Rumen Microbial Growth Rates and Yields

Effect of Amino Acids and Protein

W. J. Maeng, C. J. Van Nevel, R. L. Baldwin, James Morris

Research output: Contribution to journalArticle

127 Citations (Scopus)

Abstract

Effects of amino acids upon microbial growth, optimum ratio of nonprotein to amino acid nitrogen for microbial growth, and incorporation of amino acids into microbial cells were determined with washed cell suspension in vitro as were rumen microbial cells. Rumen microbial dry matter, nitrogen, ribonucleic acid, deoxyribonucleic acid, and substrate disappearance was greatest when a mixture of 18 amino acids was substituted for urea. Substitutions of mixtures of 10 essential amino acids, 8 nonessential amino acids, and sulfur containing amino acids and glutamate also stimulated microbial growth. Acid hydrolyzed casein markedly improved microbial growth. Branched amino acid addition did not affect growth. The optimum ratio of nonprotein to amino acid nitrogen for microbial growth was 75% urea nitrogen and 25% amino acid nitrogen. With this amount of amino acids, an average of 53% of added amino acid was incorporated into microbial cells, 14% was fermented to carbon dioxide and volatile fatty acids, and 33% remained in the supernatant. Both 100% urea and 100% amino acid in growth media were unfavorable for maximal microbial growth. With all carbohydrate substrates, 100% urea nitrogen supported the growth of 9 mg bacterial dry matter per 100 mg of substrate. Substitutions of amino acids for urea increased yields to over 20 mg/100 mg. Microbial growth yields in incubations under carbon dioxide were less than when flasks were flushed with nitrogen. However, yield of bacterial dry matter per unit of substrate was less under nitrogen than under carbon dioxide.

Original languageEnglish (US)
Pages (from-to)68-79
Number of pages12
JournalJournal of Dairy Science
Volume59
Issue number1
DOIs
StatePublished - Jan 1 1976

Fingerprint

Rumen
microbial growth
rumen
Amino Acids
amino acids
Nitrogen
Growth
Proteins
Urea
proteins
nitrogen
Carbon Dioxide
urea
carbon dioxide
urea nitrogen
Sulfur Amino Acids
Essential Amino Acids
Volatile Fatty Acids
Amino Acid Substitution
Caseins

ASJC Scopus subject areas

  • Food Science
  • Animal Science and Zoology
  • Genetics

Cite this

Rumen Microbial Growth Rates and Yields : Effect of Amino Acids and Protein. / Maeng, W. J.; Van Nevel, C. J.; Baldwin, R. L.; Morris, James.

In: Journal of Dairy Science, Vol. 59, No. 1, 01.01.1976, p. 68-79.

Research output: Contribution to journalArticle

Maeng, W. J. ; Van Nevel, C. J. ; Baldwin, R. L. ; Morris, James. / Rumen Microbial Growth Rates and Yields : Effect of Amino Acids and Protein. In: Journal of Dairy Science. 1976 ; Vol. 59, No. 1. pp. 68-79.
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