Amino Acid and Fatty Acid Composition of Bovine Ruminal Bacteria and Protozoa

GUERNSEY and Holstein calves were reared for more than 60 weeks with and without ruminal ciliated protozoal (RCP) populations. Ruminal digest a samples were collected weekly for up to 60 weeks and were analyzed for amino acid and fatty acid compositions by column and gas-liquid chromatography. RCP-species, including holotrichs and entodiniomorphs, showed relatively high levels of aspartic and glutamic acids, leucine, lysine and isoleucine, which represented over 50% of the total protein. Ruminal bacterial samples showed the same 17 amino acids as RCP-species, and in comparable ranges of concentrations. There appeared to be little variation in the amino acid composition of the microbial proteins presented to the host regardless of whether or not RCP-species were feeding on species of the ruminal microflora. Lipoidal materials from the ruminal microbes contained appreciable amounts of palmitic, stearic and oleic acids (64.4 to 79.2% of total aliphatic methyl esters). Linoleic acid was higher in the lipids of the microfauna (9.7 and 10.5%) than in microflora (5.6%). Palmitic acid was higher in the lipids of the microfauna (37.3 and 48.2%) than in the microflora (25.4%). Evidence for biohydrogenation in the rumen was noted.