HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Daugherty, M. S. Articles by Hageman, J. H. Search for Related Content PubMed PubMed Citation Articles by Daugherty, M. S. Articles by Hageman, J. H.

Vitamin B₁₂ and Monensin Effects on Performance, Liver and Serum Vitamin B₁₂ Concentrations and Activity of Propionate Metabolizing Hepatic Enzymes in Feedlot Lambs^{1, 2,}

New Mexico State University, Las Cruces 88003-009

Abstract

Monensin in ruminant diets increases production of propionic acid. We have tested the hypothesis that propionic acid may be elevated to such an extent by monensin that it cannot be optimally metabolized by the methyl malonyl-CoA pathway requiring vitamin B₁₂ (B₁₂) in the liver. Thus, the effects of weekly B₁₂ injections (10 mg·head^-1·wk^-1, intramuscularly) with and without dietary monensin (25 mg/kg diet) on average daily gain (ADG), dry matter intake (DMI), feed to gain ratio (F/G), liver and serum B₁₂ concentrations and liver activity of propionate metabolizing enzymes were examined in an 84-d trial. Sixteen lambs (27.5 kg average initial wt) were assigned randomly to one of four treatments in a factorial arrangement: monensin plus B₁₂, monensin without B₁₂, no monensin plus B₁₂ and no monensin without B₁₂. Lambs were fed an 80% concentrate diet and slaughtered at the end of the trial. Liver samples were obtained by biopsy on d 0 and at slaughter on d 84 to determine activity of propionate metabolizing enzymes and B₁₂ concentrations. Serum samples were taken on d 0, 28, 56 and 84 to determine serum B12 concentration. Neither monensin nor B₁₂ affected (P>.10) ADG, DMI or F/G. Lambs receiving B₁₂ had higher (P<.01) serum B₁₂ concentrations, but this was not reflected (P>.10) in higher liver B12 concentrations. No difference (P>.10) in liver propionate metabolizing activity among treatments was detected; however, monensin decreased (P<,05) fumarate and malate formation by liver homogenates. Liver B12 concentrations were highly correlated with endogenous propionate metabolizing activity at d 0 (r = .73, P<.01) and d 84 (r = .51, P<.05). Results suggest no advantage to providing supplemental B12 to lambs fed monensin-supplemented, high-concentrate diets.

¹ Journal Article 1152 of the New Mexico Agr. Exp. Sta., Las Cruces 88003-0009.

² The authors wish to express appreciation to Dr. Jack Ruttle for assistance in obtaining liver samples and to Dr. Melchor Ortiz for his assistance with statistical analysis.

³ Present address: Dept. of Med., Div. of Gastroenterol. Univ. of Texas Health Sci. Center, San Antonio.

⁴ Dept. of Anim. and Range Sci.

⁵ Dept. of Chem.