Content of 2-aminoethylphosphonic acid in feeds, bacteria and protozoa and its role as a rumen protozoal marker

A method is described that provides a rapid and accurate determination of 2-aminoethylphosphonic acid (AEP) in feeds and in rumen bacteria and protozoa. A wide variety of feeds examined was devoid of AEP. Six rumenfistulated cattle were fed either a high roughage (85% hay) or a high concentrate (85% concentrate) diet. Protozoa from cattle fed the high concentrate diet contained more (P < .05) AEP-N in relation to total N (.16%) than did those fed the high roughage diet (.10%). Protozoa from cattle fed the high concentrate diet contained less total N (7.8 vs 8.4%, P < .16) and more lipid (6.2 vs 3.0%, P < .05) than protozoa from cattle fed the high roughage diet. Amino acid N as a percentage of total protozoal N was greater (P < .05) for cattle fed the high roughage diet than for those fed the high concentrate (65.6 vs 57.9%). AEP was .33% of the amino acids in protozoa from cattle fed high concentrate, compared with .19% in protozoa from cattle fed high roughage (P < .05). The authors concluded that to obtain accurate predictions of protozoal production in the rumen based on AEP, it will be necessary to correct for dietary effects on chemical composition of protozoa.