage; Ionophores - pharmacology; lasalocid; Lasalocid - administration & dosage; Lasalocid - pharmacology; Male; Methane - metabolism; methane production; monensin; Monensin - administration & dosage; Monensin - pharmacology; pollution control; propionic acid; rumen fermentation; rumen fluids; rumen protozoa; steers; Terrestrial animal productions; Time Factors; Vertebrates; volatile fatty acids; yearlings; Methane; Protozoa; Antifungal agent; Farming animal; Lasalocid; Diet; enteric methane; Monensin; Livestock; cattle; Ionophore
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas.2005-652

Use of ionophores in cattle diets has been proposed as a strategy for mitigation of enteric CH₄ emissions. Short- and long-term effects of feeding a single ionophore (monensin) or rotation of 2 ionophores (monensin and lasalocid) on enteric CH₄ emissions were evaluated in 36 Angus yearling steers (328 ± 24.9 kg of BW) over a 16-wk period. Steers were randomly assigned to 6 dietary treatments of 6 steers each. The 6 diets were low-concentrate without ionophore supplementation, low-concentrate with monensin supplementation, low-concentrate with a 2-wk rotation of monensin and lasalocid supplementation, high-concentrate without ionophore supplementation, high-concentrate with monensin supplementation, and high-concentrate with a 2-wk rotation of monensin and lasalocid supplementation. Daily enteric CH₄ emissions, as measured using the SF₆ tracer gas technique, ranged from 54.7 to 369.3 L/steer daily. Supplementing ionophores decreased (P < 0.05) enteric CH₄ emissions, expressed as liters per kilogram of DMI or percentage of GE intake, by 30% for the first 2 wk and by 27% for the first 4 wk, for cattle receiving the high-concentrate and low-concentrate diets, respectively. Cattle fed a rotation of ionophores did not (P > 0.05) exhibit a greater decrease and did not (P > 0.05) have a longer period of depressed enteric CH₄ emissions compared with cattle receiving monensin only. Ionophore supplementation did not (P > 0.05) alter total ruminal fluid VFA concentration; however, the acetate:propionate ratio and ammonia-N concentration in ruminal fluid were decreased (P < 0.001) from the time that ionophores were introduced to the time they were removed from the diets. Both monensin and the rotation of monensin and lasalocid decreased (P < 0.001) total ciliate protozoal populations by 82.5% in the first 2 wk and by 76.8% in the first 4 wk during which they were supplemented in the high-concentrate and low-concentrate diets, respectively. Original ciliate protozoal populations were restored by the fourth and sixth week of supplementation when cattle were fed the high- or low-concentrate diets, respectively. No significant change was observed thereafter. These data suggest that the effects of ionophores on enteric CH₄ production are related to ciliate protozoal populations and that ciliate protozoal populations can adapt to the ionophores present in either low- or high-concentrate diets. Rotation of monensin and lasalocid did not (P > 0.05) prevent ciliate protozoal adaptation to ionophores.