Effect of orally administered pilocarpine on ruminal characteristics and nutrient digestibility in cattle.

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.