Four nonpregnant and nonlactating Holstein cows fitted with ruminal fistulas were assigned to each of four diets in a 4 X 4 Latin square design. Dietary treatments were 1) basal diet containing 50% concentrate; 2) basal diet plus 90 g/d yeast culture; 3) basal diet plus 2.63 g/d Aspergillus oryzae fermentation extract; 4) basal diet plus 90 g/d of A. oryzae fermentation extract and yeast culture. Cows were fed diets at a rate of 86 g DM/kg BW.75 for 14 d adaptation followed by an 8-d collection period. Digestibility of dry matter was increased by A. oryzae and A. oryzae and yeast culture combination treatments. Digestibility of CP was increased regardless of fungal culture addition. Hemicellulose digestibility, percent ruminal cellulolytic organisms, and acetate to propionate ratio were increased by the addition of fungal supplements.

Twenty Holstein dairy cows in early lactation were allocated equally to one of two treatments on the basis of age, days in milk, and mean daily 2-wk pretrial milk yield. All animals were fed a total mixed ration; the ration for the treatment group was top-dressed with 90 g/d of yeast culture, Saccharomyces cerevisiae. Treatment period lasted 10 wk. Mean daily DM intake, milk production, milk composition, and BW were not significantly affected by treatment. Feed and fecal samples were collected the last 3 d of the treatment period to determine apparent total tract nutrient digestibility using ADF insoluble ash as the inert marker. No significant differences in digestibility were observed between treatment groups for CP, ADF, and NDF.

Two rumen-fistulated Holstein heifers were fed three protein-free semipurified diets: 70% roughage, 30% concentrate; 50% roughage, 50% concentrate; and 30% roughage, 70% concentrate. Wheat straw was the roughage, and the concentrate was a pelleted mixture of corn starch, dextrose, fat, urea, vitamins, and minerals. Each animal received the three dietary treatments in a randomized complete block design. On days 1, 3, and 5 following a 21-day adaptation, rumen fluid samples were taken before feeding and at 1, 2, 3, 4, and 5 h after feeding. Total protozoa concentrations for low, medium, and high concentrate diets were 1.5, 2.5, 4.1 X 10(5)/ml. Dasytricha concentrations were not affected by diet, but Entodinium, Diplodinium, Isotricha, Epidinium, and Ophryoscolex increased with increases of the concentrate proportion of the diets. Entodinium, the predominant protozoa with all diets, increased as concentrate proportion of the diet increased. In a second experiment the two heifers from Experiment 1 were fed semipurified diets that contained either urea or soybean meal as the nitrogen source. There were larger populations of Dasytricha and Isotricha when the diet contained soybean meal, and larger populations of Charon, Entodinium, and total protozoa when the diet contained urea. In both experiments, holotrichs were highest 1 to 2 h after feeding, and entodiniomorphs were highest before feeding and 4 to 6 h after feeding. An active protozoan population can exist in the rumen of cattle fed diets virtually devoid of natural protein, and protozoa are influenced by energy and nitrogen source.

Four barren Holstein cows weighing 637 kg were fed a 45% concentrate diet plus the following amounts of pilocarpine: 1) 0 mg/kg; 2) 1 mg/kg; 3) 2 mg/kg; 4) 4 mg/kg body weight in a 4 X 4 Latin square design. Cows were administered the treatments for a 14-d adaptation period followed by an 8-d collection period. Digestibility of dry matter, crude protein, cellulose, and hemicellulose were determined during the first 3 d of the collection period. Ruminal liquid volume, volatile fatty acids, NH3N, bacterial mass production, viable bacteria, cellulolytic bacteria, liquid dilution rate, and particulate rate of passage were measured during the remainder of the collection period. As pilocarpine increased from 0 to 4 mg/kg body weight, digestibility of dry matter and cellulose increased by 8.5%. Digestibility of crude protein increased by 6.1%. Digestibility of hemicellulose was unchanged. Ruminal liquid volume was unchanged by treatment, whereas liquid dilution rate and particulate rate of passage increased 30% as pilocarpine increased. Ruminal volatile fatty acid concentrations and proportion were unchanged by treatment. Ruminal pH increased 4.2% and NH3N decreased by 37% as pilocarpine increased. Percent cellulolytic and bacterial mass production tended to increase as pilocarpine increased.

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