Effects of slaframine on ruminant digestive function: resting salivary flow and composition in cattle

Four esophageal- and ruminal-cannulated Angus steers (avg weight, 308 kg) were used to investigate how salivation is affected by the administration of purified slaframine (SF; 1-acetoxy-6-aminooctahydroindolizine), a cholinergic secretagogue isolated from Rhizoctonia leguminicola. Steers were fed a concentrate diet at twice the net energy requirement for maintenance in hourly increments. In trial 1, a single injection of SF was administered to four steers intramuscularly at 0, 6, 12 and 24-micrograms/kg body weight (BW) in a 4 X 4 Latin-square design. Saliva was collected via esophageal cannula at 15-min intervals 30 min after each feeding, weighted, sampled and reinfused via ruminal cannula over a 10-h period. At 12- and 24-micrograms SF/kg BW, salivary flow was 31 to 43% greater (P less than .01) than at 0- or 6-micrograms SF/kg. Response peaked within the first 3 h and returned to baseline levels at 8 h. Buffering capacity and pH of saliva were not different (P greater than .10); however, osmolality and Na concentration increased and K concentration decreased (P less than .10) as salivation rates increased. Feed intake of steers did not appear affected at any level of SF administration. In trial 2, 0-, 12- and 24-micrograms SF/kg BW were repeatedly administered intramuscularly to three steers in a 3 X 3 Latin-square design at 8-h intervals for 24 h. Salivary flow was measured and sampled over the entire 24-h period, as in trial 1. Flow rates were increased 50 to 70% (P less than .01) by SF treatment.(ABSTRACT TRUNCATED AT 250 WORDS)