Description of two anaerobic fungal strains from the bovine rumen and influence of diet on the fungal population in vivo.

Neocallimastix sp. NC71 and Piromyces sp. PC12 isolated from the calf remen grew optimally at 39 degrees C and pH 6.5-6.7, utilized a wide range of mono-, oligo- and polysaccharides and exhibited CMCase, Avicelase, cellobiase, amylase and xylanase activities. The end-products of wheat straw fermentation by both strains were acetate, formate, ethanol and lactate. The number of Neocallimastix sp. zoospores in the rumen of cows in the first 3 h after feeding with hay-silage-concentrate diets varied from 7 x 10(3) to 5.4 x 10(5) ml-1; the number of uniflagellate zoospores varied from 10(4) to 10(5) ml-1. Fungal zoosporgenesis and colonization of plant substrates in the rumen were induced by feed intake and were favoured by increased levels of crude fibre in the diet.