Introduction / J.M. Asplund -- Structure and function of the ruminant digestive tract / J.M. Asplund -- Significance and interpretation of balance methods of determining the utilization of dietary proteins / J.M. Asplund -- Nitrogen components of forages and feedstuffs / R.L. Reid -- Amino acid and protein synthesis, turnover and breakdown by ruminal microorganisms / R.J. Wallace -- Synchrony of protein and energy supply to enhance fermentation / J.T. Huber and R. Herrera-Saldana -- Absorption of amino acids and peptides / K.E. Webb, Jr. and J.C. Matthews -- Amino acid and protein metabolism in the whole body and individual tissues of ruminants / G.E. Lobley -- Influence of energy on amino acid supply and utilization in the ruminant / J.M. Asplund -- Metabolic requirement for amino acids in ruminants / J.M. Asplund -- Future research / J.M. Asplund.