|Nisbet, David - Dave|
Submitted to: American Dairy Science Association Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/21/2006
Publication Date: 7/9/2006
Citation: Anderson, R.C., Ramlachan, N., Gutierrez, H., Carstens, G.E., Majak, W., McDiarmid, R., Callaway, T.R., Harvey, R.B., Horrocks, S.M., Edrington, T.S., Nisbet, D.J. 2006. Gastrointestinal metabolism and plasma concentrations of the methane-inhibitor, nitroethane, in fed steers [abstract]. Journal of Animal Science. 89(Suppl. 1):128. Interpretive Summary:
Technical Abstract: To investigate the metabolism and absorption of the methane-inhibitor, nitroethane (NE), we fed 18 steers (403 ± 26 kg BW; mean ± SD) a 50% concentrate diet and administered 0, 80 or 160 mg NE/kg BW per day (6 steers/treatment) for 14 days. Treatments were administered via oral gavage twice daily. Ruminal fluid and feces were collected on days -1, 1, 2, 7 and 14 of treatment; blood samples were collected at 0 and 6 h and at 1, 2 and 7 d of treatment. Rates of NE degradation (dNE/dt) were determined via in vitro incubation. Concentrations of NE in samples collected from the incubations and in plasma were determined colorimetrically. Mean (± SD) NE concentrations in plasma 6 h after initiation of NE treatments were 0.12 ± 0.02 and 0.41 ± 0.05 µmol/ml for steers administered 80 or 160 mg NE/kg BW per day, respectively, thus indicating rapid absorption of NE. Plasma NE concentrations peaked 1 d after initiation of the 80 or 160 mg NE/kg BW per day treatments (0.38 ± 0.10 and 1.14 ± 0.06 µmol/ml, respectively). Plasma NE concentrations declined thereafter to 0.25 ± 0.14 and 0.78 ± 0.28 and to 0.18 ± 0.06 and 0.44 ± 0.34 µmol/ml on days 2 and 7 for the 80 or 160 mg NE/kg BW per day treatment groups, respectively, thus indicating decreased absorption or more rapid excretion or metabolism of the compound. An analysis of variance revealed that ruminal dNE/dt from steers administered NE were more than 2.5-fold higher (P < 0.05) than the mean (± SD) rate observed in steers administered no NE (0.051 ± 0.02 µmol NE/ml ruminal fluid per h). This observation suggests an enrichment of NE-degrading bacteria in the rumen of both groups of NE-treated steers. Fecal dNE/dt (0.067 ± 0.04 µmol NE/g feces per h) were unaffected by treatment thus indicating that NE was not present at high enough concentrations in the lower gut to affect a similar enrichment of NE-degrading bacteria in these steers.