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

This Article Full Text Full Text (PDF) Interpretive Summary 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 HighWire Citing Articles via Google Scholar Google Scholar Articles by Broderick, G. A. Articles by Udén, P. Search for Related Content PubMed PubMed Citation Articles by Broderick, G. A. Articles by Udén, P.

Effect of Inhibitor Concentration and End-Product Accumulation on Estimates of Ruminal in Vitro Protein Degradation^*

Glen A. Broderick¹, Michael L. Murphy^2, and Peter Udén²

¹ Agricultural Research Service, USDA, US Dairy Forage Research Center, Madison, WI 53706
² Kungsängen forskningscentrum, Sveriges Lantbruksuniversitet, 753 23 Uppsala, Sweden

Corresponding author: G. A. Broderick; e-mail: gbroderi{at}wisc.edu.

Effects of varying the concentrations of hydrazine sulfate (HS) and chloramphenicol (CAP), inhibitors of microbial-N uptake and protein synthesis, on rates of protein degradation estimated from net appearance of NH₃ and total amino acids (TAA) were studied in a ruminal in vitro fermentation system. Without inhibitors, recoveries of N added as NH₃ and TAA were 4 and 6% after 4-h incubations, and apparent degradation rates estimated from release of NH₃ and TAA for casein, solvent soybean meal (SSBM), and expeller soybean meal (ESBM) approached 0. Increasing inhibitor concentrations from the standard amounts of 1 mM HS plus 30 mg of CAP/L to 2 mM HS plus 90 mg of CAP/L gave rise to numerically greater N recoveries and degradation rates, but these differences were not statistically significant. Compared with the standard inhibitor concentrations, use of 2 mM HS, without CAP, yielded similar recoveries and rates, but 30 or 90 mg of CAP/L, without HS, was not satisfactory. Versus that with 1 mM HS plus 30 mg of CAP/L, media containing 2 mM HS plus 90 mg of CAP/L gave increased TAA recoveries and higher rates for casein, but not SSBM, in the presence of added starch. Faster degradation rates were obtained for casein, but slower rates for SSBM and ESBM, in Sweden versus Wisconsin using inocula from cows fed different diets but with similar CP and energy contents. Differences in microbial catabolism of peptides may account for differences in degradation rates observed between Sweden and Wisconsin. Adding NH₃ plus free and peptide-bound amino acids to the inoculum reduced apparent degradation rates, possibly via end-product inhibition. Analysis of data from multiple time-point incubations indicated that casein degradation followed simple, first-order kinetics, while a biexponential model fitted degradation patterns for both SSBM and ESBM.

Key Words: protein degradation • rumen • inhibitor in vitro

Abbreviation key: CAP = chloramphenicol, ESBM = expeller soybean meal, HS = hydrazine sulfate, IIV = inhibitor in vitro, SSBM = solvent soybean meal, TAA = total AA

This article has been cited by other articles:

				C. Lanzas, G. A. Broderick, and D. G. Fox Improved Feed Protein Fractionation Schemes for Formulating Rations with the Cornell Net Carbohydrate and Protein System J Dairy Sci, December 1, 2008; 91(12): 4881 - 4891. [Abstract] [Full Text] [PDF]