Evaluation of several potential bioactive agents for reducing protozoal activity in vitro

A. N. Hristov, M. Ivan, L. Neill, T. A. McAllister

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The effects of 14 bioactive agents on ruminal fermentation and protozoal activity were investigated in vitro as potential feed additives to improve feed efficiency. Agents studied were: lecithin, herring meal, canola oil, coconut oil, linseed oil, palm oil, and soybean oil, with each oil at final concentrations of 0.5, 1.0 and 2.0%; the saponin-containing plants Yucca schidigera (yucca) and Quillaja saponaria Molina (quillaja), tannic acid, and bentonite, each at 0.1, 0.2. and 0.4%; the surfactant Tween 80 (at 0.05, 0.1, and 0.2%); and the ionophores monensin (at 2.5, 5.0, and 10 mg/l) and salinomycin (at 1.25, 2.5, and 5.0 mg/l). Duplicate 4 h incubations each included controls (no additives) and 15N labeled casein as a N tracer. Yucca, tannic acid and both ionophores decreased (P < 0.05) NH3 concentrations. Total free amino acids (TFAA) were decreased (P < 0.05) by yucca and by bentonite, but were increased (P < 0.05) by fish meal, monensin and salinomycin. Tannic acid and bentonite reduced (P < 0.05) total VFA concentrations, and tannic acid reduced (P < 0.05) the acetate:propionate (A:P) ratio. Bentonite, tannic acid, palm oil, quillaja and salinomycin reduced (P < 0.05) carboxymethylcellulase (CMCase), xylanase, and amylase activities, whereas monensin, lecithin, Tween 80, yucca, and the feed oils (except coconut) decreased (P < 0.05) amylase activity only. Protozoal populations, which comprised 84% Entodinium spp., decreased (P < 0.05) with tannic acid, lecithin and quillaja. Tannic acid, fish meal, and the ionophores reduced (P < 0.05) the rate of protozoal engulfment of bacteria. Fish meal and salinomycin, and the higher concentrations of quillaja and Tween 80 depressed (P < 0.05) incorporation of 15N from casein into bacterial cells. Only lecithin effectively reduced protozoal numbers, by 27%, without impeding the extent of 15N incorporation into bacteria.

Original languageEnglish (US)
Pages (from-to)163-184
Number of pages22
JournalAnimal Feed Science and Technology
Issue number1-4
StatePublished - Mar 31 2003

All Science Journal Classification (ASJC) codes

  • Animal Science and Zoology


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